1
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Mayse LA, Movileanu L. Gating of β-Barrel Protein Pores, Porins, and Channels: An Old Problem with New Facets. Int J Mol Sci 2023; 24:12095. [PMID: 37569469 PMCID: PMC10418385 DOI: 10.3390/ijms241512095] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Revised: 07/23/2023] [Accepted: 07/25/2023] [Indexed: 08/13/2023] Open
Abstract
β barrels are ubiquitous proteins in the outer membranes of mitochondria, chloroplasts, and Gram-negative bacteria. These transmembrane proteins (TMPs) execute a wide variety of tasks. For example, they can serve as transporters, receptors, membrane-bound enzymes, as well as adhesion, structural, and signaling elements. In addition, multimeric β barrels are common structural scaffolds among many pore-forming toxins. Significant progress has been made in understanding the functional, structural, biochemical, and biophysical features of these robust and versatile proteins. One frequently encountered fundamental trait of all β barrels is their voltage-dependent gating. This process consists of reversible or permanent conformational transitions between a large-conductance, highly permeable open state and a low-conductance, solute-restrictive closed state. Several intrinsic molecular mechanisms and environmental factors modulate this universal property of β barrels. This review article outlines the typical signatures of voltage-dependent gating. Moreover, we discuss recent developments leading to a better qualitative understanding of the closure dynamics of these TMPs.
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Affiliation(s)
- Lauren A. Mayse
- Department of Physics, Syracuse University, 201 Physics Building, Syracuse, NY 13244, USA;
- Department of Biomedical and Chemical Engineering, Syracuse University, 223 Link Hall, Syracuse, NY 13244, USA
| | - Liviu Movileanu
- Department of Physics, Syracuse University, 201 Physics Building, Syracuse, NY 13244, USA;
- Department of Biomedical and Chemical Engineering, Syracuse University, 223 Link Hall, Syracuse, NY 13244, USA
- The BioInspired Institute, Syracuse University, Syracuse, NY 13244, USA
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2
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Lei Z, Karim A. The challenges and applications of nanotechnology against bacterial resistance. J Vet Pharmacol Ther 2020; 44:281-297. [PMID: 33277732 DOI: 10.1111/jvp.12936] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Revised: 10/30/2020] [Accepted: 11/17/2020] [Indexed: 12/11/2022]
Abstract
Bacterial resistance to the antibiotics develops rapidly and is increasingly serious health concern in the world. It is an insoluble topic due to the multiple resistant mechanisms. The overexpression of relative activities of the efflux pump has proven to be a frequent and important source of bacterial resistance. Efflux transporters in the membrane from the resistant bacteria could play a key role to inhibit the intracellular drug intake and impede the drug activities. However, nanoparticles (NPs), one of the most frequently used encapsulation materials, could increase the intracellular accumulation of the drug and inhibit the transporter activity effectively. The rational and successful application of nanotechnology is a key factor in overcoming bacterial resistance. Furthermore, nanoparticles such as metallic, carbon nanotubes and so on, may prevent the development of drug resistance and be associated with antibiotic agents, inhibiting biofilm formation or increasing the access into the target cell and exterminating the bacteria eventually. In the current study, the mechanisms of bacterial resistance are discussed and summarized. Additionally, the opportunities and challenges in the use of nanoparticles against bacterial resistance are also illuminated. At the same time, the use of nanoparticles to combat multidrug-resistant bacteria is also investigated by coupling natural antimicrobials or other alternatives. In short, we have provided a new perspective for the application of nanoparticles against multidrug-resistant bacteria.
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Affiliation(s)
- Zhiqun Lei
- School of Biology and Pharmaceutical Engineering, Wuhan Polytechnic University, Wuhan, China
| | - Aman Karim
- Department of Biological Sciences, National University of Medical Sciences, Rawalpindi, Pakistan
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3
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Samanta S, Bodrenko I, Acosta-Gutiérrez S, D’Agostino T, Pathania M, Ghai I, Schleberger C, Bumann D, Wagner R, Winterhalter M, van den Berg B, Ceccarelli M. Getting Drugs through Small Pores: Exploiting the Porins Pathway in Pseudomonas aeruginosa. ACS Infect Dis 2018; 4:1519-1528. [PMID: 30039960 DOI: 10.1021/acsinfecdis.8b00149] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Understanding molecular properties of outer membrane channels of Gram-negative bacteria is of fundamental significance as they are the entry point of polar antibiotics into bacteria. Outer membrane proteomics revealed OccK8 (OprE) to be among the five most expressed substrate specific channels of the clinically important Pseudomonas aeruginosa. The high-resolution X-ray structure and electrophysiology highlighted a very narrow pore. However, experimental in vitro methods showed the transport of natural amino acids and antibiotics, among them ceftazidime. We used molecular dynamics simulations to reveal the importance of the physicochemical properties of ceftazidime in modulating the translocation through OccK8, proposing a structure-function relationship. As in general porins, the internal electric field favors the translocation of polar molecules by gainful energy compensation in the central constriction region. Importantly, the comparatively narrow OccK8 pore can undergo a substrate-induced expansion to accommodate relatively large-sized substrates.
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Affiliation(s)
- Susruta Samanta
- Department of Physics, University of Cagliari, SP Monserrato-Sestu Km 0.8, Monserrato, 09042, Italy
- Department of Chemistry, Manipal University Jaipur, VPO Dehmi Kalan, Jaipur, Rajasthan 303007, India
| | - Igor Bodrenko
- Department of Physics, University of Cagliari, SP Monserrato-Sestu Km 0.8, Monserrato, 09042, Italy
| | - Silvia Acosta-Gutiérrez
- Department of Physics, University of Cagliari, SP Monserrato-Sestu Km 0.8, Monserrato, 09042, Italy
| | - Tommaso D’Agostino
- Department of Physics, University of Cagliari, SP Monserrato-Sestu Km 0.8, Monserrato, 09042, Italy
| | - Monisha Pathania
- Institute for Cell and Molecular Biosciences, The Medical School, Newcastle University, Newcastle upon Tyne, NE2 4HH, United Kingdom
| | - Ishan Ghai
- Department of Life Sciences and Chemistry, Jacobs University Bremen, 28719 Bremen, Germany
| | - Christian Schleberger
- Biozentrum, University of Basel, Klingelbergstrasse 50/70, CH-4056 Basel, Switzerland
| | - Dirk Bumann
- Biozentrum, University of Basel, Klingelbergstrasse 50/70, CH-4056 Basel, Switzerland
| | - Richard Wagner
- Department of Life Sciences and Chemistry, Jacobs University Bremen, 28719 Bremen, Germany
| | - Mathias Winterhalter
- Department of Life Sciences and Chemistry, Jacobs University Bremen, 28719 Bremen, Germany
| | - Bert van den Berg
- Institute for Cell and Molecular Biosciences, The Medical School, Newcastle University, Newcastle upon Tyne, NE2 4HH, United Kingdom
| | - Matteo Ceccarelli
- Department of Physics, University of Cagliari, SP Monserrato-Sestu Km 0.8, Monserrato, 09042, Italy
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4
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Abstract
Collective antibiotic drug resistance is a global threat, especially with respect to Gram-negative bacteria. The low permeability of the bacterial outer cell wall has been identified as a challenging barrier that prevents a sufficient antibiotic effect to be attained at low doses of the antibiotic. The Gram-negative bacterial cell envelope comprises an outer membrane that delimits the periplasm from the exterior milieu. The crucial mechanisms of antibiotic entry via outer membrane includes general diffusion porins (Omps) responsible for hydrophilic antibiotics and lipid-mediated pathway for hydrophobic antibiotics. The protein and lipid arrangements of the outer membrane have had a strong impact on the understanding of bacteria and their resistance to many types of antibiotics. Thus, one of the current challenges is effective interpretation at the molecular basis of the outer membrane permeability. This review attempts to develop a state of knowledge pertinent to Omps and their effective role in solute influx. Moreover, it aims toward further understanding and exploration of prospects to improve our knowledge of physicochemical limitations that direct the translocation of antibiotics via bacterial outer membrane.
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Affiliation(s)
- Ishan Ghai
- School of Engineering and Life Sciences, Jacobs University, Bremen, Germany.,Consultation Division, RSGBIOGEN, New Delhi, India
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5
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Benkerrou D, Ceccarelli M. Free energy calculations and molecular properties of substrate translocation through OccAB porins. Phys Chem Chem Phys 2018. [DOI: 10.1039/c7cp08299a] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
We investigated with molecular modeling the translocation of simple substrates through four similar specific bacterial porins from the Acinetobacter baumannii pathogen providing structure–function analysis at the molecular level.
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6
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Chevalier S, Bouffartigues E, Bodilis J, Maillot O, Lesouhaitier O, Feuilloley MGJ, Orange N, Dufour A, Cornelis P. Structure, function and regulation of Pseudomonas aeruginosa porins. FEMS Microbiol Rev 2017; 41:698-722. [PMID: 28981745 DOI: 10.1093/femsre/fux020] [Citation(s) in RCA: 218] [Impact Index Per Article: 31.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Accepted: 04/24/2017] [Indexed: 12/11/2022] Open
Abstract
Pseudomonas aeruginosa is a Gram-negative bacterium belonging to the γ-proteobacteria. Like other members of the Pseudomonas genus, it is known for its metabolic versatility and its ability to colonize a wide range of ecological niches, such as rhizosphere, water environments and animal hosts, including humans where it can cause severe infections. Another particularity of P. aeruginosa is its high intrinsic resistance to antiseptics and antibiotics, which is partly due to its low outer membrane permeability. In contrast to Enterobacteria, pseudomonads do not possess general diffusion porins in their outer membrane, but rather express specific channel proteins for the uptake of different nutrients. The major outer membrane 'porin', OprF, has been extensively investigated, and displays structural, adhesion and signaling functions while its role in the diffusion of nutrients is still under discussion. Other porins include OprB and OprB2 for the diffusion of glucose, the two small outer membrane proteins OprG and OprH, and the two porins involved in phosphate/pyrophosphate uptake, OprP and OprO. The remaining nineteen porins belong to the so-called OprD (Occ) family, which is further split into two subfamilies termed OccD (8 members) and OccK (11 members). In the past years, a large amount of information concerning the structure, function and regulation of these porins has been published, justifying why an updated review is timely.
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Affiliation(s)
- Sylvie Chevalier
- Laboratory of Microbiology Signals and Microenvironment LMSM EA 4312, University of Rouen, Normandy University, 27000 Evreux, France
| | - Emeline Bouffartigues
- Laboratory of Microbiology Signals and Microenvironment LMSM EA 4312, University of Rouen, Normandy University, 27000 Evreux, France
| | - Josselin Bodilis
- Laboratory of Microbiology Signals and Microenvironment LMSM EA 4312, University of Rouen, Normandy University, 27000 Evreux, France
| | - Olivier Maillot
- Laboratory of Microbiology Signals and Microenvironment LMSM EA 4312, University of Rouen, Normandy University, 27000 Evreux, France
| | - Olivier Lesouhaitier
- Laboratory of Microbiology Signals and Microenvironment LMSM EA 4312, University of Rouen, Normandy University, 27000 Evreux, France
| | - Marc G J Feuilloley
- Laboratory of Microbiology Signals and Microenvironment LMSM EA 4312, University of Rouen, Normandy University, 27000 Evreux, France
| | - Nicole Orange
- Laboratory of Microbiology Signals and Microenvironment LMSM EA 4312, University of Rouen, Normandy University, 27000 Evreux, France
| | - Alain Dufour
- IUEM, Laboratoire de Biotechnologie et Chimie Marines EA 3884, Université de Bretagne-Sud (UEB), 56321 Lorient, France
| | - Pierre Cornelis
- Laboratory of Microbiology Signals and Microenvironment LMSM EA 4312, University of Rouen, Normandy University, 27000 Evreux, France
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7
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Abstract
One of the main fundamental mechanisms of antibiotic resistance in Gram-negative bacteria comprises an effective change in the membrane permeability to antibiotics. The Gram-negative bacterial complex cell envelope comprises an outer membrane that delimits the periplasm from the exterior environment. The outer membrane contains numerous protein channels, termed as porins or nanopores, which are mainly involved in the influx of hydrophilic compounds, including antibiotics. Bacterial adaptation to reduce influx through these outer membrane proteins (Omps) is one of the crucial mechanisms behind antibiotic resistance. Thus to interpret the molecular basis of the outer membrane permeability is the current challenge. This review attempts to develop a state of knowledge pertinent to Omps and their effective role in antibiotic influx. Further, it aims to study the bacterial response to antibiotic membrane permeability and hopefully provoke a discussion toward understanding and further exploration of prospects to improve our knowledge on physicochemical parameters that direct the translocation of antibiotics through the bacterial membrane protein channels.
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Affiliation(s)
- Ishan Ghai
- School of Engineering and Life Sciences, Jacobs University, Bremen
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8
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Pothula KR, Dhanasekar NN, Lamichhane U, Younas F, Pletzer D, Benz R, Winterhalter M, Kleinekathöfer U. Single Residue Acts as Gate in OccK Channels. J Phys Chem B 2017; 121:2614-2621. [DOI: 10.1021/acs.jpcb.7b01787] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Karunakar R. Pothula
- Department
of Physics and Earth Sciences, Jacobs University Bremen, Campus Ring 1, 28759 Bremen, Germany
| | - Naresh N. Dhanasekar
- Department
of Life Sciences and Chemistry, Jacobs University Bremen, Campus Ring 1, 28759 Bremen, Germany
| | - Usha Lamichhane
- Department
of Life Sciences and Chemistry, Jacobs University Bremen, Campus Ring 1, 28759 Bremen, Germany
| | - Farhan Younas
- Department
of Life Sciences and Chemistry, Jacobs University Bremen, Campus Ring 1, 28759 Bremen, Germany
| | - Daniel Pletzer
- Department
of Life Sciences and Chemistry, Jacobs University Bremen, Campus Ring 1, 28759 Bremen, Germany
| | - Roland Benz
- Department
of Life Sciences and Chemistry, Jacobs University Bremen, Campus Ring 1, 28759 Bremen, Germany
| | - Mathias Winterhalter
- Department
of Life Sciences and Chemistry, Jacobs University Bremen, Campus Ring 1, 28759 Bremen, Germany
| | - Ulrich Kleinekathöfer
- Department
of Physics and Earth Sciences, Jacobs University Bremen, Campus Ring 1, 28759 Bremen, Germany
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9
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Mohammad MM, Tomita N, Ohta M, Movileanu L. The Transmembrane Domain of a Bicomponent ABC Transporter Exhibits Channel-Forming Activity. ACS Chem Biol 2016; 11:2506-18. [PMID: 27379442 PMCID: PMC5026576 DOI: 10.1021/acschembio.6b00383] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Pseudomonas aeruginosa is an opportunistic pathogen that expresses two unique forms of lipopolysaccharides (LPSs) on its bacterial surface, the A- and B-bands. The A-band polysaccharides (A-band PSs) are thought to be exported into the periplasm via a bicomponent ATP-binding cassette (ABC) transporter located within the inner membrane. This ABC protein complex consists of the transmembrane (TMD) Wzm and nucleotide-binding (NBD) Wzt domain proteins. Here, we were able to probe ∼1.36 nS-average conductance openings of the Wzm-based protein complex when reconstituted into a lipid membrane buffered by a 200 mM KCl solution, demonstrating the large-conductance, channel-forming ability of the TMDs. In agreement with this finding, transmission electron microscopy (TEM) imaging revealed the ring-shaped structure of the transmembrane Wzm protein complex. As hypothesized, using liposomes, we demonstrated that Wzm interacts with Wzt. Further, the Wzt polypeptide indeed hydrolyzed ATP but exhibited a ∼75% reduction in the ATPase activity when its Walker A domain was deleted. The distribution and average unitary conductance of the TMD Wzm protein complex were altered by the presence of the NBD Wzt protein, confirming the regulatory role of the latter polypeptide. To our knowledge, the large-conductance, channel-like activity of the Wzm protein complex, although often hypothesized, has not previously been demonstrated. These results constitute a platform for future structural, biophysical, and functional explorations of this bicomponent ABC transporter.
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Affiliation(s)
- Mohammad M. Mohammad
- Department of Physics, Syracuse University, 201 Physics Building, Syracuse, New York 13244-1130, USA
| | - Noriko Tomita
- Department of Physics, Syracuse University, 201 Physics Building, Syracuse, New York 13244-1130, USA
- Institute of Fluid Science, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan
| | - Makoto Ohta
- Institute of Fluid Science, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan
| | - Liviu Movileanu
- Department of Physics, Syracuse University, 201 Physics Building, Syracuse, New York 13244-1130, USA
- Structural Biology, Biochemistry, and Biophysics Program, Syracuse University, 111 College Place, Syracuse, New York 13244-4100, USA
- The Syracuse Biomaterials Institute, Syracuse University, 121 Link Hall, Syracuse, New York 13244, USA
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10
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Pothula KR, Solano CJF, Kleinekathöfer U. Simulations of outer membrane channels and their permeability. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1858:1760-71. [PMID: 26721326 DOI: 10.1016/j.bbamem.2015.12.020] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Revised: 12/15/2015] [Accepted: 12/17/2015] [Indexed: 12/25/2022]
Abstract
Channels in the outer membrane of Gram-negative bacteria provide essential pathways for the controlled and unidirectional transport of ions, nutrients and metabolites into the cell. At the same time the outer membrane serves as a physical barrier for the penetration of noxious substances such as antibiotics into the bacteria. Most antibiotics have to pass through these membrane channels to either reach cytoplasmic bound targets or to further cross the hydrophobic inner membrane. Considering the pharmaceutical significance of antibiotics, understanding the functional role and mechanism of these channels is of fundamental importance in developing strategies to design new drugs with enhanced permeation abilities. Due to the biological complexity of membrane channels and experimental limitations, computer simulations have proven to be a powerful tool to investigate the structure, dynamics and interactions of membrane channels. Considerable progress has been made in computer simulations of membrane channels during the last decade. The goal of this review is to provide an overview of the computational techniques and their roles in modeling the transport across outer membrane channels. A special emphasis is put on all-atom molecular dynamics simulations employed to better understand the transport of molecules. Moreover, recent molecular simulations of ion, substrate and antibiotics translocation through membrane pores are briefly summarized. This article is part of a Special Issue entitled: Membrane Proteins edited by J.C. Gumbart and Sergei Noskov.
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Affiliation(s)
- Karunakar R Pothula
- Department of Physics and Earth Sciences, Jacobs University Bremen, Campus Ring 1, 28759 Bremen, Germany
| | - Carlos J F Solano
- Department of Physics and Earth Sciences, Jacobs University Bremen, Campus Ring 1, 28759 Bremen, Germany
| | - Ulrich Kleinekathöfer
- Department of Physics and Earth Sciences, Jacobs University Bremen, Campus Ring 1, 28759 Bremen, Germany
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11
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Wolfe AJ, Mohammad MM, Thakur AK, Movileanu L. Global redesign of a native β-barrel scaffold. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1858:19-29. [PMID: 26456555 DOI: 10.1016/j.bbamem.2015.10.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2015] [Revised: 10/03/2015] [Accepted: 10/07/2015] [Indexed: 11/30/2022]
Abstract
One persistent challenge in membrane protein design is accomplishing extensive modifications of proteins without impairing their functionality. A truncation derivative of the ferric hydroxamate uptake component A (FhuA), which featured the deletion of the 160-residue cork domain and five large extracellular loops, produced the conversion of a non-conductive, monomeric, 22-stranded β-barrel protein into a large-conductance protein pore. Here, we show that this redesigned β-barrel protein tolerates an extensive alteration in the internal surface charge, encompassing 25 negative charge neutralizations. By using single-molecule electrophysiology, we noted that a commonality of various truncation FhuA protein pores was the occurrence of 33% blockades of the unitary current at very high transmembrane potentials. We determined that these current transitions were stimulated by their interaction with an external cationic polypeptide, which occurred in a fashion dependent on the surface charge of the pore interior as well as the polypeptide characteristics. This study shows promise for extensive engineering of a large monomeric β-barrel protein pore in molecular biomedical diagnosis, therapeutics, and biosensor technology.
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Affiliation(s)
- Aaron J Wolfe
- Department of Physics, Syracuse University, 201 Physics Building, Syracuse, NY 13244-1130, USA; Structural Biology, Biochemistry, and Biophysics Program, Syracuse University, 111 College Place, Syracuse, NY 13244-4100, USA
| | - Mohammad M Mohammad
- Department of Physics, Syracuse University, 201 Physics Building, Syracuse, NY 13244-1130, USA
| | - Avinash K Thakur
- Department of Physics, Syracuse University, 201 Physics Building, Syracuse, NY 13244-1130, USA; Structural Biology, Biochemistry, and Biophysics Program, Syracuse University, 111 College Place, Syracuse, NY 13244-4100, USA
| | - Liviu Movileanu
- Department of Physics, Syracuse University, 201 Physics Building, Syracuse, NY 13244-1130, USA; Structural Biology, Biochemistry, and Biophysics Program, Syracuse University, 111 College Place, Syracuse, NY 13244-4100, USA; The Syracuse Biomaterials Institute, Syracuse University, 121 Link Hall, Syracuse, NY 13244, USA.
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12
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Cheneke B, van den Berg B, Movileanu L. Quasithermodynamic contributions to the fluctuations of a protein nanopore. ACS Chem Biol 2015; 10:784-94. [PMID: 25479108 PMCID: PMC4372101 DOI: 10.1021/cb5008025] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Accepted: 12/05/2014] [Indexed: 12/20/2022]
Abstract
Proteins undergo thermally activated conformational fluctuations among two or more substates, but a quantitative inquiry on their kinetics is persistently challenged by numerous factors, including the complexity and dynamics of various interactions, along with the inability to detect functional substates within a resolvable time scale. Here, we analyzed in detail the current fluctuations of a monomeric β-barrel protein nanopore of known high-resolution X-ray crystal structure. We demonstrated that targeted perturbations of the protein nanopore system, in the form of loop-deletion mutagenesis, accompanying alterations of electrostatic interactions between long extracellular loops, produced modest changes of the differential activation free energies calculated at 25 °C, ΔΔG(⧧), in the range near the thermal energy but substantial and correlated modifications of the differential activation enthalpies, ΔΔH(⧧), and entropies, ΔΔS(⧧). This finding indicates that the local conformational reorganizations of the packing and flexibility of the fluctuating loops lining the central constriction of this protein nanopore were supplemented by changes in the single-channel kinetics. These changes were reflected in the enthalpy-entropy reconversions of the interactions between the loop partners with a compensating temperature, TC, of ∼300 K, and an activation free energy constant of ∼41 kJ/mol. We also determined that temperature has a much greater effect on the energetics of the equilibrium gating fluctuations of a protein nanopore than other environmental parameters, such as the ionic strength of the aqueous phase as well as the applied transmembrane potential, likely due to ample changes in the solvation activation enthalpies. There is no fundamental limitation for applying this approach to other complex, multistate membrane protein systems. Therefore, this methodology has major implications in the area of membrane protein design and dynamics, primarily by revealing a better quantitative assessment on the equilibrium transitions among multiple well-defined and functionally distinct substates of protein channels and pores.
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Affiliation(s)
- Belete
R. Cheneke
- Department
of Physics, Syracuse University, 201 Physics Building, Syracuse, New York 13244-1130, United States
| | - Bert van den Berg
- Institute
for Cellular and Molecular Biosciences, Newcastle University, Newcastle
upon Tyne, NE2 4HH, United
Kingdom
| | - Liviu Movileanu
- Department
of Physics, Syracuse University, 201 Physics Building, Syracuse, New York 13244-1130, United States
- Structural
Biology, Biochemistry, and Biophysics Program, Syracuse University, 111 College Place, Syracuse, New York 13244-4100, United States
- Syracuse
Biomaterials Institute, Syracuse University, 121 Link Hall, Syracuse, New York 13244, United States
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13
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Pothula KR, Kleinekathöfer U. Theoretical analysis of ion conductance and gating transitions in the OpdK (OccK1) channel. Analyst 2015; 140:4855-64. [DOI: 10.1039/c5an00036j] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Molecular simulations have been performed on the pore OpdK elucidating molecular details of ion conductance and a possible gating mechanism.
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14
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Movileanu L. Watching single proteins using engineered nanopores. Protein Pept Lett 2014; 21:235-46. [PMID: 24370252 PMCID: PMC3924890 DOI: 10.2174/09298665113209990078] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2012] [Revised: 11/03/2012] [Accepted: 11/10/2012] [Indexed: 12/22/2022]
Abstract
Recent studies in the area of single-molecule detection of proteins with nanopores show a great promise in fundamental science, bionanotechnology and proteomics. In this mini-review, I discuss a comprehensive array of examinations of protein detection and characterization using protein and solid-state nanopores. These investigations demonstrate the power of the single-molecule nanopore measurements to reveal a broad range of functional, structural, biochemical and biophysical features of proteins, such as their backbone flexibility, enzymatic activity, binding affinity as well as their concentration, size and folding state. Engineered nanopores in organic materials and in inorganic membranes coupled with surface modification and protein engineering might provide a new generation of sensing devices for molecular biomedical diagnostics.
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Affiliation(s)
- Liviu Movileanu
- Department of Physics, Syracuse University, 201 Physics Building, Syracuse, New York 13244-1130, USA.
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15
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Eren E, Parkin J, Adelanwa A, Cheneke B, Movileanu L, Khalid S, van den Berg B. Toward understanding the outer membrane uptake of small molecules by Pseudomonas aeruginosa. J Biol Chem 2013; 288:12042-53. [PMID: 23467408 DOI: 10.1074/jbc.m113.463570] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Because small molecules enter Gram-negative bacteria via outer membrane (OM) channels, understanding OM transport is essential for the rational design of improved and new antibiotics. In the human pathogen Pseudomonas aeruginosa, most small molecules are taken up by outer membrane carboxylate channel (Occ) proteins, which can be divided into two distinct subfamilies, OccD and OccK. Here we characterize substrate transport mediated by Occ proteins belonging to both subfamilies. Based on the determination of the OccK2-glucuronate co-crystal structure, we identify the channel residues that are essential for substrate transport. We further show that the pore regions of the channels are rigid in the OccK subfamily and highly dynamic in the OccD subfamily. We also demonstrate that the substrate carboxylate group interacts with central residues of the basic ladder, a row of arginine and lysine residues that leads to and away from the binding site at the channel constriction. Moreover, the importance of the basic ladder residues corresponds to their degree of conservation. Finally, we apply the generated insights by converting the archetype of the entire family, OccD1, from a basic amino acid-specific channel into a channel with a preference for negatively charged amino acids.
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Affiliation(s)
- Elif Eren
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA
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16
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Tomita N, Mohammad MM, Niedzwiecki DJ, Ohta M, Movileanu L. Does the lipid environment impact the open-state conductance of an engineered β-barrel protein nanopore? BIOCHIMICA ET BIOPHYSICA ACTA 2013; 1828:1057-65. [PMID: 23246446 PMCID: PMC3560310 DOI: 10.1016/j.bbamem.2012.12.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2012] [Revised: 11/16/2012] [Accepted: 12/04/2012] [Indexed: 12/11/2022]
Abstract
Using rational membrane protein design, we were recently able to obtain a β-barrel protein nanopore that was robust under an unusually broad range of experimental circumstances. This protein nanopore was based upon the native scaffold of the bacterial ferric hydroxamate uptake component A (FhuA) of Escherichia coli. In this work, we expanded the examinations of the open-state current of this engineered protein nanopore, also called FhuA ΔC/Δ4L, employing an array of lipid bilayer systems that contained charged and uncharged as well as conical and cylindrical lipids. Remarkably, systematical single-channel analysis of FhuA ΔC/Δ4L indicated that most of its biophysical features, such as the unitary conductance and the stability of the open-state current, were not altered under the conditions tested in this work. However, electrical recordings at high transmembrane potentials revealed that the presence of conical phospholipids within the bilayer catalyzes the first, stepwise current transition of the FhuA ΔC/Δ4L protein nanopore to a lower-conductance open state. This study reinforces the stability of the open-state current of the engineered FhuA ΔC/Δ4L protein nanopore under various experimental conditions, paving the way for further critical developments in biosensing and molecular biomedical diagnosis.
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Affiliation(s)
- Noriko Tomita
- Department of Physics, Syracuse University, Syracuse, New York 13244-1130, USA
- Institute of Fluid Science, Tohoku University, Sendai, Miyagi 980-8577, Japan
| | | | | | - Makoto Ohta
- Institute of Fluid Science, Tohoku University, Sendai, Miyagi 980-8577, Japan
| | - Liviu Movileanu
- Department of Physics, Syracuse University, Syracuse, New York 13244-1130, USA
- Structural Biology, Biochemistry, and Biophysics Program, Syracuse University, Syracuse, New York 13244-4100, USA
- Syracuse Biomaterials Institute, Syracuse University, Syracuse, New York 13244, USA
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17
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Maffeo C, Bhattacharya S, Yoo J, Wells D, Aksimentiev A. Modeling and simulation of ion channels. Chem Rev 2012; 112:6250-84. [PMID: 23035940 PMCID: PMC3633640 DOI: 10.1021/cr3002609] [Citation(s) in RCA: 148] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Christopher Maffeo
- Department of Physics, University of Illinois, 1110 W. Green St., Urbana, IL
| | - Swati Bhattacharya
- Department of Physics, University of Illinois, 1110 W. Green St., Urbana, IL
| | - Jejoong Yoo
- Department of Physics, University of Illinois, 1110 W. Green St., Urbana, IL
| | - David Wells
- Department of Physics, University of Illinois, 1110 W. Green St., Urbana, IL
| | - Aleksei Aksimentiev
- Department of Physics, University of Illinois, 1110 W. Green St., Urbana, IL
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18
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Mertins B, Psakis G, Grosse W, Back KC, Salisowski A, Reiss P, Koert U, Essen LO. Flexibility of the N-terminal mVDAC1 segment controls the channel's gating behavior. PLoS One 2012; 7:e47938. [PMID: 23110136 PMCID: PMC3479125 DOI: 10.1371/journal.pone.0047938] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2012] [Accepted: 09/25/2012] [Indexed: 11/26/2022] Open
Abstract
Since the solution of the molecular structures of members of the voltage dependent anion channels (VDACs), the N-terminal α-helix has been the main focus of attention, since its strategic location, in combination with its putative conformational flexibility, could define or control the channel’s gating characteristics. Through engineering of two double-cysteine mVDAC1 variants we achieved fixing of the N-terminal segment at the bottom and midpoint of the pore. Whilst cross-linking at the midpoint resulted in the channel remaining constitutively open, cross-linking at the base resulted in an “asymmetric” gating behavior, with closure only at one electric field´s orientation depending on the channel’s orientation in the lipid bilayer. Additionally, and while the native channel adopts several well-defined closed states (S1 and S2), the cross-linked variants showed upon closure a clear preference for the S2 state. With native-channel characteristics restored following reduction of the cysteines, it is evident that the conformational flexibility of the N-terminal segment plays indeed a major part in the control of the channel’s gating behavior.
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Affiliation(s)
- Barbara Mertins
- Department of Chemistry, Philipps University Marburg, Marburg, Germany
| | - Georgios Psakis
- Department of Chemistry, Philipps University Marburg, Marburg, Germany
| | - Wolfgang Grosse
- Department of Chemistry, Philipps University Marburg, Marburg, Germany
| | | | | | - Philipp Reiss
- Department of Chemistry, Philipps University Marburg, Marburg, Germany
| | - Ulrich Koert
- Department of Chemistry, Philipps University Marburg, Marburg, Germany
| | - Lars-Oliver Essen
- Department of Chemistry, Philipps University Marburg, Marburg, Germany
- * E-mail:
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19
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Wang Y, Zhao X, Sun B, Yu H, Huang X. Molecular dynamics simulation study of the vanillate transport channel of Opdk. Arch Biochem Biophys 2012; 524:132-9. [DOI: 10.1016/j.abb.2012.05.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2012] [Revised: 05/07/2012] [Accepted: 05/11/2012] [Indexed: 12/11/2022]
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20
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Liu J, Wolfe AJ, Eren E, Vijayaraghavan J, Indic M, van den Berg B, Movileanu L. Cation selectivity is a conserved feature in the OccD subfamily of Pseudomonas aeruginosa. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1818:2908-16. [PMID: 22824298 DOI: 10.1016/j.bbamem.2012.07.009] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2012] [Revised: 07/13/2012] [Accepted: 07/16/2012] [Indexed: 01/03/2023]
Abstract
To achieve the uptake of small, water-soluble nutrients, Pseudomonas aeruginosa, a pathogenic Gram-negative bacterium, employs substrate-specific channels located within its outer membrane. In this paper, we present a detailed description of the single-channel characteristics of six members of the outer membrane carboxylate channel D (OccD) subfamily. Recent structural studies showed that the OccD proteins share common features, such as a closely related, monomeric, 18-stranded β-barrel conformation and large extracellular loops, which are folded back into the channel lumen. Here, we report that the OccD proteins displayed single-channel activity with a unitary conductance covering an unusually broad range, between 20 and 670pS, as well as a diverse gating dynamics. Interestingly, we found that cation selectivity is a conserved trait among all members of the OccD subfamily, bringing a new distinction between the members of the OccD subfamily and the anion-selective OccK channels. Conserved cation selectivity of the OccD channels is in accord with an increased specificity and selectivity of these proteins for positively charged, carboxylate-containing substrates.
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Affiliation(s)
- Jiaming Liu
- Department of Physics, Syracuse University, Syracuse, NY 13244-1130, USA
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21
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Cheneke BR, Indic M, van den Berg B, Movileanu L. An outer membrane protein undergoes enthalpy- and entropy-driven transitions. Biochemistry 2012; 51:5348-58. [PMID: 22680931 DOI: 10.1021/bi300332z] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
β-Barrel membrane proteins often fluctuate among various open substates, yet the nature of these transitions is not fully understood. Using temperature-dependent, single-molecule electrophysiology analysis, along with rational protein design, we show that OccK1, a member of the outer membrane carboxylate channel from Pseudomonas aeruginosa, features a discrete gating dynamics comprising both enthalpy-driven and entropy-driven current transitions. OccK1 was chosen for the analysis of these transitions, because it is a monomeric transmembrane β-barrel of a known high-resolution crystal structure and displays three distinguishable, time-resolvable open substates. Native and loop-deletion OccK1 proteins showed substantial changes in the activation enthalpies and entropies of the channel transitions, but modest alterations in the equilibrium free energies, confirming that the system never departs from equilibrium. Moreover, some current fluctuations of OccK1 indicated a counterintuitive, negative activation enthalpy, which was compensated by a significant decrease in the activation entropy. Temperature scanning of the single-channel properties of OccK1 exhibited a thermally induced switch of the energetically most favorable open substate at the lowest examined temperature of 4 °C. Therefore, such a semiquantitative assessment of the current fluctuation dynamics not only demonstrates the complexity of channel gating but also reveals distinct functional traits of a β-barrel outer membrane protein under different temperature circumstances.
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Affiliation(s)
- Belete R Cheneke
- Department of Physics, Syracuse University, 201 Physics Building, Syracuse, NY 13244-1130, USA
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22
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Liu J, Eren E, Vijayaraghavan J, Cheneke BR, Indic M, van den Berg B, Movileanu L. OccK channels from Pseudomonas aeruginosa exhibit diverse single-channel electrical signatures but conserved anion selectivity. Biochemistry 2012; 51:2319-30. [PMID: 22369314 DOI: 10.1021/bi300066w] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Pseudomonas aeruginosa is a Gram-negative bacterium that utilizes substrate-specific outer membrane (OM) proteins for the uptake of small, water-soluble nutrients employed in the growth and function of the cell. In this paper, we present for the first time a comprehensive single-channel examination of seven members of the OM carboxylate channel K (OccK) subfamily. Recent biochemical, functional, and structural characterization of the OccK proteins revealed their common features, such as a closely related, monomeric, 18-stranded β-barrel conformation with a kidney-shaped transmembrane pore and the presence of a basic ladder within the channel lumen. Here, we report that the OccK proteins exhibited fairly distinct unitary conductance values, in a much broader range than previously expected, which includes low (~40-100 pS) and medium (~100-380 pS) conductance. These proteins showed diverse single-channel dynamics of current gating transitions, revealing one-open substate (OccK3), two-open substate (OccK4-OccK6), and three-open substate (OccK1, OccK2, and OccK7) kinetics with functionally distinct conformations. Interestingly, we discovered that anion selectivity is a conserved trait among the members of the OccK subfamily, confirming the presence of a net pool of positively charged residues within their central constriction. Moreover, these results are in accord with an increased specificity and selectivity of these protein channels for negatively charged, carboxylate-containing substrates. Our findings might ignite future functional examinations and full atomistic computational studies for unraveling a mechanistic understanding of the passage of small molecules across the lumen of substrate-specific, β-barrel OM proteins.
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Affiliation(s)
- Jiaming Liu
- Department of Physics, Syracuse University, Syracuse, New York 13244-1130, United States
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23
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Eren E, Vijayaraghavan J, Liu J, Cheneke BR, Touw DS, Lepore BW, Indic M, Movileanu L, van den Berg B. Substrate specificity within a family of outer membrane carboxylate channels. PLoS Biol 2012; 10:e1001242. [PMID: 22272184 PMCID: PMC3260308 DOI: 10.1371/journal.pbio.1001242] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2011] [Accepted: 11/30/2011] [Indexed: 12/20/2022] Open
Abstract
Characterization of a large family of outer membrane channels from gram-negative bacteria suggest how they can thrive in nutrient-poor environments and how channel inactivation can contribute to antibiotic resistance. Many Gram-negative bacteria, including human pathogens such as Pseudomonas aeruginosa, do not have large-channel porins. This results in an outer membrane (OM) that is highly impermeable to small polar molecules, making the bacteria intrinsically resistant towards many antibiotics. In such microorganisms, the majority of small molecules are taken up by members of the OprD outer membrane protein family. Here we show that OprD channels require a carboxyl group in the substrate for efficient transport, and based on this we have renamed the family Occ, for outer membrane carboxylate channels. We further show that Occ channels can be divided into two subfamilies, based on their very different substrate specificities. Our results rationalize how certain bacteria can efficiently take up a variety of substrates under nutrient-poor conditions without compromising membrane permeability. In addition, they explain how channel inactivation in response to antibiotics can cause resistance but does not lead to decreased fitness. Emerging antibiotic resistance in the treatment of infectious disease is an increasing problem that urgently requires new drug development. In Gram-negative bacteria, the outer membrane (OM) prevents permeation of small molecules, including antibiotics. A family of channel-forming proteins, called OprD proteins, are present in the OM to enable uptake of nutrients required for growth and cellular function. Since these channels also transport antibiotics, understanding how molecules are recognized and transported by these proteins should enable the design of more effective antibiotics. Here, we have characterized by biophysical and biochemical methods the structures and substrate-specificities of nine members of the OprD channel family of a common multidrug-resistant pathogen, Pseudomonas aeruginosa. Because we demonstrate that efficient passage through these channels requires the presence of a carboxyl group in the substrate, we renamed this channel family outer membrane carboxylate channels, or Occ. This broad substrate specificity suggests that such efficient transport allows bacteria to thrive in nutrient-poor environments. We also show markedly varied substrate specificities among the family members, especially for antibiotics, suggesting that mutation of a single channel can result in antibiotic resistance. These results provide the framework for studying the interaction of antibiotics with OM uptake channels, which will facilitate the development of more permeable and thus effective drugs.
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Affiliation(s)
- Elif Eren
- University of Massachusetts Medical School, Program in Molecular Medicine, Worcester, Massachusetts, United States of America
| | - Jagamya Vijayaraghavan
- University of Massachusetts Medical School, Program in Molecular Medicine, Worcester, Massachusetts, United States of America
| | - Jiaming Liu
- Syracuse University, Department of Physics, Syracuse, New York, United States of America
| | - Belete R. Cheneke
- Syracuse University, Department of Physics, Syracuse, New York, United States of America
| | - Debra S. Touw
- University of Massachusetts Medical School, Program in Molecular Medicine, Worcester, Massachusetts, United States of America
| | - Bryan W. Lepore
- University of Massachusetts Medical School, Program in Molecular Medicine, Worcester, Massachusetts, United States of America
| | - Mridhu Indic
- University of Massachusetts Medical School, Program in Molecular Medicine, Worcester, Massachusetts, United States of America
| | - Liviu Movileanu
- Syracuse University, Department of Physics, Syracuse, New York, United States of America
| | - Bert van den Berg
- University of Massachusetts Medical School, Program in Molecular Medicine, Worcester, Massachusetts, United States of America
- * E-mail:
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24
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Fologea D, Krueger E, Mazur YI, Stith C, Okuyama Y, Henry R, Salamo GJ. Bi-stability, hysteresis, and memory of voltage-gated lysenin channels. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1808:2933-9. [PMID: 21945404 DOI: 10.1016/j.bbamem.2011.09.005] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2011] [Revised: 08/28/2011] [Accepted: 09/06/2011] [Indexed: 10/17/2022]
Abstract
Lysenin, a 297 amino acid pore-forming protein extracted from the coelomic fluid of the earthworm E. foetida, inserts constitutively open large conductance channels in natural and artificial lipid membranes containing sphingomyelin. The inserted channels show voltage regulation and slowly close at positive applied voltages. We report on the consequences of slow voltage-induced gating of lysenin channels inserted into a planar Bilayer Lipid Membrane (BLM), and demonstrate that these pore-forming proteins constitute memory elements that manifest gating bi-stability in response to variable external voltages. The hysteresis in macroscopic currents dynamically changes when the time scale of the voltage variation is smaller or comparable to the characteristic conformational equilibration time, and unexpectedly persists for extremely slow-changing external voltage stimuli. The assay performed on a single lysenin channel reveals that hysteresis is a fundamental feature of the individual channel unit and an intrinsic component of the gating mechanism. The investigation conducted at different temperatures reveals a thermally stable reopening process, suggesting that major changes in the energy landscape and kinetics diagram accompany the conformational transitions of the channels. Our work offers new insights on the dynamics of pore-forming proteins and provides an understanding of how channel proteins may form an immediate record of the molecular history which then determines their future response to various stimuli. Such new functionalities may uncover a link between molecular events and macroscopic processing and transmission of information in cells, and may lead to applications such as high density biologically-compatible memories and learning networks.
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Affiliation(s)
- Daniel Fologea
- Department of Biological Sciences, University of Arkansas, Fayetteville, AR 72701, USA.
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25
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Asandei A, Mereuta L, Luchian T. The Kinetics of Ampicillin Complexation by γ-Cyclodextrins. A Single Molecule Approach. J Phys Chem B 2011; 115:10173-81. [DOI: 10.1021/jp204640t] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Alina Asandei
- Department of Physics, Laboratory of Molecular Biophysics and Medical Physics, “Alexandru I. Cuza” University, Boulevard Carol I, No. 11, Iasi 700506, Romania
| | - Loredana Mereuta
- Department of Physics, Laboratory of Molecular Biophysics and Medical Physics, “Alexandru I. Cuza” University, Boulevard Carol I, No. 11, Iasi 700506, Romania
| | - Tudor Luchian
- Department of Physics, Laboratory of Molecular Biophysics and Medical Physics, “Alexandru I. Cuza” University, Boulevard Carol I, No. 11, Iasi 700506, Romania
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