Modulation of Protein Dynamics by Glycerol in Water-Soluble Chlorophyll-Binding Protein (WSCP)

Proteins are inherently dynamic entities that rely on flexibility across multiple timescales to perform their biological functions. The surrounding environment plays a critical role in modulating protein dynamics by exerting plasticizing or stabilizing effects. In order to characterize the conformational dynamics of Water-Soluble Chlorophyll-Binding Protein (WSCP), we measured Quasielastic Neutron Scattering (QENS) spectra over a wide temperature range between 100 and 300 K. The impact of glycerol, a common stabilizer, is investigated by comparing WSCP dissolved in a glycerol–water-containing buffer (WSCPW+G) with WSCP in a water-containing buffer (WSCPW). The results indicate that conformational protein dynamics are widely suppressed below 200 K but increase above this threshold, with the appearance of localized protein motions on the picosecond timescale. Glycerol appears to limit protein mobility between 280 and 300 K due to its high viscosity and hydrogen bonding in contrast to WSCP in water. Inelastic Neutron Scattering (INS) reveals the vibrational dynamics of WSCP with pronounced low-energy protein vibrations observed at about 2.5 and 6 meV. In the presence of glycerol, however, a stiffening of the vibrational motions which shifts the vibrational peaks to higher frequencies is observed.