Structural dynamics of melanin investigated by Rayleigh scattering of Mössbauer radiation

Measurements of Rayleigh scattering of Mössbauer radiation (RSMR) have been performed on synthetic L‐Dopa melanin as a function of the scattering vector, Q, and temperature, T, and are compared with the results of X‐ray diffraction analyses. The data obtained allow us to derive a radial distribution function for the atomic positions not affected by the dynamic disorder and determined only by the distribution of equilibrium interatomic distances. The mean‐square atomic displacements, <u2>, derived from the RSMR measurements, evidence a strong anisotropy of the atomic vibrations: even at room temperature, <u2> reaches fairly high values for off‐plane displacements, as compared with those for motions within the planes of the structure. A connection is suggested between the observed dynamics and the biological screening action of melanins.