Protein dynamics studied on myoglobin

Two methods of inelastic scattering of synchrotron radiation were used to m easure the dynamics of myoglobin in the temperature range from T = 60 K to 300 K. The inelastic Rayleigh scattering of metmyoglobin was analyzed by de layed elastic nuclear forward scattering of an iron foil. This yields avera ged information on all phonons within the sample. The mean square displacem ent of the atoms due to this dynamics is [x(2)]/T = 2.1 . 10(-4) Angstrom(2 ) K-1 on average. Complementary information was obtained by phonon assisted nuclear scattering on deoxymyoglobin. This method selects the phonons coup ling to the iron atom in the active center of the protein. The mean square displacement of the iron was measured to be [x(2)]/T = 0.6 . 10(-4) Angstro m(2) K-1. The results are in agreement with Mossbauer absorption experiment s in the low temperature range. Above 200 K the results allow one to distin guish between harmonic and quasidiffusive dynamics within the protein. A co mparison with Raman spectroscopy is made.