Anomalous behavior of Brillouin light scattering at thermal denaturation of lysozyme

The thermal denaturation of lysozyme heated from $293$ to $355$ K has been studied using Brillouin light scattering. An anomalous temperature behavior of the velocity and damping of hypersound, which is accompanied by a decrease in the intensity of the Brillouin components in the experiments with the $180^\circ$ scattering geometry and almost complete their disappearance in the case of the $90^\circ$ scattering geometry, has been observed at the sol-gel transition in the vicinity of $343$ K. Such anomalies in the light scattering spectra are absent for a sodium acetate buffer used to prepare protein solutions. A mechanism describing the behavior of the intensities of the Brillouin components has been proposed.