1
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Bunne C, Roohani Y, Rosen Y, Gupta A, Zhang X, Roed M, Alexandrov T, AlQuraishi M, Brennan P, Burkhardt DB, Califano A, Cool J, Dernburg AF, Ewing K, Fox EB, Haury M, Herr AE, Horvitz E, Hsu PD, Jain V, Johnson GR, Kalil T, Kelley DR, Kelley SO, Kreshuk A, Mitchison T, Otte S, Shendure J, Sofroniew NJ, Theis F, Theodoris CV, Upadhyayula S, Valer M, Wang B, Xing E, Yeung-Levy S, Zitnik M, Karaletsos T, Regev A, Lundberg E, Leskovec J, Quake SR. How to Build the Virtual Cell with Artificial Intelligence: Priorities and Opportunities. ARXIV 2024:arXiv:2409.11654v2. [PMID: 39398201 PMCID: PMC11468656] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Subscribe] [Scholar Register] [Indexed: 10/15/2024]
Abstract
The cell is arguably the most fundamental unit of life and is central to understanding biology. Accurate modeling of cells is important for this understanding as well as for determining the root causes of disease. Recent advances in artificial intelligence (AI), combined with the ability to generate large-scale experimental data, present novel opportunities to model cells. Here we propose a vision of leveraging advances in AI to construct virtual cells, high-fidelity simulations of cells and cellular systems under different conditions that are directly learned from biological data across measurements and scales. We discuss desired capabilities of such AI Virtual Cells, including generating universal representations of biological entities across scales, and facilitating interpretable in silico experiments to predict and understand their behavior using Virtual Instruments. We further address the challenges, opportunities and requirements to realize this vision including data needs, evaluation strategies, and community standards and engagement to ensure biological accuracy and broad utility. We envision a future where AI Virtual Cells help identify new drug targets, predict cellular responses to perturbations, as well as scale hypothesis exploration. With open science collaborations across the biomedical ecosystem that includes academia, philanthropy, and the biopharma and AI industries, a comprehensive predictive understanding of cell mechanisms and interactions has come into reach.
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Affiliation(s)
- Charlotte Bunne
- Department of Computer Science, Stanford University, Stanford, CA, USA
- Genentech, South San Francisco, CA, USA
- Chan Zuckerberg Initiative, Redwood City, CA, USA
- School of Computer and Communication Sciences and School of Life Sciences, EPFL, Lausanne, Switzerland
| | - Yusuf Roohani
- Department of Computer Science, Stanford University, Stanford, CA, USA
- Chan Zuckerberg Initiative, Redwood City, CA, USA
- Arc Institute, Palo Alto, CA, USA
| | - Yanay Rosen
- Department of Computer Science, Stanford University, Stanford, CA, USA
- Chan Zuckerberg Initiative, Redwood City, CA, USA
| | - Ankit Gupta
- Chan Zuckerberg Initiative, Redwood City, CA, USA
- KTH Royal Institute of Technology, Science for Life Laboratory, Department of Protein Science, Stockholm, Sweden
| | - Xikun Zhang
- Department of Computer Science, Stanford University, Stanford, CA, USA
- Chan Zuckerberg Initiative, Redwood City, CA, USA
- Department of Bioengineering, Stanford University, Stanford, CA, USA
| | - Marcel Roed
- Department of Computer Science, Stanford University, Stanford, CA, USA
- Chan Zuckerberg Initiative, Redwood City, CA, USA
| | - Theo Alexandrov
- Department of Pharmacology, University of California, San Diego, CA, USA
- Department of Bioengineering, University of California, San Diego, CA, USA
| | | | | | | | - Andrea Califano
- Department of Systems Biology, Columbia University, New York, NY, USA
- Vagelos College of Physicians and Surgeons, Columbia University Irving Medical Center, New York, NY, USA
- Chan Zuckerberg Biohub New York, NY, USA
| | - Jonah Cool
- Chan Zuckerberg Initiative, Redwood City, CA, USA
| | - Abby F Dernburg
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA
| | - Kirsty Ewing
- Chan Zuckerberg Initiative, Redwood City, CA, USA
| | - Emily B Fox
- Department of Computer Science, Stanford University, Stanford, CA, USA
- Department of Statistics, Stanford University, Stanford, CA, USA
- Chan Zuckerberg Biohub San Francisco, CA, USA
| | - Matthias Haury
- Chan Zuckerberg Institute for Advanced Biological Imaging, Redwood City, CA, USA
| | - Amy E Herr
- Chan Zuckerberg Biohub San Francisco, CA, USA
- Department of Bioengineering, University of California, Berkeley, CA, USA
| | | | - Patrick D Hsu
- Arc Institute, Palo Alto, CA, USA
- Department of Bioengineering, University of California, Berkeley, CA, USA
- Center for Computational Biology, University of California, Berkeley, Berkeley, CA, USA
| | | | | | | | | | - Shana O Kelley
- Chan Zuckerberg Biohub Chicago, IL, USA
- Northwestern University, Evanston, IL, USA
| | - Anna Kreshuk
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Tim Mitchison
- Department of Systems Biology, Harvard Medical School, Boston, MA, USA
| | - Stephani Otte
- Chan Zuckerberg Institute for Advanced Biological Imaging, Redwood City, CA, USA
| | - Jay Shendure
- Department of Genome Sciences, University of Washington, Seattle, WA, USA
- Brotman Baty Institute for Precision Medicine, Seattle, WA, USA
- Seattle Hub for Synthetic Biology, Seattle, WA, USA
- Howard Hughes Medical Institute, Seattle, WA, USA
| | | | - Fabian Theis
- Institute of Computational Biology, Helmholtz Center Munich, Munich, Germany
- School of Computing, Information and Technology, Technical University of Munich, Munich, Germany
- TUM School of Life Sciences Weihenstephan, Technical University of Munich, Munich, Germany
| | - Christina V Theodoris
- Gladstone Institute of Cardiovascular Disease, Gladstone Institute of Data Science and Biotechnology, San Francisco, CA, USA
- Department of Pediatrics, University of California, San Francisco, CA, USA
| | - Srigokul Upadhyayula
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA
- Chan Zuckerberg Biohub San Francisco, CA, USA
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Marc Valer
- Chan Zuckerberg Initiative, Redwood City, CA, USA
| | - Bo Wang
- Department of Computer Science, University of Toronto, Toronto, Ontario, Canada
- Vector Institute, Toronto, Ontario, Canada
| | - Eric Xing
- Carnegie Mellon University, School of Computer Science, Pittsburgh, PA, USA
- Mohamed Bin Zayed University of Artificial Intelligence, Abu Dhabi, United Arab Emirates
| | - Serena Yeung-Levy
- Department of Computer Science, Stanford University, Stanford, CA, USA
- Department of Biomedical Data Science, Stanford University, Stanford, CA, USA
| | - Marinka Zitnik
- Department of Biomedical Informatics, Harvard Medical School, Boston, MA, USA
- Kempner Institute for the Study of Natural and Artificial Intelligence, Harvard University, Cambridge, MA, USA
- Broad Institute of MIT and Harvard, Cambridge, MA, USA
| | | | | | - Emma Lundberg
- Chan Zuckerberg Initiative, Redwood City, CA, USA
- KTH Royal Institute of Technology, Science for Life Laboratory, Department of Protein Science, Stockholm, Sweden
- Department of Bioengineering, Stanford University, Stanford, CA, USA
- Department of Pathology, Stanford University, Stanford, CA, USA
| | - Jure Leskovec
- Department of Computer Science, Stanford University, Stanford, CA, USA
- Chan Zuckerberg Initiative, Redwood City, CA, USA
| | - Stephen R Quake
- Chan Zuckerberg Initiative, Redwood City, CA, USA
- Department of Bioengineering, Stanford University, Stanford, CA, USA
- Department of Applied Physics, Stanford University, Stanford, CA, USA
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2
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Xu C, Lu Y, Wu Y, Yuan S, Ma J, Fu H, Wang H, Wang L, Zhang H, Yu X, Tao W, Liu C, Hu S, Peng Y, Li W, Li Y, Lu Y, Li M. Sodium Ion-Induced Structural Transition on the Surface of a DNA-Interacting Protein. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2024:e2401838. [PMID: 39301861 DOI: 10.1002/advs.202401838] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2024] [Revised: 08/02/2024] [Indexed: 09/22/2024]
Abstract
Protein surfaces have pivotal roles in interactions between proteins and other biological molecules. However, the structural dynamics of protein surfaces have rarely been explored and are poorly understood. Here, the surface of a single-stranded DNA (ssDNA) binding protein (SSB) with four DNA binding domains that bind ssDNA in binding site sizes of 35, 56, and 65 nucleotides per tetramer is investigated. Using oligonucleotides as probes to sense the charged surface, NaCl induces a two-state structural transition on the SSB surface even at moderate concentrations. Chelation of sodium ions with charged amino acids alters the network of hydrogen bonds and/or salt bridges on the surface. Such changes are associated with changes in the electrostatic potential landscape and interaction mode. These findings advance the understanding of the molecular mechanism underlying the enigmatic salt-induced transitions between different DNA binding site sizes of SSBs. This work demonstrates that monovalent salt is a key regulator of biomolecular interactions that not only play roles in non-specific electrostatic screening effects as usually assumed but also may configure the surface of proteins to contribute to the effective regulation of biomolecular recognition and other downstream events.
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Affiliation(s)
- Chunhua Xu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong, 523808, China
| | - Yue Lu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Yichao Wu
- Wenzhou Key Laboratory of Biophysics, Wenzhou Institute, University of Chinese Academy of Sciences, Wenzhou, Zhejiang, 325000, China
- School of Physics, Nanjing University, Nanjing, 210093, China
| | - Shuaikang Yuan
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Jianbing Ma
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Hang Fu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Hao Wang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Libang Wang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Hao Zhang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Xuan Yu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Wei Tao
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Chang Liu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Shuxin Hu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong, 523808, China
| | - Yi Peng
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Wenfei Li
- Wenzhou Key Laboratory of Biophysics, Wenzhou Institute, University of Chinese Academy of Sciences, Wenzhou, Zhejiang, 325000, China
- School of Physics, Nanjing University, Nanjing, 210093, China
| | - Yunliang Li
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Ying Lu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong, 523808, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Ming Li
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong, 523808, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
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3
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Ando T, Fukuda S, Ngo KX, Flechsig H. High-Speed Atomic Force Microscopy for Filming Protein Molecules in Dynamic Action. Annu Rev Biophys 2024; 53:19-39. [PMID: 38060998 DOI: 10.1146/annurev-biophys-030722-113353] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/18/2024]
Abstract
Structural biology is currently undergoing a transformation into dynamic structural biology, which reveals the dynamic structure of proteins during their functional activity to better elucidate how they function. Among the various approaches in dynamic structural biology, high-speed atomic force microscopy (HS-AFM) is unique in the ability to film individual molecules in dynamic action, although only topographical information is acquirable. This review provides a guide to the use of HS-AFM for biomolecular imaging and showcases several examples, as well as providing information on up-to-date progress in HS-AFM technology. Finally, we discuss the future prospects of HS-AFM in the context of dynamic structural biology in the upcoming era.
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Affiliation(s)
- Toshio Ando
- Nano Life Science Institute (WPI-NanoLSI), Kanazawa University, Kanazawa, Japan;
| | - Shingo Fukuda
- Nano Life Science Institute (WPI-NanoLSI), Kanazawa University, Kanazawa, Japan;
| | - Kien X Ngo
- Nano Life Science Institute (WPI-NanoLSI), Kanazawa University, Kanazawa, Japan;
| | - Holger Flechsig
- Nano Life Science Institute (WPI-NanoLSI), Kanazawa University, Kanazawa, Japan;
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4
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Madariaga-Marcos J, Aldag P, Kauert DJ, Seidel R. Correlated Single-Molecule Magnetic Tweezers and Fluorescence Measurements of DNA-Enzyme Interactions. Methods Mol Biol 2024; 2694:421-449. [PMID: 37824016 DOI: 10.1007/978-1-0716-3377-9_20] [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: 10/13/2023]
Abstract
Combining force spectroscopy and fluorescence microscopy provides a substantial improvement to the single-molecule toolbox by allowing simultaneous manipulation and orthogonal characterizations of the conformations, interactions, and activity of biomolecular complexes. Here, we describe a combined magnetic tweezers and total internal reflection fluorescence microscopy setup to carry out correlated single-molecule fluorescence spectroscopy and force/twisting experiments. We apply the setup to reveal the DNA interactions of the CRISPR-Cas surveillance complex Cascade. Single-molecule fluorescence of a labeled Cascade allows to follow the DNA association and dissociation of the protein. Simultaneously, the magnetic tweezers probe the DNA unwinding during R-loop formation by the bound Cascade complexes. Furthermore, the setup supports observation of 1D diffusion of protein complexes on stretched DNA molecules. This technique can be applied to study a vast range of protein-DNA interactions.
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Affiliation(s)
- Julene Madariaga-Marcos
- Molecular Biophysics Group, Peter Debye Institute for Soft Matter Physics, Universität Leipzig, Leipzig, Germany
| | - Pierre Aldag
- Molecular Biophysics Group, Peter Debye Institute for Soft Matter Physics, Universität Leipzig, Leipzig, Germany
| | - Dominik J Kauert
- Molecular Biophysics Group, Peter Debye Institute for Soft Matter Physics, Universität Leipzig, Leipzig, Germany
| | - Ralf Seidel
- Molecular Biophysics Group, Peter Debye Institute for Soft Matter Physics, Universität Leipzig, Leipzig, Germany.
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5
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Biswas S, Mahdy MRC, Das SC, Bhuiyan MAI, Talukder MA. Controlling the counterintuitive optical repulsive thrust of nano dimers with counter propagating type waves and background medium. PLoS One 2023; 18:e0295679. [PMID: 38128032 PMCID: PMC10734998 DOI: 10.1371/journal.pone.0295679] [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: 07/29/2023] [Accepted: 11/28/2023] [Indexed: 12/23/2023] Open
Abstract
This work focuses on the utilization of counter-propagating plane waves for optical manipulation, which provides a unique approach to control the behavior of Rayleigh and Dipolar nanoparticles immersed in a homogeneous or heterogeneous medium. Our study presents an interesting finding of a repulsive force between plasmonic-chiral heterodimers where the particles move away from each other in both near and far field regions. Interestingly, this repulsive thrust supports the wave like nature of light for the case of homogeneous background but particle type nature of light for heterogenous background. At first, we have investigated the theory underlying the optical trapping of the chiral particle and the impact of this phenomenon on the overall repulsive behavior of the heterodimers placed in air (homogeneous) background. After that, our proposed set-up has further been investigated putting in air-water interface (heterogenous background) and by varying light angle only a little bit. Our observation for this interface case is suggesting the transfer of Minkowski momentum of photon to each optically pulled Rayleigh or dipolar particle of the dimer set, which ultimately causes a broad-band giant repulsive thrust of the dimers. However, in absence of the other particle in the cluster, a single half-immersed particle does not experience the pulling force for the broad-band spectrum. The 'common' reason of the observed repulsive thrust of the dimers for both the aforementioned cases has been attributed to "modified" longitudinal Optical Binding Force (OBF). Technically, this work may open a new way to control the repulsion and attraction between the nanoparticles both in near and far field regions by utilizing the background and the counter-propagating waves. We also believe that this work manifests a possible simple set-up, which will support to observe a background dependent wave 'or' particle nature of light experimentally.
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Affiliation(s)
- Sudipta Biswas
- Department of Electrical and Computer Engineering, Baylor University, Waco, Texas, United States of America
- Department of Electrical & Computer Engineering, North South University, Bashundhara, Dhaka, Bangladesh
| | - M. R. C. Mahdy
- Department of Electrical & Computer Engineering, North South University, Bashundhara, Dhaka, Bangladesh
| | - Saikat Chandra Das
- Department of Electrical & Computer Engineering, North South University, Bashundhara, Dhaka, Bangladesh
- Abbe School of Photonics, Friedrich Schiller University Jena, Jena, Germany
| | - Md. Ariful Islam Bhuiyan
- Department of Electrical & Computer Engineering, North South University, Bashundhara, Dhaka, Bangladesh
| | - Mohammad Abir Talukder
- Department of Electrical & Computer Engineering, North South University, Bashundhara, Dhaka, Bangladesh
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6
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Rassul SM, Otsu M, Styles IB, Neely RK, Fulton D. Single-molecule tracking of myelin basic protein during oligodendrocyte differentiation. BIOLOGICAL IMAGING 2023; 3:e24. [PMID: 38510175 PMCID: PMC10951920 DOI: 10.1017/s2633903x23000259] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Revised: 08/14/2023] [Accepted: 10/10/2023] [Indexed: 03/22/2024]
Abstract
This study aimed to expand our understanding of myelin basic protein (MBP), a key component of central nervous system myelin, by developing a protocol to track and quantifying individual MBP particles during oligodendrocyte (OL) differentiation. MBP particle directionality, confinement, and diffusion were tracked by rapid TIRF and HILO imaging of Dendra2 tagged MBP in three stages of mouse oligodendroglia: OL precursors, early myelinating OLs, and mature myelinating OLs. The directionality and confinement of MBP particles increased at each stage consistent with progressive transport toward, and recruitment into, emerging myelin structures. Unexpectedly, diffusion data presented a more complex pattern with subpopulations of the most diffusive particles disappearing at the transition between the precursor and early myelinating stage, before reemerging in the membrane sheets of mature OLs. This diversity of particle behaviors, which would be undetectable by conventional ensemble-averaged methods, are consistent with a multifunctional view of MBP involving roles in myelin expansion and compaction.
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Affiliation(s)
- Sayed M. Rassul
- Neuroscience and Ophthalmology Research Group, Institute of Inflammation and Ageing, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK
- Physical Sciences of Imaging in the Biomedical Sciences Training Programme, University of Birmingham, Birmingham, UK
| | - Masahiro Otsu
- Neuroscience and Ophthalmology Research Group, Institute of Inflammation and Ageing, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK
- Braizon Therapeutics, Inc., Kanagawa, Japan
| | - Iain B. Styles
- School of Electronics, Electrical Engineering and Computer Science, Queen’s University Belfast, Belfast, UK
| | - Robert K. Neely
- School of Chemistry, University of Birmingham, Birmingham, UK
| | - Daniel Fulton
- Neuroscience and Ophthalmology Research Group, Institute of Inflammation and Ageing, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK
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7
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Panigrahy M, Dua A. Molecular noise-induced activator-inhibitor duality in enzyme inhibition kinetics. J Chem Phys 2023; 159:155101. [PMID: 37843064 DOI: 10.1063/5.0152686] [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: 03/31/2023] [Accepted: 09/25/2023] [Indexed: 10/17/2023] Open
Abstract
Classical theories of enzyme inhibition kinetics predict a monotonic decrease in the mean catalytic activity with the increase in inhibitor concentration. The steady-state result, derived from deterministic mass action kinetics, ignores molecular noise in enzyme-inhibition mechanisms. Here, we present a stochastic generalization of enzyme inhibition kinetics to mesoscopic enzyme concentrations by systematically accounting for molecular noise in competitive and uncompetitive mechanisms of enzyme inhibition. Our work reveals an activator-inhibitor duality as a non-classical effect in the transient regime in which inhibitors tend to enhance enzymatic activity. We introduce statistical measures that quantify this counterintuitive response through the stochastic analog of the Lineweaver-Burk plot that shows a merging of the inhibitor-dependent velocity with the Michaelis-Menten velocity. The statistical measures of mean and temporal fluctuations - fractional enzyme activity and waiting time correlations - show a non-monotonic rise with the increase in inhibitors before subsiding to their baseline value. The inhibitor and substrate dependence of the fractional enzyme activity yields kinetic phase diagrams for non-classical activator-inhibitor duality. Our work links this duality to a molecular memory effect in the transient regime, arising from positive correlations between consecutive product turnover times. The vanishing of memory in the steady state recovers all the classical results.
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Affiliation(s)
- Manmath Panigrahy
- Department of Chemistry, Indian Institute of Technology, Madras, Chennai 600036, India
| | - Arti Dua
- Department of Chemistry, Indian Institute of Technology, Madras, Chennai 600036, India
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8
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Bustorff N, Fitter J. Features of Protein Unfolding Transitions and Their Relation to Domain Topology Probed by Single-Molecule FRET. Biomolecules 2023; 13:1280. [PMID: 37759680 PMCID: PMC10526189 DOI: 10.3390/biom13091280] [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] [Received: 06/28/2023] [Revised: 08/10/2023] [Accepted: 08/19/2023] [Indexed: 09/29/2023] Open
Abstract
A protein fold is defined as a structural arrangement of a secondary structure in a three-dimensional space. It would be interesting to know whether a particular fold can be assigned to certain features of the corresponding folding/unfolding transitions. To understand the underlying principles of the manifold folding transitions in more detail, single-molecule FRET is the method of choice. Taking the two-domain protein phosphoglycerate kinase (PGK) as an example, we investigated denaturant-induced unfolded states of PGK using the above method. For this purpose, different intramolecular distances within the two domains were measured. In addition to the known two-state transition, a transition with a compact folding intermediate was also identified in each of the two domains. Based on the structural homology of the domains (characterized by a Rossmann fold) and the striking similarity in the features of the measured distance changes during unfolding, clear evidence emerged that the underlying domain topology plays an important role in determining the observed structural changes.
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Affiliation(s)
- Nuno Bustorff
- ER-C-3 Structural Biology & IBI-6 Cellular Structural Biology, Forschungszentrum Jülich, 52425 Jülich, Germany;
| | - Jörg Fitter
- ER-C-3 Structural Biology & IBI-6 Cellular Structural Biology, Forschungszentrum Jülich, 52425 Jülich, Germany;
- AG Biophysik, I. Physikalisches Institut (IA), RWTH Aachen University, 52074 Aachen, Germany
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9
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Haghizadeh A, Iftikhar M, Dandpat SS, Simpson T. Looking at Biomolecular Interactions through the Lens of Correlated Fluorescence Microscopy and Optical Tweezers. Int J Mol Sci 2023; 24:2668. [PMID: 36768987 PMCID: PMC9916863 DOI: 10.3390/ijms24032668] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Revised: 12/19/2022] [Accepted: 01/26/2023] [Indexed: 02/01/2023] Open
Abstract
Understanding complex biological events at the molecular level paves the path to determine mechanistic processes across the timescale necessary for breakthrough discoveries. While various conventional biophysical methods provide some information for understanding biological systems, they often lack a complete picture of the molecular-level details of such dynamic processes. Studies at the single-molecule level have emerged to provide crucial missing links to understanding complex and dynamic pathways in biological systems, which are often superseded by bulk biophysical and biochemical studies. Latest developments in techniques combining single-molecule manipulation tools such as optical tweezers and visualization tools such as fluorescence or label-free microscopy have enabled the investigation of complex and dynamic biomolecular interactions at the single-molecule level. In this review, we present recent advances using correlated single-molecule manipulation and visualization-based approaches to obtain a more advanced understanding of the pathways for fundamental biological processes, and how this combination technique is facilitating research in the dynamic single-molecule (DSM), cell biology, and nanomaterials fields.
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10
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Singh D, Punia B, Chaudhury S. Theoretical Tools to Quantify Stochastic Fluctuations in Single-Molecule Catalysis by Enzymes and Nanoparticles. ACS OMEGA 2022; 7:47587-47600. [PMID: 36591158 PMCID: PMC9798497 DOI: 10.1021/acsomega.2c06316] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Accepted: 12/02/2022] [Indexed: 06/11/2023]
Abstract
Single-molecule microscopic techniques allow the counting of successive turnover events and the study of the time-dependent fluctuations of the catalytic activities of individual enzymes and different sites on a single heterogeneous nanocatalyst. It is important to establish theoretical methods to obtain the statistical measurements of such stochastic fluctuations that provide insight into the catalytic mechanism. In this review, we discuss a few theoretical frameworks for evaluating the first passage time distribution functions using a self-consistent pathway approach and chemical master equations, to establish a connection with experimental observables. The measurable probability distribution functions and their moments depend on the molecular details of the reaction and provide a way to quantify the molecular mechanisms of the reaction process. The statistical measurements of these fluctuations should provide insight into the enzymatic mechanism.
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Affiliation(s)
- Divya Singh
- School
of Chemistry, Tel Aviv University, Tel Aviv6997801, Israel
| | - Bhawakshi Punia
- Department
of Chemistry, Indian Institute of Science
Education and Research, Dr. Homi Bhabha Road, Pune411008, Maharashtra, India
| | - Srabanti Chaudhury
- Department
of Chemistry, Indian Institute of Science
Education and Research, Dr. Homi Bhabha Road, Pune411008, Maharashtra, India
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11
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Percolation physics and density transition frameworks converge in biomolecular condensation. Proc Natl Acad Sci U S A 2022; 119:e2210177119. [PMID: 35921445 PMCID: PMC9371638 DOI: 10.1073/pnas.2210177119] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
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12
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Rahman M, Islam KR, Islam MR, Islam MJ, Kaysir MR, Akter M, Rahman MA, Alam SMM. A Critical Review on the Sensing, Control, and Manipulation of Single Molecules on Optofluidic Devices. MICROMACHINES 2022; 13:968. [PMID: 35744582 PMCID: PMC9229244 DOI: 10.3390/mi13060968] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/24/2022] [Revised: 05/19/2022] [Accepted: 05/23/2022] [Indexed: 02/06/2023]
Abstract
Single-molecule techniques have shifted the paradigm of biological measurements from ensemble measurements to probing individual molecules and propelled a rapid revolution in related fields. Compared to ensemble measurements of biomolecules, single-molecule techniques provide a breadth of information with a high spatial and temporal resolution at the molecular level. Usually, optical and electrical methods are two commonly employed methods for probing single molecules, and some platforms even offer the integration of these two methods such as optofluidics. The recent spark in technological advancement and the tremendous leap in fabrication techniques, microfluidics, and integrated optofluidics are paving the way toward low cost, chip-scale, portable, and point-of-care diagnostic and single-molecule analysis tools. This review provides the fundamentals and overview of commonly employed single-molecule methods including optical methods, electrical methods, force-based methods, combinatorial integrated methods, etc. In most single-molecule experiments, the ability to manipulate and exercise precise control over individual molecules plays a vital role, which sometimes defines the capabilities and limits of the operation. This review discusses different manipulation techniques including sorting and trapping individual particles. An insight into the control of single molecules is provided that mainly discusses the recent development of electrical control over single molecules. Overall, this review is designed to provide the fundamentals and recent advancements in different single-molecule techniques and their applications, with a special focus on the detection, manipulation, and control of single molecules on chip-scale devices.
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Affiliation(s)
- Mahmudur Rahman
- Department of Electrical and Electronic Engineering, Dhaka University of Engineering & Technology, Gazipur 1707, Bangladesh; (M.R.); (K.R.I.); (M.R.I.); (M.A.); (M.A.R.)
| | - Kazi Rafiqul Islam
- Department of Electrical and Electronic Engineering, Dhaka University of Engineering & Technology, Gazipur 1707, Bangladesh; (M.R.); (K.R.I.); (M.R.I.); (M.A.); (M.A.R.)
| | - Md. Rashedul Islam
- Department of Electrical and Electronic Engineering, Dhaka University of Engineering & Technology, Gazipur 1707, Bangladesh; (M.R.); (K.R.I.); (M.R.I.); (M.A.); (M.A.R.)
| | - Md. Jahirul Islam
- Department of Electrical and Electronic Engineering, Khulna University of Engineering & Technology, Khulna 9203, Bangladesh;
| | - Md. Rejvi Kaysir
- Department of Electrical and Computer Engineering, University of Waterloo, 200 University Ave. W, Waterloo, ON N2L 3G1, Canada;
- Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Ave. W, Waterloo, ON N2L 3G1, Canada
| | - Masuma Akter
- Department of Electrical and Electronic Engineering, Dhaka University of Engineering & Technology, Gazipur 1707, Bangladesh; (M.R.); (K.R.I.); (M.R.I.); (M.A.); (M.A.R.)
| | - Md. Arifur Rahman
- Department of Electrical and Electronic Engineering, Dhaka University of Engineering & Technology, Gazipur 1707, Bangladesh; (M.R.); (K.R.I.); (M.R.I.); (M.A.); (M.A.R.)
| | - S. M. Mahfuz Alam
- Department of Electrical and Electronic Engineering, Dhaka University of Engineering & Technology, Gazipur 1707, Bangladesh; (M.R.); (K.R.I.); (M.R.I.); (M.A.); (M.A.R.)
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13
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Wang L, Wang H, Chen X, Zhou S, Wang Y, Guan X. Chemistry solutions to facilitate nanopore detection and analysis. Biosens Bioelectron 2022; 213:114448. [PMID: 35716643 DOI: 10.1016/j.bios.2022.114448] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2022] [Revised: 05/24/2022] [Accepted: 05/30/2022] [Indexed: 11/29/2022]
Abstract
Characteristic ionic current modulations will be produced in a single molecule manner during the communication of individual molecules with a nanopore. Hence, the information regarding the length, composition, and structure of a molecule can be extracted from deciphering the electrical message. However, until now, achieving a satisfactory resolution for observation and quantification of a target analyte in a complex system remains a nontrivial task. In this review, we summarize the progress and especially the recent advance in utilizing chemistry solutions to facilitate nanopore detection and analysis. The discussed chemistry solutions are classified into several major categories, including covalent/non-covalent chemistry, redox chemistry, displacement chemistry, back titration chemistry, chelation chemistry, hydrolysis-chemistry, and click chemistry. Considering the significant success of using chemical reaction-assisted nanopore sensing strategies to improve sensor sensitivity & selectivity and to study various topics, other non-chemistry based methodologies can undoubtedly be employed by nanopore sensors to explore new applications in the interdisciplinary area of chemistry, biology, materials, and nanotechnology.
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Affiliation(s)
- Liang Wang
- Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing, 400714, China; Chongqing School, University of Chinese Academy of Sciences, Chongqing, 400714, China
| | - Han Wang
- Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing, 400714, China; Chongqing School, University of Chinese Academy of Sciences, Chongqing, 400714, China
| | - Xiaohan Chen
- Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing, 400714, China; Chongqing School, University of Chinese Academy of Sciences, Chongqing, 400714, China
| | - Shuo Zhou
- Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing, 400714, China; Chongqing School, University of Chinese Academy of Sciences, Chongqing, 400714, China
| | - Yunjiao Wang
- Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing, 400714, China; Chongqing School, University of Chinese Academy of Sciences, Chongqing, 400714, China.
| | - Xiyun Guan
- Department of Chemistry, Illinois Institute of Technology, Chicago, IL, 60616, USA.
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14
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Severins I, Joo C, van Noort J. Exploring molecular biology in sequence space: The road to next-generation single-molecule biophysics. Mol Cell 2022; 82:1788-1805. [PMID: 35561688 DOI: 10.1016/j.molcel.2022.04.024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Revised: 04/11/2022] [Accepted: 04/19/2022] [Indexed: 10/18/2022]
Abstract
Next-generation sequencing techniques have led to a new quantitative dimension in the biological sciences. In particular, integrating sequencing techniques with biophysical tools allows sequence-dependent mechanistic studies. Using the millions of DNA clusters that are generated during sequencing to perform high-throughput binding affinity and kinetics measurements enabled the construction of energy landscapes in sequence space, uncovering relationships between sequence, structure, and function. Here, we review the approaches to perform ensemble fluorescence experiments on next-generation sequencing chips for variations of DNA, RNA, and protein sequences. As the next step, we anticipate that these fluorescence experiments will be pushed to the single-molecule level, which can directly uncover kinetics and molecular heterogeneity in an unprecedented high-throughput fashion. Molecular biophysics in sequence space, both at the ensemble and single-molecule level, leads to new mechanistic insights. The wide spectrum of applications in biology and medicine ranges from the fundamental understanding of evolutionary pathways to the development of new therapeutics.
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Affiliation(s)
- Ivo Severins
- Department of BioNanoScience, Kavli Institute of Nanoscience, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, the Netherlands; Biological and Soft Matter Physics, Huygens-Kamerlingh Onnes Laboratory, Leiden University, Niels Bohrweg 2, 2333 CA Leiden, the Netherlands
| | - Chirlmin Joo
- Department of BioNanoScience, Kavli Institute of Nanoscience, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, the Netherlands.
| | - John van Noort
- Biological and Soft Matter Physics, Huygens-Kamerlingh Onnes Laboratory, Leiden University, Niels Bohrweg 2, 2333 CA Leiden, the Netherlands.
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15
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Adhikari S, Orrit M. Progress and perspectives in single-molecule optical spectroscopy. J Chem Phys 2022; 156:160903. [PMID: 35489995 DOI: 10.1063/5.0087003] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We review some of the progress of single-molecule optical experiments in the past 20 years and propose some perspectives for the coming years. We particularly focus on methodological advances in fluorescence, super-resolution, photothermal contrast, and interferometric scattering and briefly discuss a few of the applications. These advances have enabled the exploration of new emitters and quantum optics; the chemistry and biology of complex heterogeneous systems, nanoparticles, and plasmonics; and the detection and study of non-fluorescing and non-absorbing nano-objects. We conclude by proposing some ideas for future experiments. The field will move toward more and better signals of a broader variety of objects and toward a sharper view of the surprising complexity of the nanoscale world of single (bio-)molecules, nanoparticles, and their nano-environments.
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Affiliation(s)
- Subhasis Adhikari
- Huygens-Kamerlingh Onnes Laboratory, Leiden University, P.O. Box 9504, 2333 CA Leiden, The Netherlands
| | - Michel Orrit
- Huygens-Kamerlingh Onnes Laboratory, Leiden University, P.O. Box 9504, 2333 CA Leiden, The Netherlands
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16
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Baranwal J, Barse B, Fais A, Delogu GL, Kumar A. Biopolymer: A Sustainable Material for Food and Medical Applications. Polymers (Basel) 2022; 14:983. [PMID: 35267803 PMCID: PMC8912672 DOI: 10.3390/polym14050983] [Citation(s) in RCA: 125] [Impact Index Per Article: 62.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Revised: 02/23/2022] [Accepted: 02/26/2022] [Indexed: 02/06/2023] Open
Abstract
Biopolymers are a leading class of functional material suitable for high-value applications and are of great interest to researchers and professionals across various disciplines. Interdisciplinary research is important to understand the basic and applied aspects of biopolymers to address several complex problems associated with good health and well-being. To reduce the environmental impact and dependence on fossil fuels, a lot of effort has gone into replacing synthetic polymers with biodegradable materials, especially those derived from natural resources. In this regard, many types of natural or biopolymers have been developed to meet the needs of ever-expanding applications. These biopolymers are currently used in food applications and are expanding their use in the pharmaceutical and medical industries due to their unique properties. This review focuses on the various uses of biopolymers in the food and medical industry and provides a future outlook for the biopolymer industry.
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Affiliation(s)
- Jaya Baranwal
- DBT-ICGEB Centre for Advanced Bioenergy Research, International Centre for Genetic Engineering & Biotechnology, Aruna Asaf Ali Marg, New Delhi 110067, India; (J.B.); (B.B.)
| | - Brajesh Barse
- DBT-ICGEB Centre for Advanced Bioenergy Research, International Centre for Genetic Engineering & Biotechnology, Aruna Asaf Ali Marg, New Delhi 110067, India; (J.B.); (B.B.)
| | - Antonella Fais
- Department of Life and Environmental Sciences, University of Cagliari, Monserrato, 09042 Cagliari, Italy; (A.F.); (G.L.D.)
| | - Giovanna Lucia Delogu
- Department of Life and Environmental Sciences, University of Cagliari, Monserrato, 09042 Cagliari, Italy; (A.F.); (G.L.D.)
| | - Amit Kumar
- Department of Electrical and Electronic Engineering, University of Cagliari, Via Marengo 2, 09123 Cagliari, Italy
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17
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Poon GMK. The Non-continuum Nature of Eukaryotic Transcriptional Regulation. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2022; 1371:11-32. [PMID: 33616894 PMCID: PMC8380751 DOI: 10.1007/5584_2021_618] [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: 08/25/2024]
Abstract
Eukaryotic transcription factors are versatile mediators of specificity in gene regulation. This versatility is achieved through mutual specification by context-specific DNA binding on the one hand, and identity-specific protein-protein partnerships on the other. This interactivity, known as combinatorial control, enables a repertoire of complex transcriptional outputs that are qualitatively disjoint, or non-continuum, with respect to binding affinity. This feature contrasts starkly with prokaryotic gene regulators, whose activities in general vary quantitatively in step with binding affinity. Biophysical studies on prokaryotic model systems and more recent investigations on transcription factors highlight an important role for folded state dynamics and molecular hydration in protein/DNA recognition. Analysis of molecular models of combinatorial control and recent literature in low-affinity gene regulation suggest that transcription factors harbor unique conformational dynamics that are inaccessible or unused by prokaryotic DNA-binding proteins. Thus, understanding the intrinsic dynamics involved in DNA binding and co-regulator recruitment appears to be a key to understanding how transcription factors mediate non-continuum outcomes in eukaryotic gene expression, and how such capability might have evolved from ancient, structurally conserved counterparts.
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Affiliation(s)
- Gregory M K Poon
- Department of Chemistry, Georgia State University, Atlanta, GA, USA.
- Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA, USA.
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18
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Abstract
Molecular assembly in a complex cellular environment is vital for understanding underlying biological mechanisms. Biophysical parameters (such as single-molecule cluster density, cluster-area, pairwise distance, and number of molecules per cluster) related to molecular clusters directly associate with the physiological state (healthy/diseased) of a cell. Using super-resolution imaging along with powerful clustering methods (K-means, Gaussian mixture, and point clustering), we estimated these critical biophysical parameters associated with dense and sparse molecular clusters. We investigated Hemaglutinin (HA) molecules in an Influenza type A disease model. Subsequently, clustering parameters were estimated for transfected NIH3T3 cells. Investigations on test sample (randomly generated clusters) and NIH3T3 cells (expressing Dendra2-Hemaglutinin (Dendra2-HA) photoactivable molecules) show a significant disparity among the existing clustering techniques. It is observed that a single method is inadequate for estimating all relevant biophysical parameters accurately. Thus, a multimodel approach is necessary in order to characterize molecular clusters and determine critical parameters. The proposed study involving optical system development, photoactivable sample synthesis, and advanced clustering methods may facilitate a better understanding of single molecular clusters. Potential applications are in the emerging field of cell biology, biophysics, and fluorescence imaging.
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19
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Cao F, Li Y, Wu J, Liu W, Ngai T. Measurements of interactions between fluorescent molecules and polyethylene glycol self-assembled monolayers. SOFT MATTER 2021; 18:236-243. [PMID: 34874390 DOI: 10.1039/d1sm01329g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Blocking the non-specific binding of fluorescent biomolecules to substrates is one of the most important approaches to minimize the background noise in single-molecule fluorescence detection. Polyethylene glycol (PEG) and its derivatives are the most frequently used self-assembled monolayers (SAMs) for surface passivation because they are particularly effective to reduce the adsorption of a majority of biomolecules. Most studies related to PEG SAMs focus only on the interactions between biomolecules and substrates, while few reports exist in which the interactions between fluorophores and organosilane SAMs are directly examined. The objective of this study is to try to clarify the interactions between fluorescein isothiocyanate (FITC) and PEG SAMs at different ionic strengths. Total internal reflection microscopy (TIRM) was utilized for quantitative analysis of the interactions. At low ionic strength, long-range attractions between FITC-modified polystyrene-silica particles and PEG SAM grafting substrates were observed, even though both of them had an ensemble-averaged negative charge. The origin of this attraction could be correlated to their nonuniformly charged surfaces. At high ionic strength, van der Waals attraction at short distances was measured as the electrostatic interactions were completely screened. Due to the polarizability of the FITC molecule, the van der Waals attractions increased with the thickness of the PEG SAMs. This phenomenon is explained by the hydration shell of the PEG SAMs.
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Affiliation(s)
- Feng Cao
- Department of Chemistry, The Chinese University of Hong Kong, N.T., Shatin, Hong Kong, China.
| | - Yinan Li
- Department of Chemistry, The Chinese University of Hong Kong, N.T., Shatin, Hong Kong, China.
| | - Jiahao Wu
- Department of Chemistry, The Chinese University of Hong Kong, N.T., Shatin, Hong Kong, China.
| | - Wei Liu
- Department of Chemistry, The Chinese University of Hong Kong, N.T., Shatin, Hong Kong, China.
| | - To Ngai
- Department of Chemistry, The Chinese University of Hong Kong, N.T., Shatin, Hong Kong, China.
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20
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Zuckerman DM, Russo JD. A gentle introduction to the non-equilibrium physics of trajectories: Theory, algorithms, and biomolecular applications. AMERICAN JOURNAL OF PHYSICS 2021; 89:1048-1061. [PMID: 35530173 PMCID: PMC9075726 DOI: 10.1119/10.0005603] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Accepted: 06/25/2021] [Indexed: 06/14/2023]
Abstract
Despite the importance of non-equilibrium statistical mechanics in modern physics and related fields, the topic is often omitted from undergraduate and core-graduate curricula. Key aspects of non-equilibrium physics, however, can be understood with a minimum of formalism based on a rigorous trajectory picture. The fundamental object is the ensemble of trajectories, a set of independent time-evolving systems, which easily can be visualized or simulated (e.g., for protein folding) and which can be analyzed rigorously in analogy to an ensemble of static system configurations. The trajectory picture provides a straightforward basis for understanding first-passage times, "mechanisms" in complex systems, and fundamental constraints on the apparent reversibility of complex processes. Trajectories make concrete the physics underlying the diffusion and Fokker-Planck partial differential equations. Last but not least, trajectory ensembles underpin some of the most important algorithms that have provided significant advances in biomolecular studies of protein conformational and binding processes.
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21
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Marenda M, Lazarova E, van de Linde S, Gilbert N, Michieletto D. Parameter-free molecular super-structures quantification in single-molecule localization microscopy. J Cell Biol 2021; 220:211893. [PMID: 33734291 PMCID: PMC7980255 DOI: 10.1083/jcb.202010003] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Revised: 01/06/2021] [Accepted: 02/23/2021] [Indexed: 12/18/2022] Open
Abstract
Understanding biological function requires the identification and characterization of complex patterns of molecules. Single-molecule localization microscopy (SMLM) can quantitatively measure molecular components and interactions at resolutions far beyond the diffraction limit, but this information is only useful if these patterns can be quantified and interpreted. We provide a new approach for the analysis of SMLM data that develops the concept of structures and super-structures formed by interconnected elements, such as smaller protein clusters. Using a formal framework and a parameter-free algorithm, (super-)structures formed from smaller components are found to be abundant in classes of nuclear proteins, such as heterogeneous nuclear ribonucleoprotein particles (hnRNPs), but are absent from ceramides located in the plasma membrane. We suggest that mesoscopic structures formed by interconnected protein clusters are common within the nucleus and have an important role in the organization and function of the genome. Our algorithm, SuperStructure, can be used to analyze and explore complex SMLM data and extract functionally relevant information.
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Affiliation(s)
- Mattia Marenda
- Medical Research Council Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh, UK.,Scottish Universities Physics Alliance, School of Physics and Astronomy, University of Edinburgh, Edinburgh, UK
| | - Elena Lazarova
- Medical Research Council Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh, UK
| | - Sebastian van de Linde
- Scottish Universities Physics Alliance, Department of Physics, University of Strathclyde, Glasgow, UK
| | - Nick Gilbert
- Medical Research Council Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh, UK
| | - Davide Michieletto
- Medical Research Council Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh, UK.,Scottish Universities Physics Alliance, School of Physics and Astronomy, University of Edinburgh, Edinburgh, UK
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22
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Bandyopadhyay D, Mishra PP. Decoding the Structural Dynamics and Conformational Alternations of DNA Secondary Structures by Single-Molecule FRET Microspectroscopy. Front Mol Biosci 2021; 8:725541. [PMID: 34540899 PMCID: PMC8446445 DOI: 10.3389/fmolb.2021.725541] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Accepted: 07/30/2021] [Indexed: 12/02/2022] Open
Abstract
In addition to the canonical double helix form, DNA is known to be extrapolated into several other secondary structural patterns involving themselves in inter- and intramolecular type hydrogen bonding. The secondary structures of nucleic acids go through several stages of multiple, complex, and interconvertible heterogeneous conformations. The journey of DNA through these conformers has significant importance and has been monitored thoroughly to establish qualitative and quantitative information about the transition between the unfolded, folded, misfolded, and partially folded states. During this structural interconversion, there always exist specific populations of intermediates, which are short-lived or sometimes even do not accumulate within a heterogeneous population and are challenging to characterize using conventional ensemble techniques. The single-molecule FRET(sm-FRET) microspectroscopic method has the advantages to overcome these limitations and monitors biological phenomena transpiring at a measurable high rate and balanced stochastically over time. Thus, tracing the time trajectory of a particular molecule enables direct measurement of the rate constant of each transition step, including the intermediates that are hidden in the ensemble level due to their low concentrations. This review is focused on the advantages of the employment of single-molecule Forster's resonance energy transfer (sm-FRET), which is worthwhile to access the dynamic architecture and structural transition of various secondary structures that DNA adopts, without letting the donor of one molecule to cross-talk with the acceptor of any other. We have emphasized the studies performed to explore the states of folding and unfolding of several nucleic acid secondary structures, for example, the DNA hairpin, Holliday junction, G-quadruplex, and i-motif.
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Affiliation(s)
- Debolina Bandyopadhyay
- Single-Molecule Biophysics Lab, Chemical Sciences Division, Saha Institute of Nuclear Physics, Kolkata, India
- HBNI, Mumbai, India
| | - Padmaja P. Mishra
- Single-Molecule Biophysics Lab, Chemical Sciences Division, Saha Institute of Nuclear Physics, Kolkata, India
- HBNI, Mumbai, India
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23
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Robertson JW, Ghimire M, Reiner JE. Nanopore sensing: A physical-chemical approach. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2021; 1863:183644. [PMID: 33989531 PMCID: PMC9793329 DOI: 10.1016/j.bbamem.2021.183644] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 04/22/2021] [Accepted: 04/26/2021] [Indexed: 12/30/2022]
Abstract
Protein nanopores have emerged as an important class of sensors for the understanding of biophysical processes, such as molecular transport across membranes, and for the detection and characterization of biopolymers. Here, we trace the development of these sensors from the Coulter counter and squid axon studies to the modern applications including exquisite detection of small volume changes and molecular reactions at the single molecule (or reactant) scale. This review focuses on the chemistry of biological pores, and how that influences the physical chemistry of molecular detection.
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Affiliation(s)
- Joseph W.F. Robertson
- Biophysical and Biomedical Measurement Group, Microsystems and Nanotechnology Division, Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg MD. 20899, correspondence to:
| | - Madhav Ghimire
- Department of Physics, Virginia Commonwealth University, Richmond, VA
| | - Joseph E. Reiner
- Department of Physics, Virginia Commonwealth University, Richmond, VA
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24
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Rahman M, Sampad MJN, Hawkins A, Schmidt H. Recent advances in integrated solid-state nanopore sensors. LAB ON A CHIP 2021; 21:3030-3052. [PMID: 34137407 PMCID: PMC8372664 DOI: 10.1039/d1lc00294e] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
The advent of single-molecule probing techniques has revolutionized the biomedical and life science fields and has spurred the development of a new class of labs-on-chip based on powerful biosensors. Nanopores represent one of the most recent and most promising single molecule sensing paradigms that is seeing increased chip-scale integration for improved convenience and performance. Due to their physical structure, nanopores are highly sensitive, require low sample volume, and offer label-free, amplification-free, high-throughput real-time detection and identification of biomolecules. Over the last 25 years, nanopores have been extensively employed to detect a variety of biomolecules with a growing range of applicatons ranging from nucleic acid sequencing to ultrasensitive diagnostics to single-molecule biophysics. Nanopores, in particular those in solid-state membranes, also have the potential for integration with other technologies such as optics, plasmonics, microfluidics, and optofluidics to perform more complex tasks for an ever-expanding demand. A number of breakthrough results using integrated nanopore platforms have already been reported, and more can be expected as nanopores remain the focus of innovative research and are finding their way into commercial instruments. This review provides an overview of different aspects and challenges of nanopore technology with a focus on chip-scale integration of solid-state nanopores for biosensing and bioanalytical applications.
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Affiliation(s)
- Mahmudur Rahman
- School of Engineering, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA, 95064 USA. and Dhaka University of Engineering & Technology, Gazipur, Bangladesh
| | | | - Aaron Hawkins
- ECEn Department, Brigham Young University, 459 Clyde Building, Provo, UT, 84602 USA
| | - Holger Schmidt
- School of Engineering, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA, 95064 USA.
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25
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Mondal B, Thirumalai D, Reddy G. Energy Landscape of Ubiquitin Is Weakly Multidimensional. J Phys Chem B 2021; 125:8682-8689. [PMID: 34319720 DOI: 10.1021/acs.jpcb.1c02762] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Single molecule pulling experiments report time-dependent changes in the extension (X) of a biomolecule as a function of the applied force (f). By fitting the data to one-dimensional analytical models of the energy landscape, we can extract the hopping rates between the folded and unfolded states in two-state folders as well as the height and the location of the transition state (TS). Although this approach is remarkably insightful, there are cases for which the energy landscape is multidimensional (catch bonds being the most prominent). To assess if the unfolding energy landscape in small single domain proteins could be one-dimensional, we simulated force-induced unfolding of ubiquitin (Ub) using the coarse-grained self-organized polymer-side chain (SOP-SC) model. Brownian dynamics simulations using the SOP-SC model reveal that the Ub energy landscape is weakly multidimensional (WMD), governed predominantly by a single barrier. The unfolding pathway is confined to a narrow reaction pathway that could be described as diffusion in a quasi-1D X-dependent free energy profile. However, a granular analysis using the Pfold analysis, which does not assume any form for the reaction coordinate, shows that X alone does not account for the height and, more importantly, the location of the TS. The f-dependent TS location moves toward the folded state as f increases, in accord with the Hammond postulate. Our study shows that, in addition to analyzing the f-dependent hopping rates, the transition state ensemble must also be determined without resorting to X as a reaction coordinate to describe the unfolding energy landscapes of single domain proteins, especially if they are only WMD.
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Affiliation(s)
- Balaka Mondal
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bengaluru, Karnataka 560012, India
| | - D Thirumalai
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States
| | - Govardhan Reddy
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bengaluru, Karnataka 560012, India
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Niina T, Matsunaga Y, Takada S. Rigid-body fitting to atomic force microscopy images for inferring probe shape and biomolecular structure. PLoS Comput Biol 2021; 17:e1009215. [PMID: 34283829 PMCID: PMC8323932 DOI: 10.1371/journal.pcbi.1009215] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2021] [Revised: 07/30/2021] [Accepted: 06/26/2021] [Indexed: 12/01/2022] Open
Abstract
Atomic force microscopy (AFM) can visualize functional biomolecules near the physiological condition, but the observed data are limited to the surface height of specimens. Since the AFM images highly depend on the probe tip shape, for successful inference of molecular structures from the measurement, the knowledge of the probe shape is required, but is often missing. Here, we developed a method of the rigid-body fitting to AFM images, which simultaneously finds the shape of the probe tip and the placement of the molecular structure via an exhaustive search. First, we examined four similarity scores via twin-experiments for four test proteins, finding that the cosine similarity score generally worked best, whereas the pixel-RMSD and the correlation coefficient were also useful. We then applied the method to two experimental high-speed-AFM images inferring the probe shape and the molecular placement. The results suggest that the appropriate similarity score can differ between target systems. For an actin filament image, the cosine similarity apparently worked best. For an image of the flagellar protein FlhAC, we found the correlation coefficient gave better results. This difference may partly be attributed to the flexibility in the target molecule, ignored in the rigid-body fitting. The inferred tip shape and placement results can be further refined by other methods, such as the flexible fitting molecular dynamics simulations. The developed software is publicly available. Observation of functional dynamics of individual biomolecules is important to understand molecular mechanisms of cellular phenomena. High-speed (HS) atomic force microscopy (AFM) is a powerful tool that enables us to visualize the real-time dynamics of working biomolecules under near-physiological conditions. However, the information available by the AFM images is limited to the two-dimensional surface shape detected via the force to the probe. While the surface information is affected by the shape of the probe tip, the probe shape itself cannot be directly measured before each AFM measurement. To overcome this problem, we have developed a computational method to simultaneously infer the probe tip shape and the molecular placement from an AFM image. We show that our method successfully estimates the effective AFM tip shape and visualizes a structure with a more accurate placement. The estimation of a molecular placement with the correct probe tip shape enables us to obtain more insights into functional dynamics of the molecule from HS-AFM images.
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Affiliation(s)
- Toru Niina
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto, Japan
| | - Yasuhiro Matsunaga
- Graduate School of Science and Engineering, Saitama University, Saitama, Japan
| | - Shoji Takada
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto, Japan
- * E-mail:
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27
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Marenda M, Lazarova E, van de Linde S, Gilbert N, Michieletto D. Parameter-free molecular super-structures quantification in single-molecule localization microscopy. J Cell Biol 2021. [PMID: 33734291 DOI: 10.1101/2020.08.19.254540] [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] [Indexed: 05/12/2023] Open
Abstract
Understanding biological function requires the identification and characterization of complex patterns of molecules. Single-molecule localization microscopy (SMLM) can quantitatively measure molecular components and interactions at resolutions far beyond the diffraction limit, but this information is only useful if these patterns can be quantified and interpreted. We provide a new approach for the analysis of SMLM data that develops the concept of structures and super-structures formed by interconnected elements, such as smaller protein clusters. Using a formal framework and a parameter-free algorithm, (super-)structures formed from smaller components are found to be abundant in classes of nuclear proteins, such as heterogeneous nuclear ribonucleoprotein particles (hnRNPs), but are absent from ceramides located in the plasma membrane. We suggest that mesoscopic structures formed by interconnected protein clusters are common within the nucleus and have an important role in the organization and function of the genome. Our algorithm, SuperStructure, can be used to analyze and explore complex SMLM data and extract functionally relevant information.
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Affiliation(s)
- Mattia Marenda
- Medical Research Council Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh, UK
- Scottish Universities Physics Alliance, School of Physics and Astronomy, University of Edinburgh, Edinburgh, UK
| | - Elena Lazarova
- Medical Research Council Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh, UK
| | - Sebastian van de Linde
- Scottish Universities Physics Alliance, Department of Physics, University of Strathclyde, Glasgow, UK
| | - Nick Gilbert
- Medical Research Council Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh, UK
| | - Davide Michieletto
- Medical Research Council Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh, UK
- Scottish Universities Physics Alliance, School of Physics and Astronomy, University of Edinburgh, Edinburgh, UK
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28
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Chen Z, Wei W, Peng H, Jiang H, Xiong B, Zhu J. Revealing the dynamic adsorption and diffusion of peptide amphiphile on supported lipid bilayer by single molecule experiment and simulation. Colloids Surf B Biointerfaces 2021; 204:111809. [PMID: 33965750 DOI: 10.1016/j.colsurfb.2021.111809] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Revised: 04/21/2021] [Accepted: 04/27/2021] [Indexed: 10/21/2022]
Abstract
Dynamic adsorption and diffusion of peptide amphiphiles (PAs) with different numbers of alkyl tails on supported lipid bilayers (SLBs) were investigated by single molecule tracking experiment and molecule dynamic simulation. Experimental results show two distinct populations of PAs with different residence time. Residence time of adsorbed PAs increases with the increase of the alkyl tails, whereas diffusion coefficient monotonically decreases with rising the number of alkyl tails and also decreases with increasing the mobility of SLBs. All-atom molecule dynamic simulation results prove that the adsorption and diffusion of PAs on SLB surface are mainly determined by interactions between PAs and SLBs and also the intrinsic mobility of PAs in aqueous solution. The electrostatic interactions and the mobility of PAs are two dominated but contradictory coefficients for the adsorption and diffusion of PAs. By increasing the alkyl tails, the mobility of PAs decreases while the electrostatic property does not change significantly, resulting in the increase of residence time and decrease of diffusivity of PAs. Additionally, for the PAs with large number of alkyl tails (≥ 3 alkyl tails), steric hindrance of alkyl tails leads to the decrease of adsorption probability of PAs on SLB surface. These findings lay the groundwork for guiding the design of PAs with high cell affinity, potentially useful for efficient drug delivery.
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Affiliation(s)
- Zhenxian Chen
- Key Laboratory of Materials Chemistry for Energy Conversion and Storage (HUST) of Ministry of Education, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology (HUST), Wuhan, 430074, China
| | - Wei Wei
- Key Laboratory of Materials Chemistry for Energy Conversion and Storage (HUST) of Ministry of Education, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology (HUST), Wuhan, 430074, China
| | - Haiyan Peng
- Key Laboratory of Materials Chemistry for Energy Conversion and Storage (HUST) of Ministry of Education, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology (HUST), Wuhan, 430074, China
| | - Hao Jiang
- Key Laboratory of Materials Chemistry for Energy Conversion and Storage (HUST) of Ministry of Education, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology (HUST), Wuhan, 430074, China.
| | - Bijin Xiong
- Key Laboratory of Materials Chemistry for Energy Conversion and Storage (HUST) of Ministry of Education, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology (HUST), Wuhan, 430074, China.
| | - Jintao Zhu
- Key Laboratory of Materials Chemistry for Energy Conversion and Storage (HUST) of Ministry of Education, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology (HUST), Wuhan, 430074, China
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Soteriou C, Kalli AC, Connell SD, Tyler AII, Thorne JL. Advances in understanding and in multi-disciplinary methodology used to assess lipid regulation of signalling cascades from the cancer cell plasma membrane. Prog Lipid Res 2020; 81:101080. [PMID: 33359620 DOI: 10.1016/j.plipres.2020.101080] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Revised: 12/18/2020] [Accepted: 12/18/2020] [Indexed: 12/31/2022]
Abstract
The lipid bilayer is a functional component of cells, forming a stable platform for the initiation of key biological processes, including cell signalling. There are distinct changes in the lipid composition of cell membranes during oncogenic transformation resulting in aberrant activation and inactivation of signalling transduction pathways. Studying the role of the cell membrane in cell signalling is challenging, since techniques are often limited to by timescale, resolution, sensitivity, and averaging. To overcome these limitations, combining 'computational', 'wet-lab' and 'semi-dry' approaches offers the best opportunity to resolving complex biological processes involved in membrane organisation. In this review, we highlight analytical tools that have been applied for the study of cell signalling initiation from the cancer cell membranes through computational microscopy, biological assays, and membrane biophysics. The cancer therapeutic potential of extracellular membrane-modulating agents, such as cholesterol-reducing agents is also discussed, as is the need for future collaborative inter-disciplinary research for studying the role of the cell membrane and its components in cancer therapy.
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Affiliation(s)
- C Soteriou
- School of Food Science and Nutrition, University of Leeds, Leeds LS29JT, UK; Leeds Institute of Cardiovascular and Metabolic Medicine and Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, UK; Molecular and Nanoscale Physics Group, School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, UK
| | - A C Kalli
- Leeds Institute of Cardiovascular and Metabolic Medicine and Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, UK
| | - S D Connell
- Molecular and Nanoscale Physics Group, School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, UK
| | - A I I Tyler
- School of Food Science and Nutrition, University of Leeds, Leeds LS29JT, UK
| | - J L Thorne
- School of Food Science and Nutrition, University of Leeds, Leeds LS29JT, UK.
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30
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Abraham Punnoose J, Hayden A, Zhou L, Halvorsen K. Wi-Fi Live-Streaming Centrifuge Force Microscope for Benchtop Single-Molecule Experiments. Biophys J 2020; 119:2231-2239. [PMID: 33121943 PMCID: PMC7732769 DOI: 10.1016/j.bpj.2020.10.017] [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: 07/14/2020] [Revised: 10/02/2020] [Accepted: 10/08/2020] [Indexed: 11/21/2022] Open
Abstract
The ability to apply controlled forces to individual molecules has been revolutionary in shaping our understanding of biophysics in areas as diverse as dynamic bond strength, biological motor operation, and DNA replication. However, the methodology to perform single-molecule experiments remains relatively inaccessible because of cost and complexity. In 2010, we introduced the centrifuge force microscope (CFM) as a platform for accessible and high-throughput single-molecule experimentation. The CFM consists of a rotating microscope with which prescribed centrifugal forces can be applied to microsphere-tethered biomolecules. In this work, we develop and demonstrate a next-generation Wi-Fi CFM that offers unprecedented ease of use and flexibility in design. The modular CFM unit fits within a standard benchtop centrifuge and connects by Wi-Fi to an external computer for live control and streaming at near gigabit speeds. The use of commercial wireless hardware allows for flexibility in programming and provides a streamlined upgrade path as Wi-Fi technology advances. To facilitate ease of use, detailed build and setup instructions, as well as LabVIEW-based control software and MATLAB-based analysis software, are provided. We demonstrate the instrument’s performance by analysis of force-dependent dissociation of short DNA duplexes of 7, 8, and 9 bp. We showcase the sensitivity of the approach by resolving distinct dissociation kinetic rates for a 7 bp duplex in which one G-C basepair is mutated to an A-T basepair.
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Affiliation(s)
| | | | - Lifeng Zhou
- RNA Institute, SUNY at Albany, Albany, New York
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31
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Ukogu OA, Smith AD, Devenica LM, Bediako H, McMillan RB, Ma Y, Balaji A, Schwab RD, Anwar S, Dasgupta M, Carter AR. Protamine loops DNA in multiple steps. Nucleic Acids Res 2020; 48:6108-6119. [PMID: 32392345 PMCID: PMC7293030 DOI: 10.1093/nar/gkaa365] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Revised: 04/12/2020] [Accepted: 04/27/2020] [Indexed: 11/13/2022] Open
Abstract
Protamine proteins dramatically condense DNA in sperm to almost crystalline packing levels. Here, we measure the first step in the in vitro pathway, the folding of DNA into a single loop. Current models for DNA loop formation are one-step, all-or-nothing models with a looped state and an unlooped state. However, when we use a Tethered Particle Motion (TPM) assay to measure the dynamic, real-time looping of DNA by protamine, we observe the presence of multiple folded states that are long-lived (∼100 s) and reversible. In addition, we measure folding on DNA molecules that are too short to form loops. This suggests that protamine is using a multi-step process to loop the DNA rather than a one-step process. To visualize the DNA structures, we used an Atomic Force Microscopy (AFM) assay. We see that some folded DNA molecules are loops with a ∼10-nm radius and some of the folded molecules are partial loops—c-shapes or s-shapes—that have a radius of curvature of ∼10 nm. Further analysis of these structures suggest that protamine is bending the DNA to achieve this curvature rather than increasing the flexibility of the DNA. We therefore conclude that protamine loops DNA in multiple steps, bending it into a loop.
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Affiliation(s)
- Obinna A Ukogu
- Department of Physics, Amherst College, Amherst, MA 01002, USA
| | - Adam D Smith
- Department of Physics, Amherst College, Amherst, MA 01002, USA
| | - Luka M Devenica
- Department of Physics, Amherst College, Amherst, MA 01002, USA
| | - Hilary Bediako
- Department of Physics, Amherst College, Amherst, MA 01002, USA
| | - Ryan B McMillan
- Department of Physics, Amherst College, Amherst, MA 01002, USA
| | - Yuxing Ma
- Department of Physics, Amherst College, Amherst, MA 01002, USA
| | - Ashwin Balaji
- Department of Physics, Amherst College, Amherst, MA 01002, USA
| | - Robert D Schwab
- Department of Physics, Amherst College, Amherst, MA 01002, USA
| | - Shahzad Anwar
- Department of Physics, Amherst College, Amherst, MA 01002, USA
| | | | - Ashley R Carter
- Department of Physics, Amherst College, Amherst, MA 01002, USA
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32
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Single-Molecule Biophysical Techniques to Study Actomyosin Force Transduction. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020. [PMID: 32451857 DOI: 10.1007/978-3-030-38062-5_6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/29/2023]
Abstract
Inside the cellular environment, molecular motors can work in concert to conduct a variety of important physiological functions and processes that are vital for the survival of a cell. However, in order to decipher the mechanism of how these molecular motors work, single-molecule microscopy techniques have been popular methods to understand the molecular basis of the emerging ensemble behavior of these motor proteins.In this chapter, we discuss various single-molecule biophysical imaging techniques that have been used to expose the mechanics and kinetics of myosins. The chapter should be taken as a general overview and introductory guide to the many existing techniques; however, since other chapters will discuss some of these techniques more thoroughly, the readership should refer to those chapters for further details and discussions. In particular, we will focus on scattering-based single-molecule microscopy methods, some of which have become more popular in the recent years and around which the work in our laboratories has been centered.
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33
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Platnich CM, Hariri AA, Sleiman HF, Cosa G. Advancing Wireframe DNA Nanostructures Using Single-Molecule Fluorescence Microscopy Techniques. Acc Chem Res 2019; 52:3199-3210. [PMID: 31675207 DOI: 10.1021/acs.accounts.9b00424] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
DNA nanotechnology relies on the molecular recognition properties of DNA to produce complex architectures through self-assembly. The resulting DNA nanostructures allow scientists to organize functional materials at the nanoscale and have therefore found applications in many domains of materials science over the past several years. These scaffolds have been used to position proteins, nanoparticles, carbon nanotubes, and other nanomaterials with high spatial resolution. In addition to their remarkable performance as frameworks for other species, DNA constructs also possess interesting dynamic properties, which have led to their use in logic circuits, drug delivery vehicles, and molecular walkers. Although DNA nanostructures have become increasingly complex, the development of tools to study them has lagged. Currently, gel electrophoresis, dynamic light scattering, and ensemble fluorescence measurements are widely used to characterize DNA-based assemblies. Unfortunately, ensemble averaging in these methods obscures malformed structures and may mask properties associated with structure, length, and shape in polydisperse samples. While atomic force microscopy allows for the determination of morphology at the single-molecule level, this technique cannot typically be used to assess the dynamic properties of these constructs. To analyze the function of DNA-based devices such as molecular motors and reconfigurable nanostructures in real time, new single-molecule techniques are required. This Account details the work from our laboratories toward developing single-molecule fluorescence (SMF) methodologies for the structural and dynamic characterization of wireframe DNA nanostructures, one at a time. The methods described herein provide us with two separate yet related sets of information: First, we can statically examine the nanostructures one by one to assess their robustness, structural fidelity, and morphology. This is primarily done using two-color stepwise photobleaching, wherein we can examine the subunit stoichiometry of our assemblies before and after various perturbations to the structures. For example, we can introduce length mismatches to cause the nanotube to bend or perform strand displacement reactions to generate single-stranded, flexible analogues of our materials. Second, due to the unmatched spatiotemporal resolution of SMF techniques, we can study the dynamic character of these assemblies by implementing structural changes to the nanotube and monitoring them in real time. With this structural and dynamic information in hand, our groups have additionally developed new tools for the improved construction of DNA nanotubes, inspired by solid-phase DNA synthesis. By assembling the nanotubes in a stepwise manner, highly monodisperse nanostructures of any desired length can be made without a template strand. In this way, unique building blocks can also be added sequence-specifically, allowing for the production of user-defined scaffolds to organize nanoscale materials in three dimensions. This method, in combination with our imaging and analysis protocols, may be extended to assemble and inspect other supramolecular constructs in a controlled manner. Overall, by combining synthesis, characterization, and analysis, these single-molecule techniques hold the potential to advance the study of DNA nanostructures and dynamic DNA-based devices.
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Affiliation(s)
- Casey M. Platnich
- Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec H3A 0B8, Canada
| | - Amani A. Hariri
- Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec H3A 0B8, Canada
| | - Hanadi F. Sleiman
- Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec H3A 0B8, Canada
| | - Gonzalo Cosa
- Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec H3A 0B8, Canada
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34
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Abstract
Single-molecule techniques have been used successfully to visualize real-time enzymatic activities, revealing transient complex properties and heterogeneity of various biological events. Especially, conventional force spectroscopy including optical tweezers and magnetic tweezers has been widely used to monitor change in DNA length by enzymes with high spatiotemporal resolutions of ~ nanometers and ~ milliseconds. However, DNA metabolism results from coordination of a number of components during the processes, requiring efficient monitoring of a complex of proteins catalyzing DNA substrates. In this min-review, we will introduce a simple and multiplexed single-molecule assay to detect DNA substrates catalyzed by enzymes with high-throughput data collection. We conclude with a perspective of possible directions that enhance capability of the assay to reveal complex biological events with higher resolution.
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Affiliation(s)
- Ryanggeun Lee
- Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang 37673, Korea
| | - Keunsang Yang
- School of Interdisciplinary Bioscience and Bioengineering, POSTECH, Pohang 37673, Korea
| | - Jong-Bong Lee
- Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang 37673, Korea
- School of Interdisciplinary Bioscience and Bioengineering, POSTECH, Pohang 37673, Korea
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35
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Abstract
Delivery of the drug to a desired point of body and controlled release of the therapeutic agent are important features, provided by drug delivery systems (DDSs), for development of today's effective medicines. A variety of nanomaterials or nanomolecules such as lipids/liposomes, nucleic acids, peptides/proteins, composites, polymers, or carbon nanotubes can be used as DDSs. Single-molecule characterization of these small materials in terms of their size, shape, surface, encapsulation efficiency, as well as interaction with the drug-receiving cell has importance for their efficiency. The loading, distribution, or leakage of the drug as well as its interaction with DDS should also be characterized. Although diverse techniques are present for characterization of specific DDS material, methods such as electron microscopy and fluorescence microscopy are widely used. In this review, the current methodologies utilized for the single-molecule characterization of mostly preferred DDS materials were presented.
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Affiliation(s)
- Sezer Okay
- Department of Vaccine Technology, Vaccine Institute, Hacettepe University, Ankara, Turkey.,Department of Biology, Faculty of Science, Çankırı Karatekin University, Çankırı, Turkey
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36
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Krainer G, Keller S, Schlierf M. Structural dynamics of membrane-protein folding from single-molecule FRET. Curr Opin Struct Biol 2019; 58:124-137. [DOI: 10.1016/j.sbi.2019.05.025] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Accepted: 05/27/2019] [Indexed: 12/15/2022]
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37
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Jansson LI, Stone MD. Single-Molecule Analysis of Reverse Transcriptase Enzymes. Cold Spring Harb Perspect Biol 2019; 11:11/9/a032458. [PMID: 31481455 DOI: 10.1101/cshperspect.a032458] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The original discovery of enzymes that synthesize DNA using an RNA template appeared to contradict the central dogma of biology, in which information is transferred, in a unidirectional way, from DNA genes into RNA molecules. The paradigm-shifting discovery of RNA-dependent DNA polymerases, also called reverse transcriptases (RTs), reshaped existing views for how cells function; however, the scope of the impact RTs impose on biology had yet to be realized. In the decades of research since the early 1970s, the biomedical and biotechnological significance of retroviral RTs, as well as the evolutionarily related telomerase enzyme, has become exceedingly clear. One common theme that has emerged in the course of RT-related research is the central role of nucleic acid binding and dynamics during enzyme function. However, directly interrogating these dynamic properties is challenging because of the stochastic properties of biological macromolecules. In this review, we describe how the development of single-molecule biophysical techniques has opened new windows through which to observe the dynamic behavior of this remarkable class of enzymes. Specifically, we focus on how the powerful single-molecule Förster resonance energy transfer (FRET) method has been exploited to study the structure and function of the human immunodeficiency virus (HIV) RT and telomerase ribonucleoprotein (RNP) enzymes. These exciting studies have refined our understanding of RT catalysis, have revealed unforeseen structural rearrangements between RTs and their nucleic acid substrates, and have helped to characterize the mode of action of RT-inhibiting drugs. We conclude with a discussion of how the ongoing development of single-molecule technologies will continue to empower researchers to probe RT mechanisms in new and exciting ways.
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Affiliation(s)
- Linnea I Jansson
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, California 95064.,The Center for Molecular Biology of RNA, University of California, Santa Cruz, California 95064
| | - Michael D Stone
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064.,The Center for Molecular Biology of RNA, University of California, Santa Cruz, California 95064
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38
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Is the cell really a machine? J Theor Biol 2019; 477:108-126. [PMID: 31173758 DOI: 10.1016/j.jtbi.2019.06.002] [Citation(s) in RCA: 50] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2018] [Revised: 05/06/2019] [Accepted: 06/03/2019] [Indexed: 01/03/2023]
Abstract
It has become customary to conceptualize the living cell as an intricate piece of machinery, different to a man-made machine only in terms of its superior complexity. This familiar understanding grounds the conviction that a cell's organization can be explained reductionistically, as well as the idea that its molecular pathways can be construed as deterministic circuits. The machine conception of the cell owes a great deal of its success to the methods traditionally used in molecular biology. However, the recent introduction of novel experimental techniques capable of tracking individual molecules within cells in real time is leading to the rapid accumulation of data that are inconsistent with an engineering view of the cell. This paper examines four major domains of current research in which the challenges to the machine conception of the cell are particularly pronounced: cellular architecture, protein complexes, intracellular transport, and cellular behaviour. It argues that a new theoretical understanding of the cell is emerging from the study of these phenomena which emphasizes the dynamic, self-organizing nature of its constitution, the fluidity and plasticity of its components, and the stochasticity and non-linearity of its underlying processes.
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39
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Single-molecule fluorescence studies of intrinsically disordered proteins and liquid phase separation. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2019; 1867:980-987. [PMID: 31054969 DOI: 10.1016/j.bbapap.2019.04.007] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Revised: 04/24/2019] [Accepted: 04/26/2019] [Indexed: 01/09/2023]
Abstract
Intrinsically disordered proteins (IDPs) are ubiquitous in proteomes and serve in a range of cellular functions including signaling, regulation, transport and enzyme function. IDP misfunction and aggregation are also associated with several diseases including neurodegenerative diseases and cancer. During the past decade, single-molecule methods have become popular for detailed biophysical and structural studies of these complex proteins. This work has included recent applications to cellular liquid-liquid phase separation (LLPS), relevant for functional dynamics of membraneless organelles such as the nucleolus and stress granules. In this concise review, we cover the conceptual motivations for development and application of single-molecule fluorescence methods for such IDP studies. We follow with a few key examples of systems and biophysical problems that have been addressed, and conclude with thoughts for emerging and future directions.
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40
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Bentley EP, Frey BB, Deniz AA. Physical Chemistry of Cellular Liquid-Phase Separation. Chemistry 2019; 25:5600-5610. [PMID: 30589142 PMCID: PMC6551525 DOI: 10.1002/chem.201805093] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2018] [Revised: 12/11/2018] [Indexed: 01/05/2023]
Abstract
Compartmentalization of biochemical processes is essential for cell function. Although membrane-bound organelles are well studied in this context, recent work has shown that phase separation is a key contributor to cellular compartmentalization through the formation of liquid-like membraneless organelles (MLOs). In this Minireview, the key mechanistic concepts that underlie MLO dynamics and function are first briefly discussed, including the relevant noncovalent interaction chemistry and polymer physical chemistry. Next, a few examples of MLOs and relevant proteins are given, along with their functions, which highlight the relevance of the above concepts. The developing area of active matter and non-equilibrium systems, which can give rise to unexpected effects in fluctuating cellular conditions, are also discussed. Finally, our thoughts for emerging and future directions in the field are discussed, including in vitro and in vivo studies of MLO physical chemistry and function.
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Affiliation(s)
- Emily P Bentley
- The Scripps Research Institute, 10550 N. Torrey Pines Rd., La Jolla, CA, 92037, USA
| | - Benjamin B Frey
- The Scripps Research Institute, 10550 N. Torrey Pines Rd., La Jolla, CA, 92037, USA
| | - Ashok A Deniz
- The Scripps Research Institute, 10550 N. Torrey Pines Rd., La Jolla, CA, 92037, USA
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41
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Analysing single-molecule trajectories to reconstruct free-energy landscapes of cyclic motor proteins. J Theor Biol 2019; 462:321-328. [PMID: 30465778 DOI: 10.1016/j.jtbi.2018.11.015] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2018] [Revised: 10/08/2018] [Accepted: 11/16/2018] [Indexed: 11/24/2022]
Abstract
Stochastic trajectories measured in single-molecule experiments have provided key insights into the microscopic behaviour of cyclic motor proteins. However, the fundamental free-energy landscapes of motor proteins are currently only able to be determined by computationally intensive numerical methods that do not take advantage of available single-trajectory data. In this paper we present a robust method for analysing single-molecule trajectories of cyclic motor proteins to reconstruct their free-energy landscapes. We use simulated trajectories on model potential landscapes to show the reliable reconstruction of the potentials. We determine the accuracy of the reconstruction method for common precision limitations and show that the method converges logarithmically. These results are then used to determine the experimental precision required to reconstruct a potential with a desired accuracy. The key advantages of the method are that it is simple to implement, is free of numerical difficulties that plague existing methods and is easily generalizable to higher dimensions.
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Haridasan N, Kannam SK, Mogurampelly S, Sathian SP. Translational mobilities of proteins in nanochannels: A coarse-grained molecular dynamics study. Phys Rev E 2018; 97:062415. [PMID: 30011556 DOI: 10.1103/physreve.97.062415] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2018] [Indexed: 05/18/2023]
Abstract
We investigated the translation of a protein through model nanopores using coarse-grained (CG) nonequilibrium molecular dynamics (NEMD) simulations and compared the mobilities with those obtained from previous coarse-grained equilibrium molecular dynamics model. We considered the effects of nanopore confinement and external force on the translation of streptavidin through nanopores of dimensions representative of experiments. As the nanopore radius approaches the protein hydrodynamic radius, r_{h}/r_{p}→1 (where r_{h} is the hydrodynamic radius of protein and r_{p} is the pore radius), the translation times are observed to increase by two orders of magnitude. The translation times are found to be in good agreement with the one-dimensional biased diffusion model. The results presented in this paper provide useful insights on nanopore designs intended to control the motion of biomolecules.
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Affiliation(s)
- Navaneeth Haridasan
- Department of Applied Mechanics, Indian Institute of Technology Madras, Chennai 600036, India
| | - Sridhar Kumar Kannam
- Faculty of Science, Engineering and Technology, Swinburne University of Technology, Hawthorn, Victoria 3122, Australia
- School of Sciences, RMIT University, Melbourne, Victoria 3001, Australia
| | - Santosh Mogurampelly
- Institute for Computational Molecular Science, Temple University, Philadelphia, Pennsylvania 19122, USA
| | - Sarith P Sathian
- Department of Applied Mechanics, Indian Institute of Technology Madras, Chennai 600036, India
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Cai H, Depoil D, Muller J, Sheetz MP, Dustin ML, Wind SJ. Spatial Control of Biological Ligands on Surfaces Applied to T Cell Activation. Methods Mol Biol 2018; 1584:307-331. [PMID: 28255709 DOI: 10.1007/978-1-4939-6881-7_18] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
In this chapter, we present techniques, based on molecular-scale nanofabrication and selective self-assembly, for the presentation of biomolecules of interest (ligands, receptors, etc.) on a surface with precise spatial control and arbitrary geometry at the single-molecule level. Metallic nanodot arrays are created on glass coverslips and are then used as anchors for the immobilization of biological ligands via thiol linking chemistry. The nanodot size is controlled by both lithography and metallization. The reagent concentration in self-assembly can be adjusted to ensure single-molecule occupancy for a given dot size. The surrounding glass is backfilled by a protein-repellent layer to prevent nonspecific adsorption. Moreover, bifunctional surfaces are created, whereby a second ligand is presented on the background, which is frequently a requirement for simulating complex cellular functions involving more than one key ligand. This platform serves as a novel and powerful tool for molecular and cellular biology, e.g., to study the fundamental mechanisms of receptor-mediated signaling.
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Affiliation(s)
- Haogang Cai
- Department of Mechanical Engineering, Columbia University, New York, USA
| | - David Depoil
- Kennedy Institute of Rheumatology, NDORMS, The University of Oxford, Oxford, UK
| | - James Muller
- Department of Pathology, Skirball Institute, New York University School of Medicine, New York, USA
| | - Michael P Sheetz
- Department of Biological Sciences, Columbia University, New York, USA.,National University of Singapore, Singapore, Singapore
| | - Michael L Dustin
- Kennedy Institute of Rheumatology, NDORMS, The University of Oxford, Oxford, UK.,Department of Pathology, Skirball Institute, New York University School of Medicine, New York, USA
| | - Shalom J Wind
- Department of Applied Physics and Applied Mathematics, Columbia University, 500 W 120th St, New York, NY, 10027, USA.
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Patra S, Anders C, Schummel PH, Winter R. Antagonistic effects of natural osmolyte mixtures and hydrostatic pressure on the conformational dynamics of a DNA hairpin probed at the single-molecule level. Phys Chem Chem Phys 2018; 20:13159-13170. [DOI: 10.1039/c8cp00907d] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Osmolyte mixtures from deep sea organisms are able to rescue nucleic acids from pressure-induced unfolding.
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Affiliation(s)
- Satyajit Patra
- Physical Chemistry I – Biophysical Chemistry
- Faculty of Chemistry and Chemical Biology
- TU Dortmund University
- D-44227 Dortmund
- Germany
| | - Christian Anders
- Physical Chemistry I – Biophysical Chemistry
- Faculty of Chemistry and Chemical Biology
- TU Dortmund University
- D-44227 Dortmund
- Germany
| | - Paul Hendrik Schummel
- Physical Chemistry I – Biophysical Chemistry
- Faculty of Chemistry and Chemical Biology
- TU Dortmund University
- D-44227 Dortmund
- Germany
| | - Roland Winter
- Physical Chemistry I – Biophysical Chemistry
- Faculty of Chemistry and Chemical Biology
- TU Dortmund University
- D-44227 Dortmund
- Germany
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Pandey V, Gupta S, Elangovan R. Compact 3D printed module for fluorescence and label-free imaging using evanescent excitation. Methods Appl Fluoresc 2017; 6:015007. [PMID: 29076809 DOI: 10.1088/2050-6120/aa967a] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Total internal reflection fluorescence (TIRF) microscopy is widely used for selective excitation and high-resolution imaging of fluorophores, and more recently label-free nanosized objects, with high vertical confinement near a liquid-solid interface. Traditionally, high numerical aperture objectives (>1.4) are used to simultaneously generate evanescent waves and collect fluorescence emission signals which limits their use to small area imaging (<0.1 mm2). Objective-based TIRFs are also expensive as they require dichroic mirrors and efficient notch filters to prevent specular reflection within the objective lenses. We have developed a compact 3D module called cTIRF that can generate evanescent waves in microscope glass slides via a planar waveguide illumination. The module can be attached as a fixture to any existing optical microscope, converting it into a TIRF and enabling high signal-to-noise ratio (SNR) fluorescence imaging using any magnification objective. As the incidence optics is perpendicular to the detector, label-free evanescent scattering-based imaging of submicron objects can also be performed without using emission filters. SNR is significantly enhanced in this case as compared to cTIRF alone, as seen through our model experiments performed on latex beads and mammalian cells. Extreme flexibility and the low cost of our approach makes it scalable for limited resource settings.
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Affiliation(s)
- Vikas Pandey
- Department of Chemical Engineering, Indian Institute of Technology, Delhi, 110016, India
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Salehi-Reyhani A. Evaluating single molecule detection methods for microarrays with high dynamic range for quantitative single cell analysis. Sci Rep 2017; 7:17957. [PMID: 29263350 PMCID: PMC5738400 DOI: 10.1038/s41598-017-18303-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2017] [Accepted: 12/07/2017] [Indexed: 11/09/2022] Open
Abstract
Single molecule microarrays have been used in quantitative proteomics, in particular, single cell analysis requiring high sensitivity and ultra-low limits of detection. In this paper, several image analysis methods are evaluated for their ability to accurately enumerate single molecules bound to a microarray spot. Crucially, protein abundance in single cells can vary significantly and may span several orders of magnitude. This poses a challenge to single molecule image analysis. In order to quantitatively assess the performance of each method, synthetic image datasets are generated with known ground truth whereby the number of single molecules varies over 5 orders of magnitude with a range of signal to noise ratios. Experiments were performed on synthetic datasets whereby the number of single molecules per spot corresponds to realistic single cell distributions whose ground truth summary statistics are known. The methods of image analysis are assessed in their ability to accurately estimate the distribution parameters. It is shown that super-resolution image analysis methods can significantly improve counting accuracy and better cope with single molecule congestion. The results highlight the challenge posed by quantitative single cell analysis and the implications to performing such analyses using microarray based approaches are discussed.
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Affiliation(s)
- Ali Salehi-Reyhani
- Department Chemistry, Institute of Chemical Biology, Imperial College London, London, SW7 2AZ, UK.
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Johnson AG, Grosely R, Petrov AN, Puglisi JD. Dynamics of IRES-mediated translation. Philos Trans R Soc Lond B Biol Sci 2017; 372:rstb.2016.0177. [PMID: 28138065 DOI: 10.1098/rstb.2016.0177] [Citation(s) in RCA: 66] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/16/2016] [Indexed: 12/19/2022] Open
Abstract
Viral internal ribosome entry sites (IRESs) are unique RNA elements, which use stable and dynamic RNA structures to recruit ribosomes and drive protein synthesis. IRESs overcome the high complexity of the canonical eukaryotic translation initiation pathway, often functioning with a limited set of eukaryotic initiation factors. The simplest types of IRESs are typified by the cricket paralysis virus intergenic region (CrPV IGR) and hepatitis C virus (HCV) IRESs, both of which independently form high-affinity complexes with the small (40S) ribosomal subunit and bypass the molecular processes of cap-binding and scanning. Owing to their simplicity and ribosomal affinity, the CrPV and HCV IRES have been important models for structural and functional studies of the eukaryotic ribosome during initiation, serving as excellent targets for recent technological breakthroughs in cryogenic electron microscopy (cryo-EM) and single-molecule analysis. High-resolution structural models of ribosome : IRES complexes, coupled with dynamics studies, have clarified decades of biochemical research and provided an outline of the conformational and compositional trajectory of the ribosome during initiation. Here we review recent progress in the study of HCV- and CrPV-type IRESs, highlighting important structural and dynamics insights and the synergy between cryo-EM and single-molecule studies.This article is part of the themed issue 'Perspectives on the ribosome'.
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Affiliation(s)
- Alex G Johnson
- Department of Chemical and Systems Biology, Stanford University, Stanford, CA 94305, USA.,Department of Structural Biology, Stanford University, Stanford, CA 94305, USA
| | - Rosslyn Grosely
- Department of Structural Biology, Stanford University, Stanford, CA 94305, USA
| | - Alexey N Petrov
- Department of Structural Biology, Stanford University, Stanford, CA 94305, USA
| | - Joseph D Puglisi
- Department of Structural Biology, Stanford University, Stanford, CA 94305, USA
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Kantor Y, Kardar M. Attractive and repulsive polymer-mediated forces between scale-free surfaces. Phys Rev E 2017; 96:022148. [PMID: 28950594 DOI: 10.1103/physreve.96.022148] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Indexed: 11/07/2022]
Abstract
We consider forces acting on objects immersed in, or attached to, long fluctuating polymers. The confinement of the polymer by the obstacles results in polymer-mediated forces that can be repulsive (due to loss of entropy) or attractive (if some or all surfaces are covered by adsorbing layers). The strength and sign of the force in general depends on the detailed shape and adsorption properties of the obstacles but assumes simple universal forms if characteristic length scales associated with the objects are large. This occurs for scale-free shapes (such as a flat plate, straight wire, or cone) when the polymer is repelled by the obstacles or is marginally attracted to it (close to the depinning transition where the absorption length is infinite). In such cases, the separation h between obstacles is the only relevant macroscopic length scale, and the polymer-mediated force equals Ak_{B}T/h, where T is temperature. The amplitude A is akin to a critical exponent, depending only on geometry and universality of the polymer system. The value of A, which we compute for simple geometries and ideal polymers, can be positive or negative. Remarkably, we find A=0 for ideal polymers at the adsorption transition point, irrespective of shapes of the obstacles, i.e., at this special point there is no polymer-mediated force between obstacles (scale free or not).
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Affiliation(s)
- Yacov Kantor
- Raymond and Beverly Sackler School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978, Israel
| | - Mehran Kardar
- Massachusetts Institute of Technology, Department of Physics, Cambridge, Massachusetts 02139, USA
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