Low-Frequency Dynamics of BSA Complementarily Studied by Raman and Inelastic Neutron Spectroscopy.

The present study focuses on protein motions on the picosecond time scale, generally characterized by the overlapping of vibrational and relaxational dynamics in disordered molecular systems. Recently, it has been demonstrated that a dry protein, bovine serum albumin (BSA), shows a glass-like transition in the temperature range between 240 and 260 K. Here, we present the results of combined low-frequency Raman and inelastic neutron scattering studies of dry BSA under conditions similar to those of this glass-like transition. The use of both techniques allows us to perform a detailed comparison of the dynamic susceptibility and vibrational density of states of BSA obtained at different temperatures and to calculate the light-vibration coupling coefficient, C(ω). Moreover, we analyzed the temperature evolution of the boson peak and a peak located at ∼80 cm-1, which has previously been identified to originate from protein dynamics, and observed that both modes show anomalous temperature behavior in the vicinity of Tg.