Tyrosine fluorescence probing of the surfactant-induced conformational changes of albumin.

Tyrosine fluorescence in native proteins is known to be effectively quenched, whereas its emission increases upon proteins' unfolding. This suggests that tyrosine fluorescence could be exploited for probing structural rearrangements of proteins in addition to the extensively used tryptophan emission. We studied the possibility of using tyrosine fluorescence as an indicator of surfactant-induced conformational changes in albumins. It was shown that fluorescence of tyrosine residues, which are uniformly distributed all over the protein molecules, allows the detection of subtle structural rearrangements of proteins upon surfactant binding, which do not influence the properties of a single tryptophan residue buried in the inner hydrophobic region of human serum albumin. Tyrosine fluorescence properties, including its fluorescence lifetime, revealed the multistage character of surfactant binding to albumin, consistent with the data provided by other methods. The obtained results demonstrate the possibility of probing conformational changes in proteins using tyrosine photophysical parameters as indicators.