DYNAMIC STRUCTURE OF PROTEINS IN SOLID-STATE - H-1 AND C-13 NMR RELAXATION STUDY

Temperature dependencies of H-1 non-selective NMR T-1 and T-2 relaxati on times measured at two resonance frequencies and natural abundance C -13 NMR relaxation times T-1 and T-1r measured at room temperature hav e been studied in a set of dry and wet solid proteins - Bacterial RNas e, lysozyme and Bovine serum albumin (BSA). The proton and carbon data were interpreted in terms of a model supposing three kinds of interna l motions in a protein. These are rotation of the methyl protons aroun d the axis of symmetry of the methyl group, and fast and slow oscillat ions of all atoms. The correlation times of these motions in solid sta te are found around 10(-11), 10(-9) and 10(-6) s, respectively. All ki nds of motion are characterized by the inhomogeneous distribution of t he correlation times. The protein dehydration affects only the slow in ternal motion. The amplitude of the slow motion obtained from the carb on data is substantially less than that obtained from the proton data. This difference can be explained by taking into account different rel ative inter- and intra- chemical group contributions to the proton and carbon second moments. The comparison of the solid state and solution proton relaxation data showed that the internal protein dynamics in t hese states is different: the slow motion seems to be few orders of ma gnitude faster in solution.