The Spectral and Kinetic Characteristics of Tryptophan Fluorescence in Human and Bovine Serum Albumin at Different Temperatures

The temperature dependence of the duration of tryptophan fluorescence in human and bovine serum albumin in an aqueous solution and glycerol in the temperature range of –170 to 20°C has been studied. A model of forward and reverse electronic transitions in the tryptophan molecule from the excited state to the ground state and to the charge transfer state has been constructed. Three main spectral regions of tryptophan fluorescence with different behaviors of the temperature dependences of transition rates from the excited state of tryptophan to the state with charge transfer were determined. It was found that the dynamics of the hydrogen bonding system in the selected spectral regions had a determining influence on the character of the changes in the duration of tryptophan fluorescence. The nonlinear dependence of intramolecular transition rates on temperature found in this work is determined by the interaction of tryptophan molecules with the microenvironment. The rearrangements in the hydrogen bonding system of albumin protein containing tryptophan molecule have a determining influence on the processes of excitation deactivation in tryptophan.