1
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Chamberlain SR, Moore S, Grant TD. Fitting high-resolution electron density maps from atomic models to solution scattering data. Biophys J 2023; 122:4567-4581. [PMID: 37924208 PMCID: PMC10719074 DOI: 10.1016/j.bpj.2023.10.034] [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: 06/05/2023] [Revised: 08/29/2023] [Accepted: 10/31/2023] [Indexed: 11/06/2023] Open
Abstract
Solution scattering techniques, such as small- and wide-angle X-ray scattering (SWAXS), provide valuable insights into the structure and dynamics of biological macromolecules in solution. In this study, we present an approach to accurately predict solution X-ray scattering profiles at wide angles from atomic models by generating high-resolution electron density maps. Our method accounts for the excluded volume of bulk solvent by calculating unique adjusted atomic volumes directly from the atomic coordinates. This approach eliminates the need for one of the free fitting parameters commonly used in existing algorithms, resulting in improved accuracy of the calculated SWAXS profile. An implicit model of the hydration shell is generated that uses the form factor of water. Two parameters, namely the bulk solvent density and the mean hydration shell contrast, are adjusted to best fit the data. Results using eight publicly available SWAXS profiles show high-quality fits to the data. In each case, the optimized parameter values show small adjustments demonstrating that the default values are close to the true solution. Disabling parameter optimization produces significantly more accurate predicted scattering profiles compared to the leading software. The algorithm is computationally efficient, comparable to the leading software and up to 10 times faster for large molecules. The algorithm is encoded in a command line script called denss.pdb2mrc.py and is available open source as part of the DENSS v1.7.0 software package. In addition to improving the ability to compare atomic models to experimental SWAXS data, these developments pave the way for increasing the accuracy of modeling algorithms using SWAXS data and decreasing the risk of overfitting.
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Affiliation(s)
- Sarah R Chamberlain
- Department of Structural Biology, Jacobs School of Medicine and Biomedical Sciences, SUNY University at Buffalo, Buffalo, New York
| | - Stephen Moore
- Department of Structural Biology, Jacobs School of Medicine and Biomedical Sciences, SUNY University at Buffalo, Buffalo, New York
| | - Thomas D Grant
- Department of Structural Biology, Jacobs School of Medicine and Biomedical Sciences, SUNY University at Buffalo, Buffalo, New York.
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2
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Raviv U, Asor R, Shemesh A, Ginsburg A, Ben-Nun T, Schilt Y, Levartovsky Y, Ringel I. Insight into structural biophysics from solution X-ray scattering. J Struct Biol 2023; 215:108029. [PMID: 37741561 DOI: 10.1016/j.jsb.2023.108029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2023] [Revised: 08/09/2023] [Accepted: 09/18/2023] [Indexed: 09/25/2023]
Abstract
The current challenges of structural biophysics include determining the structure of large self-assembled complexes, resolving the structure of ensembles of complex structures and their mass fraction, and unraveling the dynamic pathways and mechanisms leading to the formation of complex structures from their subunits. Modern synchrotron solution X-ray scattering data enable simultaneous high-spatial and high-temporal structural data required to address the current challenges of structural biophysics. These data are complementary to crystallography, NMR, and cryo-TEM data. However, the analysis of solution scattering data is challenging; hence many different analysis tools, listed in the SAS Portal (http://smallangle.org/), were developed. In this review, we start by briefly summarizing classical X-ray scattering analyses providing insight into fundamental structural and interaction parameters. We then describe recent developments, integrating simulations, theory, and advanced X-ray scattering modeling, providing unique insights into the structure, energetics, and dynamics of self-assembled complexes. The structural information is essential for understanding the underlying physical chemistry principles leading to self-assembled supramolecular architectures and computational structural refinement.
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Affiliation(s)
- Uri Raviv
- Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, Jerusalem 9190401, Israel; The Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, Jerusalem 9190401, Israel.
| | - Roi Asor
- Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, Jerusalem 9190401, Israel
| | - Asaf Shemesh
- Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, Jerusalem 9190401, Israel
| | - Avi Ginsburg
- Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, Jerusalem 9190401, Israel
| | - Tal Ben-Nun
- Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, Jerusalem 9190401, Israel
| | - Yaelle Schilt
- Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, Jerusalem 9190401, Israel
| | - Yehonatan Levartovsky
- Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, Jerusalem 9190401, Israel
| | - Israel Ringel
- Institute for Drug Research, School of Pharmacy, The Hebrew University of Jerusalem, 9112102 Jerusalem, Israel
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3
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Chamberlain SR, Moore S, Grant TD. Fitting high-resolution electron density maps from atomic models to solution scattering data. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.06.02.543451. [PMID: 37398274 PMCID: PMC10312546 DOI: 10.1101/2023.06.02.543451] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/04/2023]
Abstract
Solution scattering techniques, such as small and wide-angle X-ray scattering (SWAXS), provide valuable insights into the structure and dynamics of biological macromolecules in solution. In this study, we present an approach to accurately predict solution X-ray scattering profiles at wide angles from atomic models by generating high-resolution electron density maps. Our method accounts for the excluded volume of bulk solvent by calculating unique adjusted atomic volumes directly from the atomic coordinates. This approach eliminates the need for a free fitting parameter commonly used in existing algorithms, resulting in improved accuracy of the calculated SWAXS profile. An implicit model of the hydration shell is generated which uses the form factor of water. Two parameters, namely the bulk solvent density and the mean hydration shell contrast, are adjusted to best fit the data. Results using eight publicly available SWAXS profiles show high quality fits to the data. In each case, the optimized parameter values show small adjustments demonstrating that the default values are close to the true solution. Disabling parameter optimization results in a significant improvement of the calculated scattering profiles compared to the leading software. The algorithm is computationally efficient, showing more than tenfold reduction in execution time compared to the leading software. The algorithm is encoded in a command line script called denss.pdb2mrc.py and is available open source as part of the DENSS v1.7.0 software package (https://github.com/tdgrant1/denss). In addition to improving the ability to compare atomic models to experimental SWAXS data, these developments pave the way for increasing the accuracy of modeling algorithms utilizing SWAXS data while decreasing the risk of overfitting.
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Affiliation(s)
- Sarah R. Chamberlain
- Department of Structural Biology, Jacobs School of Medicine and Biomedical Sciences, SUNY University at Buffalo, Buffalo, NY, USA
| | - Stephen Moore
- Department of Structural Biology, Jacobs School of Medicine and Biomedical Sciences, SUNY University at Buffalo, Buffalo, NY, USA
| | - Thomas D. Grant
- Department of Structural Biology, Jacobs School of Medicine and Biomedical Sciences, SUNY University at Buffalo, Buffalo, NY, USA
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4
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Trewhella J, Jeffries CM, Whitten AE. 2023 update of template tables for reporting biomolecular structural modelling of small-angle scattering data. Acta Crystallogr D Struct Biol 2023; 79:122-132. [PMID: 36762858 PMCID: PMC9912924 DOI: 10.1107/s2059798322012141] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2022] [Accepted: 12/23/2022] [Indexed: 02/10/2023] Open
Abstract
In 2017, guidelines were published for reporting structural modelling of small-angle scattering (SAS) data from biomolecules in solution that exemplified best-practice documentation of experiments and analysis. Since then, there has been significant progress in SAS data and model archiving, and the IUCr journal editors announced that the IUCr biology journals will require the deposition of SAS data used in biomolecular structure solution into a public archive, as well as adherence to the 2017 reporting guidelines. In this context, the reporting template tables accompanying the 2017 publication guidelines have been reviewed with a focus on making them both easier to use and more general. With input from the SAS community via the IUCr Commission on SAS and attendees of the triennial 2022 SAS meeting (SAS2022, Campinas, Brazil), an updated reporting template table has been developed that includes standard descriptions for proteins, glycosylated proteins, DNA and RNA, with some reorganization of the data to improve readability and interpretation. In addition, a specialized template has been developed for reporting SAS contrast-variation (SAS-cv) data and models that incorporates the additional reporting requirements from the 2017 guidelines for these more complicated experiments. To demonstrate their utility, examples of reporting with these new templates are provided for a SAS study of a DNA-protein complex and a SAS-cv experiment on a protein complex. The examples demonstrate how the tabulated information promotes transparent reporting that, in combination with the recommended figures and additional information best presented in the main text, enables the reader of the work to readily draw their own conclusions regarding the quality of the data and the validity of the models presented.
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Affiliation(s)
- Jill Trewhella
- School of Life and Environmental Sciences, The University of Sydney, Sydney, NSW 2006, Australia,Correspondence e-mail:
| | - Cy M. Jeffries
- European Molecular Biology Laboratory (EMBL), Hamburg Unit, Notkestrasse 85, c/o Deutsches Elektronen-Synchrotron, 22607 Hamburg, Germany
| | - Andrew E. Whitten
- Australian Nuclear Science and Technology Organisation, New Illawarra Road, Lucas Heights, NSW 2234, Australia
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5
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Data quality assurance, model validation, and data sharing for biomolecular structures from small-angle scattering. Methods Enzymol 2022; 678:1-22. [PMID: 36641205 DOI: 10.1016/bs.mie.2022.11.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Key to small-angle scattering (SAS) maturing and becoming a mainstream structural biology technique was the work done by the SAS community to establish standards for data quality, model validation and data sharing. Through a consultative process spanning more than a decade and a half, guidelines for publication have been established that include criteria for evaluating data quality and for model validation. In this process gaps were identified that stimulated innovation and development of new tools, for example new measures of model ambiguity and of the goodness-of-fit of a model to SAS data that complement the traditional global fit parameter χ2. The need for a global repository for biomolecular SAS data and models was identified and the SASBDB was established as a searchable, curated, freely accessible, downloadable database of experimental data, experimental conditions, sample details, derived models, and their fit to the data. Importantly, the SASBDB uses a common dictionary format that supports archiving of structures solved using integrative methods to support seamless data exchange with a federated system of public databanks that includes the world-wide Protein Data Bank (wwPDB) as the major repository for structural biology. Thus, biomolecular SAS is now well-positioned to achieve its full potential as a mainstream structural biology technique contributing at the frontier of integrative structural biology and meeting "best practice" standards for data quality assurance and data sharing.
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6
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Trewhella J, Vachette P, Bierma J, Blanchet C, Brookes E, Chakravarthy S, Chatzimagas L, Cleveland TE, Cowieson N, Crossett B, Duff AP, Franke D, Gabel F, Gillilan RE, Graewert M, Grishaev A, Guss JM, Hammel M, Hopkins J, Huang Q, Hub JS, Hura GL, Irving TC, Jeffries CM, Jeong C, Kirby N, Krueger S, Martel A, Matsui T, Li N, Pérez J, Porcar L, Prangé T, Rajkovic I, Rocco M, Rosenberg DJ, Ryan TM, Seifert S, Sekiguchi H, Svergun D, Teixeira S, Thureau A, Weiss TM, Whitten AE, Wood K, Zuo X. A round-robin approach provides a detailed assessment of biomolecular small-angle scattering data reproducibility and yields consensus curves for benchmarking. Acta Crystallogr D Struct Biol 2022; 78:1315-1336. [PMID: 36322416 PMCID: PMC9629491 DOI: 10.1107/s2059798322009184] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2022] [Accepted: 09/15/2022] [Indexed: 12/14/2022] Open
Abstract
Through an expansive international effort that involved data collection on 12 small-angle X-ray scattering (SAXS) and four small-angle neutron scattering (SANS) instruments, 171 SAXS and 76 SANS measurements for five proteins (ribonuclease A, lysozyme, xylanase, urate oxidase and xylose isomerase) were acquired. From these data, the solvent-subtracted protein scattering profiles were shown to be reproducible, with the caveat that an additive constant adjustment was required to account for small errors in solvent subtraction. Further, the major features of the obtained consensus SAXS data over the q measurement range 0-1 Å-1 are consistent with theoretical prediction. The inherently lower statistical precision for SANS limited the reliably measured q-range to <0.5 Å-1, but within the limits of experimental uncertainties the major features of the consensus SANS data were also consistent with prediction for all five proteins measured in H2O and in D2O. Thus, a foundation set of consensus SAS profiles has been obtained for benchmarking scattering-profile prediction from atomic coordinates. Additionally, two sets of SAXS data measured at different facilities to q > 2.2 Å-1 showed good mutual agreement, affirming that this region has interpretable features for structural modelling. SAS measurements with inline size-exclusion chromatography (SEC) proved to be generally superior for eliminating sample heterogeneity, but with unavoidable sample dilution during column elution, while batch SAS data collected at higher concentrations and for longer times provided superior statistical precision. Careful merging of data measured using inline SEC and batch modes, or low- and high-concentration data from batch measurements, was successful in eliminating small amounts of aggregate or interparticle interference from the scattering while providing improved statistical precision overall for the benchmarking data set.
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Affiliation(s)
- Jill Trewhella
- School of Life and Environmental Sciences, The University of Sydney, Sydney, NSW 2006, Australia
| | - Patrice Vachette
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), Paris, 91198 Gif-sur-Yvette, France
| | - Jan Bierma
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA
| | - Clement Blanchet
- European Molecular Biology Laboratory (EMBL) Hamburg Unit, Notkestrasse 85, c/o Deutsches Elektronen-Synchrotron, 22607 Hamburg, Germany
| | - Emre Brookes
- Chemistry and Biochemistry, University of Montana, 32 Campus Drive, Missoula, MT 59812, USA
| | - Srinivas Chakravarthy
- BioCAT, Department of Biological Sciences, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Leonie Chatzimagas
- Theoretical Physics and Center for Biophysics, Saarland University, Campus E2.6, 66123 Saarbrücken, Germany
| | - Thomas E. Cleveland
- Institute for Bioscience and Biotechnology Research, 9600 Gudelsky Drive, Rockville, MD 20850, USA
- National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, MD 20899, USA
| | - Nathan Cowieson
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, United Kingdom
| | - Ben Crossett
- Sydney Mass Spectrometry, The University of Sydney, Sydney, NSW 2006, Australia
| | - Anthony P. Duff
- Australian Nuclear Science and Technology Organisation, New Illawara Road, Lucas Heights, NSW 2234, Australia
| | - Daniel Franke
- European Molecular Biology Laboratory (EMBL) Hamburg Unit, Notkestrasse 85, c/o Deutsches Elektronen-Synchrotron, 22607 Hamburg, Germany
| | - Frank Gabel
- Institut de Biologie Structurale, CEA, CNRS, Université Grenoblé Alpes, 41 Rue Jules Horowitz, 38027 Grenoble, France
| | - Richard E. Gillilan
- Cornell High-Energy Synchrotron Source, 161 Synchrotron Drive, Ithaca, NY 14853, USA
| | - Melissa Graewert
- European Molecular Biology Laboratory (EMBL) Hamburg Unit, Notkestrasse 85, c/o Deutsches Elektronen-Synchrotron, 22607 Hamburg, Germany
| | - Alexander Grishaev
- Institute for Bioscience and Biotechnology Research, 9600 Gudelsky Drive, Rockville, MD 20850, USA
- National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, MD 20899, USA
| | - J. Mitchell Guss
- School of Life and Environmental Sciences, The University of Sydney, Sydney, NSW 2006, Australia
| | - Michal Hammel
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA
| | - Jesse Hopkins
- BioCAT, Department of Biological Sciences, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Qingqui Huang
- Cornell High-Energy Synchrotron Source, 161 Synchrotron Drive, Ithaca, NY 14853, USA
| | - Jochen S. Hub
- Theoretical Physics and Center for Biophysics, Saarland University, Campus E2.6, 66123 Saarbrücken, Germany
| | - Greg L. Hura
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA
| | - Thomas C. Irving
- BioCAT, Department of Biological Sciences, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Cy Michael Jeffries
- European Molecular Biology Laboratory (EMBL) Hamburg Unit, Notkestrasse 85, c/o Deutsches Elektronen-Synchrotron, 22607 Hamburg, Germany
| | - Cheol Jeong
- Department of Physics, Wesleyan University, Middletown, CT 06459, USA
| | - Nigel Kirby
- Australian Synchrotron, ANSTO, 800 Blackburn Road, Clayton, VIC 3158, Australia
| | - Susan Krueger
- National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, MD 20899, USA
| | - Anne Martel
- Institut Laue–Langevin, 71 Avenue des Martyrs, 38042 Grenoble CEDEX 9, France
| | - Tsutomu Matsui
- Stanford Synchrotron Radiation Lightsource, Stanford University, 2575 Sand Hill Road, Menlo Park, CA 94025, USA
| | - Na Li
- National Facility for Protein Science in Shanghai, Zhangjiang Laboratory, Shanghai Advanced Research Institute, Chinese Academy of Sciences, Road No. 333, Haike Road, Shanghai 201210, People’s Republic of China
| | - Javier Pérez
- Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin BP 48, 91192 Gif-sur-Yvette, France
| | - Lionel Porcar
- Institut Laue–Langevin, 71 Avenue des Martyrs, 38042 Grenoble CEDEX 9, France
| | - Thierry Prangé
- CITCoM (UMR 8038 CNRS), Faculté de Pharmacie, 4 Avenue de l’Observatoire, 75006 Paris, France
| | - Ivan Rajkovic
- Stanford Synchrotron Radiation Lightsource, Stanford University, 2575 Sand Hill Road, Menlo Park, CA 94025, USA
| | - Mattia Rocco
- Proteomica e Spettrometria di Massa, IRCCS Ospedale Policlinico San Martino, Largo R. Benzi 10, 16132 Genova, Italy
| | - Daniel J. Rosenberg
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA
| | - Timothy M. Ryan
- Australian Synchrotron, ANSTO, 800 Blackburn Road, Clayton, VIC 3158, Australia
| | - Soenke Seifert
- X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Lemont, IL 60439, USA
| | - Hiroshi Sekiguchi
- SPring-8, Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyōgo 679-5198, Japan
| | - Dmitri Svergun
- European Molecular Biology Laboratory (EMBL) Hamburg Unit, Notkestrasse 85, c/o Deutsches Elektronen-Synchrotron, 22607 Hamburg, Germany
| | - Susana Teixeira
- National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, MD 20899, USA
- Department of Chemical and Biomolecular Engineering, University of Delaware, 150 Academy Street, Newark, DE 19716, USA
| | - Aurelien Thureau
- Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin BP 48, 91192 Gif-sur-Yvette, France
| | - Thomas M. Weiss
- Stanford Synchrotron Radiation Lightsource, Stanford University, 2575 Sand Hill Road, Menlo Park, CA 94025, USA
| | - Andrew E. Whitten
- Australian Nuclear Science and Technology Organisation, New Illawara Road, Lucas Heights, NSW 2234, Australia
| | - Kathleen Wood
- Australian Nuclear Science and Technology Organisation, New Illawara Road, Lucas Heights, NSW 2234, Australia
| | - Xiaobing Zuo
- X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Lemont, IL 60439, USA
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Structural interpretations of a flexible cold-active AMS8 lipase by combining small-angle X-ray scattering and molecular dynamics simulation (SAXS-MD). Int J Biol Macromol 2022; 220:1095-1103. [PMID: 36029961 DOI: 10.1016/j.ijbiomac.2022.08.145] [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: 06/03/2022] [Revised: 07/25/2022] [Accepted: 08/22/2022] [Indexed: 11/22/2022]
Abstract
Determining structure of highly flexible protein with multiple conformations can be challenging. This paper aims to combine molecular dynamics (MD) and small angle X-ray diffraction (SAX) techniques as a solution to overcome issues related to protein conformation in hardly crystallized protein. Based on prior studies, a cold-active lipase AMS8 was simulated in solvents showing stability in its N-terminal and high flexibility in its C-terminal. However, MD in its own algorithm could not explain the basis of macromolecule conformational transitions or changes related to protein through folding. Hence, by combining SAXS with MD, it is possible to understand the structure of flexible AMS8 lipase in natural space. Based on the findings, SAXS ab-initio model of AMS8 lipase was identified as a monomeric protein in which the optimized model of cold-active lipase AMS8 derived from SAXS data was found to be aligned with AMS8 homology model under series of MD timeframe.
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8
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Predicting solution scattering patterns with explicit-solvent molecular simulations. Methods Enzymol 2022; 677:433-456. [DOI: 10.1016/bs.mie.2022.08.035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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9
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Delhommel F, Gabel F, Sattler M. Current approaches for integrating solution NMR spectroscopy and small-angle scattering to study the structure and dynamics of biomolecular complexes. J Mol Biol 2020; 432:2890-2912. [DOI: 10.1016/j.jmb.2020.03.014] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Revised: 02/27/2020] [Accepted: 03/10/2020] [Indexed: 01/24/2023]
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10
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Prior C, Davies OR, Bruce D, Pohl E. Obtaining Tertiary Protein Structures by the ab Initio Interpretation of Small Angle X-ray Scattering Data. J Chem Theory Comput 2020; 16:1985-2001. [PMID: 32023061 PMCID: PMC7145352 DOI: 10.1021/acs.jctc.9b01010] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
![]()
Small angle X-ray scattering (SAXS)
is an important tool for investigating
the structure of proteins in solution. We present a novel ab initio
method representing polypeptide chains as discrete curves used to
derive a meaningful three-dimensional model from only the primary sequence and SAXS data. High resolution structures were
used to generate probability density functions for each common secondary
structural element found in proteins, which are used to place realistic
restraints on the model curve’s geometry. This is coupled with
a novel explicit hydration shell model in order to derive physically
meaningful three-dimensional models by optimizing against experimental
SAXS data. The efficacy of this model is verified on an established
benchmark protein set, and then it is used to predict the lysozyme
structure using only its primary sequence and SAXS data. The method
is used to generate a biologically plausible model of the coiled-coil
component of the human synaptonemal complex central element protein.
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Affiliation(s)
- Christopher Prior
- Department of Mathematical Sciences, Durham University, Durham DH1 3LE, United Kingdom
| | - Owen R Davies
- Institute for Cell and Molecular Bioscience, Medical School, University of Newcastle, Newcastle upon Tyne, NE2 4HH, United Kingdom
| | - Daniel Bruce
- Department of Biosciences Durham University, Durham DH1 3LE, United Kingdom.,Department of Chemistry, Durham University, Durham DH1 3LE, United Kingdom
| | - Ehmke Pohl
- Department of Biosciences Durham University, Durham DH1 3LE, United Kingdom.,Department of Chemistry, Durham University, Durham DH1 3LE, United Kingdom
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11
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He H, Liu C, Liu H. Model Reconstruction from Small-Angle X-Ray Scattering Data Using Deep Learning Methods. iScience 2020; 23:100906. [PMID: 32092702 PMCID: PMC7037568 DOI: 10.1016/j.isci.2020.100906] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2019] [Revised: 11/18/2019] [Accepted: 02/07/2020] [Indexed: 02/03/2023] Open
Abstract
Small-angle X-ray scattering (SAXS) method is widely used in investigating protein structures in solution, but high-quality 3D model reconstructions are challenging. We present a new algorithm based on a deep learning method for model reconstruction from SAXS data. An auto-encoder for protein 3D models was trained to compress 3D shape information into vectors of a 200-dimensional latent space, and the vectors are optimized using genetic algorithms to build 3D models that are consistent with the scattering data. The program has been tested with experimental SAXS data, demonstrating the capacity and robustness of accurate model reconstruction. Furthermore, the model size information can be optimized using this algorithm, enhancing the automation in model reconstruction directly from SAXS data. The program was implemented using Python with the TensorFlow framework, with source code and webserver available from http://liulab.csrc.ac.cn/decodeSAXS. A convolutional neural network auto-encoder framework for 3D models is developed The auto-encoder compresses protein shape information to 200 parameters Accurate 3D models (both shape and radius) can be reconstructed from 1D SAXS data
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Affiliation(s)
- Hao He
- Complex Systems Division, Beijing Computational Science Research Center, 8 E Xibeiwang Road, Haidian, Beijing 100193, People's Republic of China; School of Software Engineering, University of Science and Technology China, Suzhou, Jiang Su 215123, People's Republic of China
| | - Can Liu
- Complex Systems Division, Beijing Computational Science Research Center, 8 E Xibeiwang Road, Haidian, Beijing 100193, People's Republic of China; School of Software Engineering, University of Science and Technology China, Suzhou, Jiang Su 215123, People's Republic of China
| | - Haiguang Liu
- Complex Systems Division, Beijing Computational Science Research Center, 8 E Xibeiwang Road, Haidian, Beijing 100193, People's Republic of China; Physics Department, Beijing Normal University, Haidian, Beijing 100875, People's Republic of China.
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12
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Ekimoto T, Kokabu Y, Oroguchi T, Ikeguchi M. Combination of coarse-grained molecular dynamics simulations and small-angle X-ray scattering experiments. Biophys Physicobiol 2019; 16:377-390. [PMID: 31984192 PMCID: PMC6976007 DOI: 10.2142/biophysico.16.0_377] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Accepted: 08/11/2019] [Indexed: 12/01/2022] Open
Abstract
The combination of molecular dynamics (MD) simulations and small-angle X-ray scattering (SAXS), called the MD-SAXS method, is efficient for investigating protein dynamics. To overcome the time-scale limitation of all-atom MD simulations, coarse-grained (CG) representations are often utilized for biomolecular simulations. In this study, we propose a method to combine CG MD simulations with SAXS, termed the CG-MD-SAXS method. In the CG-MD-SAXS method, the scattering factors of CG particles for proteins and nucleic acids are evaluated using high-resolution structural data in the Protein Data Bank, and the excluded volume and the hydration shell are modeled using two adjustable parameters to incorporate solvent effects. To avoid overfitting, only the two parameters are adjusted for an entire structure ensemble. To verify the developed method, theoretical SAXS profiles for various proteins, DNA/RNA, and a protein-RNA complex are compared with both experimental profiles and theoretical profiles obtained by the all-atom representation. In the present study, we applied the CG-MD-SAXS method to the Swi5-Sfr1 complex and three types of nucleosomes to obtain reliable ensemble models consistent with the experimental SAXS data.
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Affiliation(s)
- Toru Ekimoto
- Graduate School of Medical Life Science, Yokohama City University, Yokohama, Kanagawa 230-0045, Japan
| | - Yuichi Kokabu
- Bioscience Department, Mitsui Knowledge Industry Co., Ltd., Minato-ku, Tokyo 105-6215, Japan
| | - Tomotaka Oroguchi
- Graduate School of Medical Life Science, Yokohama City University, Yokohama, Kanagawa 230-0045, Japan.,Department of Physics, Faculty of Science and Technology, Keio University, Yokohama, Kanagawa 223-8522, Japan
| | - Mitsunori Ikeguchi
- Graduate School of Medical Life Science, Yokohama City University, Yokohama, Kanagawa 230-0045, Japan.,Medical Sciences Innovation Hub Program RIKEN, Yokohama, Kanagawa 230-0045, Japan
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13
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Chen PC, Shevchuk R, Strnad FM, Lorenz C, Karge L, Gilles R, Stadler AM, Hennig J, Hub JS. Combined Small-Angle X-ray and Neutron Scattering Restraints in Molecular Dynamics Simulations. J Chem Theory Comput 2019; 15:4687-4698. [DOI: 10.1021/acs.jctc.9b00292] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- Po-chia Chen
- Structural and Computational Biology Unit, EMBL Heidelberg, Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Roman Shevchuk
- Institute for Microbiology and Genetics, Georg-August-Universität Göttingen, Justus-von-Liebig-Weg 11, 37077 Göttingen, Germany
| | - Felix M. Strnad
- Institute for Microbiology and Genetics, Georg-August-Universität Göttingen, Justus-von-Liebig-Weg 11, 37077 Göttingen, Germany
| | - Charlotte Lorenz
- Jülich Centre for Neutron Science (JCNS-1) and Institute for Complex Systems ICS (ICS-1), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
- Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52056 Aachen, Germany
| | - Lukas Karge
- Heinz Maier-Leibnitz Zentrum, Technische Universität München, Lichtenbergstrasse 1, 85748 Garching, Germany
| | - Ralph Gilles
- Heinz Maier-Leibnitz Zentrum, Technische Universität München, Lichtenbergstrasse 1, 85748 Garching, Germany
| | - Andreas M. Stadler
- Jülich Centre for Neutron Science (JCNS-1) and Institute for Complex Systems ICS (ICS-1), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
- Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52056 Aachen, Germany
| | - Janosch Hennig
- Structural and Computational Biology Unit, EMBL Heidelberg, Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Jochen S. Hub
- Theoretical Physics and Center for Biophysics, Saarland University, Campus E2 6, 66123 Saarbrücken, Germany
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14
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Ginsburg A, Ben-Nun T, Asor R, Shemesh A, Fink L, Tekoah R, Levartovsky Y, Khaykelson D, Dharan R, Fellig A, Raviv U. D+: software for high-resolution hierarchical modeling of solution X-ray scattering from complex structures. J Appl Crystallogr 2019; 52:219-242. [PMID: 31057345 PMCID: PMC6495662 DOI: 10.1107/s1600576718018046] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Accepted: 12/20/2018] [Indexed: 11/10/2022] Open
Abstract
This paper presents the computer program D+ (https://scholars.huji.ac.il/uriraviv/book/d-0), where the reciprocal-grid (RG) algorithm is implemented. D+ efficiently computes, at high-resolution, the X-ray scattering curves from complex structures that are isotropically distributed in random orientations in solution. Structures are defined in hierarchical trees in which subunits can be represented by geometric or atomic models. Repeating subunits can be docked into their assembly symmetries, describing their locations and orientations in space. The scattering amplitude of the entire structure can be calculated by computing the amplitudes of the basic subunits on 3D reciprocal-space grids, moving up in the hierarchy, calculating the RGs of the larger structures, and repeating this process for all the leaves and nodes of the tree. For very large structures (containing over 100 protein subunits), a hybrid method can be used to avoid numerical artifacts. In the hybrid method, only grids of smaller subunits are summed and used as subunits in a direct computation of the scattering amplitude. D+ can accurately analyze both small- and wide-angle solution X-ray scattering data. This article describes how D+ applies the RG algorithm, accounts for rotations and translations of subunits, processes atomic models, accounts for the contribution of the solvent as well as the solvation layer of complex structures in a scalable manner, writes and accesses RGs, interpolates between grid points, computes numerical integrals, enables the use of scripts to define complicated structures, applies fitting algorithms, accounts for several coexisting uncorrelated populations, and accelerates computations using GPUs. D+ may also account for different X-ray energies to analyze anomalous solution X-ray scattering data. An accessory tool that can identify repeating subunits in a Protein Data Bank file of a complex structure is provided. The tool can compute the orientation and translation of repeating subunits needed for exploiting the advantages of the RG algorithm in D+. A Python wrapper (https://scholars.huji.ac.il/uriraviv/book/python-api) is also available, enabling more advanced computations and integration of D+ with other computational tools. Finally, a large number of tests are presented. The results of D+ are compared with those of other programs when possible, and the use of D+ to analyze solution scattering data from dynamic microtubule structures with different protofilament number is demonstrated. D+ and its source code are freely available for academic users and developers (https://bitbucket.org/uriraviv/public-dplus/src/master/).
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Affiliation(s)
- Avi Ginsburg
- Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 9190401, Jerusalem, Israel
- Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 9190401, Jerusalem, Israel
| | - Tal Ben-Nun
- Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 9190401, Jerusalem, Israel
- Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 9190401, Jerusalem, Israel
- School of Computer Science and Engineering, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 9190401 Jerusalem, Israel
| | - Roi Asor
- Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 9190401, Jerusalem, Israel
- Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 9190401, Jerusalem, Israel
| | - Asaf Shemesh
- Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 9190401, Jerusalem, Israel
- Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 9190401, Jerusalem, Israel
| | - Lea Fink
- Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 9190401, Jerusalem, Israel
- Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 9190401, Jerusalem, Israel
| | - Roee Tekoah
- Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 9190401, Jerusalem, Israel
- Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 9190401, Jerusalem, Israel
| | - Yehonatan Levartovsky
- Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 9190401, Jerusalem, Israel
- Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 9190401, Jerusalem, Israel
| | - Daniel Khaykelson
- Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 9190401, Jerusalem, Israel
- Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 9190401, Jerusalem, Israel
| | - Raviv Dharan
- Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 9190401, Jerusalem, Israel
- Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 9190401, Jerusalem, Israel
| | - Amos Fellig
- Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 9190401, Jerusalem, Israel
- Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 9190401, Jerusalem, Israel
| | - Uri Raviv
- Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 9190401, Jerusalem, Israel
- Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 9190401, Jerusalem, Israel
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15
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Ginsburg A, Ben-Nun T, Asor R, Shemesh A, Fink L, Tekoah R, Levartovsky Y, Khaykelson D, Dharan R, Fellig A, Raviv U. D+: software for high-resolution hierarchical modeling of solution X-ray scattering from complex structures. J Appl Crystallogr 2019; 52:219-242. [PMID: 31057345 DOI: 10.26434/chemrxiv.7012622] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Accepted: 12/20/2018] [Indexed: 05/23/2023] Open
Abstract
This paper presents the computer program D+ (https://scholars.huji.ac.il/uriraviv/book/d-0), where the reciprocal-grid (RG) algorithm is implemented. D+ efficiently computes, at high-resolution, the X-ray scattering curves from complex structures that are isotropically distributed in random orientations in solution. Structures are defined in hierarchical trees in which subunits can be represented by geometric or atomic models. Repeating subunits can be docked into their assembly symmetries, describing their locations and orientations in space. The scattering amplitude of the entire structure can be calculated by computing the amplitudes of the basic subunits on 3D reciprocal-space grids, moving up in the hierarchy, calculating the RGs of the larger structures, and repeating this process for all the leaves and nodes of the tree. For very large structures (containing over 100 protein subunits), a hybrid method can be used to avoid numerical artifacts. In the hybrid method, only grids of smaller subunits are summed and used as subunits in a direct computation of the scattering amplitude. D+ can accurately analyze both small- and wide-angle solution X-ray scattering data. This article describes how D+ applies the RG algorithm, accounts for rotations and translations of subunits, processes atomic models, accounts for the contribution of the solvent as well as the solvation layer of complex structures in a scalable manner, writes and accesses RGs, interpolates between grid points, computes numerical integrals, enables the use of scripts to define complicated structures, applies fitting algorithms, accounts for several coexisting uncorrelated populations, and accelerates computations using GPUs. D+ may also account for different X-ray energies to analyze anomalous solution X-ray scattering data. An accessory tool that can identify repeating subunits in a Protein Data Bank file of a complex structure is provided. The tool can compute the orientation and translation of repeating subunits needed for exploiting the advantages of the RG algorithm in D+. A Python wrapper (https://scholars.huji.ac.il/uriraviv/book/python-api) is also available, enabling more advanced computations and integration of D+ with other computational tools. Finally, a large number of tests are presented. The results of D+ are compared with those of other programs when possible, and the use of D+ to analyze solution scattering data from dynamic microtubule structures with different protofilament number is demonstrated. D+ and its source code are freely available for academic users and developers (https://bitbucket.org/uriraviv/public-dplus/src/master/).
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Affiliation(s)
- Avi Ginsburg
- Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 9190401, Jerusalem, Israel
- Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 9190401, Jerusalem, Israel
| | - Tal Ben-Nun
- Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 9190401, Jerusalem, Israel
- Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 9190401, Jerusalem, Israel
- School of Computer Science and Engineering, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 9190401 Jerusalem, Israel
| | - Roi Asor
- Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 9190401, Jerusalem, Israel
- Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 9190401, Jerusalem, Israel
| | - Asaf Shemesh
- Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 9190401, Jerusalem, Israel
- Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 9190401, Jerusalem, Israel
| | - Lea Fink
- Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 9190401, Jerusalem, Israel
- Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 9190401, Jerusalem, Israel
| | - Roee Tekoah
- Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 9190401, Jerusalem, Israel
- Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 9190401, Jerusalem, Israel
| | - Yehonatan Levartovsky
- Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 9190401, Jerusalem, Israel
- Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 9190401, Jerusalem, Israel
| | - Daniel Khaykelson
- Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 9190401, Jerusalem, Israel
- Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 9190401, Jerusalem, Israel
| | - Raviv Dharan
- Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 9190401, Jerusalem, Israel
- Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 9190401, Jerusalem, Israel
| | - Amos Fellig
- Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 9190401, Jerusalem, Israel
- Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 9190401, Jerusalem, Israel
| | - Uri Raviv
- Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 9190401, Jerusalem, Israel
- Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 9190401, Jerusalem, Israel
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16
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High Resolution Distance Distributions Determined by X-Ray and Neutron Scattering. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1009:167-181. [PMID: 29218559 DOI: 10.1007/978-981-10-6038-0_10] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Measuring distances within or between macromolecules is necessary to understand the chemistry that biological systems uniquely enable. In performing their chemistry, biological macromolecules undergo structural changes over distances ranging from atomic to micrometer scales. X-ray and neutron scattering provide three key assets for tackling this challenge. First, they may be conducted on solutions where the macromolecules are free to sample the conformations that enable their chemistry. Second, there are few limitations on chemical environment for experiments. Third, the techniques can inform upon a wide range of distances at once. Thus scattering, particularly recorded at small angles (SAS), has been applied to a large variety of phenomenon. A challenge in interpreting scattering data is that the desired three dimensional distance information is averaged onto one dimension. Furthermore, the scales and variety of phenomenon interrogated have led to an assortment of functions that describe distances and changes thereof. Here we review scattering studies that characterize biological phenomenon at distances ranging from atomic to 50 nm. We also distinguish the distance distribution functions that are commonly used to describe results from these systems. With available X-ray and neutron scattering facilities, bringing the action that occurs at the atomic to the micrometer scale is now reasonably accessible. Notably, the combined distance and dynamic information recorded by SAS is frequently key to connecting structure to biological activity and to improve macromolecular design strategies and outcomes. We anticipate widespread utilization particularly in macromolecular engineering and time-resolved studies where many contrasting experiments are necessary for resolving chemical mechanisms through structural changes.
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17
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Interpreting solution X-ray scattering data using molecular simulations. Curr Opin Struct Biol 2018; 49:18-26. [DOI: 10.1016/j.sbi.2017.11.002] [Citation(s) in RCA: 73] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Revised: 10/20/2017] [Accepted: 11/04/2017] [Indexed: 01/23/2023]
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18
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Hybrid Methods for Modeling Protein Structures Using Molecular Dynamics Simulations and Small-Angle X-Ray Scattering Data. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1105:237-258. [PMID: 30617833 DOI: 10.1007/978-981-13-2200-6_15] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Small-angle X-ray scattering (SAXS) is an efficient experimental tool to measure the overall shape of macromolecular structures in solution. However, due to the low resolution of SAXS data, high-resolution data obtained from X-ray crystallography or NMR and computational methods such as molecular dynamics (MD) simulations are complementary to SAXS data for understanding protein functions based on their structures at atomic resolution. Because MD simulations provide a physicochemically proper structural ensemble for flexible proteins in solution and a precise description of solvent effects, the hybrid analysis of SAXS and MD simulations is a promising method to estimate reasonable solution structures and structural ensembles in solution. Here, we review typical and useful in silico methods for modeling three dimensional protein structures, calculating theoretical SAXS profiles, and analyzing ensemble structures consistent with experimental SAXS profiles. We also review two examples of the hybrid analysis, termed MD-SAXS method in which MD simulations are carried out without any knowledge of experimental SAXS data, and the experimental SAXS data are used only to assess the consistency of the solution model from MD simulations with those observed in experiments. One example is an investigation of the intrinsic dynamics of EcoO109I using the computational method to obtain a theoretical profile from the trajectory of an MD simulation. The other example is a structural investigation of the vitamin D receptor ligand-binding domain using snapshots generated by MD simulations and assessment of the snapshots by experimental SAXS data.
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19
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Peti W, Page R, Boura E, Różycki B. Structures of Dynamic Protein Complexes: Hybrid Techniques to Study MAP Kinase Complexes and the ESCRT System. Methods Mol Biol 2018; 1688:375-389. [PMID: 29151218 DOI: 10.1007/978-1-4939-7386-6_17] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The integration of complementary molecular methods (including X-ray crystallography, NMR spectroscopy, small angle X-ray/neutron scattering, and computational techniques) is frequently required to obtain a comprehensive understanding of dynamic macromolecular complexes. In particular, these techniques are critical for studying intrinsically disordered protein regions (IDRs) or intrinsically disordered proteins (IDPs) that are part of large protein:protein complexes. Here, we explain how to prepare IDP samples suitable for study using NMR spectroscopy, and describe a novel SAXS modeling method (ensemble refinement of SAXS; EROS) that integrates the results from complementary methods, including crystal structures and NMR chemical shift perturbations, among others, to accurately model SAXS data and describe ensemble structures of dynamic macromolecular complexes.
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Affiliation(s)
- Wolfgang Peti
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, 85721, USA.
| | - Rebecca Page
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, 85721, USA
| | - Evzen Boura
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, 16610, Prague, Czech Republic
| | - Bartosz Różycki
- Institute of Physics, Polish Academy of Sciences, 02668, Warsaw, Poland
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20
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Trewhella J. Small Angle Scattering and Structural Biology: Data Quality and Model Validation. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1105:77-100. [PMID: 30617825 DOI: 10.1007/978-981-13-2200-6_7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
This chapter provides a brief review of the current state-of-the-art in small-angle scattering (SAS) from biomolecules in solution in regard to: (1) sample preparation and instrumentation, (2) data reduction and analysis, and (3) three-dimensional structural modelling and validation. In this context, areas of ongoing research in regard to the interpretation of SAS data will be discussed with a particular focus on structural modelling using computational methods and data from different experimental techniques, including SAS (hybrid methods). Finally, progress made in establishing community accepted publication guidelines and a standard reporting framework that includes SAS data deposition in a public data bank will be described. Importantly, SAS data with associated meta-data can now be held in a format that supports exchange between data archives and seamless interoperability with the world-wide Protein Data Bank (wwPDB). Biomolecular SAS is thus well positioned to contribute to an envisioned federation of data archives in support of hybrid structural biology.
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Affiliation(s)
- Jill Trewhella
- School of Life and Environmental Sciences, The University of Sydney, NSW, Australia. .,Department of Chemistry, University of Utah, Salt Lake City, UT, USA.
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21
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Cordeiro TN, Chen PC, De Biasio A, Sibille N, Blanco FJ, Hub JS, Crehuet R, Bernadó P. Disentangling polydispersity in the PCNA-p15PAF complex, a disordered, transient and multivalent macromolecular assembly. Nucleic Acids Res 2017; 45:1501-1515. [PMID: 28180305 PMCID: PMC5388412 DOI: 10.1093/nar/gkw1183] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2016] [Revised: 10/25/2016] [Accepted: 11/16/2016] [Indexed: 11/13/2022] Open
Abstract
The intrinsically disordered p15PAF regulates DNA replication and repair when interacting with the Proliferating Cell Nuclear Antigen (PCNA) sliding clamp. As many interactions between disordered proteins and globular partners involved in signaling and regulation, the complex between p15PAF and trimeric PCNA is of low affinity, forming a transient complex that is difficult to characterize at a structural level due to its inherent polydispersity. We have determined the structure, conformational fluctuations, and relative population of the five species that coexist in solution by combining small-angle X-ray scattering (SAXS) with molecular modelling. By using explicit ensemble descriptions for the individual species, built using integrative approaches and molecular dynamics (MD) simulations, we collectively interpreted multiple SAXS profiles as population-weighted thermodynamic mixtures. The analysis demonstrates that the N-terminus of p15PAF penetrates the PCNA ring and emerges on the back face. This observation substantiates the role of p15PAF as a drag regulating PCNA processivity during DNA repair. Our study reveals the power of ensemble-based approaches to decode structural, dynamic, and thermodynamic information from SAXS data. This strategy paves the way for deciphering the structural bases of flexible, transient and multivalent macromolecular assemblies involved in pivotal biological processes.
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Affiliation(s)
- Tiago N Cordeiro
- Centre de Biochimie Structurale, INSERM-U1054, CNRS UMR-5048, Université de Montpellier, Montpellier, France
| | - Po-Chia Chen
- Institute for Microbiology and Genetics, Georg-August-University Göttingen, Göttingen, Lower Saxony, Germany
| | | | - Nathalie Sibille
- Centre de Biochimie Structurale, INSERM-U1054, CNRS UMR-5048, Université de Montpellier, Montpellier, France
| | - Francisco J Blanco
- CIC-bioGUNE, Derio, Spain.,IKERBASQUE, Basque Foundation for Science, Bilbao, Spain
| | - Jochen S Hub
- Institute for Microbiology and Genetics, Georg-August-University Göttingen, Göttingen, Lower Saxony, Germany
| | - Ramon Crehuet
- Institute of Advanced Chemistry of Catalonia, CSIC, Barcelona 08034, Spain
| | - Pau Bernadó
- Centre de Biochimie Structurale, INSERM-U1054, CNRS UMR-5048, Université de Montpellier, Montpellier, France
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22
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Bernadó P, Shimizu N, Zaccai G, Kamikubo H, Sugiyama M. Solution scattering approaches to dynamical ordering in biomolecular systems. Biochim Biophys Acta Gen Subj 2017; 1862:253-274. [PMID: 29107147 DOI: 10.1016/j.bbagen.2017.10.015] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2017] [Revised: 10/23/2017] [Accepted: 10/24/2017] [Indexed: 01/09/2023]
Abstract
Clarification of solution structure and its modulation in proteins and protein complexes is crucially important to understand dynamical ordering in macromolecular systems. Small-angle x-ray scattering (SAXS) and small-angle neutron scattering (SANS) are among the most powerful techniques to derive structural information. Recent progress in sample preparation, instruments and software analysis is opening up a new era for small-angle scattering. In this review, recent progress and trends of SAXS and SANS are introduced from the point of view of instrumentation and analysis, touching on general features and standard methods of small-angle scattering. This article is part of a Special Issue entitled "Biophysical Exploration of Dynamical Ordering of Biomolecular Systems" edited by Dr. Koichi Kato.
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Affiliation(s)
- Pau Bernadó
- Centre de Biochimie Structurale, INSERM, CNRS, Université de Montpellier, France
| | - Nobutaka Shimizu
- Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan
| | - Giuseppe Zaccai
- Institut Laue Langevin, Institut de Biologie Structurale, CNRS, CNRS, UGA, Grenoble, France
| | - Hironari Kamikubo
- Graduate School of Materials Science, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0192, Japan.
| | - Masaaki Sugiyama
- Research Reactor Institute, Kyoto University, Kumatori, Sennan-gun, Osaka 590-0494, Japan..
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23
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Chetnani B, Mondragón A. Molecular envelope and atomic model of an anti-terminated glyQS T-box regulator in complex with tRNAGly. Nucleic Acids Res 2017; 45:8079-8090. [PMID: 28531275 PMCID: PMC5570125 DOI: 10.1093/nar/gkx451] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2017] [Revised: 05/03/2017] [Accepted: 05/08/2017] [Indexed: 11/26/2022] Open
Abstract
A T-box regulator or riboswitch actively monitors the levels of charged/uncharged tRNA and participates in amino acid homeostasis by regulating genes involved in their utilization or biosynthesis. It has an aptamer domain for cognate tRNA recognition and an expression platform to sense the charge state and modulate gene expression. These two conserved domains are connected by a variable linker that harbors additional secondary structural elements, such as Stem III. The structural basis for specific tRNA binding is known, but the structural basis for charge sensing and the role of other elements remains elusive. To gain new structural insights on the T-box mechanism, a molecular envelope was calculated from small angle X-ray scattering data for the Bacillus subtilis glyQS T-box riboswitch in complex with an uncharged tRNAGly. A structural model of an anti-terminated glyQS T-box in complex with its cognate tRNAGly was derived based on the molecular envelope. It shows the location and relative orientation of various secondary structural elements. The model was validated by comparing the envelopes of the wild-type complex and two variants. The structural model suggests that in addition to a possible regulatory role, Stem III could aid in preferential stabilization of the T-box anti-terminated state allowing read-through of regulated genes.
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MESH Headings
- Bacillus subtilis/genetics
- Bacillus subtilis/metabolism
- Base Sequence
- Models, Molecular
- Nucleic Acid Conformation
- RNA, Bacterial/chemistry
- RNA, Bacterial/genetics
- RNA, Bacterial/metabolism
- RNA, Transfer, Gly/chemistry
- RNA, Transfer, Gly/genetics
- RNA, Transfer, Gly/metabolism
- Riboswitch/genetics
- Scattering, Small Angle
- X-Ray Diffraction
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Affiliation(s)
- Bhaskar Chetnani
- Department of Molecular Biosciences, Northwestern University, 2205 Tech Drive, Evanston, IL 60208, USA
| | - Alfonso Mondragón
- Department of Molecular Biosciences, Northwestern University, 2205 Tech Drive, Evanston, IL 60208, USA
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Abstract
X-ray scattering is uniquely suited to the study of disordered systems and thus has the potential to provide insight into dynamic processes where diffraction methods fail. In particular, while X-ray crystallography has been a staple of structural biology for more than half a century and will continue to remain so, a major limitation of this technique has been the lack of dynamic information. Solution X-ray scattering has become an invaluable tool in structural and mechanistic studies of biological macromolecules where large conformational changes are involved. Such systems include allosteric enzymes that play key roles in directing metabolic fluxes of biochemical pathways, as well as large, assembly-line type enzymes that synthesize secondary metabolites with pharmaceutical applications. Furthermore, crystallography has the potential to provide information on protein dynamics via the diffuse scattering patterns that are overlaid with Bragg diffraction. Historically, these patterns have been very difficult to interpret, but recent advances in X-ray detection have led to a renewed interest in diffuse scattering analysis as a way to probe correlated motions. Here, we will review X-ray scattering theory and highlight recent advances in scattering-based investigations of protein solutions and crystals, with a particular focus on complex enzymes.
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Affiliation(s)
- Steve P Meisburger
- Department of Chemistry, Princeton University , Princeton, New Jersey 08544, United States
| | - William C Thomas
- Department of Chemistry, Princeton University , Princeton, New Jersey 08544, United States
| | - Maxwell B Watkins
- Department of Chemistry, Princeton University , Princeton, New Jersey 08544, United States
| | - Nozomi Ando
- Department of Chemistry, Princeton University , Princeton, New Jersey 08544, United States
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25
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Grudinin S, Garkavenko M, Kazennov A. Pepsi-SAXS: an adaptive method for rapid and accurate computation of small-angle X-ray scattering profiles. ACTA CRYSTALLOGRAPHICA SECTION D-STRUCTURAL BIOLOGY 2017; 73:449-464. [PMID: 28471369 DOI: 10.1107/s2059798317005745] [Citation(s) in RCA: 75] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Accepted: 04/15/2017] [Indexed: 11/10/2022]
Abstract
A new method called Pepsi-SAXS is presented that calculates small-angle X-ray scattering profiles from atomistic models. The method is based on the multipole expansion scheme and is significantly faster compared with other tested methods. In particular, using the Nyquist-Shannon-Kotelnikov sampling theorem, the multipole expansion order is adapted to the size of the model and the resolution of the experimental data. It is argued that by using the adaptive expansion order, this method has the same quadratic dependence on the number of atoms in the model as the Debye-based approach, but with a much smaller prefactor in the computational complexity. The method has been systematically validated on a large set of over 50 models collected from the BioIsis and SASBDB databases. Using a laptop, it was demonstrated that Pepsi-SAXS is about seven, 29 and 36 times faster compared with CRYSOL, FoXS and the three-dimensional Zernike method in SAStbx, respectively, when tested on data from the BioIsis database, and is about five, 21 and 25 times faster compared with CRYSOL, FoXS and SAStbx, respectively, when tested on data from SASBDB. On average, Pepsi-SAXS demonstrates comparable accuracy in terms of χ2 to CRYSOL and FoXS when tested on BioIsis and SASBDB profiles. Together with a small allowed variation of adjustable parameters, this demonstrates the effectiveness of the method. Pepsi-SAXS is available at http://team.inria.fr/nano-d/software/pepsi-saxs.
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Affiliation(s)
| | - Maria Garkavenko
- Moscow Institute of Physics and Technology, Dolgoprudniy, Russian Federation
| | - Andrei Kazennov
- Moscow Institute of Physics and Technology, Dolgoprudniy, Russian Federation
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26
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Sedlak SM, Bruetzel LK, Lipfert J. Quantitative evaluation of statistical errors in small-angle X-ray scattering measurements. J Appl Crystallogr 2017; 50:621-630. [PMID: 28381982 PMCID: PMC5377352 DOI: 10.1107/s1600576717003077] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2017] [Accepted: 02/23/2017] [Indexed: 12/12/2022] Open
Abstract
A model is presented for the errors in small-angle X-ray scattering profiles that takes into account the physics of the measurement process. The model agrees quantitatively with the variations observed in experimental measurements and provides a straightforward prescription to add realistic errors to simulated scattering profiles. A new model is proposed for the measurement errors incurred in typical small-angle X-ray scattering (SAXS) experiments, which takes into account the setup geometry and physics of the measurement process. The model accurately captures the experimentally determined errors from a large range of synchrotron and in-house anode-based measurements. Its most general formulation gives for the variance of the buffer-subtracted SAXS intensity σ2(q) = [I(q) + const.]/(kq), where I(q) is the scattering intensity as a function of the momentum transfer q; k and const. are fitting parameters that are characteristic of the experimental setup. The model gives a concrete procedure for calculating realistic measurement errors for simulated SAXS profiles. In addition, the results provide guidelines for optimizing SAXS measurements, which are in line with established procedures for SAXS experiments, and enable a quantitative evaluation of measurement errors.
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Affiliation(s)
- Steffen M Sedlak
- Department of Physics, Nanosystems Initiative Munich, and Center for NanoScience, LMU Munich , Amalienstrasse 54, Munich, 80799, Germany
| | - Linda K Bruetzel
- Department of Physics, Nanosystems Initiative Munich, and Center for NanoScience, LMU Munich , Amalienstrasse 54, Munich, 80799, Germany
| | - Jan Lipfert
- Department of Physics, Nanosystems Initiative Munich, and Center for NanoScience, LMU Munich , Amalienstrasse 54, Munich, 80799, Germany
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27
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Atomistic structural ensemble refinement reveals non-native structure stabilizes a sub-millisecond folding intermediate of CheY. Sci Rep 2017; 7:44116. [PMID: 28272524 PMCID: PMC5341065 DOI: 10.1038/srep44116] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2016] [Accepted: 02/03/2017] [Indexed: 01/25/2023] Open
Abstract
The dynamics of globular proteins can be described in terms of transitions between a folded native state and less-populated intermediates, or excited states, which can play critical roles in both protein folding and function. Excited states are by definition transient species, and therefore are difficult to characterize using current experimental techniques. Here, we report an atomistic model of the excited state ensemble of a stabilized mutant of an extensively studied flavodoxin fold protein CheY. We employed a hybrid simulation and experimental approach in which an aggregate 42 milliseconds of all-atom molecular dynamics were used as an informative prior for the structure of the excited state ensemble. This prior was then refined against small-angle X-ray scattering (SAXS) data employing an established method (EROS). The most striking feature of the resulting excited state ensemble was an unstructured N-terminus stabilized by non-native contacts in a conformation that is topologically simpler than the native state. Using these results, we then predict incisive single molecule FRET experiments as a means of model validation. This study demonstrates the paradigm of uniting simulation and experiment in a statistical model to study the structure of protein excited states and rationally design validating experiments.
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28
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Perkins SJ, Wright DW, Zhang H, Brookes EH, Chen J, Irving TC, Krueger S, Barlow DJ, Edler KJ, Scott DJ, Terrill NJ, King SM, Butler PD, Curtis JE. Atomistic modelling of scattering data in the Collaborative Computational Project for Small Angle Scattering (CCP-SAS). J Appl Crystallogr 2016; 49:1861-1875. [PMID: 27980506 PMCID: PMC5139988 DOI: 10.1107/s160057671601517x] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Accepted: 09/26/2016] [Indexed: 11/10/2022] Open
Abstract
The capabilities of current computer simulations provide a unique opportunity to model small-angle scattering (SAS) data at the atomistic level, and to include other structural constraints ranging from molecular and atomistic energetics to crystallography, electron microscopy and NMR. This extends the capabilities of solution scattering and provides deeper insights into the physics and chemistry of the systems studied. Realizing this potential, however, requires integrating the experimental data with a new generation of modelling software. To achieve this, the CCP-SAS collaboration (http://www.ccpsas.org/) is developing open-source, high-throughput and user-friendly software for the atomistic and coarse-grained molecular modelling of scattering data. Robust state-of-the-art molecular simulation engines and molecular dynamics and Monte Carlo force fields provide constraints to the solution structure inferred from the small-angle scattering data, which incorporates the known physical chemistry of the system. The implementation of this software suite involves a tiered approach in which GenApp provides the deployment infrastructure for running applications on both standard and high-performance computing hardware, and SASSIE provides a workflow framework into which modules can be plugged to prepare structures, carry out simulations, calculate theoretical scattering data and compare results with experimental data. GenApp produces the accessible web-based front end termed SASSIE-web, and GenApp and SASSIE also make community SAS codes available. Applications are illustrated by case studies: (i) inter-domain flexibility in two- to six-domain proteins as exemplified by HIV-1 Gag, MASP and ubiquitin; (ii) the hinge conformation in human IgG2 and IgA1 antibodies; (iii) the complex formed between a hexameric protein Hfq and mRNA; and (iv) synthetic 'bottlebrush' polymers.
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Affiliation(s)
- Stephen J. Perkins
- Department of Structural and Molecular Biology, University College London, Darwin Building, Gower Street, London WC1E 6BT, UK
| | - David W. Wright
- Department of Structural and Molecular Biology, University College London, Darwin Building, Gower Street, London WC1E 6BT, UK
| | - Hailiang Zhang
- Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD 20899-8562, USA
| | - Emre H. Brookes
- Department of Biochemistry, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229-3900, USA
| | - Jianhan Chen
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, KS 66506, USA
| | - Thomas C. Irving
- Department of Biology, Illinois Institute of Technology, 3101 S. Dearborn, Chicago, IL 60616, USA
| | - Susan Krueger
- Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD 20899-8562, USA
| | - David J. Barlow
- Pharmacy Department, Franklin-Wilkins Building, King’s College London, 150 Stamford Street, London SE1 9NH, UK
| | - Karen J. Edler
- Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, UK
| | - David J. Scott
- School of Biosciences, University of Nottingham, Sutton Bonington Campus, Leicestershire LE12 5RD, UK
- Research Complex at Harwell, STFC Rutherford Appleton Laboratory, Harwell Campus, Didcot, Oxfordshire OX11 0FA, UK
- ISIS Facility, STFC Rutherford Appleton Laboratory, Harwell Campus, Didcot, Oxfordshire OX11 0QX, UK
| | - Nicholas J. Terrill
- Diamond Light Source Ltd, Diamond House, Harwell Science and Innovation Campus, Chilton, Didcot, Oxfordshire OX11 0DE, UK
| | - Stephen M. King
- ISIS Facility, STFC Rutherford Appleton Laboratory, Harwell Campus, Didcot, Oxfordshire OX11 0QX, UK
| | - Paul D. Butler
- Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD 20899-8562, USA
- Department of Chemistry, The University of Tennessee, Knoxville, TN 37996-1600, USA
| | - Joseph E. Curtis
- Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD 20899-8562, USA
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29
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On the ability of molecular dynamics simulation and continuum electrostatics to treat interfacial water molecules in protein-protein complexes. Sci Rep 2016; 6:38259. [PMID: 27905545 PMCID: PMC5131287 DOI: 10.1038/srep38259] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Accepted: 10/28/2016] [Indexed: 01/23/2023] Open
Abstract
Interfacial waters are increasingly appreciated as playing a key role in protein-protein interactions. We report on a study of the prediction of interfacial water positions by both Molecular Dynamics and explicit solvent-continuum electrostatics based on the Dipolar Poisson-Boltzmann Langevin (DPBL) model, for three test cases: (i) the barnase/barstar complex (ii) the complex between the DNase domain of colicin E2 and its cognate Im2 immunity protein and (iii) the highly unusual anti-freeze protein Maxi which contains a large number of waters in its interior. We characterize the waters at the interface and in the core of the Maxi protein by the statistics of correctly predicted positions with respect to crystallographic water positions in the PDB files as well as the dynamic measures of diffusion constants and position lifetimes. Our approach provides a methodology for the evaluation of predicted interfacial water positions through an investigation of water-mediated inter-chain contacts. While our results show satisfactory behaviour for molecular dynamics simulation, they also highlight the need for improvement of continuum methods.
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30
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Sushko ML, Thomas DG, Pabit SA, Pollack L, Onufriev AV, Baker NA. The Role of Correlation and Solvation in Ion Interactions with B-DNA. Biophys J 2016; 110:315-326. [PMID: 26789755 DOI: 10.1016/j.bpj.2015.12.011] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2015] [Revised: 11/30/2015] [Accepted: 12/07/2015] [Indexed: 01/28/2023] Open
Abstract
The ionic atmospheres around nucleic acids play important roles in biological function. Large-scale explicit solvent simulations coupled to experimental assays such as anomalous small-angle x-ray scattering can provide important insights into the structure and energetics of such atmospheres but are time- and resource intensive. In this article, we use classical density functional theory to explore the balance among ion-DNA, ion-water, and ion-ion interactions in ionic atmospheres of RbCl, SrCl2, and CoHexCl3 (cobalt hexamine chloride) around a B-form DNA molecule. The accuracy of the classical density functional theory calculations was assessed by comparison between simulated and experimental anomalous small-angle x-ray scattering curves, demonstrating that an accurate model should take into account ion-ion correlation and ion hydration forces, DNA topology, and the discrete distribution of charges on the DNA backbone. As expected, these calculations revealed significant differences among monovalent, divalent, and trivalent cation distributions around DNA. Approximately half of the DNA-bound Rb(+) ions penetrate into the minor groove of the DNA and half adsorb on the DNA backbone. The fraction of cations in the minor groove decreases for the larger Sr(2+) ions and becomes zero for CoHex(3+) ions, which all adsorb on the DNA backbone. The distribution of CoHex(3+) ions is mainly determined by Coulomb and steric interactions, while ion-correlation forces play a central role in the monovalent Rb(+) distribution and a combination of ion-correlation and hydration forces affect the Sr(2+) distribution around DNA. This does not imply that correlations in CoHex solutions are weaker or stronger than for other ions. Steric inaccessibility of the grooves to large CoHex ions leads to their binding at the DNA surface. In this binding mode, first-order electrostatic interactions (Coulomb) dominate the overall binding energy as evidenced by low sensitivity of ionic distribution to the presence or absence of second-order electrostatic correlation interactions.
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Affiliation(s)
- Maria L Sushko
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, Washington
| | - Dennis G Thomas
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington
| | - Suzette A Pabit
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York
| | - Lois Pollack
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York
| | - Alexey V Onufriev
- Department of Computer Science and Department of Physics, Virginia Tech, Blacksburg, Virginia
| | - Nathan A Baker
- Computational and Statistical Analytics Division, Pacific Northwest National Laboratory, Richland, Washington; Division of Applied Mathematics, Brown University, Providence, Rhode Island.
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31
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Small-angle scattering and 3D structure interpretation. Curr Opin Struct Biol 2016; 40:1-7. [DOI: 10.1016/j.sbi.2016.05.003] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2016] [Revised: 05/12/2016] [Accepted: 05/12/2016] [Indexed: 12/29/2022]
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32
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Buyukdagli S, Blossey R. Beyond Poisson-Boltzmann: fluctuations and fluid structure in a self-consistent theory. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2016; 28:343001. [PMID: 27357125 DOI: 10.1088/0953-8984/28/34/343001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Poisson-Boltzmann (PB) theory is the classic approach to soft matter electrostatics and has been applied to numerous physical chemistry and biophysics problems. Its essential limitations are in its neglect of correlation effects and fluid structure. Recently, several theoretical insights have allowed the formulation of approaches that go beyond PB theory in a systematic way. In this topical review, we provide an update on the developments achieved in the self-consistent formulations of correlation-corrected Poisson-Boltzmann theory. We introduce a corresponding system of coupled non-linear equations for both continuum electrostatics with a uniform dielectric constant, and a structured solvent-a dipolar Coulomb fluid-including non-local effects. While the approach is only approximate and also limited to corrections in the so-called weak fluctuation regime, it allows us to include physically relevant effects, as we show for a range of applications of these equations.
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Affiliation(s)
- S Buyukdagli
- Department of Physics, Bilkent University, Ankara 06800, Turkey
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33
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Bruetzel LK, Gerling T, Sedlak SM, Walker PU, Zheng W, Dietz H, Lipfert J. Conformational Changes and Flexibility of DNA Devices Observed by Small-Angle X-ray Scattering. NANO LETTERS 2016; 16:4871-4879. [PMID: 27356232 DOI: 10.1021/acs.nanolett.6b01338] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Self-assembled DNA origami nanostructures enable the creation of precisely defined shapes at the molecular scale. Dynamic DNA devices that are capable of switching between defined conformations could afford completely novel functionalities for diagnostic, therapeutic, or engineering applications. Developing such objects benefits strongly from experimental feedback about conformational changes and 3D structures, ideally in solution, free of potential biases from surface attachment or labeling. Here, we demonstrate that small-angle X-ray scattering (SAXS) can quantitatively resolve the conformational changes of a DNA origami two-state switch device as a function of the ionic strength of the solution. In addition, we show how SAXS data allow for refinement of the predicted idealized three-dimensional structure of the DNA object using a normal mode approach based on an elastic network model. The results reveal deviations from the idealized design geometries that are otherwise difficult to resolve. Our results establish SAXS as a powerful tool to investigate conformational changes and solution structures of DNA origami and we anticipate our methodology to be broadly applicable to increasingly complex DNA and RNA devices.
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Affiliation(s)
- Linda K Bruetzel
- Department of Physics, Nanosystems Initiative Munich, and Center for Nanoscience, LMU Munich , Amalienstrasse 54, 80799 Munich, Germany
| | - Thomas Gerling
- Physik Department, Walter Schottky Institute, Technische Universität München , Am Coulombwall 4a, 85748 Garching near Munich, Germany
| | - Steffen M Sedlak
- Department of Physics, Nanosystems Initiative Munich, and Center for Nanoscience, LMU Munich , Amalienstrasse 54, 80799 Munich, Germany
| | - Philipp U Walker
- Department of Physics, Nanosystems Initiative Munich, and Center for Nanoscience, LMU Munich , Amalienstrasse 54, 80799 Munich, Germany
| | - Wenjun Zheng
- Physics Department, State University of New York at Buffalo , Buffalo, New York 14260, United States
| | - Hendrik Dietz
- Physik Department, Walter Schottky Institute, Technische Universität München , Am Coulombwall 4a, 85748 Garching near Munich, Germany
| | - Jan Lipfert
- Department of Physics, Nanosystems Initiative Munich, and Center for Nanoscience, LMU Munich , Amalienstrasse 54, 80799 Munich, Germany
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34
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Schindler C, de Vries S, Sasse A, Zacharias M. SAXS Data Alone can Generate High-Quality Models of Protein-Protein Complexes. Structure 2016; 24:1387-1397. [DOI: 10.1016/j.str.2016.06.007] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2016] [Revised: 06/08/2016] [Accepted: 06/08/2016] [Indexed: 11/29/2022]
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35
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Tong D, Yang S, Lu L. Accurate optimization of amino acid form factors for computing small-angle X-ray scattering intensity of atomistic protein structures. J Appl Crystallogr 2016; 49:1148-1161. [PMID: 28074088 PMCID: PMC5223287 DOI: 10.1107/s1600576716007962] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2016] [Accepted: 05/15/2016] [Indexed: 02/04/2023] Open
Abstract
Structure modelling via small-angle X-ray scattering (SAXS) data generally requires intensive computations of scattering intensity from any given biomolecular structure, where the accurate evaluation of SAXS profiles using coarse-grained (CG) methods is vital to improve computational efficiency. To date, most CG SAXS computing methods have been based on a single-bead-per-residue approximation but have neglected structural correlations between amino acids. To improve the accuracy of scattering calculations, accurate CG form factors of amino acids are now derived using a rigorous optimization strategy, termed electron-density matching (EDM), to best fit electron-density distributions of protein structures. This EDM method is compared with and tested against other CG SAXS computing methods, and the resulting CG SAXS profiles from EDM agree better with all-atom theoretical SAXS data. By including the protein hydration shell represented by explicit CG water molecules and the correction of protein excluded volume, the developed CG form factors also reproduce the selected experimental SAXS profiles with very small deviations. Taken together, these EDM-derived CG form factors present an accurate and efficient computational approach for SAXS computing, especially when higher molecular details (represented by the q range of the SAXS data) become necessary for effective structure modelling.
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Affiliation(s)
- Dudu Tong
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, 637551, Singapore
| | - Sichun Yang
- Center for Proteomics and Department of Nutrition, Case Western Reserve University, 10900 Euclid Avenue, BRB 929, Cleveland, OH 44106-4988, USA
| | - Lanyuan Lu
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, 637551, Singapore
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36
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Ginsburg A, Ben-Nun T, Asor R, Shemesh A, Ringel I, Raviv U. Reciprocal Grids: A Hierarchical Algorithm for Computing Solution X-ray Scattering Curves from Supramolecular Complexes at High Resolution. J Chem Inf Model 2016; 56:1518-27. [DOI: 10.1021/acs.jcim.6b00159] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
| | | | | | | | - Israel Ringel
- Azrieli College of Engineering, Jerusalem 9103501, Israel
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37
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Vestergaard B. Analysis of biostructural changes, dynamics, and interactions – Small-angle X-ray scattering to the rescue. Arch Biochem Biophys 2016; 602:69-79. [DOI: 10.1016/j.abb.2016.02.029] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2016] [Revised: 02/17/2016] [Accepted: 02/26/2016] [Indexed: 12/27/2022]
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38
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Hydration of proteins and nucleic acids: Advances in experiment and theory. A review. Biochim Biophys Acta Gen Subj 2016; 1860:1821-35. [PMID: 27241846 DOI: 10.1016/j.bbagen.2016.05.036] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Revised: 05/20/2016] [Accepted: 05/26/2016] [Indexed: 11/21/2022]
Abstract
BACKGROUND Most biological processes involve water, and the interactions of biomolecules with water affect their structure, function and dynamics. SCOPE OF REVIEW This review summarizes the current knowledge of protein and nucleic acid interactions with water, with a special focus on the biomolecular hydration layer. Recent developments in both experimental and computational methods that can be applied to the study of hydration structure and dynamics are reviewed, including software tools for the prediction and characterization of hydration layer properties. MAJOR CONCLUSIONS In the last decade, important advances have been made in our understanding of the factors that determine how biomolecules and their aqueous environment influence each other. Both experimental and computational methods contributed to the gradually emerging consensus picture of biomolecular hydration. GENERAL SIGNIFICANCE An improved knowledge of the structural and thermodynamic properties of the hydration layer will enable a detailed understanding of the various biological processes in which it is involved, with implications for a wide range of applications, including protein-structure prediction and structure-based drug design.
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39
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Kim HS, Martel A, Girard E, Moulin M, Härtlein M, Madern D, Blackledge M, Franzetti B, Gabel F. SAXS/SANS on Supercharged Proteins Reveals Residue-Specific Modifications of the Hydration Shell. Biophys J 2016; 110:2185-94. [PMID: 27224484 PMCID: PMC4880798 DOI: 10.1016/j.bpj.2016.04.013] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2015] [Revised: 03/09/2016] [Accepted: 04/08/2016] [Indexed: 11/26/2022] Open
Abstract
Water molecules in the immediate vicinity of biomacromolecules, including proteins, constitute a hydration layer characterized by physicochemical properties different from those of bulk water and play a vital role in the activity and stability of these structures, as well as in intermolecular interactions. Previous studies using solution scattering, crystallography, and molecular dynamics simulations have provided valuable information about the properties of these hydration shells, including modifications in density and ionic concentration. Small-angle scattering of x-rays (SAXS) and neutrons (SANS) are particularly useful and complementary techniques to study biomacromolecular hydration shells due to their sensitivity to electronic and nuclear scattering-length density fluctuations, respectively. Although several sophisticated SAXS/SANS programs have been developed recently, the impact of physicochemical surface properties on the hydration layer remains controversial, and systematic experimental data from individual biomacromolecular systems are scarce. Here, we address the impact of physicochemical surface properties on the hydration shell by a systematic SAXS/SANS study using three mutants of a single protein, green fluorescent protein (GFP), with highly variable net charge (+36, -6, and -29). The combined analysis of our data shows that the hydration shell is locally denser in the vicinity of acidic surface residues, whereas basic and hydrophilic/hydrophobic residues only mildly modify its density. Moreover, the data demonstrate that the density modifications result from the combined effect of residue-specific recruitment of ions from the bulk in combination with water structural rearrangements in their vicinity. Finally, we find that the specific surface-charge distributions of the different GFP mutants modulate the conformational space of flexible parts of the protein.
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Affiliation(s)
- Henry S Kim
- University Grenoble Alpes, Grenoble, France; CNRS, Grenoble, France; CEA, IBS, Grenoble, France
| | | | - Eric Girard
- University Grenoble Alpes, Grenoble, France; CNRS, Grenoble, France; CEA, IBS, Grenoble, France
| | | | | | - Dominique Madern
- University Grenoble Alpes, Grenoble, France; CNRS, Grenoble, France; CEA, IBS, Grenoble, France; Institut Laue-Langevin, Grenoble, France
| | - Martin Blackledge
- University Grenoble Alpes, Grenoble, France; CNRS, Grenoble, France; CEA, IBS, Grenoble, France
| | - Bruno Franzetti
- University Grenoble Alpes, Grenoble, France; CNRS, Grenoble, France; CEA, IBS, Grenoble, France; Institut Laue-Langevin, Grenoble, France
| | - Frank Gabel
- University Grenoble Alpes, Grenoble, France; CNRS, Grenoble, France; CEA, IBS, Grenoble, France; Institut Laue-Langevin, Grenoble, France.
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40
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Abstract
In experimental studies of solubilized membrane proteins, the detergent corona influences the protein behavior and the resulting measurement. Thus, combinations of experimental techniques with atomistic modeling have been used to resolve corona structural parameters and distributions. Here, we used small-angle X-ray scattering (SAXS) data and molecular dynamics simulations to study a model protein-detergent complex (PDC) consisting of aquaporin-0 and dodecyl-β-maltoside molecules (βDDM). The corona morphology of single snapshots was found to be rough, but it is smooth and compacted in 100-ns-scale ensemble averages. Individual snapshots therefore were unable to accurately represent the ensemble information as captured by experimental SAXS. Mimicking of annular lipids by detergent was also observed. SAXS prediction using different published methods was used to identify optimal βDDM numbers. Explicit-solvent methods predicted best agreement using 290-βDDM PDCs, but implicit-solvent methods gave unclear predictions due to overcompensation by free solvation-layer density parameters. Thus, ensemble-based approaches and physically motivated constraints will help to extract structural information from SAXS data.
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Affiliation(s)
- Po-Chia Chen
- Institute for Microbiology and Genetics, Georg-August-University Göttingen , Justus-von-Liebig weg 11, 37077 Göttingen, Germany
| | - Jochen S Hub
- Institute for Microbiology and Genetics, Georg-August-University Göttingen , Justus-von-Liebig weg 11, 37077 Göttingen, Germany
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41
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Nguyen HT, Pabit SA, Meisburger SP, Pollack L, Case DA. Accurate small and wide angle x-ray scattering profiles from atomic models of proteins and nucleic acids. J Chem Phys 2015; 141:22D508. [PMID: 25494779 DOI: 10.1063/1.4896220] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
A new method is introduced to compute X-ray solution scattering profiles from atomic models of macromolecules. The three-dimensional version of the Reference Interaction Site Model (RISM) from liquid-state statistical mechanics is employed to compute the solvent distribution around the solute, including both water and ions. X-ray scattering profiles are computed from this distribution together with the solute geometry. We describe an efficient procedure for performing this calculation employing a Lebedev grid for the angular averaging. The intensity profiles (which involve no adjustable parameters) match experiment and molecular dynamics simulations up to wide angle for two proteins (lysozyme and myoglobin) in water, as well as the small-angle profiles for a dozen biomolecules taken from the BioIsis.net database. The RISM model is especially well-suited for studies of nucleic acids in salt solution. Use of fiber-diffraction models for the structure of duplex DNA in solution yields close agreement with the observed scattering profiles in both the small and wide angle scattering (SAXS and WAXS) regimes. In addition, computed profiles of anomalous SAXS signals (for Rb(+) and Sr(2+)) emphasize the ionic contribution to scattering and are in reasonable agreement with experiment. In cases where an absolute calibration of the experimental data at q = 0 is available, one can extract a count of the excess number of waters and ions; computed values depend on the closure that is assumed in the solution of the Ornstein-Zernike equations, with results from the Kovalenko-Hirata closure being closest to experiment for the cases studied here.
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Affiliation(s)
- Hung T Nguyen
- BioMaPS Institute for Quantitative Biology, Rutgers University, Piscataway, New Jersey 08854, USA
| | - Suzette A Pabit
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA
| | - Steve P Meisburger
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA
| | - Lois Pollack
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA
| | - David A Case
- BioMaPS Institute for Quantitative Biology, Rutgers University, Piscataway, New Jersey 08854, USA
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42
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Chen PC, Hub JS. Interpretation of solution x-ray scattering by explicit-solvent molecular dynamics. Biophys J 2015; 108:2573-2584. [PMID: 25992735 PMCID: PMC4457003 DOI: 10.1016/j.bpj.2015.03.062] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2014] [Revised: 02/19/2015] [Accepted: 03/09/2015] [Indexed: 11/19/2022] Open
Abstract
Small- and wide-angle x-ray scattering (SWAXS) and molecular dynamics (MD) simulations are complementary approaches that probe conformational transitions of biomolecules in solution, even in a time-resolved manner. However, the structural interpretation of the scattering signals is challenging, while MD simulations frequently suffer from incomplete sampling or from a force-field bias. To combine the advantages of both techniques, we present a method that incorporates solution scattering data as a differentiable energetic restraint into explicit-solvent MD simulations, termed SWAXS-driven MD, with the aim to direct the simulation into conformations satisfying the experimental data. Because the calculations fully rely on explicit solvent, no fitting parameters associated with the solvation layer or excluded solvent are required, and the calculations remain valid at wide angles. The complementarity of SWAXS and MD is illustrated using three biological examples, namely a periplasmic binding protein, aspartate carbamoyltransferase, and a nuclear exportin. The examples suggest that SWAXS-driven MD is capable of refining structures against SWAXS data without foreknowledge of possible reaction paths. In turn, the SWAXS data accelerates conformational transitions in MD simulations and reduces the force-field bias.
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Affiliation(s)
- Po-Chia Chen
- Institute for Microbiology and Genetics, Georg-August-University Göttingen, Göttingen, Lower Saxony, Germany
| | - Jochen S Hub
- Institute for Microbiology and Genetics, Georg-August-University Göttingen, Göttingen, Lower Saxony, Germany.
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43
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Knight CJ, Hub JS. WAXSiS: a web server for the calculation of SAXS/WAXS curves based on explicit-solvent molecular dynamics. Nucleic Acids Res 2015; 43:W225-30. [PMID: 25855813 PMCID: PMC4489308 DOI: 10.1093/nar/gkv309] [Citation(s) in RCA: 121] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Accepted: 03/28/2015] [Indexed: 11/23/2022] Open
Abstract
Small- and wide-angle X-ray scattering (SWAXS) has evolved into a powerful tool to study biological macromolecules in solution. The interpretation of SWAXS curves requires their accurate predictions from structural models. Such predictions are complicated by scattering contributions from the hydration layer and by effects from thermal fluctuations. Here, we describe the new web server WAXSiS (WAXS in solvent) that computes SWAXS curves based on explicit-solvent all-atom molecular dynamics (MD) simulations (http://waxsis.uni-goettingen.de/). The MD simulations provide a realistic model for both the hydration layer and the excluded solvent, thereby avoiding any solvent-related fitting parameters, while naturally accounting for thermal fluctuations.
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Affiliation(s)
- Christopher J Knight
- Institute for Microbiology and Genetics, Georg-August-University Göttingen, Justus-von-Liebig-Weg 11, 37077 Göttingen, Germany
| | - Jochen S Hub
- Institute for Microbiology and Genetics, Georg-August-University Göttingen, Justus-von-Liebig-Weg 11, 37077 Göttingen, Germany
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44
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Chaudhuri BN. Emerging applications of small angle solution scattering in structural biology. Protein Sci 2015; 24:267-76. [PMID: 25516491 PMCID: PMC4353354 DOI: 10.1002/pro.2624] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2014] [Accepted: 12/05/2014] [Indexed: 12/12/2022]
Abstract
Small angle solution X-ray and neutron scattering recently resurfaced as powerful tools to address an array of biological problems including folding, intrinsic disorder, conformational transitions, macromolecular crowding, and self or hetero-assembling of biomacromolecules. In addition, small angle solution scattering complements crystallography, nuclear magnetic resonance spectroscopy, and other structural methods to aid in the structure determinations of multidomain or multicomponent proteins or nucleoprotein assemblies. Neutron scattering with hydrogen/deuterium contrast variation, or X-ray scattering with sucrose contrast variation to a certain extent, is a convenient tool for characterizing the organizations of two-component systems such as a nucleoprotein or a lipid-protein assembly. Time-resolved small and wide-angle solution scattering to study biological processes in real time, and the use of localized heavy-atom labeling and anomalous solution scattering for applications as FRET-like molecular rulers, are amongst promising newer developments. Despite the challenges in data analysis and interpretation, these X-ray/neutron solution scattering based approaches hold great promise for understanding a wide variety of complex processes prevalent in the biological milieu.
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Affiliation(s)
- Barnali N Chaudhuri
- Faculty of Life Sciences and Biotechnology, South Asian UniversityAkbar Bhawan, Chanakyapuri, New Delhi, India
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45
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Boldon L, Laliberte F, Liu L. Review of the fundamental theories behind small angle X-ray scattering, molecular dynamics simulations, and relevant integrated application. NANO REVIEWS 2015; 6:25661. [PMID: 25721341 PMCID: PMC4342503 DOI: 10.3402/nano.v6.25661] [Citation(s) in RCA: 90] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/06/2014] [Revised: 11/24/2014] [Accepted: 01/18/2015] [Indexed: 12/16/2022]
Abstract
In this paper, the fundamental concepts and equations necessary for performing small angle X-ray scattering (SAXS) experiments, molecular dynamics (MD) simulations, and MD-SAXS analyses were reviewed. Furthermore, several key biological and non-biological applications for SAXS, MD, and MD-SAXS are presented in this review; however, this article does not cover all possible applications. SAXS is an experimental technique used for the analysis of a wide variety of biological and non-biological structures. SAXS utilizes spherical averaging to produce one- or two-dimensional intensity profiles, from which structural data may be extracted. MD simulation is a computer simulation technique that is used to model complex biological and non-biological systems at the atomic level. MD simulations apply classical Newtonian mechanics' equations of motion to perform force calculations and to predict the theoretical physical properties of the system. This review presents several applications that highlight the ability of both SAXS and MD to study protein folding and function in addition to non-biological applications, such as the study of mechanical, electrical, and structural properties of non-biological nanoparticles. Lastly, the potential benefits of combining SAXS and MD simulations for the study of both biological and non-biological systems are demonstrated through the presentation of several examples that combine the two techniques.
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Affiliation(s)
- Lauren Boldon
- Department of Mechanical Aerospace and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, NY, USA;
| | - Fallon Laliberte
- Department of Mechanical Aerospace and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, NY, USA
| | - Li Liu
- Department of Mechanical Aerospace and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, NY, USA;
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46
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Kim HS, Gabel F. Uniqueness of models from small-angle scattering data: the impact of a hydration shell and complementary NMR restraints. ACTA CRYSTALLOGRAPHICA. SECTION D, BIOLOGICAL CRYSTALLOGRAPHY 2015; 71:57-66. [PMID: 25615860 PMCID: PMC4304686 DOI: 10.1107/s1399004714013923] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/24/2014] [Accepted: 06/13/2014] [Indexed: 01/04/2023]
Abstract
Small-angle scattering (SAS) has witnessed a breathtaking renaissance and expansion over the past 15 years regarding the determination of biomacromolecular structures in solution. While important issues such as sample quality, good experimental practice and guidelines for data analysis, interpretation, presentation, publication and deposition are increasingly being recognized, crucial topics such as the uniqueness, precision and accuracy of the structural models obtained by SAS are still only poorly understood and addressed. The present article provides an overview of recent developments in these fields with a focus on the influence of complementary NMR restraints and of a hydration shell on the uniqueness of biomacromolecular models. As a first topic, the impact of incorporating NMR orientational restraints in addition to SAS distance restraints is discussed using a quantitative visual representation that illustrates how the possible conformational space of a two-body system is reduced as a function of the available data. As a second topic, the impact of a hydration shell on modelling parameters of a two-body system is illustrated, in particular on its inter-body distance. Finally, practical recommendations are provided to take both effects into account and promising future perspectives of SAS approaches are discussed.
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Affiliation(s)
- Henry S. Kim
- Université Grenoble Alpes, IBS, 71 avenue des Martyrs, 38044 Grenoble, France
- CNRS, IBS, 71 avenue des Martyrs, 38044 Grenoble, France
- CEA, IBS, 71 avenue des Martyrs, 38044 Grenoble, France
| | - Frank Gabel
- Université Grenoble Alpes, IBS, 71 avenue des Martyrs, 38044 Grenoble, France
- CNRS, IBS, 71 avenue des Martyrs, 38044 Grenoble, France
- CEA, IBS, 71 avenue des Martyrs, 38044 Grenoble, France
- Institut Laue–Langevin, 38042 Grenoble CEDEX 9, France
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47
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Yang S. Methods for SAXS-based structure determination of biomolecular complexes. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2014; 26:7902-10. [PMID: 24888261 PMCID: PMC4285438 DOI: 10.1002/adma.201304475] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2013] [Revised: 03/10/2014] [Indexed: 05/20/2023]
Abstract
Measurements from small-angle X-ray scattering (SAXS) are highly informative to determine the structures of bimolecular complexes in solution. Here, current and recent SAXS-driven developments are described, with an emphasis on computational modeling. In particular, accurate methods to computing one theoretical scattering profile from a given structure model are discussed, with a key focus on structure factor coarse-graining and hydration contribution. Methods for reconstructing topological structures from an experimental SAXS profile are currently under active development. We report on several modeling tools designed for conformation generation that make use of either atomic-level or coarse-grained representations. Furthermore, since large, flexible biomolecules can adopt multiple well-defined conformations, a traditional single-conformation SAXS analysis is inappropriate, so we also discuss recent methods that utilize the concept of ensemble optimization, weighing in on the SAXS contributions of a heterogeneous mixture of conformations. These tools will ultimately posit the usefulness of SAXS data beyond a simple space-filling approach by providing a reliable structure characterization of biomolecular complexes under physiological conditions.
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Affiliation(s)
- Sichun Yang
- Center for Proteomics and Department of Pharmacology, Department of Physiology and Biophysics, Case Western Reserve University, 10900 Euclid Ave, Cleveland, OH 44106-4988, USA
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48
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Cantara WA, Olson ED, Musier-Forsyth K. Progress and outlook in structural biology of large viral RNAs. Virus Res 2014; 193:24-38. [PMID: 24956407 PMCID: PMC4252365 DOI: 10.1016/j.virusres.2014.06.007] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2014] [Revised: 06/11/2014] [Accepted: 06/12/2014] [Indexed: 02/05/2023]
Abstract
The field of viral molecular biology has reached a precipice for which pioneering studies on the structure of viral RNAs are beginning to bridge the gap. It has become clear that viral genomic RNAs are not simply carriers of hereditary information, but rather are active players in many critical stages during replication. Indeed, functions such as cap-independent translation initiation mechanisms are, in some cases, primarily driven by RNA structural determinants. Other stages including reverse transcription initiation in retroviruses, nuclear export and viral packaging are specifically dependent on the proper 3-dimensional folding of multiple RNA domains to recruit necessary viral and host factors required for activity. Furthermore, a large-scale conformational change within the 5'-untranslated region of HIV-1 has been proposed to regulate the temporal switch between viral protein synthesis and packaging. These RNA-dependent functions are necessary for replication of many human disease-causing viruses such as severe acute respiratory syndrome (SARS)-associated coronavirus, West Nile virus, and HIV-1. The potential for antiviral development is currently hindered by a poor understanding of RNA-driven molecular mechanisms, resulting from a lack of structural information on large RNAs and ribonucleoprotein complexes. Herein, we describe the recent progress that has been made on characterizing these large RNAs and provide brief descriptions of the techniques that will be at the forefront of future advances. Ongoing and future work will contribute to a more complete understanding of the lifecycles of retroviruses and RNA viruses and potentially lead to novel antiviral strategies.
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Affiliation(s)
| | | | - Karin Musier-Forsyth
- Department of Chemistry and Biochemistry, Center for Retrovirus Research, Center for RNA Biology, The Ohio State University, Columbus, OH 43210, United States
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49
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Różycki B, Boura E. Large, dynamic, multi-protein complexes: a challenge for structural biology. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:463103. [PMID: 25335513 DOI: 10.1088/0953-8984/26/46/463103] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Structural biology elucidates atomic structures of macromolecules such as proteins, DNA, RNA, and their complexes to understand the basic mechanisms of their functions. Among proteins that pose the most difficult problems to current efforts are those which have several large domains connected by long, flexible polypeptide segments. Although abundant and critically important in biological cells, such proteins have proven intractable by conventional techniques. This gap has recently led to the advancement of hybrid methods that use state-of-the-art computational tools to combine complementary data from various high- and low-resolution experiments. In this review, we briefly discuss the individual experimental techniques to illustrate their strengths and limitations, and then focus on the use of hybrid methods in structural biology. We describe how representative structures of dynamic multi-protein complexes are obtained utilizing the EROS hybrid method that we have co-developed.
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Affiliation(s)
- Bartosz Różycki
- Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw, Poland
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50
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Vestergaard B, Sayers Z. Investigating increasingly complex macromolecular systems with small-angle X-ray scattering. IUCRJ 2014; 1:523-9. [PMID: 25485132 PMCID: PMC4224470 DOI: 10.1107/s2052252514020843] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2014] [Accepted: 09/17/2014] [Indexed: 05/04/2023]
Abstract
The biological solution small-angle X-ray scattering (BioSAXS) field has undergone tremendous development over recent decades. This means that increasingly complex biological questions can be addressed by the method. An intricate synergy between advances in hardware and software development, data collection and evaluation strategies and implementations that readily allow integration with complementary techniques result in significant results and a rapidly growing user community with ever increasing ambitions. Here, a review of these developments, by including a selection of novel BioSAXS method-ologies and recent results, is given.
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Affiliation(s)
- Bente Vestergaard
- Department of Drug Design and Pharmacology, University of Copenhagen, Universitetsparken 2, Copenhagen, DK-2100, Denmark
- Correspondence e-mail:
| | - Zehra Sayers
- Faculty of Engineering and Natural Science, Sabanci University, Orhanli, Istanbul Tuzla 34956, Turkey
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