title: Water-proton nuclear magnetic relaxation in heterogeneous systems: hydrated lysozyme results.
abstract: Spin-lattice relaxation rates of water protons in hydrated immobilized lysozyme are measured as a function of magnetic field strength. The dependence of water relaxation versus hydration is presented from 35 to 55% by weight water content. The water-proton relaxation is directly coupled to that of the protein and the coupling exists in the absence of chemical exchange. A model is applied where relaxation within the two proton phases is coupled through a dipolar cross-relaxation mechanism as well as chemical exchange. The observed amplitudes of the water-proton relaxation profiles scale with the ratio of protein to water protons as well as the protein-proton relaxation rate. The field dependence of the protein-proton spin-lattice relaxation is presented in the presence of D2O where a cross-relaxation coupling is absent. The coupled relaxation model accounts well for the NMR relaxation data as a function of magnetic field strength which is similar to measurements on other heterogeneous systems such as tissues.
authors.affiliation: Department of Biophysics, University of Rochester, New York 14642.
authors.forename: C C
authors.initials: CC
authors.lastname: Lester
authors.forename: R G
authors.initials: RG
authors.lastname: Bryant
mesh_terms: D009682:Magnetic Resonance Spectroscopy; D009113:Muramidase; D011522:Protons; D014867:Water
chemical_list: D011522:Protons; D014867:Water; D009113:Muramidase