Phase Transition In Tetragonal Hen Egg-White Lysozyme Crystals

Lattice dynamics of tetragonal hen egg-white lysozyme crystals was studied by Brillouin light scattering and differential ac-nanocalorimetry with controlled relative humidity from 298 to 330 K. Temperature dependences of fast quasitransverse phonon velocity and integral intensity were found to exhibit anomalies in the vicinity of 306 K. An anomaly in the temperature behavior of heat capacity was also observed near this temperature. It is concluded that the anomalies point to a structural phase transition. Possible mechanisms of phase transition in lysozyme crystals are discussed.