title: Thermodynamic and magnetic resonance studies on the hydration of polymers: II. Protein-water interactions in powered ribonuclease.
abstract: ESR studies on spin-labeled amorphous RNase A as a function of varying concentrations of sorbed H2O and D2O will be presented. A relaxation analysis of saturation transfer (ST-)ESR spectra of 14N(1H) nitroxide spin-label molecules essentially fixed at amino acid residue His-105 will be given. A characteristic correlation has been observed between the microdynamic behavior--expressed by the rotational correlation times of the paramagnetic label--and the macroscopic thermodynamic entropy for the sorption process of H2O and D2O at RNase. This correlation is particularly pronounced at low water concentrations, vis., nH2O/nprotein less than or equal to 100. A significant difference in this concentration range exists between the two systems "RNase-H2O" and "RNase-D2O", which is manifested not only by the thermodynamic data but also by the microdynamic behavior extracted from the corresponding non-linear ESR absorption line shapes.
authors.affiliation: Institut für Biophysik, Universität Witten/Herdecke, Witten-Annen, Bundesrepublik Deutschland.
authors.forename: H
authors.initials: H
authors.lastname: Janzen
authors.forename: E
authors.initials: E
authors.lastname: Matuszak
authors.forename: E
authors.initials: E
authors.lastname: von Goldammer
authors.forename: H R
authors.initials: HR
authors.lastname: Wenzel
mesh_terms: D003198:Computer Simulation; D004578:Electron Spin Resonance Spectroscopy; D011487:Protein Conformation; D011506:Proteins; D012259:Ribonuclease, Pancreatic; D013816:Thermodynamics; D014867:Water
chemical_list: D011506:Proteins; D014867:Water; D012259:Ribonuclease, Pancreatic