1
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Mallick S, Agmon N. Lateral diffusion of ions near membrane surface. Phys Chem Chem Phys 2024; 26:19433-19449. [PMID: 38973628 DOI: 10.1039/d3cp04112c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/09/2024]
Abstract
Biological membranes isolate living cells from their environment, while allowing selective molecular transport between the inner and outer realms. For example, Na+ and K+ permeability through ionic channels contributes to neural conduction. Whether the ionic currents arise directly from cations in the bulk, or from the interface, is currently unclear. There are only scant results concerning lateral diffusion of ions on aquated membrane surfaces (and strong belief that this occurs through binding to a diffusing lipid). We performed classical molecular dynamics (MD) simulations of monovalent ions, Na+, K+, and Cl-, near the surface of the zwitterionic palmitoyl-oleoyl-phosphatidylcholine (POPC) membrane. Realistic force-fields for lipids (Amber's Lipid17 and Lipid21) and water (TIP4P-Ew) are tested for the mass and charge densities and the electrostatic potential across the membrane. These calculations reveal that the chloride can bind to the choline moiety through an intervening water molecule by forming a CH⋯OH hydrogen bond, while cations bind to both the phosphatic and carbonyl oxygens of phosphatidylcholine moieties. Upon transitioning from the bulk to the interface, a cation sheds some of its hydration water, which are replaced by headgroup atoms. Notably, an interfacial cation can bind 1-4 headgroup atoms, which is a key to understanding its surface hopping mechanism. We find that cation binding to three headgroup atoms immobilizes it, while binding to four energizes it. Consequently, the lateral cation diffusion rate is only 15-25 times slower than in the bulk, and 4-5 times faster than lipid self-diffusion. K+ diffusion is notably more anomalous than Na+, switching from sub- to super-diffusion after about 2 ns.
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Affiliation(s)
- Subhasish Mallick
- The Fritz Haber Research Center, Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel.
| | - Noam Agmon
- The Fritz Haber Research Center, Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel.
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2
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Mehrafrooz B, Yu L, Pandey L, Siwy ZS, Wanunu M, Aksimentiev A. Electro-osmotic Flow Generation via a Sticky Ion Action. ACS NANO 2024; 18:17521-17533. [PMID: 38832758 PMCID: PMC11233251 DOI: 10.1021/acsnano.4c00829] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2024]
Abstract
Selective transport of ions through nanometer-sized pores is fundamental to cell biology and central to many technological processes such as water desalination and electrical energy storage. Conventional methods for generating ion selectivity include placement of fixed electrical charges at the inner surface of a nanopore through either point mutations in a protein pore or chemical treatment of a solid-state nanopore surface, with each nanopore type requiring a custom approach. Here, we describe a general method for transforming a nanoscale pore into a highly selective, anion-conducting channel capable of generating a giant electro-osmotic effect. Our molecular dynamics simulations and reverse potential measurements show that exposure of a biological nanopore to high concentrations of guanidinium chloride renders the nanopore surface positively charged due to transient binding of guanidinium cations to the protein surface. A comparison of four biological nanopores reveals the relationship between ion selectivity, nanopore shape, composition of the nanopore surface, and electro-osmotic flow. Guanidinium ions are also found to produce anion selectivity and a giant electro-osmotic flow in solid-state nanopores via the same mechanism. Our sticky-ion approach to generate electro-osmotic flow can have numerous applications in controlling molecular transport at the nanoscale and for detection, identification, and sequencing of individual proteins.
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Affiliation(s)
- Behzad Mehrafrooz
- Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Luning Yu
- Department of Physics, Northeastern University, Boston, Massachusetts 02115, United States
| | - Laxmi Pandey
- Department of Physics, Northeastern University, Boston, Massachusetts 02115, United States
| | - Zuzanna S Siwy
- Department of Physics, University of California at Irvine, Irvine, California 92697, United States
| | - Meni Wanunu
- Department of Physics, Northeastern University, Boston, Massachusetts 02115, United States
- Department of Bioengineering, Northeastern University, Boston, Massachusetts 02115, United States
| | - Aleksei Aksimentiev
- Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
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3
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Monck C, Elani Y, Ceroni F. Genetically programmed synthetic cells for thermo-responsive protein synthesis and cargo release. Nat Chem Biol 2024:10.1038/s41589-024-01673-7. [PMID: 38969863 DOI: 10.1038/s41589-024-01673-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Accepted: 06/06/2024] [Indexed: 07/07/2024]
Abstract
Synthetic cells containing genetic programs and protein expression machinery are increasingly recognized as powerful counterparts to engineered living cells in the context of biotechnology, therapeutics and cellular modelling. So far, genetic regulation of synthetic cell activity has been largely confined to chemical stimuli; to unlock their potential in applied settings, engineering stimuli-responsive synthetic cells under genetic regulation is imperative. Here we report the development of temperature-sensitive synthetic cells that control protein production by exploiting heat-responsive mRNA elements. This is achieved by combining RNA thermometer technology, cell-free protein expression and vesicle-based synthetic cell design to create cell-sized capsules able to initiate synthesis of both soluble proteins and membrane proteins at defined temperatures. We show that the latter allows for temperature-controlled cargo release phenomena with potential implications for biomedicine. Platforms like the one presented here can pave the way for customizable, genetically programmed synthetic cells under thermal control to be used in biotechnology.
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Affiliation(s)
- Carolina Monck
- Department of Chemical Engineering, Imperial College London, London, UK
- Imperial College Centre for Synthetic Biology, London, UK
- fabriCELL, Imperial College London, London, UK
| | - Yuval Elani
- Department of Chemical Engineering, Imperial College London, London, UK.
- Imperial College Centre for Synthetic Biology, London, UK.
- fabriCELL, Imperial College London, London, UK.
| | - Francesca Ceroni
- Department of Chemical Engineering, Imperial College London, London, UK.
- Imperial College Centre for Synthetic Biology, London, UK.
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4
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Baldelli M, Di Muccio G, Sauciuc A, Morozzo Della Rocca B, Viola F, Balme S, Bonini A, Maglia G, Chinappi M. Controlling Electroosmosis in Nanopores Without Altering the Nanopore Sensing Region. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024:e2401761. [PMID: 38860821 DOI: 10.1002/adma.202401761] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2024] [Revised: 05/24/2024] [Indexed: 06/12/2024]
Abstract
Nanopores are powerful tools for single-molecule sensing of biomolecules and nanoparticles. The signal coming from the molecule to be analyzed strongly depends on its interaction with the narrower section of the nanopore (constriction) that may be tailored to increase sensing accuracy. Modifications of nanopore constriction have also been commonly used to induce electroosmosis, that favors the capture of molecules in the nanopore under a voltage bias and independently of their charge. However, engineering nanopores for increasing both electroosmosis and sensing accuracy is challenging. Here it is shown that large electroosmotic flows can be achieved without altering the nanopore constriction. Using continuum electrohydrodynamic simulations, it is found that an external charged ring generates strong electroosmosis in cylindrical nanopores. Similarly, for conical nanopores it is shown that moving charges away from the cone tip still results in an electroosmotic flow (EOF), whose intensity reduces increasing the diameter of the nanopore section where charges are placed. This paradigm is applied to engineered biological nanopores showing, via atomistic simulations and experiments, that mutations outside the constriction induce a relatively intense electroosmosis. This strategy provides much more flexibility in nanopore design since electroosmosis can be controlled independently from the constriction, which can be optimized to improve sensing accuracy.
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Affiliation(s)
- Matteo Baldelli
- Department of Industrial Engeenering, University of Rome Tor Vergata, Roma, 00133, Italy
| | - Giovanni Di Muccio
- Department of Mechanical and Aerospace Engineering, University of Rome Sapienza, Roma, 00184, Italy
| | - Adina Sauciuc
- Groningen Biomolecular Sciences & Biotechnology Institute, University of Groningen, Groningen, 9747 AG, The Netherlands
| | | | | | - Sébastien Balme
- Institut Europeen des Membranes, UMR5635, University of Montpellier ENCSM CNRS, Montpellier, 34095, France
| | - Andrea Bonini
- Groningen Biomolecular Sciences & Biotechnology Institute, University of Groningen, Groningen, 9747 AG, The Netherlands
| | - Giovanni Maglia
- Groningen Biomolecular Sciences & Biotechnology Institute, University of Groningen, Groningen, 9747 AG, The Netherlands
| | - Mauro Chinappi
- Department of Industrial Engeenering, University of Rome Tor Vergata, Roma, 00133, Italy
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5
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Nan Y, MacKerell AD. Balancing Group I Monatomic Ion-Polar Compound Interactions for Condensed Phase Simulation in the Polarizable Drude Force Field. J Chem Theory Comput 2024; 20:3242-3257. [PMID: 38588064 PMCID: PMC11039353 DOI: 10.1021/acs.jctc.3c01380] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/10/2024]
Abstract
Molecular dynamics (MD) simulations are a commonly used method for investigating molecular behavior at the atomic level. Achieving reliable MD simulation results necessitates the use of an accurate force field. In the present work, we present a protocol to enhance the quality of group 1 monatomic ions (specifically Li+, Na+, K+, Rb+, and Cs+) with respect to their interactions with common polar model compounds in biomolecules in condensed phases in the context of the Drude polarizable force field. Instead of adjusting preexisting individual parameters for ions, model compounds, and water, we employ atom-pair specific Lennard-Jones (LJ) (known as NBFIX in CHARMM) and through-space Thole dipole screening (NBTHOLE) terms to fine-tune the balance of ion-model compound, ion-water, and model compound-water interactions. This involved establishing a protocol for the optimization of NBFIX and NBTHOLE parameters targeting the difference between molecular mechanical (MM) and quantum mechanical (QM) potential energy scans (PES). It is shown that targeting PES involving complexes that include multiple model compounds and/or ions as trimers and tetramers yields parameters that produce condensed phase properties in agreement with experimental data. Validation of this protocol involved the reproduction of experimental thermodynamic benchmarks, including solvation free energies of ions in methanol and N-methylacetamide, osmotic pressures, ionic conductivities, and diffusion coefficients within the condensed phase. These results show the importance of including more complex ion-model compound complexes beyond dimers in the QM target data to account for many-body effects during parameter fitting. The presented parameters represent a significant refinement of the Drude polarizable force field, which will lead to improved accuracy for modeling ion-biomolecular interactions.
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Affiliation(s)
- Yiling Nan
- University of Maryland Computer-Aided Drug Design Center, Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, MD 21201 MD
| | - Alexander D. MacKerell
- University of Maryland Computer-Aided Drug Design Center, Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, MD 21201 MD
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6
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Mondal R, Vaissier Welborn V. Dynamics accelerate the kinetics of ion diffusion through channels: Continuous-time random walk models beyond the mean field approximation. J Chem Phys 2024; 160:144109. [PMID: 38597306 DOI: 10.1063/5.0188469] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2023] [Accepted: 03/14/2024] [Indexed: 04/11/2024] Open
Abstract
Ion channels are proteins that play a significant role in physiological processes, including neuronal excitability and signal transduction. However, the precise mechanisms by which these proteins facilitate ion diffusion through cell membranes are not well understood. This is because experimental techniques to characterize ion channel activity operate on a time scale too large to understand the role of the various protein conformations on diffusion. Meanwhile, computational approaches operate on a time scale too short to rationalize the observed behavior at the microscopic scale. In this paper, we present a continuous-time random walk model that aims to bridge the scales between the atomistic models of ion channels and the experimental measurement of their conductance. We show how diffusion slows down in complex systems by using 3D lattices that map out the pore geometry of two channels: Nav1.7 and gramicidin. We also introduce spatial and dynamic site disorder to account for system heterogeneity beyond the mean field approximation. Computed diffusion coefficients show that an increase in spatial disorder slows down diffusion kinetics, while dynamic disorder has the opposite effect. Our results imply that microscopic or phenomenological models based on the potential of mean force data overlook the functional importance of protein dynamics on ion diffusion through channels.
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Affiliation(s)
- Ronnie Mondal
- Department of Chemistry, Virginia Tech, Blacksburg, Virginia 24061, USA
- Macromolecules Innovation Institute, Virginia Tech, Blacksburg, Virginia 24061, USA
| | - Valerie Vaissier Welborn
- Department of Chemistry, Virginia Tech, Blacksburg, Virginia 24061, USA
- Macromolecules Innovation Institute, Virginia Tech, Blacksburg, Virginia 24061, USA
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7
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Oh H, Tu YM, Samineni L, De Respino S, Mehrafrooz B, Joshi H, Massenburg L, Lopez-Marques H, Elessawy N, Song W, Behera H, Dhiman R, Boorla VS, Kher K, Lin YC, Maranas C, Aksimentiev A, D Freeman B, Kumar M. Dehydrated Biomimetic Membranes with Skinlike Structure and Function. ACS APPLIED MATERIALS & INTERFACES 2024. [PMID: 38598825 DOI: 10.1021/acsami.3c19572] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2024]
Abstract
Novel vapor-permeable materials are sought after for applications in protective wear, energy generation, and water treatment. Current impermeable protective materials effectively block harmful agents but trap heat due to poor water vapor transfer. Here we present a new class of materials, vapor permeable dehydrated nanoporous biomimetic membranes (DBMs), based on channel proteins. This application for biomimetic membranes is unexpected as channel proteins and biomimetic membranes were assumed to be unstable under dry conditions. DBMs mimic human skin's structure to offer both high vapor transport and small molecule exclusion under dry conditions. DBMs feature highly organized pores resembling sweat pores in human skin, but at super high densities (>1012 pores/cm2). These DBMs achieved exceptional water vapor transport rates, surpassing commercial breathable fabrics by up to 6.2 times, despite containing >2 orders of magnitude smaller pores (1 nm vs >700 nm). These DBMs effectively excluded model biological agents and harmful chemicals both in liquid and vapor phases, again in contrast with the commercial breathable fabrics. Remarkably, while hydrated biomimetic membranes were highly permeable to liquid water, they exhibited higher water resistances after dehydration at values >38 times that of commercial breathable fabrics. Molecular dynamics simulations support our hypothesis that dehydration induced protein hydrophobicity increases which enhanced DBM performance. DBMs hold promise for various applications, including membrane distillation, dehumidification, and protective barriers for atmospheric water harvesting materials.
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Affiliation(s)
- Hyeonji Oh
- McKetta Department of Chemical Engineering, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Yu-Ming Tu
- McKetta Department of Chemical Engineering, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Laximicharan Samineni
- McKetta Department of Chemical Engineering, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Sophie De Respino
- Maseeh Department of Civil, Architectural and Environmental Engineering, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Behzad Mehrafrooz
- Center for Biophysics and Quantitative Biology, The University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
- Department of Physics and Beckman Institute for Advanced Science and Technology, The University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Himanshu Joshi
- Department of Biotechnology, Indian Institute of Technology, Hyderabad 502285, India
| | - Lynnicia Massenburg
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Horacio Lopez-Marques
- McKetta Department of Chemical Engineering, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Nada Elessawy
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Woochul Song
- Division of Environmental Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 37673, South Korea
| | - Harekrushna Behera
- Maseeh Department of Civil, Architectural and Environmental Engineering, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Raman Dhiman
- McKetta Department of Chemical Engineering, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Veda Sheersh Boorla
- Department of Chemical Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Kartik Kher
- McKetta Department of Chemical Engineering, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Yi-Chih Lin
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Costas Maranas
- Department of Chemical Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Aleksei Aksimentiev
- Center for Biophysics and Quantitative Biology, The University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
- Department of Physics and Beckman Institute for Advanced Science and Technology, The University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Benny D Freeman
- McKetta Department of Chemical Engineering, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Manish Kumar
- McKetta Department of Chemical Engineering, The University of Texas at Austin, Austin, Texas 78712, United States
- Maseeh Department of Civil, Architectural and Environmental Engineering, The University of Texas at Austin, Austin, Texas 78712, United States
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8
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Cubisino SAM, Milenkovic S, Conti-Nibali S, Musso N, Bonacci P, De Pinto V, Ceccarelli M, Reina S. Electrophysiological properties and structural prediction of the SARS-CoV-2 viroprotein E. Front Mol Biosci 2024; 11:1334819. [PMID: 38606285 PMCID: PMC11007222 DOI: 10.3389/fmolb.2024.1334819] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2023] [Accepted: 01/15/2024] [Indexed: 04/13/2024] Open
Abstract
COVID-19, the infectious disease caused by the most recently discovered coronavirus SARS- CoV-2, has caused millions of sick people and thousands of deaths all over the world. The viral positive-sense single-stranded RNA encodes 31 proteins among which the spike (S) is undoubtedly the best known. Recently, protein E has been reputed as a potential pharmacological target as well. It is essential for the assembly and release of the virions in the cell. Literature describes protein E as a voltage-dependent channel with preference towards monovalent cations whose intracellular expression, though, alters Ca2+ homeostasis and promotes the activation of the proinflammatory cascades. Due to the extremely high sequence identity of SARS-CoV-2 protein E (E-2) with the previously characterized E-1 (i.e., protein E from SARS-CoV) many data obtained for E-1 were simply adapted to the other. Recent solid state NMR structure revealed that the transmembrane domain (TMD) of E-2 self-assembles into a homo-pentamer, albeit the oligomeric status has not been validated with the full-length protein. Prompted by the lack of a common agreement on the proper structural and functional features of E-2, we investigated the specific mechanism/s of pore-gating and the detailed molecular structure of the most cryptic protein of SARS-CoV-2 by means of MD simulations of the E-2 structure and by expressing, refolding and analyzing the electrophysiological activity of the transmembrane moiety of the protein E-2, in its full length. Our results show a clear agreement between experimental and predictive studies and foresee a mechanism of activity based on Ca2+ affinity.
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Affiliation(s)
| | | | - Stefano Conti-Nibali
- Department of Biomedical and Biotechnological Sciences, University of Catania, Catania, Italy
| | - Nicolò Musso
- Department of Biomedical and Biotechnological Sciences, University of Catania, Catania, Italy
| | - Paolo Bonacci
- Department of Biomedical and Biotechnological Sciences, University of Catania, Catania, Italy
| | - Vito De Pinto
- Department of Biomedical and Biotechnological Sciences, University of Catania, Catania, Italy
- We.MitoBiotech S.R.L, Catania, Italy
| | | | - Simona Reina
- Department of Biomedical and Biotechnological Sciences, University of Catania, Catania, Italy
- We.MitoBiotech S.R.L, Catania, Italy
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9
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Onishi N, Mazzaferro N, Kunstelj Š, Alvarado DA, Muller AM, Vázquez FX. Flanking Domains Modulate α-Synuclein Monomer Structure: A Molecular Dynamics Domain Deletion Study. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.23.586267. [PMID: 38586052 PMCID: PMC10996548 DOI: 10.1101/2024.03.23.586267] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/09/2024]
Abstract
Aggregates of misfolded α-synuclein proteins (asyn) are key markers of Parkinson's disease. Asyn proteins have three domains: an N-terminal domain, a hydrophobic NAC core implicated in aggregation, and a proline-rich C-terminal domain. Proteins with truncated C-terminal domains are known to be prone to aggregation and suggest that studying domain-domain interactions in asyn monomers could help elucidate the role of the flanking domains in modulating protein structure. To this end, we used Gaussian accelerated molecular dynamics (GAMD) to simulate wild-type (WT), N-terminal truncated (DN), C-terminal truncated (ΔC), and isolated NAC domain variants (isoNAC). Using clustering and contact analysis, we found that N- and C-terminal domains interact via electrostatic interactions, while the NAC and N-terminal domains interact through hydrophobic contacts. Our work also suggests that the C-terminal domain does not interact directly with the NAC domain but instead interacts with the N-terminal domain. Removal of the N-terminal domain led to increased contacts between NAC and C-terminal domains and the formation of interdomain β-sheets. Removal of either flanking domain also resulted in increased compactness of every domain. We also found that the contacts between flanking domains results in an electrostatic potential (ESP) that could possibly lead to favorable interactions with anionic lipid membranes. Removal of the C-terminal domain disrupts the ESP in a way that is likely to over-stabilize protein-membrane interactions. All of this suggests that one of the roles of the flanking domains may be to modulate the protein structure in a way that helps maintain elongation, hide hydrophobic residue from the solvent, and maintain an ESP that aids favorable interactions with the membrane.
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Affiliation(s)
- Noriyo Onishi
- Department of Chemistry, St. John’s University, Queens, NY 11439, USA
| | | | - Špela Kunstelj
- Department of Chemistry, St. John’s University, Queens, NY 11439, USA
| | - Daisy A. Alvarado
- Department of Chemistry, St. John’s University, Queens, NY 11439, USA
| | - Anna M. Muller
- Department of Chemistry, St. John’s University, Queens, NY 11439, USA
| | - Frank X. Vázquez
- Department of Chemistry, St. John’s University, Queens, NY 11439, USA
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10
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Coshic K, Maffeo C, Winogradoff D, Aksimentiev A. The structure and physical properties of a packaged bacteriophage particle. Nature 2024; 627:905-914. [PMID: 38448589 PMCID: PMC11196859 DOI: 10.1038/s41586-024-07150-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2023] [Accepted: 02/01/2024] [Indexed: 03/08/2024]
Abstract
A string of nucleotides confined within a protein capsid contains all the instructions necessary to make a functional virus particle, a virion. Although the structure of the protein capsid is known for many virus species1,2, the three-dimensional organization of viral genomes has mostly eluded experimental probes3,4. Here we report all-atom structural models of an HK97 virion5, including its entire 39,732 base pair genome, obtained through multiresolution simulations. Mimicking the action of a packaging motor6, the genome was gradually loaded into the capsid. The structure of the packaged capsid was then refined through simulations of increasing resolution, which produced a 26 million atom model of the complete virion, including water and ions confined within the capsid. DNA packaging occurs through a loop extrusion mechanism7 that produces globally different configurations of the packaged genome and gives each viral particle individual traits. Multiple microsecond-long all-atom simulations characterized the effect of the packaged genome on capsid structure, internal pressure, electrostatics and diffusion of water, ions and DNA, and revealed the structural imprints of the capsid onto the genome. Our approach can be generalized to obtain complete all-atom structural models of other virus species, thereby potentially revealing new drug targets at the genome-capsid interface.
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Affiliation(s)
- Kush Coshic
- Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Christopher Maffeo
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL, USA
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - David Winogradoff
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Aleksei Aksimentiev
- Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
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11
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Li M, Muthukumar M. Electro-osmotic flow in nanoconfinement: Solid-state and protein nanopores. J Chem Phys 2024; 160:084905. [PMID: 38411234 DOI: 10.1063/5.0185574] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Accepted: 01/05/2024] [Indexed: 02/28/2024] Open
Abstract
Electro-osmotic flow (EOF) is a phenomenon where fluid motion occurs in porous materials or micro/nano-channels when an external electric field is applied. In the particular example of single-molecule electrophoresis using single nanopores, the role of EOF on the translocation velocity of the analyte molecule through the nanopore is not fully understood. The complexity arises from a combination of effects from hydrodynamics in restricted environments, electrostatics emanating from charge decorations and geometry of the pores. We address this fundamental issue using the Poisson-Nernst-Planck and Navier-Stokes (PNP-NS) equations for cylindrical solid-state nanopores and three representative protein nanopores (α-hemolysin, MspA, and CsgG). We present the velocity profiles inside the nanopores as a function of charge decoration and geometry of the pore and applied electric field. We report several unexpected results: (a) The apparent charges of the protein nanopores are different from their net charge and the surface charge of the whole protein geometry, and the net charge of inner surface is consistent with the apparent charge. (b) The fluid velocity depends non-monotonically on voltage. The three protein nanopores exhibit unique EOF and velocity-voltage relations, which cannot be simply deduced from their net charge. Furthermore, effective point mutations can significantly change both the direction and the magnitude of EOF. The present computational analysis offers an opportunity to further understand the origins of the speed of transport of charged macromolecules in restricted space and to design desirable nanopores for tuning the speed of macromolecules through nanopores.
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Affiliation(s)
- Minglun Li
- Department of Polymer Science and Engineering, University of Massachusetts, Amherst, Massachusetts 01003, USA
| | - Murugappan Muthukumar
- Department of Polymer Science and Engineering, University of Massachusetts, Amherst, Massachusetts 01003, USA
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12
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Liu J, Aksimentiev A. Molecular Determinants of Current Blockade Produced by Peptide Transport Through a Nanopore. ACS NANOSCIENCE AU 2024; 4:21-29. [PMID: 38406313 PMCID: PMC10885333 DOI: 10.1021/acsnanoscienceau.3c00046] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/15/2023] [Revised: 10/28/2023] [Accepted: 11/03/2023] [Indexed: 02/27/2024]
Abstract
The nanopore sensing method holds the promise of delivering a single molecule technology for identification of biological proteins, direct detection of post-translational modifications, and perhaps de novo determination of a protein's amino acid sequence. The key quantity measured in such nanopore sensing experiments is the magnitude of the ionic current passing through a nanopore blocked by a polypeptide chain. Establishing a relationship between the amino acid sequence of a peptide fragment confined within a nanopore and the blockade current flowing through the nanopore remains a major challenge for realizing the nanopore protein sequencing. Using the results of all-atom molecular dynamics simulations, here we compare nanopore sequencing of DNA with nanopore sequencing of proteins. We then delineate the factors affecting the blockade current modulation by the peptide sequence, showing that the current can be determined by (i) the steric footprint of an amino acid, (ii) its interactions with the pore wall, (iii) the local stretching of a polypeptide chain, and (iv) the local enhancement of the ion concentration at the nanopore constriction. We conclude with a brief discussion of the prospects for purely computational prediction of the blockade currents.
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Affiliation(s)
- Jingqian Liu
- Center
for Biophysics and Quantitative Biology, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
- Beckman
Institute for Advanced Science and Technology, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
| | - Aleksei Aksimentiev
- Center
for Biophysics and Quantitative Biology, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
- Beckman
Institute for Advanced Science and Technology, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
- Department
of Physics, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
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13
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DeLuca M, Sensale S, Lin PA, Arya G. Prediction and Control in DNA Nanotechnology. ACS APPLIED BIO MATERIALS 2024; 7:626-645. [PMID: 36880799 DOI: 10.1021/acsabm.2c01045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/08/2023]
Abstract
DNA nanotechnology is a rapidly developing field that uses DNA as a building material for nanoscale structures. Key to the field's development has been the ability to accurately describe the behavior of DNA nanostructures using simulations and other modeling techniques. In this Review, we present various aspects of prediction and control in DNA nanotechnology, including the various scales of molecular simulation, statistical mechanics, kinetic modeling, continuum mechanics, and other prediction methods. We also address the current uses of artificial intelligence and machine learning in DNA nanotechnology. We discuss how experiments and modeling are synergistically combined to provide control over device behavior, allowing scientists to design molecular structures and dynamic devices with confidence that they will function as intended. Finally, we identify processes and scenarios where DNA nanotechnology lacks sufficient prediction ability and suggest possible solutions to these weak areas.
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Affiliation(s)
- Marcello DeLuca
- Thomas Lord Department of Mechanical Engineering and Materials Science, Duke University, Durham, North Carolina 27708, United States
| | - Sebastian Sensale
- Department of Physics, Cleveland State University, Cleveland, Ohio 44115, United States
| | - Po-An Lin
- Thomas Lord Department of Mechanical Engineering and Materials Science, Duke University, Durham, North Carolina 27708, United States
| | - Gaurav Arya
- Thomas Lord Department of Mechanical Engineering and Materials Science, Duke University, Durham, North Carolina 27708, United States
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14
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Shen R, Roux B, Perozo E. Anionic omega currents from single countercharge mutants in the voltage-sensing domain of Ci-VSP. J Gen Physiol 2024; 156:e202213311. [PMID: 38019193 PMCID: PMC10686229 DOI: 10.1085/jgp.202213311] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2022] [Revised: 06/08/2023] [Accepted: 10/30/2023] [Indexed: 11/30/2023] Open
Abstract
The S4 segment of voltage-sensing domains (VSDs) directly responds to voltage changes by reorienting within the electric field as a permion. A narrow hydrophobic "gasket" or charge transfer center at the core of most VSDs focuses the electric field into a narrow region and catalyzes the sequential and reversible translocation of S4 positive gating charge residues across the electric field while preventing the permeation of physiological ions. Mutating specific S4 gating charges can cause ionic leak currents through the VSDs. These gating pores or omega currents play important pathophysiological roles in many diseases of excitability. Here, we show that mutating D129, a key countercharge residue in the Ciona intestinalis voltage-sensing phosphatase (Ci-VSP), leads to the generation of unique anionic omega currents. Neutralizing D129 causes a dramatic positive shift of activation, facilitates the formation of a continuous water path through the VSD, and creates a positive electrostatic potential landscape inside the VSD that contributes to its unique anionic selectivity. Increasing the population or dwell time of the conducting state by a high external pH or an engineered Cd2+ bridge markedly increases the current magnitude. Our findings uncover a new role of countercharge residues in the impermeable VSD of Ci-VSP and offer insights into mechanisms of the conduction of anionic omega currents linked to countercharge residue mutations.
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Affiliation(s)
- Rong Shen
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA
| | - Benoît Roux
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA
| | - Eduardo Perozo
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA
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15
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Mehrafrooz B, Yu L, Siwy Z, Wanunu M, Aksimentiev A. Electro-Osmotic Flow Generation via a Sticky Ion Action. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.12.14.571673. [PMID: 38168277 PMCID: PMC10760089 DOI: 10.1101/2023.12.14.571673] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2024]
Abstract
Selective transport of ions through nanometer-sized pores is fundamental to cell biology and central to many technological processes such as water desalination and electrical energy storage. Conventional methods for generating ion selectivity include placement of fixed electrical charges at the inner surface of a nanopore through either point mutations in a protein pore or chemical treatment of a solid-state nanopore surface, with each nanopore type requiring a custom approach. Here, we describe a general method for transforming a nanoscale pore into a highly selective, anion-conducting channel capable of generating a giant electro-osmotic effect. Our molecular dynamics simulations and reverse potential measurements show that exposure of a biological nanopore to high concentrations of guanidinium chloride renders the nanopore surface positively charged due to transient binding of guanidinium cations to the protein surface. A comparison of four biological nanopores reveals the relationship between ion selectivity, nanopore shape, composition of the nanopore surface, and electro-osmotic flow. Remarkably, guanidinium ions are also found to produce anion selectivity and a giant electro-osmotic flow in solid-state nanopores via the same mechanism. Our sticky-ion approach to generate electro-osmotic flow can have numerous applications in controlling molecular transport at the nanoscale and for detection, identification, and sequencing of individual proteins.
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Affiliation(s)
- Behzad Mehrafrooz
- Center for Biophysics and Quantitative Biology
- Beckman Institute for Advanced Science and Technology
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Luning Yu
- Department of Physics, Northeastern University, Boston, MA 02115 USA
| | - Zuzanna Siwy
- Department of Physics, University of California at Irvine, Irvine, CA 92697, USA
| | - Meni Wanunu
- Department of Physics, Northeastern University, Boston, MA 02115 USA
- Department of Bioengineering, Northeastern University, Boston, MA 02115, USA
| | - Aleksei Aksimentiev
- Center for Biophysics and Quantitative Biology
- Beckman Institute for Advanced Science and Technology
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois
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16
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Yu YS, Ren Q, Tan RR, Ding HM. Exploring the non-monotonic DNA capture behavior in a charged graphene nanopore. Phys Chem Chem Phys 2023; 25:28034-28042. [PMID: 37846110 DOI: 10.1039/d3cp03767c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2023]
Abstract
Nanopore-based biomolecule detection has emerged as a promising and sought-after innovation, offering high throughput, rapidity, label-free analysis, and cost-effectiveness, with potential applications in personalized medicine. However, achieving efficient and tunable biomolecule capture into the nanopore remains a significant challenge. In this study, we employ all-atom molecular dynamics simulations to investigate the capture of double-stranded DNA (dsDNA) molecules into graphene nanopores with varying positive charges. We discover a non-monotonic relationship between the DNA capture rate and the charge of the graphene nanopore. Specifically, the capture rate initially decreases and then increases with an increase in nanopore charge. This behavior is primarily attributed to differences in the electrophoretic force, rather than the influence of electroosmosis or counterions. Furthermore, we also observe this non-monotonic trend in various ionic solutions, but not in ionless solutions. Our findings shed light on the design of novel DNA sequencing devices, offering valuable insights into enhancing biomolecule capture rates in nanopore-based sensing platforms.
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Affiliation(s)
- You-Sheng Yu
- School of Science, East China University of Technology, Nanchang 330013, China
- National Lab of Solid State Microstructures, Nanjing University, Nanjing 210093, China
| | - Qiang Ren
- School of Science, East China University of Technology, Nanchang 330013, China
| | - Rong-Ri Tan
- Department of Physics, Jiangxi Science & Technology Normal University, Nanchang 330013, China.
| | - Hong-Ming Ding
- Center for Soft Condensed Matter Physics and Interdisciplinary Research, Soochow University, Suzhou 215006, China.
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17
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Das D, Bharadwaz P, Mattaparthi VSK. Computational investigation on the effect of the peptidomimetic inhibitors (NPT100-18A and NPT200-11) on the α-synuclein and lipid membrane interactions. J Biomol Struct Dyn 2023:1-12. [PMID: 37768058 DOI: 10.1080/07391102.2023.2262599] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2023] [Accepted: 09/18/2023] [Indexed: 09/29/2023]
Abstract
Parkinson's disease (PD) is associated with α-synuclein (α-Syn), a presynaptic protein that binds to cell membranes. The molecular pathophysiology of PD most likely begins with the binding of α-Syn to membranes. Recently, two peptidomimetic inhibitors (NPT100-18A and NPT200-11) were identified to potentially interact with α-Syn and affect the interaction of α-Syn with the membrane. In this study, the effect of the two peptidomimetic inhibitors on the α-Syn-membrane interaction was demonstrated. DFT calculations were performed for optimization of the two inhibitors, and the nucleophilicity (N) and electrophilicity (ω) of NPT100-18A and NPT200-11 were calculated to be 3.90 and 3.86 (N); 1.06 and 1.04 (ω), respectively. Using the docking tool (CB-dock2), the two α-Syn-peptidomimetic inhibitor complexes (α-Syn-NPT100-18A and α-Syn-NPT200-11) have been prepared. Then all-atom molecular dynamics (MD) simulation was carried out on the α-Syn (control), α-Syn-NPT100-18A and α-Syn-NPT200-11 complex systems in presence of DOPE: DOPS: DOPC (5:3:2) lipid bilayer. From the conformational dynamics analysis, the 3-D structure of α-Syn was found to be stable, and the helices present in the regions (1-37) and (45-95) of α-Syn were found to be retained in the presence of the two peptidomimetic inhibitors. The electron density profile analysis revealed the binding modes of NAC and C-terminal region of α-Syn (in the presence of NPT200-11 inhibitor) with lipid membrane are in the close vicinity from the lipid bilayer centre. Our findings in this study on α-Syn-membrane interactions may be useful for developing a new therapeutic approach for treating PD and other neurodegenerative disorders.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Dorothy Das
- Molecular Modelling and Simulation Laboratory, Department of Molecular Biology and Biotechnology, Tezpur University, Tezpur, Assam, India
| | - Priyam Bharadwaz
- J. Heyrovský Institute of Physical Chemistry, Czech Academy of Sciences, Prague, Czech Republic
| | - Venkata Satish Kumar Mattaparthi
- Molecular Modelling and Simulation Laboratory, Department of Molecular Biology and Biotechnology, Tezpur University, Tezpur, Assam, India
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18
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Krishnan S, Aksimentiev A, Lindsay S, Matyushov D. Long-Range Conductivity in Proteins Mediated by Aromatic Residues. ACS PHYSICAL CHEMISTRY AU 2023; 3:444-455. [PMID: 37780537 PMCID: PMC10540285 DOI: 10.1021/acsphyschemau.3c00017] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Revised: 05/18/2023] [Accepted: 05/19/2023] [Indexed: 09/30/2023]
Abstract
Single-molecule measurements show that many proteins, lacking any redox cofactors, nonetheless exhibit electrical conductance on the order of a nanosiemen over 10 nm distances, implying that electrons can transit an entire protein in less than a nanosecond when subject to a potential difference of less than 1 V. This is puzzling because, for fast transport (i.e., a free energy barrier of zero), the hopping rate is determined by the reorganization energy of approximately 0.8 eV, and this sets the time scale of a single hop to at least 1 μs. Furthermore, the Fermi energies of typical metal electrodes are far removed from the energies required for sequential oxidation and reduction of the aromatic residues of the protein, which should further reduce the hopping current. Here, we combine all-atom molecular dynamics (MD) simulations of non-redox-active proteins (consensus tetratricopeptide repeats) with an electron transfer theory to demonstrate a molecular mechanism that can account for the unexpectedly fast electron transport. According to our MD simulations, the reorganization energy produced by the energy shift on charging (the Stokes shift) is close to the conventional value of 0.8 eV. However, the non-ergodic sampling of molecular configurations by the protein results in reaction-reorganization energies, extracted directly from the distribution of the electrostatic energy fluctuations, that are only ∼0.2 eV, which is small enough to enable long-range conductivity, without invoking quantum coherent transport. Using the MD values of the reorganization energies, we calculate a current decay with distance that is in agreement with experiment.
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Affiliation(s)
- Siddharth Krishnan
- Department
of Physics and Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Aleksei Aksimentiev
- Department
of Physics and Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Stuart Lindsay
- Department
of Physics, Arizona State University, Tempe, Arizona 85281, United States
- School
of Molecular Sciences, Arizona State University, Tempe, Arizona 85281, United States
- Biodesign
Institute, Arizona State University, Tempe, Arizona 85281, United States
| | - Dmitry Matyushov
- Department
of Physics, Arizona State University, Tempe, Arizona 85281, United States
- School
of Molecular Sciences, Arizona State University, Tempe, Arizona 85281, United States
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19
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Chen X, Ferchaud N, Briozzo P, Machover D, Simonson T. PLP-Dependent Enzyme Methionine γ-Lyase: Insights into the Michaelis Complex from Molecular Dynamics and Free Energy Simulations. Biochemistry 2023; 62:2791-2801. [PMID: 37668546 DOI: 10.1021/acs.biochem.3c00355] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/06/2023]
Abstract
Methionine γ-lyase (MGL) breaks down methionine, with the help of its cofactor pyridoxal-5'-phosphate (PLP), or vitamin B6. Methionine depletion is damaging for cancer cells but not normal cells, so MGL is of interest as a therapeutic protein. To increase our understanding and help engineer improved activity, we focused on the reactive, Michaelis complex M between MGL, covalently bound PLP, and substrate Met. M is not amenable to crystallography, as it proceeds to products. Experimental activity measurements helped exclude a mechanism that would bypass M . We then used molecular dynamics and alchemical free energy simulations to elucidate its structure and dynamics. We showed that the PLP phosphate has a pKa strongly downshifted by the protein, whether Met is present or not. Met binding affects the structure surrounding the reactive atoms. With Met, the Schiff base linkage between PLP and a nearby lysine shifts from a zwitterionic, keto form to a neutral, enol form that makes it easier for Met to approach its labile, target atom. The Met ligand also stabilizes the correct orientation of the Schiff base, more strongly than in simulations without Met, and in agreement with structures in the Protein Data Bank, where the Schiff base orientation correlates with the presence or absence of a co-bound anion or substrate analogue in the active site. Overall, the Met ligand helps organize the active site for the enzyme reaction by reducing fluctuations and shifting protonation states and conformational populations.
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Affiliation(s)
- Xingyu Chen
- Laboratoire de Biologie Structurale de la Cellule (CNRS UMR7654), Ecole Polytechnique, Palaiseau 91128, France
| | - Nathan Ferchaud
- Institut Jean-Pierre Bourgin, INRAE-AgroParisTech, University Paris-Saclay, Versailles 78026, France
| | - Pierre Briozzo
- Institut Jean-Pierre Bourgin, INRAE-AgroParisTech, University Paris-Saclay, Versailles 78026, France
| | - David Machover
- INSERM U935-UA09, University Paris-Saclay, Hôpital Paul-Brousse, 12, Avenue Paul Vaillant-Couturier, 94800 Villejuif, France
| | - Thomas Simonson
- Laboratoire de Biologie Structurale de la Cellule (CNRS UMR7654), Ecole Polytechnique, Palaiseau 91128, France
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20
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Sauciuc A, Morozzo Della Rocca B, Tadema MJ, Chinappi M, Maglia G. Translocation of linearized full-length proteins through an engineered nanopore under opposing electrophoretic force. Nat Biotechnol 2023:10.1038/s41587-023-01954-x. [PMID: 37723268 DOI: 10.1038/s41587-023-01954-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Accepted: 08/17/2023] [Indexed: 09/20/2023]
Abstract
Nanopores have recently been used to identify and fingerprint proteins. However, because proteins, unlike DNA, do not have a uniform charge, the electrophoretic force cannot in general be used to translocate or linearize them. Here we show that the introduction of sets of charges in the lumen of the CytK nanopore spaced by ~1 nm creates an electroosmotic flow that induces the unidirectional transport of unstructured natural polypeptides against a strong electrophoretic force. Molecular dynamics simulations indicate that this electroosmotic-dominated force has a strength of ~20 pN at -100 mV, which is similar to the electric force on single-stranded DNA. Unfolded polypeptides produce current signatures as they traverse the nanopore, which may be used to identify proteins. This approach can be used to translocate and stretch proteins for enzymatic and non-enzymatic protein identification and sequencing.
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Affiliation(s)
- Adina Sauciuc
- Groningen Biomolecular Sciences & Biotechnology Institute, University of Groningen, Groningen, The Netherlands
| | | | - Matthijs Jonathan Tadema
- Groningen Biomolecular Sciences & Biotechnology Institute, University of Groningen, Groningen, The Netherlands
| | - Mauro Chinappi
- Department of Industrial Engineering, University of Rome Tor Vergata, Rome, Italy
| | - Giovanni Maglia
- Groningen Biomolecular Sciences & Biotechnology Institute, University of Groningen, Groningen, The Netherlands.
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21
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Youngworth R, Roux B. Simulating the Voltage-Dependent Fluorescence of Di-8-ANEPPS in a Lipid Membrane. J Phys Chem Lett 2023; 14:8268-8276. [PMID: 37676243 PMCID: PMC10510438 DOI: 10.1021/acs.jpclett.3c01257] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Accepted: 08/25/2023] [Indexed: 09/08/2023]
Abstract
Voltage-sensitive fluorescent dyes such as di-8-ANEPPS (di-8-aminonaphthylethylenepyridinium propylsulfonate) are powerful tools to study biological membranes. Its fluorescence is affected by changes in the membrane potential and other factors, requiring extensive calibration to extract meaningful quantitative results. The amphiphilic di-8-ANEPPS molecule is expected to bind at the membrane-solution interface. However, atomic-level information is sparse about its position and orientation in the membrane, especially in regards to how the latter dynamically fluctuates to affect the observed fluorescence. In the present work, molecular dynamics simulations of the ground and excited states of di-8-ANEPPS embedded in a DPPC membrane as represented by classical force fields were used to investigate how the fluorescence is affected by externally applied potential. The calculations reproduce the shifts in the wavelength of emission as a function of voltage that are observed experimentally, indicating that the approach can help better understand the various factors that can affect the fluorescence of membrane-bound dyes.
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Affiliation(s)
- Rachael Youngworth
- Department
of Chemistry, The University of Chicago, 5735 S. Ellis Avenue, Chicago, Illinois 60637, United States
| | - Benoît Roux
- Department
of Biochemistry and Molecular Biology, The
University of Chicago, 929 E. 57th Street W225, Chicago, Illinois 60637, United States
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22
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Wei X, Penkauskas T, Reiner JE, Kennard C, Uline MJ, Wang Q, Li S, Aksimentiev A, Robertson JW, Liu C. Engineering Biological Nanopore Approaches toward Protein Sequencing. ACS NANO 2023; 17:16369-16395. [PMID: 37490313 PMCID: PMC10676712 DOI: 10.1021/acsnano.3c05628] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/26/2023]
Abstract
Biotechnological innovations have vastly improved the capacity to perform large-scale protein studies, while the methods we have for identifying and quantifying individual proteins are still inadequate to perform protein sequencing at the single-molecule level. Nanopore-inspired systems devoted to understanding how single molecules behave have been extensively developed for applications in genome sequencing. These nanopore systems are emerging as prominent tools for protein identification, detection, and analysis, suggesting realistic prospects for novel protein sequencing. This review summarizes recent advances in biological nanopore sensors toward protein sequencing, from the identification of individual amino acids to the controlled translocation of peptides and proteins, with attention focused on device and algorithm development and the delineation of molecular mechanisms with the aid of simulations. Specifically, the review aims to offer recommendations for the advancement of nanopore-based protein sequencing from an engineering perspective, highlighting the need for collaborative efforts across multiple disciplines. These efforts should include chemical conjugation, protein engineering, molecular simulation, machine-learning-assisted identification, and electronic device fabrication to enable practical implementation in real-world scenarios.
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Affiliation(s)
- Xiaojun Wei
- Biomedical Engineering Program, University of South Carolina, Columbia, SC 29208, United States
- Department of Chemical Engineering, University of South Carolina, Columbia, SC 29208, United States
| | - Tadas Penkauskas
- Biophysics and Biomedical Measurement Group, Microsystems and Nanotechnology Division, National Institute of Standards and Technology, Gaithersburg, MD 20899, United States
- School of Engineering, Brown University, Providence, RI 02912, United States
| | - Joseph E. Reiner
- Department of Physics, Virginia Commonwealth University, Richmond, VA 23284, United States
| | - Celeste Kennard
- Biomedical Engineering Program, University of South Carolina, Columbia, SC 29208, United States
| | - Mark J. Uline
- Biomedical Engineering Program, University of South Carolina, Columbia, SC 29208, United States
- Department of Chemical Engineering, University of South Carolina, Columbia, SC 29208, United States
| | - Qian Wang
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC 29208, United States
| | - Sheng Li
- School of Data Science, University of Virginia, Charlottesville, VA 22903, United States
| | - Aleksei Aksimentiev
- Department of Physics and Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States
| | - Joseph W.F. Robertson
- Biophysics and Biomedical Measurement Group, Microsystems and Nanotechnology Division, National Institute of Standards and Technology, Gaithersburg, MD 20899, United States
| | - Chang Liu
- Biomedical Engineering Program, University of South Carolina, Columbia, SC 29208, United States
- Department of Chemical Engineering, University of South Carolina, Columbia, SC 29208, United States
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23
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Kreiter J, Škulj S, Brkljača Z, Bardakji S, Vazdar M, Pohl EE. FA Sliding as the Mechanism for the ANT1-Mediated Fatty Acid Anion Transport in Lipid Bilayers. Int J Mol Sci 2023; 24:13701. [PMID: 37762012 PMCID: PMC10531397 DOI: 10.3390/ijms241813701] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2023] [Revised: 08/27/2023] [Accepted: 08/29/2023] [Indexed: 09/29/2023] Open
Abstract
Mitochondrial adenine nucleotide translocase (ANT) exchanges ADP for ATP to maintain energy production in the cell. Its protonophoric function in the presence of long-chain fatty acids (FA) is also recognized. Our previous results imply that proton/FA transport can be best described with the FA cycling model, in which protonated FA transports the proton to the mitochondrial matrix. The mechanism by which ANT1 transports FA anions back to the intermembrane space remains unclear. Using a combined approach involving measurements of the current through the planar lipid bilayers reconstituted with ANT1, site-directed mutagenesis and molecular dynamics simulations, we show that the FA anion is first attracted by positively charged arginines or lysines on the matrix side of ANT1 before moving along the positively charged protein-lipid interface and binding to R79, where it is protonated. We show that R79 is also critical for the competitive binding of ANT1 substrates (ADP and ATP) and inhibitors (carboxyatractyloside and bongkrekic acid). The binding sites are well conserved in mitochondrial SLC25 members, suggesting a general mechanism for transporting FA anions across the inner mitochondrial membrane.
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Affiliation(s)
- Jürgen Kreiter
- Institute of Physiology, Pathophysiology, and Biophysics, Department of Biomedical Sciences, University of Veterinary Medicine, 1210 Vienna, Austria; (J.K.); (S.Š.); (S.B.)
| | - Sanja Škulj
- Institute of Physiology, Pathophysiology, and Biophysics, Department of Biomedical Sciences, University of Veterinary Medicine, 1210 Vienna, Austria; (J.K.); (S.Š.); (S.B.)
| | - Zlatko Brkljača
- Division of Organic Chemistry and Biochemistry, Rudjer Bošković Institute, 10000 Zagreb, Croatia;
| | - Sarah Bardakji
- Institute of Physiology, Pathophysiology, and Biophysics, Department of Biomedical Sciences, University of Veterinary Medicine, 1210 Vienna, Austria; (J.K.); (S.Š.); (S.B.)
| | - Mario Vazdar
- Department of Mathematics, Informatics, and Cybernetics, University of Chemistry and Technology, 166 28 Prague, Czech Republic
| | - Elena E. Pohl
- Institute of Physiology, Pathophysiology, and Biophysics, Department of Biomedical Sciences, University of Veterinary Medicine, 1210 Vienna, Austria; (J.K.); (S.Š.); (S.B.)
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24
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McGuinness S, Li P, Li Y, Fuladi S, Konar S, Sajjadi S, Sidahmed M, Li Y, Shen L, Araghi FK, Weber CR. Molecular dynamics analyses of CLDN15 pore size and charge selectivity. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.16.553400. [PMID: 37645840 PMCID: PMC10461993 DOI: 10.1101/2023.08.16.553400] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/31/2023]
Abstract
The Claudin-15 (CLDN15) channel is important for nutrient, electrolyte, and water transport in the gastrointestinal tract. We used cell culture studies and molecular dynamics simulations to elucidate its structure and permeability mechanisms. We provide a model that underscores the crucial role of the D55 residue in the CLDN15 selectivity filter, which interacts with permeating cations. Our studies demonstrated the mechanisms whereby the size and charge of the D55 residue influence paracellular permeability. By altering D55 to larger, negatively charged glutamic acid (E) or similarly sized neutral asparagine (N), we observed changes in pore size and selectivity, respectively. D55E mutation decreased pore size, favoring small ion permeability without affecting charge selectivity, while D55N mutation led to reduced charge selectivity without markedly altering size selectivity. These findings shed light on the complex interplay of size and charge selectivity of CLDN15 channels. This knowledge can inform the development of strategies to modulate the function of CLDN15 and similar channels, which has implications for tight junction modulation in health and disease.
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25
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Yu L, Kang X, Li F, Mehrafrooz B, Makhamreh A, Fallahi A, Foster JC, Aksimentiev A, Chen M, Wanunu M. Unidirectional single-file transport of full-length proteins through a nanopore. Nat Biotechnol 2023; 41:1130-1139. [PMID: 36624148 PMCID: PMC10329728 DOI: 10.1038/s41587-022-01598-3] [Citation(s) in RCA: 32] [Impact Index Per Article: 32.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Accepted: 11/02/2022] [Indexed: 01/10/2023]
Abstract
The electrical current blockade of a peptide or protein threading through a nanopore can be used as a fingerprint of the molecule in biosensor applications. However, threading of full-length proteins has only been achieved using enzymatic unfolding and translocation. Here we describe an enzyme-free approach for unidirectional, slow transport of full-length proteins through nanopores. We show that the combination of a chemically resistant biological nanopore, α-hemolysin (narrowest part is ~1.4 nm in diameter), and a high concentration guanidinium chloride buffer enables unidirectional, single-file protein transport propelled by an electroosmotic effect. We show that the mean protein translocation velocity depends linearly on the applied voltage and translocation times depend linearly on length, resembling the translocation dynamics of ssDNA. Using a supervised machine-learning classifier, we demonstrate that single-translocation events contain sufficient information to distinguish their threading orientation and identity with accuracies larger than 90%. Capture rates of protein are increased substantially when either a genetically encoded charged peptide tail or a DNA tag is added to a protein.
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Affiliation(s)
- Luning Yu
- Department of Physics, Northeastern University, Boston, MA, USA
| | - Xinqi Kang
- Department of Bioengineering, Northeastern University, Boston, MA, USA
| | - Fanjun Li
- Department of Chemistry, University of Massachusetts at Amherst, Amherst, MA, USA
| | - Behzad Mehrafrooz
- Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Amr Makhamreh
- Department of Bioengineering, Northeastern University, Boston, MA, USA
| | - Ali Fallahi
- Department of Bioengineering, Northeastern University, Boston, MA, USA
| | - Joshua C Foster
- Molecular and Cellular Biology Program, University of Massachusetts at Amherst, Amherst, MA, USA
| | - Aleksei Aksimentiev
- Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, Urbana, IL, USA
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, IL, USA
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Min Chen
- Department of Chemistry, University of Massachusetts at Amherst, Amherst, MA, USA
- Molecular and Cellular Biology Program, University of Massachusetts at Amherst, Amherst, MA, USA
| | - Meni Wanunu
- Department of Physics, Northeastern University, Boston, MA, USA.
- Department of Bioengineering, Northeastern University, Boston, MA, USA.
- Chemistry and Chemical Biology, Northeastern University, Boston, MA, USA.
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26
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Straathof S, Di Muccio G, Yelleswarapu M, Alzate Banguero M, Wloka C, van der Heide NJ, Chinappi M, Maglia G. Protein Sizing with 15 nm Conical Biological Nanopore YaxAB. ACS NANO 2023; 17:13685-13699. [PMID: 37458334 PMCID: PMC10373527 DOI: 10.1021/acsnano.3c02847] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/26/2023]
Abstract
Nanopores are promising single-molecule tools for the electrical identification and sequencing of biomolecules. However, the characterization of proteins, especially in real-time and in complex biological samples, is complicated by the sheer variety of sizes and shapes in the proteome. Here, we introduce a large biological nanopore, YaxAB for folded protein analysis. The 15 nm cis-opening and a 3.5 nm trans-constriction describe a conical shape that allows the characterization of a wide range of proteins. Molecular dynamics showed proteins are captured by the electroosmotic flow, and the overall resistance is largely dominated by the narrow trans constriction region of the nanopore. Conveniently, proteins in the 35-125 kDa range remain trapped within the conical lumen of the nanopore for a time that can be tuned by the external bias. Contrary to cylindrical nanopores, in YaxAB, the current blockade decreases with the size of the trapped protein, as smaller proteins penetrate deeper into the constriction region than larger proteins do. These characteristics are especially useful for characterizing large proteins, as shown for pentameric C-reactive protein (125 kDa), a widely used health indicator, which showed a signal that could be identified in the background of other serum proteins.
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Affiliation(s)
- Sabine Straathof
- Groningen Biomolecular Sciences & Biotechnology Institute, University of Groningen, 9747 AG Groningen, The Netherlands
| | - Giovanni Di Muccio
- Department of Industrial Engineering, University of Rome Tor Vergata, Via del Politecnico 1, 00133 Rome, Italy
| | - Maaruthy Yelleswarapu
- Groningen Biomolecular Sciences & Biotechnology Institute, University of Groningen, 9747 AG Groningen, The Netherlands
| | - Melissa Alzate Banguero
- Department of Industrial Engineering, University of Rome Tor Vergata, Via del Politecnico 1, 00133 Rome, Italy
| | - Carsten Wloka
- Groningen Biomolecular Sciences & Biotechnology Institute, University of Groningen, 9747 AG Groningen, The Netherlands
- Experimental Ophthalmology, Department of Ophthalmology, Charité - Universitätsmedizin Berlin, A Corporate Member of Freie Universität, Humboldt-University, The Berlin Institute of Health, Berlin 10178, Germany
| | - Nieck Jordy van der Heide
- Groningen Biomolecular Sciences & Biotechnology Institute, University of Groningen, 9747 AG Groningen, The Netherlands
| | - Mauro Chinappi
- Department of Industrial Engineering, University of Rome Tor Vergata, Via del Politecnico 1, 00133 Rome, Italy
| | - Giovanni Maglia
- Groningen Biomolecular Sciences & Biotechnology Institute, University of Groningen, 9747 AG Groningen, The Netherlands
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27
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Wei C, Pohorille A. Multi-oligomeric states of alamethicin ion channel: Assemblies and conductance. Biophys J 2023; 122:2531-2543. [PMID: 37161094 PMCID: PMC10323028 DOI: 10.1016/j.bpj.2023.05.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2022] [Revised: 04/03/2023] [Accepted: 05/04/2023] [Indexed: 05/11/2023] Open
Abstract
Transmembrane assemblies of the peptaibol alamethicin (ALM) are among the most extensively studied ion channels not only because of their antimicrobial activity but also as models for channel structure and aggregation. In this study, several oligomeric states of ALM are investigated with molecular dynamics simulations to establish properties of the channel and obtain free energy profiles for ion transport and the corresponding values of conductance. The hexamer, heptamer, and octamer of ALM in phospholipid membrane are found to be stable but highly dynamic in barrel-stave structures, with calculated conductance equal to 18, 195, and 1270 pS, respectively, in 1 M KCl ion solution. The corresponding free energy profiles, reported for the first time, are reconstructed from simulations at applied voltage of 200 mV with the aid of the electrodiffusion model both with and without the knowledge of diffusivity. The calculated free energy barriers are equal to 2.5, 1.5, and 0.5 kcal/mol for K+ and 4.0, 2.2, and 1.5 kcal/mol for Cl-, for hexamer, heptamer, and octamer, respectively. The calculated conductance and the ratio between conductance in consecutive states are in good agreement with those measured experimentally. This suggests that the hexamer is the lowest conducting state, with measured conductance equal to 19 pS. The selectivity of K+ over Cl- is calculated as 1.5 and 2.3 for the octameric and heptameric channels, close to the selectivity measured for high-conductance states. Selectivity increases to 13 in the hexameric channel in which the narrowest Gln7 site has a pore radius of only ∼1.6 Å, again in accord with experiment. A good agreement found between calculated and measured conductance through a hexamer templated on cyclodextrin lands additional support for the results of our simulations, and the comparison with ALM reveals the dependence of conductance on the nature of phospholipid membrane.
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Affiliation(s)
- Chenyu Wei
- NASA Ames Research Center, Moffett Field, California; SETI Institute, Mountain View, California.
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28
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Chingarande RG, Tian K, Kuang Y, Sarangee A, Hou C, Ma E, Ren J, Hawkins S, Kim J, Adelstein R, Chen S, Gillis KD, Gu LQ. Real-time label-free detection of dynamic aptamer-small molecule interactions using a nanopore nucleic acid conformational sensor. Proc Natl Acad Sci U S A 2023; 120:e2108118120. [PMID: 37276386 PMCID: PMC10268594 DOI: 10.1073/pnas.2108118120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Accepted: 04/14/2023] [Indexed: 06/07/2023] Open
Abstract
Nucleic acids can undergo conformational changes upon binding small molecules. These conformational changes can be exploited to develop new therapeutic strategies through control of gene expression or triggering of cellular responses and can also be used to develop sensors for small molecules such as neurotransmitters. Many analytical approaches can detect dynamic conformational change of nucleic acids, but they need labeling, are expensive, and have limited time resolution. The nanopore approach can provide a conformational snapshot for each nucleic acid molecule detected, but has not been reported to detect dynamic nucleic acid conformational change in response to small -molecule binding. Here we demonstrate a modular, label-free, nucleic acid-docked nanopore capable of revealing time-resolved, small molecule-induced, single nucleic acid molecule conformational transitions with millisecond resolution. By using the dopamine-, serotonin-, and theophylline-binding aptamers as testbeds, we found that these nucleic acids scaffolds can be noncovalently docked inside the MspA protein pore by a cluster of site-specific charged residues. This docking mechanism enables the ion current through the pore to characteristically vary as the aptamer undergoes conformational changes, resulting in a sequence of current fluctuations that report binding and release of single ligand molecules from the aptamer. This nanopore tool can quantify specific ligands such as neurotransmitters, elucidate nucleic acid-ligand interactions, and pinpoint the nucleic acid motifs for ligand binding, showing the potential for small molecule biosensing, drug discovery assayed via RNA and DNA conformational changes, and the design of artificial riboswitch effectors in synthetic biology.
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Affiliation(s)
- Rugare G. Chingarande
- Department of Chemical and Biomedical Engineering, University of Missouri, Columbia, MO65211
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO65211
| | - Kai Tian
- Department of Chemical and Biomedical Engineering, University of Missouri, Columbia, MO65211
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO65211
| | - Yu Kuang
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO65211
| | - Aby Sarangee
- Department of Chemical and Biomedical Engineering, University of Missouri, Columbia, MO65211
| | - Chengrui Hou
- Department of Chemical and Biomedical Engineering, University of Missouri, Columbia, MO65211
| | - Emily Ma
- Department of Chemical and Biomedical Engineering, University of Missouri, Columbia, MO65211
| | - Jarett Ren
- Department of Chemical and Biomedical Engineering, University of Missouri, Columbia, MO65211
| | - Sam Hawkins
- Department of Chemical and Biomedical Engineering, University of Missouri, Columbia, MO65211
| | - Joshua Kim
- Department of Chemical and Biomedical Engineering, University of Missouri, Columbia, MO65211
| | - Ray Adelstein
- Department of Chemical and Biomedical Engineering, University of Missouri, Columbia, MO65211
| | - Sally Chen
- Department of Chemical and Biomedical Engineering, University of Missouri, Columbia, MO65211
| | - Kevin D. Gillis
- Department of Chemical and Biomedical Engineering, University of Missouri, Columbia, MO65211
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO65211
| | - Li-Qun Gu
- Department of Chemical and Biomedical Engineering, University of Missouri, Columbia, MO65211
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO65211
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29
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Ives CM, Thomson NJ, Zachariae U. A cooperative knock-on mechanism underpins Ca2+-selective cation permeation in TRPV channels. J Gen Physiol 2023; 155:213957. [PMID: 36943243 PMCID: PMC10038842 DOI: 10.1085/jgp.202213226] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2022] [Revised: 11/15/2022] [Accepted: 02/28/2023] [Indexed: 03/23/2023] Open
Abstract
The selective exchange of ions across cellular membranes is a vital biological process. Ca2+-mediated signaling is implicated in a broad array of physiological processes in cells, while elevated intracellular concentrations of Ca2+ are cytotoxic. Due to the significance of this cation, strict Ca2+ concentration gradients are maintained across the plasma and organelle membranes. Therefore, Ca2+ signaling relies on permeation through selective ion channels that control the flux of Ca2+ ions. A key family of Ca2+-permeable membrane channels is the polymodal signal-detecting transient receptor potential (TRP) ion channels. TRP channels are activated by a wide variety of cues including temperature, small molecules, transmembrane voltage, and mechanical stimuli. While most members of this family permeate a broad range of cations non-selectively, TRPV5 and TRPV6 are unique due to their strong Ca2+ selectivity. Here, we address the question of how some members of the TRPV subfamily show a high degree of Ca2+ selectivity while others conduct a wider spectrum of cations. We present results from all-atom molecular dynamics simulations of ion permeation through two Ca2+-selective and two non-selective TRPV channels. Using a new method to quantify permeation cooperativity based on mutual information, we show that Ca2+-selective TRPV channel permeation occurs by a three-binding site knock-on mechanism, whereas a two-binding site knock-on mechanism is observed in non-selective TRPV channels. Each of the ion binding sites involved displayed greater affinity for Ca2+ over Na+. As such, our results suggest that coupling to an extra binding site in the Ca2+-selective TRPV channels underpins their increased selectivity for Ca2+ over Na+ ions. Furthermore, analysis of all available TRPV channel structures shows that the selectivity filter entrance region is wider for the non-selective TRPV channels, slightly destabilizing ion binding at this site, which is likely to underlie mechanistic decoupling.
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Affiliation(s)
- Callum M Ives
- Computational Biology, School of Life Sciences, University of Dundee , Dundee, UK
| | - Neil J Thomson
- Computational Biology, School of Life Sciences, University of Dundee , Dundee, UK
| | - Ulrich Zachariae
- Computational Biology, School of Life Sciences, University of Dundee , Dundee, UK
- Biochemistry and Drug Discovery, School of Life Sciences, University of Dundee , Dundee, UK
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30
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Kasparyan G, Hub JS. Equivalence of Charge Imbalance and External Electric Fields during Free Energy Calculations of Membrane Electroporation. J Chem Theory Comput 2023; 19:2676-2683. [PMID: 37052575 DOI: 10.1021/acs.jctc.3c00065] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/14/2023]
Abstract
Electric fields across lipid membranes play important roles in physiology, medicine, and biotechnology, rationalizing the wide interest in modeling transmembrane potentials in molecular dynamics simulations. Transmembrane potentials have been implemented with external electric fields or by imposing charge imbalance between the two water compartments of a stacked double-membrane system. We compare the two methods in the context of membrane electroporation, which involves a large change of membrane structure and capacitance. We show that, given that Ewald electrostatics are defined with tinfoil boundary conditions, the two methods lead to (i) identical potentials of mean force (PMFs) of pore formation and expansion at various potentials, demonstrating that the two methods impose equivalent driving forces for large-scale transitions at membranes, and (ii) to identical polarization of water within thin water wires or open pores, suggesting that the two methods furthermore impose equivalent local electric fields. Without tinfoil boundary conditions, effects from external fields on pore formation are spuriously suppressed or even removed. Together, our study shows that both methods, external fields and charge imbalance, are well suitable for studying large-scale transitions of lipid membranes that involve changes of membrane capacitance. However, using charge imbalance is technically more challenging for maintaining a constant transmembrane potential since it requires updating of the charge imbalance as the membrane capacitance changes.
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Affiliation(s)
- Gari Kasparyan
- Theoretical Physics and Center for Biophysics, Saarland University, 66123 Saarbrücken, Germany
| | - Jochen S Hub
- Theoretical Physics and Center for Biophysics, Saarland University, 66123 Saarbrücken, Germany
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31
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Jiang J, Li MY, Wu XY, Ying YL, Han HX, Long YT. Protein nanopore reveals the renin-angiotensin system crosstalk with single-amino-acid resolution. Nat Chem 2023; 15:578-586. [PMID: 36805037 DOI: 10.1038/s41557-023-01139-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Accepted: 01/13/2023] [Indexed: 02/22/2023]
Abstract
The discovery of crosstalk effects on the renin-angiotensin system (RAS) is limited by the lack of approaches to quantitatively monitor, in real time, multiple components with subtle differences and short half-lives. Here we report a nanopore framework to quantitatively determine the effect of the hidden crosstalk between angiotensin-converting enzyme (ACE) and angiotensin-converting enzyme 2 (ACE2) on RAS. By developing an engineered aerolysin nanopore capable of single-amino-acid resolution, we show that the ACE can be selectively inhibited by ACE2 to prevent cleavage of angiotensin I, even when the concentration of ACE is more than 30-fold higher than that of ACE2. We also show that the activity of ACE2 for cleaving angiotensin peptides is clearly suppressed by the spike protein of SARS-CoV-2. This leads to the relaxation of ACE and the increased probability of accumulation of the principal effector angiotensin II. The spike protein of the SARS-CoV-2 Delta variant is demonstrated to have a much greater impact on the crosstalk than the wild type.
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Affiliation(s)
- Jie Jiang
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, China
| | - Meng-Yin Li
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, China
- Chemistry and Biomedicine Innovation Center, Nanjing University, Nanjing, China
| | - Xue-Yuan Wu
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, China
| | - Yi-Lun Ying
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, China
- Chemistry and Biomedicine Innovation Center, Nanjing University, Nanjing, China
| | - Huan-Xing Han
- Department of Pharmacy, Shanghai Changzheng Hospital, Shanghai, China
| | - Yi-Tao Long
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, China.
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32
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Amin JB, He M, Prasad R, Leng X, Zhou HX, Wollmuth LP. Two gates mediate NMDA receptor activity and are under subunit-specific regulation. Nat Commun 2023; 14:1623. [PMID: 36959168 PMCID: PMC10036335 DOI: 10.1038/s41467-023-37260-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2022] [Accepted: 03/09/2023] [Indexed: 03/25/2023] Open
Abstract
Kinetics of NMDA receptor (NMDAR) ion channel opening and closing contribute to their unique role in synaptic signaling. Agonist binding generates free energy to open a canonical gate at the M3 helix bundle crossing. Single channel activity is characterized by clusters, or periods of rapid opening and closing, that are separated by long silent periods. A conserved glycine in the outer most transmembrane helices, the M4 helices, regulates NMDAR function. Here we find that the GluN1 glycine mainly regulates single channel events within a cluster, whereas the GluN2 glycine mainly regulates entry and exit from clusters. Molecular dynamics simulations suggest that, whereas the GluN2 M4 (along with GluN2 pre-M1) regulates the gate at the M3 helix bundle crossing, the GluN1 glycine regulates a 'gate' at the M2 loop. Subsequent functional experiments support this interpretation. Thus, the distinct kinetics of NMDARs are mediated by two gates that are under subunit-specific regulation.
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Affiliation(s)
- Johansen B Amin
- Graduate Program in Cellular and Molecular Pharmacology, Stony Brook University, Stony Brook, NY, 11794-5230, USA
- Medical Scientist Training Program (MSTP), Stony Brook University, Stony Brook, NY, 11794-5230, USA
| | - Miaomiao He
- Graduate Program in Biochemistry and Structural Biology, Stony Brook University, Stony Brook, NY, 11794-5230, USA
| | - Ramesh Prasad
- Department of Chemistry, University of Illinois at Chicago, Chicago, IL, 60607, USA
| | - Xiaoling Leng
- Department of Chemistry, University of Illinois at Chicago, Chicago, IL, 60607, USA
| | - Huan-Xiang Zhou
- Department of Chemistry, University of Illinois at Chicago, Chicago, IL, 60607, USA
- Department of Physics, University of Illinois at Chicago, Chicago, IL, 60607, USA
| | - Lonnie P Wollmuth
- Center for Nervous System Disorders, Stony Brook University, Stony Brook, NY, 11794-5230, USA.
- Department of Neurobiology & Behavior, Stony Brook University, Stony Brook, NY, 11794-5230, USA.
- Department of Biochemistry & Cell Biology, Stony Brook University, Stony Brook, NY, 11794-5230, USA.
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33
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Lee SN, Cho HJ, Jeong H, Ryu B, Lee HJ, Kim M, Yoo J, Woo JS, Lee HH. Cryo-EM structures of human Cx36/GJD2 neuronal gap junction channel. Nat Commun 2023; 14:1347. [PMID: 36906653 PMCID: PMC10008584 DOI: 10.1038/s41467-023-37040-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Accepted: 02/28/2023] [Indexed: 03/13/2023] Open
Abstract
Connexin 36 (Cx36) is responsible for signal transmission in electrical synapses by forming interneuronal gap junctions. Despite the critical role of Cx36 in normal brain function, the molecular architecture of the Cx36 gap junction channel (GJC) is unknown. Here, we determine cryo-electron microscopy structures of Cx36 GJC at 2.2-3.6 Å resolutions, revealing a dynamic equilibrium between its closed and open states. In the closed state, channel pores are obstructed by lipids, while N-terminal helices (NTHs) are excluded from the pore. In the open state with pore-lining NTHs, the pore is more acidic than those in Cx26 and Cx46/50 GJCs, explaining its strong cation selectivity. The conformational change during channel opening also includes the α-to-π-helix transition of the first transmembrane helix, which weakens the protomer-protomer interaction. Our structural analyses provide high resolution information on the conformational flexibility of Cx36 GJC and suggest a potential role of lipids in the channel gating.
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Affiliation(s)
- Seu-Na Lee
- Department of Life Sciences, Korea University, Seoul, 02841, Republic of Korea
| | - Hwa-Jin Cho
- Department of Chemistry, College of Natural Sciences, Seoul National University, Seoul, 08826, Korea
| | - Hyeongseop Jeong
- Center for Research Equipment, Korea Basic Science Institute, Chungcheongbuk-do, 28119, Korea
| | - Bumhan Ryu
- Research Solution Center, Institute for Basic Science, Daejeon, 34126, Republic of Korea
| | - Hyuk-Joon Lee
- Department of Life Sciences, Korea University, Seoul, 02841, Republic of Korea
| | - Minsoo Kim
- Department of Physics, Sungkyunkwan University, Suwon, 16419, South Korea
| | - Jejoong Yoo
- Department of Physics, Sungkyunkwan University, Suwon, 16419, South Korea
| | - Jae-Sung Woo
- Department of Life Sciences, Korea University, Seoul, 02841, Republic of Korea.
| | - Hyung Ho Lee
- Department of Chemistry, College of Natural Sciences, Seoul National University, Seoul, 08826, Korea.
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34
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Maffeo C, Quednau L, Wilson J, Aksimentiev A. DNA double helix, a tiny electromotor. NATURE NANOTECHNOLOGY 2023; 18:238-242. [PMID: 36564521 DOI: 10.1038/s41565-022-01285-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Accepted: 11/04/2022] [Indexed: 06/17/2023]
Abstract
Flowing fluid past chiral objects has been used for centuries to power rotary motion in man-made machines. By contrast, rotary motion in nanoscale biological or chemical systems is produced by biasing Brownian motion through cyclic chemical reactions. Here we show that a chiral biological molecule, a DNA or RNA duplex rotates unidirectionally at billions of revolutions per minute when an electric field is applied along the duplex, with the rotation direction being determined by the chirality of the duplex. The rotation is found to be powered by the drag force of the electro-osmotic flow, realizing the operating principle of a macroscopic turbine at the nanoscale. The resulting torques are sufficient to power rotation of nanoscale beads and rods, offering an engineering principle for constructing nanoscale systems powered by electric field.
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Affiliation(s)
- Christopher Maffeo
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, IL, USA
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Lauren Quednau
- Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - James Wilson
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Aleksei Aksimentiev
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
- Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
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35
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Zhou W, Guo Y, Zhang Z, Guo W, Qiu H. Field-Induced Hydration Shell Reorganization Enables Electro-osmotic Flow in Nanochannels. PHYSICAL REVIEW LETTERS 2023; 130:084001. [PMID: 36898090 DOI: 10.1103/physrevlett.130.084001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2022] [Revised: 10/31/2022] [Accepted: 01/17/2023] [Indexed: 06/18/2023]
Abstract
Electro-osmotic flow is the motion of fluid driven by an applied electric field, for which an electric double layer near a charged surface is deemed essential. Here, we find that electro-osmotic flow can occur in electrically neutral nanochannels in the absence of definable electric double layers through extensive molecular dynamics simulations. An applied electric field is shown to cause an intrinsic channel selectivity between cations and anions, by reorienting the hydration shells of these confined ions. The ion selectivity then results in a net charge density in the channel that induces the unconventional electro-osmotic flow. The flow direction is amenable to manipulation by the field strength and the channel size, which will inform ongoing efforts to develop highly integrated nanofluidic systems capable of complex flow control.
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Affiliation(s)
- Wanqi Zhou
- State Key Laboratory of Mechanics and Control of Mechanical Structures and Key Laboratory for Intelligent Nano Materials and Devices of MOE, Institute of Nano Science, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
| | - Yufeng Guo
- State Key Laboratory of Mechanics and Control of Mechanical Structures and Key Laboratory for Intelligent Nano Materials and Devices of MOE, Institute of Nano Science, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
| | - Zhuhua Zhang
- State Key Laboratory of Mechanics and Control of Mechanical Structures and Key Laboratory for Intelligent Nano Materials and Devices of MOE, Institute of Nano Science, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
| | - Wanlin Guo
- State Key Laboratory of Mechanics and Control of Mechanical Structures and Key Laboratory for Intelligent Nano Materials and Devices of MOE, Institute of Nano Science, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
| | - Hu Qiu
- State Key Laboratory of Mechanics and Control of Mechanical Structures and Key Laboratory for Intelligent Nano Materials and Devices of MOE, Institute of Nano Science, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
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36
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Prajapati A, Srivastava A, Sankaranarayanan SA, Pebam M, Buddhiraju HS, Patra P, Yadav P, Joshi H, Rengan AK. High-Affinity DNA Nanomatrix: A Platform Technology for Synergistic Drug Delivery and Photothermal Therapy. ACS Macro Lett 2023; 12:255-262. [PMID: 36723076 DOI: 10.1021/acsmacrolett.2c00642] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
With the advent of nucleosome/nucleotide intercalating drugs, DNA-based nanocarriers have recently gained impetus. However, most of the newly proposed DNA nanosystems are rather complex, thereby having low scalability and translatability. In this study, we propose a simple DNA nanomatrix core encapsulated within a chitosan shell, which is expected to enhance the encapsulation efficiency of intercalating drugs. This has been demonstrated using proflavine hemisulfate (PfHS), a model intercalating agent that shows improved ROS generation, among other anticancerous properties. The release of the drug from the nanomatrix is triggered by providing a heat trigger using IR-792 perchlorate, a known NIR photothermal sensitizer.
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Affiliation(s)
- Akshit Prajapati
- Department of Biomedical Engineering, Indian institute of Technology Hyderabad, Kandi, Sangareddy, Telangana 502284, India
| | - Aditya Srivastava
- Department of Biomedical Engineering, Indian institute of Technology Hyderabad, Kandi, Sangareddy, Telangana 502284, India
| | - Sri Amruthaa Sankaranarayanan
- Department of Biomedical Engineering, Indian institute of Technology Hyderabad, Kandi, Sangareddy, Telangana 502284, India
| | - Monika Pebam
- Department of Biomedical Engineering, Indian institute of Technology Hyderabad, Kandi, Sangareddy, Telangana 502284, India
| | - Hima Sree Buddhiraju
- Department of Biomedical Engineering, Indian institute of Technology Hyderabad, Kandi, Sangareddy, Telangana 502284, India
| | - Paloma Patra
- Department of Biomedical Engineering, Indian institute of Technology Hyderabad, Kandi, Sangareddy, Telangana 502284, India
| | - Priyanka Yadav
- Department of Biotechnology, Indian institute of Technology Hyderabad, Kandi, Sangareddy, Telangana 502284, India
| | - Himanshu Joshi
- Department of Biotechnology, Indian institute of Technology Hyderabad, Kandi, Sangareddy, Telangana 502284, India
| | - Aravind Kumar Rengan
- Department of Biomedical Engineering, Indian institute of Technology Hyderabad, Kandi, Sangareddy, Telangana 502284, India
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37
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Joshi H, Li CY, Aksimentiev A. All-Atom Molecular Dynamics Simulations of Membrane-Spanning DNA Origami Nanopores. Methods Mol Biol 2023; 2639:113-128. [PMID: 37166714 DOI: 10.1007/978-1-0716-3028-0_7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Building on the recent technological advances, all-atom molecular dynamics (MD) simulations have become an indispensable tool to study the molecular behavior at nanoscale. Molecular simulations have been used to characterize the structure, dynamics, and mechanical and electrical properties of DNA origami objects. In this chapter we describe a method to build all-atom model of lipid-spanning DNA origami nanopores and perform molecular dynamics simulations in explicit electrolyte solutions.
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Affiliation(s)
- Himanshu Joshi
- Department of Physics and Beckman Institute for Advanced Science and Technology, University of Illinois Urbana-Champaign, Urbana, IL, USA
- Department of Biotechnology, Indian Institute of Technology Hyderabad, Kandi, Sangareddy, Telangana, India
| | - Chen-Yu Li
- Department of Physics and Beckman Institute for Advanced Science and Technology, University of Illinois Urbana-Champaign, Urbana, IL, USA
| | - Aleksei Aksimentiev
- Department of Physics and Beckman Institute for Advanced Science and Technology, University of Illinois Urbana-Champaign, Urbana, IL, USA.
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38
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Wilson MA, Pohorille A. Structure and Computational Electrophysiology of Ac-LS3, a Synthetic Ion Channel. J Phys Chem B 2022; 126:8985-8999. [PMID: 36306164 DOI: 10.1021/acs.jpcb.2c05965] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Computer simulations are reported on Ac-LS3, a synthetic ion channel, containing 21 residues with a Leu-Ser-Ser-Leu-Leu-Ser-Leu heptad repeat, which forms ions channels upon application of voltage. A hexameric, coiled-coil bundle initially positioned perpendicular to the membrane settled into a stable, tilted structure after 1.5 μs, most likely to improve contacts between the non-polar exterior of the channel and the hydrophobic core of the membrane. Once tilted, the bundle remained in this state during subsequent simulations of nearly 10 μs at voltages ranging from 200 to -100 mV. In contrast, attempts to identify a stable pentameric structure failed, thus supporting the hypothesis that the channel is a hexamer. Results at 100 mV were used to reconstruct the free energy profiles for K+ and Cl- in the channel. This was done by way of several methods in which results of molecular dynamics (MD) simulations were combined with the electrodiffusion model. Two of them developed recently do not require knowledge of the diffusivity. Instead, they utilize one-sided density profiles and committor probabilities. The consistency between different methods is very good, supporting the utility of the newly developed methods for reconstructing free energies of ions in channels. The flux of K+, which accounts for most of the current through the channel, calculated directly from MD matches well the total measured current. However, the current of Cl- is somewhat overestimated, possibly due to a slightly unbalanced force field involving chloride. The current-voltage dependence was also reconstructed by way of a recently developed, efficient method that requires simulations only at a single voltage, yielding good agreement with the experiment. Taken together, the results demonstrate that computational electrophysiology has become a reliable tool for studying how channels mediate ion transport through membranes.
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Affiliation(s)
- Michael A Wilson
- Exobiology Branch, MS239-4, NASA Ames Research Center, Moffett Field, California94035, United States.,SETI Institute, 189 Bernardo Avenue, Suite 200, Mountain View, California94043, United States
| | - Andrew Pohorille
- Exobiology Branch, MS239-4, NASA Ames Research Center, Moffett Field, California94033, United States.,Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California94132, United States
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39
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Mechanism of 4-aminopyridine inhibition of the lysosomal channel TMEM175. Proc Natl Acad Sci U S A 2022; 119:e2208882119. [PMID: 36279431 PMCID: PMC9636928 DOI: 10.1073/pnas.2208882119] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Transmembrane protein 175 (TMEM175) is an evolutionarily distinct lysosomal cation channel whose mutation is associated with the development of Parkinson’s disease. Here, we present a cryoelectron microscopy structure and molecular simulations of TMEM175 bound to 4-aminopyridine (4-AP), the only known small-molecule inhibitor of TMEM175 and a broad K
+
channel inhibitor, as well as a drug approved by the Food and Drug Administration against multiple sclerosis. The structure shows that 4-AP, whose mode of action had not been previously visualized, binds near the center of the ion conduction pathway, in the open state of the channel. Molecular dynamics simulations reveal that this binding site is near the middle of the transmembrane potential gradient, providing a rationale for the voltage-dependent dissociation of 4-AP from TMEM175. Interestingly, bound 4-AP rapidly switches between three predominant binding poses, stabilized by alternate interaction patterns dictated by the twofold symmetry of the channel. Despite this highly dynamic binding mode, bound 4-AP prevents not only ion permeation but also water flow. Together, these studies provide a framework for the rational design of novel small-molecule inhibitors of TMEM175 that might reveal the role of this channel in human lysosomal physiology both in health and disease.
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40
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Berselli A, Benfenati F, Maragliano L, Alberini G. Multiscale modelling of claudin-based assemblies: a magnifying glass for novel structures of biological interfaces. Comput Struct Biotechnol J 2022; 20:5984-6010. [DOI: 10.1016/j.csbj.2022.10.038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Revised: 10/24/2022] [Accepted: 10/24/2022] [Indexed: 11/03/2022] Open
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41
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Utesch T, Staffa J, Katz S, Yao G, Kozuch J, Hildebrandt P. Potential Distribution across Model Membranes. J Phys Chem B 2022; 126:7664-7675. [PMID: 36137267 DOI: 10.1021/acs.jpcb.2c05372] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Membrane models assembled on electrodes are widely used tools to study potential-dependent molecular processes at or in membranes. However, the relationship between the electrode potential and the potential across the membrane is not known. Here we studied lipid bilayers immobilized on mixed self-assembled monolayers (SAM) on Au electrodes. The mixed SAM was composed of thiol derivatives of different chain lengths such that between the islands of the short one, mercaptobenzonitrile (MBN), and the tethered lipid bilayer an aqueous compartment was formed. The nitrile function of MBN, which served as a reporter group for the vibrational Stark effect (VSE), was probed by surface-enhanced infrared absorption spectroscopy to determine the local electric field as a function of the electrode potential for pure MBN, mixed SAM, and the bilayer system. In parallel, we calculated electric fields at the VSE probe by molecular dynamics (MD) simulations for different charge densities on the metal, thereby mimicking electrode potential changes. The agreement with the experiments was very good for the calculations of the pure MBN SAM and only slightly worse for the mixed SAM. The comparison with the experiments also guided the design of the bilayer system in the MD setups, which were selected to calculate the electrode potential dependence of the transmembrane potential, a quantity that is not directly accessible by the experiments. The results agree very well with estimates in previous studies and thus demonstrate that the present combined experimental-theoretical approach is a promising tool for describing potential-dependent processes at biomimetic interfaces.
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Affiliation(s)
- Tillmann Utesch
- Leibniz-Institut für Molekulare Pharmakologie (FMP), Robert-Rössle-Strasse 10, D-13125 Berlin, Germany
| | - Jana Staffa
- Institut für Chemie, Technische Universität Berlin, Sekr. PC14, Straße des 17. Juni 135, D-10623 Berlin, Germany
| | - Sagie Katz
- Institut für Chemie, Technische Universität Berlin, Sekr. PC14, Straße des 17. Juni 135, D-10623 Berlin, Germany
| | - Guiyang Yao
- Institut für Chemie, Technische Universität Berlin, Sekr. PC14, Straße des 17. Juni 135, D-10623 Berlin, Germany
| | - Jacek Kozuch
- Fachbereich Physik, Experimentelle Molekulare Biophysik, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin, Germany.,Forschungsbau SupraFAB, Altensteinstr. 23a, D-14195 Berlin, Germany
| | - Peter Hildebrandt
- Institut für Chemie, Technische Universität Berlin, Sekr. PC14, Straße des 17. Juni 135, D-10623 Berlin, Germany
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42
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Bignucolo O, Chipot C, Kellenberger S, Roux B. Galvani Offset Potential and Constant-pH Simulations of Membrane Proteins. J Phys Chem B 2022; 126:6868-6877. [PMID: 36049129 PMCID: PMC9483922 DOI: 10.1021/acs.jpcb.2c04593] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
![]()
A central problem
in computational biophysics is the
treatment
of titratable residues in molecular dynamics simulations of large
biological macromolecular systems. Conventional simulation methods
ascribe a fixed ionization state to titratable residues in accordance
with their pKa and the pH of the system,
assuming that an effective average model will be able to capture the
predominant behavior of the system. While this assumption may be justifiable
in many cases, it is certainly limited, and it is important to design
alternative methodologies allowing a more realistic treatment. Constant-pH
simulation methods provide powerful approaches to handle titratable
residues more realistically by allowing the ionization state to vary
statistically during the simulation. Extending the molecular mechanical
(MM) potential energy function to a family of potential functions
accounting for different ionization states, constant-pH simulations
are designed to sample all accessible configurations and ionization
states, properly weighted according to their Boltzmann factor. Because
protonation and deprotonation events correspond to a change in the
total charge, difficulties arise when the long-range Coulomb interaction
is treated on the basis of an idealized infinite simulation model
and periodic boundary conditions with particle-mesh Ewald lattice
sums. Charging free-energy calculations performed under these conditions
in aqueous solution depend on the Galvani potential of the bulk water
phase. This has important implications for the equilibrium and nonequilibrium
constant-pH simulation methods grounded in the relative free-energy
difference corresponding to the protonated and unprotonated residues.
Here, the effect of the Galvani potential is clarified, and a simple
practical solution is introduced to address this issue in constant-pH
simulations of the acid-sensing ion channel (ASIC).
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Affiliation(s)
- Olivier Bignucolo
- Department of Biomedical Sciences, University of Lausanne, 1015 Lausanne, Switzerland.,SIB Swiss Institute of Bioinformatics, 1015 Lausanne, Switzerland
| | - Christophe Chipot
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, Illinois 60637, United States.,Laboratoire International Associé Centre National de la Recherche Scientifique et University of Illinois at Urbana-Champaign, Unité Mixte de Recherche n◦7019, Université de Lorraine, B.P. 70239, 54506 Cedex Vandœuvre-lès-Nancy, France.,Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61820, United States
| | - Stephan Kellenberger
- Department of Biomedical Sciences, University of Lausanne, 1015 Lausanne, Switzerland
| | - Benoît Roux
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, Illinois 60637, United States.,Department of Chemistry, The University of Chicago, 5735 S. Ellis Ave., Chicago, Illinois 60637, United States
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43
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Chen LY. Quantitative characterization of the path of glucose diffusion facilitated by human glucose transporter 1. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2022; 1864:183975. [PMID: 35654150 DOI: 10.1016/j.bbamem.2022.183975] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Revised: 05/24/2022] [Accepted: 05/25/2022] [Indexed: 06/15/2023]
Abstract
Glucose transporter GLUT1 is ubiquitously expressed in the human body from the red cells to the blood-brain barrier to the skeletal muscles. It is physiologically relevant to understand how GLUT1 facilitates diffusion of glucose across the cell membrane. It is also pathologically relevant because GLUT1 deficiency causes neurological disorders and anemia and because GLUT1 overexpression fuels the abnormal growth of cancer cells. This article presents a quantitative investigation of GLUT1 based on all-atom molecular-dynamics (MD) simulations of the transporter embedded in lipid bilayers of asymmetric inner-and-outer-leaflet lipid compositions, subject to asymmetric intra-and-extra-cellular environments. This is in contrast with the current literature of MD studies that have not considered both of the aforementioned asymmetries of the cell membrane. The equilibrium (unbiased) dynamics of GLUT1 shows that it can facilitate glucose diffusion across the cell membrane without undergoing large-scale conformational motions. The Gibbs free-energy profile, which is still lacking in the current literature of GLUT1, quantitatively characterizes the diffusion path of glucose from the periplasm, through an extracellular gate of GLUT1, on to the binding site, and off to the cytoplasm. This transport mechanism is validated by the experimental data that GLUT1 has low water-permeability, uptake-efflux symmetry, and 10 kcal/mol Arrhenius activation barrier around 37 °C.
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Affiliation(s)
- Liao Y Chen
- Department of Physics, The University of Texas at San Antonio, San Antonio, TX 78249, USA.
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44
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Ensslen T, Sarthak K, Aksimentiev A, Behrends JC. Resolving Isomeric Posttranslational Modifications Using a Biological Nanopore as a Sensor of Molecular Shape. J Am Chem Soc 2022; 144:16060-16068. [PMID: 36007197 DOI: 10.1021/jacs.2c06211] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The chemical nature and precise position of posttranslational modifications (PTMs) in proteins or peptides are crucial for various severe diseases, such as cancer. State-of-the-art PTM diagnosis is based on elaborate and costly mass-spectrometry or immunoassay-based approaches, which are limited in selectivity and specificity. Here, we demonstrate the use of a protein nanopore to differentiate peptides─derived from human histone H4 protein─of identical mass according to the positions of acetylated and methylated lysine residues. Unlike sequencing by stepwise threading, our method detects PTMs and their positions by sensing the shape of a fully entrapped peptide, thus eliminating the need for controlled translocation. Molecular dynamics simulations show that the sensitivity to molecular shape derives from a highly nonuniform electric field along the pore. This molecular shape-sensing principle offers a path to versatile, label-free, and high-throughput characterizations of protein isoforms.
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Affiliation(s)
- Tobias Ensslen
- Laboratory for Membrane Physiology and Technology, Department of Physiology, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany
| | - Kumar Sarthak
- Center for the Physics of Living Cells, Beckman Institute for Advanced Science and Technology and Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Aleksei Aksimentiev
- Center for the Physics of Living Cells, Beckman Institute for Advanced Science and Technology and Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Jan C Behrends
- Laboratory for Membrane Physiology and Technology, Department of Physiology, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany
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45
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Tiwari S, Adupa V, Das DS, Anki Reddy K, Bharat TV. Structural and Dynamic Insights into SARS-CoV-2 Spike-Protein-Montmorillonite Interactions. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:9186-9194. [PMID: 35855632 PMCID: PMC9344787 DOI: 10.1021/acs.langmuir.2c00837] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Revised: 06/21/2022] [Indexed: 06/01/2023]
Abstract
The spike (S) protein of SARS-CoV-2 has been found to play a decisive role in the cell entry mechanism of the virus and has been the prime target of most vaccine development efforts. Although numerous vaccines are already in use and more than half of the world population has been fully vaccinated, the emergence of new variants of the virus poses a challenge to the existing vaccines. Hence, developing an effective drug therapy is a crucial step in ending the pandemic. Nanoparticles can play a crucial role as a drug or a drug carrier and help tackle the pandemic effectively. Here, we performed explicit all-atom molecular dynamics simulations to probe interactions between S protein and Montmorillonite (MMT) nano clay surface. We built two systems with different counterions (Na+ and Ca2+), namely Na-MMT and Ca-MMT, to investigate the effect of different ions on S protein-MMT interaction. Structural modification of S protein was observed in the presence of MMT surface, particularly the loss of helical content of S protein. We revealed that electrostatic and hydrophobic interactions synergistically govern the S protein-MMT interactions. However, hydrophobic interactions were more pronounced in the Na-MMT system than in Ca-MMT. We also revealed residues and glycans of S protein closely interacting with the MMT surface. Interestingly, N165 and N343, which we found to be closely interacting with MMT in our simulations, also have a critical role in cell entry and in thwarting the cell's immune response in recent studies. Overall, our work provides atomistic insights into S protein-MMT interaction and enriches our understanding of the nanoparticle-S protein interaction mechanism, which will help develop advanced therapeutic techniques in the future.
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Affiliation(s)
- Shivam Tiwari
- Department
of Chemical Engineering, Indian Institute
of Technology, Guwahati, Assam 781039, India
| | - Vasista Adupa
- Department
of Chemical Engineering, Indian Institute
of Technology, Guwahati, Assam 781039, India
| | - Dhanesh Sing Das
- Department
of Civil Engineering, Indian Institute of
Technology, Guwahati, Assam 781039, India
| | - K. Anki Reddy
- Department
of Chemical Engineering, Indian Institute
of Technology, Tirupati, Andhra Pradesh 517506, India
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46
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Kuang Z, Luginsland J, Thomas RJ, Dennis PB, Kelley-Loughnane N, Roach WP, Naik RR. Molecular dynamics simulations explore effects of electric field orientations on spike proteins of SARS-CoV-2 virions. Sci Rep 2022; 12:12986. [PMID: 35906467 PMCID: PMC9334739 DOI: 10.1038/s41598-022-17009-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2021] [Accepted: 07/19/2022] [Indexed: 11/21/2022] Open
Abstract
Emergence of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its current worldwide spread have caused a pandemic of acute respiratory disease COVID-19. The virus can result in mild to severe, and even to fatal respiratory illness in humans, threatening human health and public safety. The spike (S) protein on the surface of viral membrane is responsible for viral entry into host cells. The discovery of methods to inactivate the entry of SARS-CoV-2 through disruption of the S protein binding to its cognate receptor on the host cell is an active research area. To explore other prevention strategies against the quick spread of the virus and its mutants, non-equilibrium molecular dynamics simulations have been employed to explore the possibility of manipulating the structure–activity of the SARS-CoV-2 spike glycoprotein by applying electric fields (EFs) in both the protein axial directions and in the direction perpendicular to the protein axis. We have found out the application of EFs perpendicular to the protein axis is most effective in denaturing the HR2 domain which plays critical role in viral-host membrane fusion. This finding suggests that varying irradiation angles may be an important consideration in developing EF based non-invasive technologies to inactivate the virus.
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Affiliation(s)
- Zhifeng Kuang
- Materials and Manufacturing Directorate, Air Force Research Laboratory, WPAFB, Dayton, OH, 45433, USA.
| | - John Luginsland
- Work Performed With Confluent Sciences, LLC, Albuquerque, NM, 87111, USA
| | - Robert J Thomas
- 711th Human Performance Wing, Air Force Research Laboratory, JBSA Fort Sam Houston, San Antonio, TX, 78234, USA
| | - Patrick B Dennis
- Materials and Manufacturing Directorate, Air Force Research Laboratory, WPAFB, Dayton, OH, 45433, USA
| | - Nancy Kelley-Loughnane
- Materials and Manufacturing Directorate, Air Force Research Laboratory, WPAFB, Dayton, OH, 45433, USA
| | - William P Roach
- Air Force Office of Scientific Research, Arlington, VA, 22203, USA
| | - Rajesh R Naik
- 711Th Human Performance Wing, Air Force Research Laboratory, WPAFB, Dayton, OH, 45433, USA.
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47
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Karlova M, Abramochkin DV, Pustovit KB, Nesterova T, Novoseletsky V, Loussouarn G, Zaklyazminskaya E, Sokolova OS. Disruption of a Conservative Motif in the C-Terminal Loop of the KCNQ1 Channel Causes LQT Syndrome. Int J Mol Sci 2022; 23:ijms23147953. [PMID: 35887302 PMCID: PMC9316142 DOI: 10.3390/ijms23147953] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2022] [Revised: 07/13/2022] [Accepted: 07/15/2022] [Indexed: 02/04/2023] Open
Abstract
We identified a single nucleotide variation (SNV) (c.1264A > G) in the KCNQ1 gene in a 5-year-old boy who presented with a prolonged QT interval. His elder brother and mother, but not sister and father, also had this mutation. This missense mutation leads to a p.Lys422Glu (K422E) substitution in the Kv7.1 protein that has never been mentioned before. We inserted this substitution in an expression plasmid containing Kv7.1 cDNA and studied the electrophysiological characteristics of the mutated channel expressed in CHO-K1, using the whole-cell configuration of the patch-clamp technique. Expression of the mutant Kv7.1 channel in both homo- and heterozygous conditions in the presence of auxiliary subunit KCNE1 results in a significant decrease in tail current densities compared to the expression of wild-type (WT) Kv7.1 and KCNE1. This study also indicates that K422E point mutation causes a dominant negative effect. The mutation was not associated with a trafficking defect; the mutant channel protein was confirmed to localize at the cell membrane. This mutation disrupts the poly-Lys strip in the proximal part of the highly conserved cytoplasmic A−B linker of Kv7.1 that was not shown before to be crucial for channel functioning.
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Affiliation(s)
- Maria Karlova
- Faculty of Biology, Lomonosov Moscow State University, 119234 Moscow, Russia; (M.K.); (D.V.A.); (K.B.P.); (V.N.)
| | - Denis V. Abramochkin
- Faculty of Biology, Lomonosov Moscow State University, 119234 Moscow, Russia; (M.K.); (D.V.A.); (K.B.P.); (V.N.)
| | - Ksenia B. Pustovit
- Faculty of Biology, Lomonosov Moscow State University, 119234 Moscow, Russia; (M.K.); (D.V.A.); (K.B.P.); (V.N.)
| | - Tatiana Nesterova
- Institute of Immunology and Physiology, Ural Branch of Russian Academy of Sciences, 620049 Ekaterinburg, Russia;
- Institute of Natural Sciences and Mathematics, Ural Federal University, 620075 Ekaterinburg, Russia
| | - Valery Novoseletsky
- Faculty of Biology, Lomonosov Moscow State University, 119234 Moscow, Russia; (M.K.); (D.V.A.); (K.B.P.); (V.N.)
- Biology Department, Shenzhen MSU-BIT University, Shenzhen 517182, China
| | - Gildas Loussouarn
- Nantes Université, CNRS, INSERM, l’institut du Thorax, F-44000 Nantes, France;
| | | | - Olga S. Sokolova
- Faculty of Biology, Lomonosov Moscow State University, 119234 Moscow, Russia; (M.K.); (D.V.A.); (K.B.P.); (V.N.)
- Biology Department, Shenzhen MSU-BIT University, Shenzhen 517182, China
- Correspondence: or
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48
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Di Muccio G, Morozzo della Rocca B, Chinappi M. Geometrically Induced Selectivity and Unidirectional Electroosmosis in Uncharged Nanopores. ACS NANO 2022; 16:8716-8728. [PMID: 35587777 PMCID: PMC9245180 DOI: 10.1021/acsnano.1c03017] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Selectivity toward positive and negative ions in nanopores is often associated with electroosmotic flow, the control of which is pivotal in several micro-nanofluidic technologies. Selectivity is traditionally understood to be a consequence of surface charges that alter the ion distribution in the pore lumen. Here we present a purely geometrical mechanism to induce ionic selectivity and electroosmotic flow in uncharged nanopores, and we tested it via molecular dynamics simulations. Our approach exploits the accumulation of charges, driven by an external electric field, in a coaxial cavity that decorates the membrane close to the pore entrance. The selectivity was shown to depend on the applied voltage and becomes completely inverted when reversing the voltage. The simultaneous inversion of ionic selectivity and electric field direction causes a unidirectional electroosmotic flow. We developed a quantitatively accurate theoretical model for designing pore geometry to achieve the desired electroosmotic velocity. Finally, we show that unidirectional electroosmosis also occurs in much more complex scenarios, such as a biological pore whose structure presents a coaxial cavity surrounding the pore constriction as well as a complex surface charge pattern. The capability to induce ion selectivity without altering the pore lumen shape or the surface charge may be useful for a more flexible design of selective membranes.
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Affiliation(s)
- Giovanni Di Muccio
- Dipartimento
di Ingegneria Industriale, Università
di Roma Tor Vergata, Via del Politecnico 1, 00133, Rome, Italy
| | - Blasco Morozzo della Rocca
- Dipartimento
di Biologia, Università di Roma Tor
Vergata, Via della Ricerca Scientifica 1, 00133, Rome, Italy
| | - Mauro Chinappi
- Dipartimento
di Ingegneria Industriale, Università
di Roma Tor Vergata, Via del Politecnico 1, 00133, Rome, Italy
- E-mail:
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Wu ZQ, Li CY, Ding XL, Li ZQ, Xia XH. Synergistic Effect of Electrostatic Interaction and Ionic Dehydration on Asymmetric Ion Transport in Nanochannel/Ion Channel Composite Membrane. J Phys Chem Lett 2022; 13:5267-5274. [PMID: 35674726 DOI: 10.1021/acs.jpclett.2c01166] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Ion transport in nanochannels of a size comparable to that of hydrated ions exhibits unique properties due to the synergistic effect of various forces. Here, we design a nanochannel/ion channel composite (NIC) membrane that shows a high ion current rectification (ICR) ratio in different electrolytes. Experimental and theoretical results demonstrate that the synergistic effect of electrostatic interaction and ionic dehydration plays an important role in regulating the ICR behavior of the NIC membrane. We find that electrostatic attraction between ions and the channel surface in the ultraconfined space increases the probability of ionic dehydarion, resulting in different dehydration energy costs for different ions. This further alters the driving force for ion transport and thus regulates ICR of the NIC membrane. This work provides fundamental knowledge of ion transport in ion channels, which aids in the understanding of the function of biological systems and the design of high-performance nanochannel devices.
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Affiliation(s)
- Zeng-Qiang Wu
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
- School of Public Health, Nantong University, Nantong 226019, China
| | - Cheng-Yong Li
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
- School of Chemistry & Environment, Guangdong Ocean University, Zhanjiang 524088, China
| | - Xin-Lei Ding
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Zhong-Qiu Li
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Xing-Hua Xia
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
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50
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Dessaux D, Mathé J, Ramirez R, Basdevant N. Current Rectification and Ionic Selectivity of α-Hemolysin: Coarse-Grained Molecular Dynamics Simulations. J Phys Chem B 2022; 126:4189-4199. [PMID: 35657610 DOI: 10.1021/acs.jpcb.2c01028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In order to understand the physical processes of nanopore experiments at the molecular level, microscopic information from molecular dynamics is greatly needed. Coarse-grained models are a good alternative to classical all-atom models since they allow longer and faster simulations. We performed coarse-grained molecular dynamics of the ionic transport through the α-hemolysin protein nanopore, inserted into a lipid bilayer surrounded by solvent and ions. For this purpose, we used the MARTINI coarse-grained force field and its polarizable water solvent (PW). Moreover, the electric potential difference applied experimentally was mimicked by the application of an electric field to the system. We present, in this study, the results of 1.5 μs long-molecular dynamics simulations of 12 different systems for which different charged amino acids were neutralized, each of them in the presence of nine different electric fields ranging between ±0.04 V/nm (a total of around 100 simulations). We were able to observe several specific features of this pore, current asymmetry and anion selectivity, in agreement with previous studies and experiments, and we identified the charged amino acids responsible for these current behaviors, therefore validating our coarse-grain approach to study ionic transport through nanopores. We also propose a microscopic explanation of these ionic current features using ionic density maps.
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Affiliation(s)
- Delphine Dessaux
- Université Paris-Saclay, Univ Evry, CNRS, LAMBE UMR8587, Évry-Courcouronnes 91025, France
| | - Jérôme Mathé
- Université Paris-Saclay, Univ Evry, CNRS, LAMBE UMR8587, Évry-Courcouronnes 91025, France
| | - Rosa Ramirez
- Université Paris-Saclay, Univ Evry, CNRS, LAMBE UMR8587, Évry-Courcouronnes 91025, France
| | - Nathalie Basdevant
- Université Paris-Saclay, Univ Evry, CNRS, LAMBE UMR8587, Évry-Courcouronnes 91025, France
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