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Philo JS. SEDNTERP: a calculation and database utility to aid interpretation of analytical ultracentrifugation and light scattering data. EUROPEAN BIOPHYSICS JOURNAL : EBJ 2023; 52:233-266. [PMID: 36792822 DOI: 10.1007/s00249-023-01629-0] [Citation(s) in RCA: 24] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2022] [Revised: 01/16/2023] [Accepted: 01/19/2023] [Indexed: 02/17/2023]
Abstract
Proper interpretation of analytical ultracentrifugation (AUC) data for purified proteins requires ancillary information and calculations to account for factors such as buoyancy, buffer viscosity, hydration, and temperature. The utility program SEDNTERP has been widely used by the AUC community for this purpose since its introduction in the mid-1990s. Recent extensions to this program (1) allow it to incorporate data from diffusion as well as AUC experiments; and (2) allow it to calculate the refractive index of buffer solutions (based on the solute composition of the buffer), as well as the specific refractive increment (dn/dc) of proteins based on their composition. These two extensions should be quite useful to the light scattering community as well as helpful for AUC users. The latest version also adds new terms to the partial specific volume calculations which should improve the accuracy, particularly for smaller proteins and peptides, and can calculate the viscosity of buffers containing heavy isotopes of water. It also uses newer, more accurate equations for the density of water and for the hydrodynamic properties of rods and disks. This article will summarize and review all the equations used in the current program version and the scientific background behind them. It will tabulate the values used to calculate the partial specific volume and dn/dc, as well as the polynomial coefficients used in calculating the buffer density and viscosity (most of which have not been previously published), as well as the new ones used in calculating the buffer refractive index.
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Affiliation(s)
- John S Philo
- Alliance Protein Laboratories, San Diego, CA, USA.
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Abstract
Based on molecular dynamics simulations of four globular proteins in dilute aqueous solution, with three different water models, we examine several, essentially geometrical, aspects of the protein-water interface that remain controversial or incompletely understood. First, we compare different hydration shell definitions, based on spatial or topological proximity criteria. We find that the best method for constructing monolayer shells with nearly complete coverage is to use a 5 Å water-carbon cutoff and a 4 Å water-water cutoff. Using this method, we determine a mean interfacial water area of 11.1 Å2 which appears to be a universal property of the protein-water interface. We then analyze the local coordination and packing density of water molecules in the hydration shells and in subsets of the first shell. The mean polar water coordination number in the first shell remains within 1% of the bulk-water value, and it is 5% lower in the nonpolar part of the first shell. The local packing density is obtained from additively weighted Voronoi tessellation, arguably the most physically realistic method for allocating space between protein and water. We find that water in all parts of the first hydration shell, including the nonpolar part, is more densely packed than in the bulk, with a shell-averaged density excess of 6% for all four proteins. We suggest reasons why this value differs from previous experimental and computational results, emphasizing the importance of a realistic placement of the protein-water dividing surface and the distinction between spatial correlation and packing density. The protein-induced perturbation of water coordination and packing density is found to be short-ranged, with an exponential decay "length" of 0.6 shells. We also compute the protein partial volume, analyze its decomposition, and argue against the relevance of electrostriction.
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Affiliation(s)
- Filip Persson
- Division of Biophysical Chemistry, Department of Chemistry, Lund University, P.O. Box 124, SE-22100 Lund, Sweden
| | - Pär Söderhjelm
- Division of Biophysical Chemistry, Department of Chemistry, Lund University, P.O. Box 124, SE-22100 Lund, Sweden
| | - Bertil Halle
- Division of Biophysical Chemistry, Department of Chemistry, Lund University, P.O. Box 124, SE-22100 Lund, Sweden
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3
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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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Henriques J, Arleth L, Lindorff-Larsen K, Skepö M. On the Calculation of SAXS Profiles of Folded and Intrinsically Disordered Proteins from Computer Simulations. J Mol Biol 2018; 430:2521-2539. [PMID: 29548755 DOI: 10.1016/j.jmb.2018.03.002] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Revised: 03/02/2018] [Accepted: 03/02/2018] [Indexed: 11/15/2022]
Abstract
Solution techniques such as small-angle X-ray scattering (SAXS) play a central role in structural studies of intrinsically disordered proteins (IDPs); yet, due to low resolution, it is generally necessary to combine SAXS with additional experimental sources of data and to use molecular simulations. Computational methods for the calculation of theoretical SAXS intensity profiles can be separated into two groups, depending on whether the solvent is modeled implicitly as continuous electron density or considered explicitly. The former offers reduced computational cost but requires the definition of a number of free parameters to account for, for example, the excess density of the solvation layer. Overfitting can thus be an issue, particularly when the structural ensemble is unknown. Here, we investigate and show how small variations of the contrast of the hydration shell, δρ, severely affect the outcome, analysis and interpretation of computed SAXS profiles for folded and disordered proteins. For both the folded and disordered proteins studied here, using a default δρ may, in some cases, result in the calculation of non-representative SAXS profiles, leading to an overestimation of their size and a misinterpretation of their structural nature. The solvation layer of the different IDP simulations also impacts their size estimates differently, depending on the protein force field used. The same is not true for the folded protein simulations, suggesting differences in the solvation of the two classes of proteins, and indicating that different force fields optimized for IDPs may cause expansion of the polypeptide chain through different physical mechanisms.
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Affiliation(s)
- João Henriques
- Division of Theoretical Chemistry, Department of Chemistry, Lund University, Kemicentrum, PO Box 124, S-221 00 Lund, Sweden; Structural Biology and NMR Laboratory & Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, DK-2200 Copenhagen N, Denmark.
| | - Lise Arleth
- Structural Biophysics, Section for Neutron and X-ray Science, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark.
| | - Kresten Lindorff-Larsen
- Structural Biology and NMR Laboratory & Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, DK-2200 Copenhagen N, Denmark.
| | - Marie Skepö
- Division of Theoretical Chemistry, Department of Chemistry, Lund University, Kemicentrum, PO Box 124, S-221 00 Lund, Sweden.
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Nguyen HT, Pabit SA, Pollack L, Case DA. Extracting water and ion distributions from solution x-ray scattering experiments. J Chem Phys 2017; 144:214105. [PMID: 27276943 DOI: 10.1063/1.4953037] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Small-angle X-ray scattering measurements can provide valuable information about the solvent environment around biomolecules, but it can be difficult to extract solvent-specific information from observed intensity profiles. Intensities are proportional to the square of scattering amplitudes, which are complex quantities. Amplitudes in the forward direction are real, and the contribution from a solute of known structure (and from the waters it excludes) can be estimated from theory; hence, the amplitude arising from the solvent environment can be computed by difference. We have found that this "square root subtraction scheme" can be extended to non-zero q values, out to 0.1 Å(-1) for the systems considered here, since the phases arising from the solute and from the water environment are nearly identical in this angle range. This allows us to extract aspects of the water and ion distributions (beyond their total numbers), by combining experimental data for the complete system with calculations for the solutes. We use this approach to test molecular dynamics and integral-equation (3D-RISM (three-dimensional reference interaction site model)) models for solvent structure around myoglobin, lysozyme, and a 25 base-pair duplex DNA. Comparisons can be made both in Fourier space and in terms of the distribution of interatomic distances in real space. Generally, computed solvent distributions arising from the MD simulations fit experimental data better than those from 3D-RISM, even though the total small-angle X-ray scattering patterns are very similar; this illustrates the potential power of this sort of analysis to guide the development of computational models.
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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
| | - Lois Pollack
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA
| | - David A Case
- Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, New Jersey 08854, USA
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Nejad KH, Dianat M, Sarkaki A, Naseri MKG, Badavi M, Farbood Y. Ellagic acid improves electrocardiogram waves and blood pressure against global cerebral ischemia rat experimental models. Electron Physician 2015; 7:1153-62. [PMID: 26396728 PMCID: PMC4578534 DOI: 10.14661/2015.1153-1162] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2015] [Accepted: 07/25/2015] [Indexed: 11/06/2022] Open
Abstract
BACKGROUND Global cerebral ischemia (GCIR) arises in patients that are shown a variety of clinical difficulty including cardiac arrest, asphyxia, and shock. In spite of advances in understanding of the brain, ischemia and protective effects to improve ischemic injury still remain unknown. The aim of our study was to investigate the effect of ellagic acid (EA) pretreatment in the rat models of global cerebral ischemia reperfusion. METHODS This experimental study was conducted in 2014 at the Physiology Research Center of the Ahvaz Jundishapur University of Medical Sciences in Ahvaz, Iran. Adult male Wistar rats (250-300 g) were used in this study. GCIR was induced by bilateral vertebral and common carotid arteries occlusion (4-VO). 32 rats were divided randomly to four groups: 1) So (Sham) received normal saline as vehicle of EA, 2) EA, 3) normal saline + GCIR, and 4) EA + GCIR. After anesthesia (a mix of xylazine and ketamine), animal subjected to 20 minutes of ischemia followed by 30 minutes of reperfusion in related groups. EA (100 mg/kg, dissolved in normal saline) or 1.5 ml/kg normal saline was administered (gavage, 10 days) to the related groups. EEG was recorded from NTS in GCIR treated groups. RESULTS Present data showed that: 1) EEG in GCIR treated groups was flattened; 2) Blood pressure, voltage of QRS and P-R interval were reduced significantly in the ischemic groups compared to before ischemia, and pretreatment with EA prevented this reduction; and 3) MDA level and heart rate was increased by GCIR and pretreatment with EA reduced MDA level and restored the HR to normal level. CONCLUSION Results indicate that global cerebral ischemia-reperfusion impairs certain heart functions and ellagic acid as an antioxidant can restore these parameters. The results of this study suggest the possible utility of ellagic acid in patients with brain stroke.
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Affiliation(s)
- Khojasteh Hoseiny Nejad
- Ph.D. Student, Abadan Arvand International Division, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
| | - Mahin Dianat
- Faculty Member, Physiology Research Center and Department of Physiology, Faculty of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
| | - Alireza Sarkaki
- Faculty Member, Physiology Research Center and Department of Physiology, Faculty of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
| | - Mohammad Kazem Gharib Naseri
- Faculty Member, Physiology Research Center and Department of Physiology, Faculty of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
| | - Mohammad Badavi
- Faculty Member, Physiology Research Center and Department of Physiology, Faculty of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
| | - Yaghoub Farbood
- Faculty Member, Physiology Research Center and Department of Physiology, Faculty of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
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8
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Seki Y, Shimbo Y, Nonaka T, Soda K. A New Efficient Method for Generating Conformations of Unfolded Proteins with Diverse Main-Chain Dihedral-Angle Distributions. J Chem Theory Comput 2011; 7:2126-36. [DOI: 10.1021/ct100708p] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Yasutaka Seki
- School of Pharmacy, Iwate Medical University, Yahaba, Iwate 028-3694, Japan
| | - Yudai Shimbo
- Department of Bioengineering, Nagaoka University of Technology, Nagaoka, Niigata 940-2188, Japan
- Laboratory for Computational Molecular Design, Center for Computational Life Science, RIKEN, Kobe, Hyogo 650-0047, Japan
| | - Takamasa Nonaka
- School of Pharmacy, Iwate Medical University, Yahaba, Iwate 028-3694, Japan
| | - Kunitsugu Soda
- Laboratory for Computational Molecular Design, Center for Computational Life Science, RIKEN, Kobe, Hyogo 650-0047, Japan
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Oroguchi T, Ikeguchi M. Effects of ionic strength on SAXS data for proteins revealed by molecular dynamics simulations. J Chem Phys 2011; 134:025102. [PMID: 21241150 DOI: 10.1063/1.3526488] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The combination of small-angle X-ray solution scattering (SAXS) experiments and molecular dynamics (MD) simulations is now becoming a powerful tool to study protein conformations in solution at an atomic resolution. In this study, we investigated effects of ionic strength on SAXS data theoretically by using MD simulations of hen egg white lysozyme at various NaCl concentrations from 0 to 1 M. The calculated SAXS excess intensities showed a significant dependence on ion concentration, which originates from the different solvent density distributions in the presence and absence of ions. The addition of ions induced a slow convergence of the SAXS data, and a ∼20 ns simulation is required to obtain convergence of the SAXS data with the presence of ions whereas only a 0.2 ns simulation is sufficient in the absence of ions. To circumvent the problem of the slow convergence in the presence of ions, we developed a novel method that reproduces the SAXS excess intensities with the presence of ions from short MD trajectories in pure water. By applying this method to SAXS data for the open and closed forms of transferrin at 1 M ion concentration, the correct form could be identified by simply using short MD simulations of the protein in pure water for 0.2 ns.
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Affiliation(s)
- Tomotaka Oroguchi
- Department of Supramolecular Biology, Graduate School of Nanobioscience, Yokohama City University, 1-7-29 Suehiro-cho, Tsurumi-ku, Yokohama 230-0045, Japan
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Oroguchi T, Ikeguchi M, Sato M. Towards the Structural Characterization of Intrinsically Disordered Proteins by SAXS and MD Simulation. ACTA ACUST UNITED AC 2011. [DOI: 10.1088/1742-6596/272/1/012005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Bardhan J, Park S, Makowski L. SoftWAXS: a computational tool for modeling wide-angle X-ray solution scattering from biomolecules. J Appl Crystallogr 2009; 42:932-943. [PMID: 21339902 PMCID: PMC3041499 DOI: 10.1107/s0021889809032919] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2009] [Accepted: 08/18/2009] [Indexed: 11/10/2022] Open
Abstract
This paper describes a computational approach to estimating wide-angle X-ray solution scattering (WAXS) from proteins, which has been implemented in a computer program called SoftWAXS. The accuracy and efficiency of SoftWAXS are analyzed for analytically solvable model problems as well as for proteins. Key features of the approach include a numerical procedure for performing the required spherical averaging and explicit representation of the solute-solvent boundary and the surface of the hydration layer. These features allow the Fourier transform of the excluded volume and hydration layer to be computed directly and with high accuracy. This approach will allow future investigation of different treatments of the electron density in the hydration shell. Numerical results illustrate the differences between this approach to modeling the excluded volume and a widely used model that treats the excluded-volume function as a sum of Gaussians representing the individual atomic excluded volumes. Comparison of the results obtained here with those from explicit-solvent molecular dynamics clarifies shortcomings inherent to the representation of solvent as a time-averaged electron-density profile. In addition, an assessment is made of how the calculated scattering patterns depend on input parameters such as the solute-atom radii, the width of the hydration shell and the hydration-layer contrast. These results suggest that obtaining predictive calculations of high-resolution WAXS patterns may require sophisticated treatments of solvent.
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Affiliation(s)
- Jaydeep Bardhan
- Biosciences Division, Argonne National Laboratory, IL, USA
- Department of Molecular Biophysics and Physiology, Rush University Medical Center, Chicago, IL, USA
| | - Sanghyun Park
- Mathematics and Computer Science Division, Argonne National Laboratory, IL, USA
| | - Lee Makowski
- Biosciences Division, Argonne National Laboratory, IL, USA
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12
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Oroguchi T, Hashimoto H, Shimizu T, Sato M, Ikeguchi M. Intrinsic dynamics of restriction endonuclease EcoO109I studied by molecular dynamics simulations and X-ray scattering data analysis. Biophys J 2009; 96:2808-22. [PMID: 19348764 PMCID: PMC2711268 DOI: 10.1016/j.bpj.2008.12.3914] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2008] [Revised: 11/19/2008] [Accepted: 12/08/2008] [Indexed: 11/30/2022] Open
Abstract
EcoO109I is a type II restriction endonuclease that functions as a dimer in solution. Upon DNA binding to the enzyme, the two subunits rotate counterclockwise relative to each other, as the two catalytic domains undergo structural changes to capture the cognate DNA. Using a 150-ns molecular dynamics simulation, we investigated the intrinsic dynamics of the DNA-free enzyme in solution to elucidate the relationship between enzyme dynamics and structural changes. The simulation revealed that the enzyme is considerably flexible, and thus exhibits large fluctuations in the radius of gyration. The small-angle x-ray scattering profile calculated from the simulation, including scattering from explicit hydration water, was in agreement with the experimentally observed profile. Principal component analysis revealed that the major dynamics were represented by the open-close and counterclockwise motions: the former is required for the enzyme to access DNA, whereas the latter corresponds to structural changes upon DNA binding. Furthermore, the intrinsic dynamics in the catalytic domains were consistent with motions capturing the cognate DNA. These results indicate that the structure of EcoO109I is intrinsically flexible in the direction of its functional movement, to facilitate effective structural changes for sequence-specific DNA recognition and processing.
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Affiliation(s)
| | | | | | | | - Mitsunori Ikeguchi
- International Graduate School of Arts and Sciences, Yokohama City University, Yokohama 230-0045, Japan
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Chen X, Weber I, Harrison RW. Hydration water and bulk water in proteins have distinct properties in radial distributions calculated from 105 atomic resolution crystal structures. J Phys Chem B 2008; 112:12073-80. [PMID: 18754631 PMCID: PMC2768875 DOI: 10.1021/jp802795a] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Water plays a critical role in the structure and function of proteins, although the experimental properties of water around protein structures are not well understood. The water can be classified by the separation from the protein surface into bulk water and hydration water. Hydration water interacts closely with the protein and contributes to protein folding, stability, and dynamics, as well as interacting with the bulk water. Water potential functions are often parametrized to fit bulk water properties because of the limited experimental data for hydration water. Therefore, the structural and energetic properties of the hydration water were assessed for 105 atomic resolution (
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Affiliation(s)
- Xianfeng Chen
- Department of Biology, Georgia State University, Atlanta, Georgia 30302–4010, USA
| | - Irene Weber
- Department of Biology, Georgia State University, Atlanta, Georgia 30302–4010, USA
| | - Robert W. Harrison
- Department of Biology, Georgia State University, Atlanta, Georgia 30302–4010, USA
- Department of Computer Science, Georgia State University, Atlanta, Georgia 30302–4010, USA
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14
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Determination of the effective correlation time modulating 1H NMR relaxation processes of bound water in protein solutions. Magn Reson Imaging 2008; 26:254-60. [DOI: 10.1016/j.mri.2007.05.008] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2007] [Revised: 05/18/2007] [Accepted: 05/25/2007] [Indexed: 11/16/2022]
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Bui HH, Schiewe AJ, Haworth IS. WATGEN: an algorithm for modeling water networks at protein-protein interfaces. J Comput Chem 2007; 28:2241-51. [PMID: 17471455 DOI: 10.1002/jcc.20751] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Water molecules at protein-protein interfaces contribute to the close packing of atoms and ensure complementarity between the protein surfaces, as well as mediating polar interactions. Therefore, modeling of interface water is of importance in understanding the structural basis of biomolecular association. We present an algorithm, WATGEN, which predicts locations for water molecules at a protein-protein or protein-peptide interface, given the atomic coordinates of the protein and peptide. A key element of the WATGEN algorithm is the prediction of water sites that can form multiple hydrogen bonds that bridge the binding interface. Trial calculations were performed on water networks predicted by WATGEN at 126 protein-peptide interfaces (X-ray resolutions <or= 2.0 A), using different criteria for water placement. The energies of the predicted water networks were evaluated in AMBER8 and used in the choice of parameters for WATGEN. The 126 interfaces include 1264 experimentally determined bridging water sites, and the WATGEN algorithm predicts 72 and 88% of these sites within 1.5 and 2.0 A, respectively. The predicted number of water molecules at each interface was much higher than the number of water molecules identified experimentally. Therefore, random placement of the same number of water molecules as that predicted at each interface was performed as a control, and resulted in only 22 and 40% of water sites placed within 1.5 and 2.0 A of experimental sites, respectively. Based on these data, we conclude that WATGEN can accurately predict the location of water molecules at a protein-peptide interface, and this may be of value for understanding the energetics and specificity of biomolecular association.
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Affiliation(s)
- Huynh-Hoa Bui
- Division of Vaccine Discovery, La Jolla Institute of Allergy and Immunology, 9420 Athena Circle, La Jolla, California 92037, USA
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Heugen U, Schwaab G, Bründermann E, Heyden M, Yu X, Leitner DM, Havenith M. Solute-induced retardation of water dynamics probed directly by terahertz spectroscopy. Proc Natl Acad Sci U S A 2006; 103:12301-6. [PMID: 16895986 PMCID: PMC1567875 DOI: 10.1073/pnas.0604897103] [Citation(s) in RCA: 340] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The dynamics of water surrounding a solute is of fundamental importance in chemistry and biology. The properties of water molecules near the surface of a bio-molecule have been the subject of numerous, sometimes controversial experimental and theoretical studies, with some suggesting the existence of rather rigid water structures around carbohydrates and proteins [Pal, S. K., Peon, J., Bagchi, B. and Zewail A. H. (2002) J. Phys. Chem. B 106, 12376-12395]. Hydrogen bond rearrangement in water occurs on the picosecond time scale, so relevant experiments must access these times. Here, we show that terahertz spectroscopy can directly investigate hydration layers. By a precise measurement of absorption coefficients between 2.3 THz and 2.9 THz we could determine the size and the characteristics of the hydration shell. The hydration layer around a carbohydrate (lactose) is determined to extend to 5.13 +/- 0.24 A from the surface corresponding to approximately 123 water molecules beyond the first solvation shell. Accompanying molecular modeling calculations support this result and provide a microscopic visualization. Terahertz spectroscopy is shown to probe the collective modes in the water network. The observed increase of the terahertz absorption of the water in the hydration layer is explained in terms of coherent oscillations of the hydration water and solute. Simulations also reveal a slowing down of the hydrogen bond rearrangement dynamics for water molecules near lactose, which occur on the picosecond time scale. The present study demonstrates that terahertz spectroscopy is a sensitive tool to detect solute-induced changes in the water network.
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Affiliation(s)
- U. Heugen
- *Lehrstuhl für Physikalische Chemie II, Ruhr-Universität Bochum, 44780 Bochum, Germany; and
| | - G. Schwaab
- *Lehrstuhl für Physikalische Chemie II, Ruhr-Universität Bochum, 44780 Bochum, Germany; and
| | - E. Bründermann
- *Lehrstuhl für Physikalische Chemie II, Ruhr-Universität Bochum, 44780 Bochum, Germany; and
| | | | - X. Yu
- Department of Chemistry, University of Nevada, Reno, NV 89557
| | - D. M. Leitner
- Department of Chemistry, University of Nevada, Reno, NV 89557
| | - M. Havenith
- *Lehrstuhl für Physikalische Chemie II, Ruhr-Universität Bochum, 44780 Bochum, Germany; and
- To whom correspondence should be addressed. E-mail:
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Halle B. Protein hydration dynamics in solution: a critical survey. Philos Trans R Soc Lond B Biol Sci 2004; 359:1207-23; discussion 1223-4, 1323-8. [PMID: 15306377 PMCID: PMC1693401 DOI: 10.1098/rstb.2004.1499] [Citation(s) in RCA: 387] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The properties of water in biological systems have been studied for well over a century by a wide range of physical techniques, but progress has been slow and erratic. Protein hydration--the perturbation of water structure and dynamics by the protein surface--has been a particularly rich source of controversy and confusion. Our aim here is to critically examine central concepts in the description of protein hydration, and to assess the experimental basis for the current view of protein hydration, with the focus on dynamic aspects. Recent oxygen-17 magnetic relaxation dispersion (MRD) experiments have shown that the vast majority of water molecules in the protein hydration layer suffer a mere twofold dynamic retardation compared with bulk water. The high mobility of hydration water ensures that all thermally activated processes at the protein-water interface, such as binding, recognition and catalysis, can proceed at high rates. The MRD-derived picture of a highly mobile hydration layer is consistent with recent molecular dynamics simulations, but is incompatible with results deduced from intermolecular nuclear Overhauser effect spectroscopy, dielectric relaxation and fluorescence spectroscopy. It is also inconsistent with the common view of hydration effects on protein hydrodynamics. Here, we show how these discrepancies can be resolved.
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Affiliation(s)
- Bertil Halle
- Department of Biophysical Chemistry, Lund University, SE-22100 Lund, Sweden.
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Higurashi T, Hiragi Y, Ichimura K, Seki Y, Soda K, Mizobata T, Kawata Y. Structural Stability and Solution Structure of Chaperonin GroES Heptamer Studied by Synchrotron Small-angle X-ray Scattering. J Mol Biol 2003; 333:605-20. [PMID: 14556748 DOI: 10.1016/j.jmb.2003.08.056] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The GroES protein from Escherichia coli is a well-known member of the molecular chaperones. GroES consists of seven identical 10 kDa subunits, and forms a dome-like oligomeric structure. In order to obtain information on the structural stability and unfolding-refolding mechanism of GroES protein, especially at protein concentrations (0.4-1.2 mM GroES monomer) that would mimic heat stress conditions in vivo, we have performed synchrotron small-angle X-ray scattering (SAXS) experiments. Surprisingly, in spite of the high protein concentration, reversibility in the unfolding-refolding reaction was confirmed by SAXS experiments structurally. Although the unfolding-refolding reaction showed an apparent single transition with a Cm of 1.1 M guanidium hydrochloride, a more detailed analysis of this transition demonstrated that the unfolding mechanism could be best explained by a sequential three-state model, which consists of native heptamer, dissociated monomer, and unfolded monomer. Together with our previous result that GroES unfolded completely via a partially folded monomer according to a three-state model at low protein concentration (5 microM monomer), the unfolding-refolding mechanism of GroES protein could be explained uniformly by the three-state model from low to high protein concentrations. Furthermore, to clarify an ambiguity of the native GroES structure in solution, especially mobile loop structures, we have estimated a solution structure of GroES using SAXS profiles obtained from experiments and simulation analysis. The result suggested that the native structure of GroES in solution was very similar to that seen in GroES-GroEL complex determined by crystallography.
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Affiliation(s)
- Takashi Higurashi
- Department of Biotechnology, Faculty of Engineering, Tottori University, Koyama-Minami, Tottori 680-8552, Japan
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