[Similarity of Spectral Profiles with Individual Fluorescence Lifetime of Tryptophan in Proteins of Different Structure]

This work presents the results of the analysis of the fluorescence lifetime of tryptophan in three proteins: human serum albumin, bovine serum albumin and bacterial luciferase, containing 1, 2 and 7 tryptophan residues, respectively. It was shown that for all proteins fluorescence decay can be fitted by three lifetimes: τ1 = 6-7 ns, τ2 = -2,0-2,3 ns and τ3 ≤ 0,1 ns (the native state) and τ1 = 4,4-4,6 ns, τ2 = 1,7-1,8 ns and τ3 ≤ 0,1 ns (the denaturated state). It was found that spectral profiles with individual protein fluorescence lifetime have similar peak wavelength and identical half-width of the spectrum as in the native state (λ(max)τ1 = 342 nm, λ(max)τ2 = 328 nm and λ(max)τ3 = 3i5 nm), and in the denaturated state (λ(max)τ1 = 350 nm, λ(max)τ2 = 343 nm and λ(max)τ3 = 317 nm). In addition, the differences in the steady-state spectra of the studied proteins are caused by the individual ratio of lifetime contributions. The correlation between. lifetime components and a known classification of the tryptophan residues in the structure of proteins, under study was performed within the discrete states model.