skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Hydration water dynamics and instigation of protein structuralrelaxation

Abstract

Until a critical hydration level is reached, proteins do not function. This critical level of hydration is analogous to a similar lack of protein function observed for temperatures below a dynamical temperature range of 180-220K that also is connected to the dynamics of protein surface water. Restoration of some enzymatic activity is observed in partially hydrated protein powders, sometimes corresponding to less than a single hydration layer on the protein surface, which indicates that the dynamical and structural properties of the surface water is intimately connected to protein stability and function. Many elegant studies using both experiment and simulation have contributed important information about protein hydration structure and timescales. The molecular mechanism of the solvent motion that is required to instigate the protein structural relaxation above a critical hydration level or transition temperature has yet to be determined. In this work we use experimental quasi-elastic neutron scattering (QENS) and molecular dynamics simulation to investigate hydration water dynamics near a greatly simplified protein system. We consider the hydration water dynamics near the completely deuterated N-acetyl-leucine-methylamide (NALMA) solute, a hydrophobic amino acid side chain attached to a polar blocked polypeptide backbone, as a function of concentration between 0.5M-2.0M under ambient conditions. Wemore » note that roughly 50-60% of a folded protein's surface is equally distributed between hydrophobic and hydrophilic domains, domains whose lengths are on the order of a few water diameters, that justify our study of hydration dynamics of this simple model protein system. The QENS experiment was performed at the NIST Center for Neutron Research, using the disk chopper time of flight spectrometer (DCS). In order to separate the translational and rotational components in the spectra, two sets of experiments were carried out using different incident neutron wavelengths of 7.5{angstrom} and 5.5{angstrom} to give two different time resolutions. All the spectra have been measure at room temperature. The spectra were corrected for the sample holder contribution and normalized using the vanadium standard. The resulting data were analyzed with DAVE programs (http://www.ncnr.nist.gov/dave/). The AMBER force field and SPCE water model were used for modeling the NALMA solute and water, respectively. For the analysis of the water dynamics in the NALMA aqueous solutions, we performed simulations of a dispersed solute configuration consistent with our previous structural analysis, where we had primarily focused on the structural organization of these peptide solutions and their connection to protein folding. Further details of the QENS experiment and molecular dynamics simulations are reported elsewhere.« less

Authors:
; ;
Publication Date:
Research Org.:
COLLABORATION - UCBerkeley
OSTI Identifier:
927173
Report Number(s):
LBNL-53864
R&D Project: 449801; BnR: KJ0101010; TRN: US200811%%201
DOE Contract Number:  
DE-AC02-05CH11231
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
59; AMINO ACIDS; AQUEOUS SOLUTIONS; HYDRATION; PEPTIDES; POLYPEPTIDES; PROTEINS; RELAXATION; SAMPLE HOLDERS; SPECTRA; SURFACE WATERS; TIME RESOLUTION; TRANSITION TEMPERATURE; VANADIUM; WATER

Citation Formats

Russo, Daniela, Hura, Greg, and Head-Gordon, Teresa. Hydration water dynamics and instigation of protein structuralrelaxation. United States: N. p., 2003. Web. doi:10.2172/927173.
Russo, Daniela, Hura, Greg, & Head-Gordon, Teresa. Hydration water dynamics and instigation of protein structuralrelaxation. United States. doi:10.2172/927173.
Russo, Daniela, Hura, Greg, and Head-Gordon, Teresa. Mon . "Hydration water dynamics and instigation of protein structuralrelaxation". United States. doi:10.2172/927173. https://www.osti.gov/servlets/purl/927173.
@article{osti_927173,
title = {Hydration water dynamics and instigation of protein structuralrelaxation},
author = {Russo, Daniela and Hura, Greg and Head-Gordon, Teresa},
abstractNote = {Until a critical hydration level is reached, proteins do not function. This critical level of hydration is analogous to a similar lack of protein function observed for temperatures below a dynamical temperature range of 180-220K that also is connected to the dynamics of protein surface water. Restoration of some enzymatic activity is observed in partially hydrated protein powders, sometimes corresponding to less than a single hydration layer on the protein surface, which indicates that the dynamical and structural properties of the surface water is intimately connected to protein stability and function. Many elegant studies using both experiment and simulation have contributed important information about protein hydration structure and timescales. The molecular mechanism of the solvent motion that is required to instigate the protein structural relaxation above a critical hydration level or transition temperature has yet to be determined. In this work we use experimental quasi-elastic neutron scattering (QENS) and molecular dynamics simulation to investigate hydration water dynamics near a greatly simplified protein system. We consider the hydration water dynamics near the completely deuterated N-acetyl-leucine-methylamide (NALMA) solute, a hydrophobic amino acid side chain attached to a polar blocked polypeptide backbone, as a function of concentration between 0.5M-2.0M under ambient conditions. We note that roughly 50-60% of a folded protein's surface is equally distributed between hydrophobic and hydrophilic domains, domains whose lengths are on the order of a few water diameters, that justify our study of hydration dynamics of this simple model protein system. The QENS experiment was performed at the NIST Center for Neutron Research, using the disk chopper time of flight spectrometer (DCS). In order to separate the translational and rotational components in the spectra, two sets of experiments were carried out using different incident neutron wavelengths of 7.5{angstrom} and 5.5{angstrom} to give two different time resolutions. All the spectra have been measure at room temperature. The spectra were corrected for the sample holder contribution and normalized using the vanadium standard. The resulting data were analyzed with DAVE programs (http://www.ncnr.nist.gov/dave/). The AMBER force field and SPCE water model were used for modeling the NALMA solute and water, respectively. For the analysis of the water dynamics in the NALMA aqueous solutions, we performed simulations of a dispersed solute configuration consistent with our previous structural analysis, where we had primarily focused on the structural organization of these peptide solutions and their connection to protein folding. Further details of the QENS experiment and molecular dynamics simulations are reported elsewhere.},
doi = {10.2172/927173},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2003},
month = {9}
}