Thermodynamic and magnetic resonance studies on the hydration of polymers: II. Protein-water interactions in powered ribonuclease.
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.
Janzen
H
H
Institut für Biophysik, Universität Witten/Herdecke, Witten-Annen, Bundesrepublik Deutschland.
Matuszak
E
E
von Goldammer
E
E
Wenzel
H R
HR
D003198:Computer Simulation; D004578:Electron Spin Resonance Spectroscopy; D011487:Protein Conformation; D011506:Proteins; D012259:Ribonuclease, Pancreatic; D013816:Thermodynamics; D014867:Water
D011506:Proteins; D014867:Water; D012259:Ribonuclease, Pancreatic