Dynamic and thermodynamic effects of glycerol on bovine serum albumin in aqueous solution: a tryptophan phosphorescence study.

The phosphorescence decay of bovine serum albumin in water-glycerol solutions at room temperature is analysed by the maximum entropy method. While in pure water the decay was found to be quasi-monoexponential, in water-glycerol mixtures it is associated with more complex lifetime distributions. This is a direct proof for the existence of multiple protein conformers. It was also found that the increase of the glycerol concentration induces a continuous shift of the lifetime pattern to longer lifetimes. This effect is analysed in connection with the coupling between the solvent viscosity and the internal protein mobility.