Long-lived fluorescence lifetime from tyrosine in a peptide derived from S-100b

It was shown in an earlier report (Turner et al., 1989, Biochem. Cell Biol. 67; 179-186) that the anomalous steady-state fluorescence emission spectra observed for the protein S-100b in aqueous solution at pH 7.5 contains a long-lived fluorescence decay component. In this study, a peptide consisting of residues 11 to 27 of the beta-subunit, was investigated. 11Ile-Asp-Val-Phe-His15-Gln-Tyr-Ser-Gly-Arg20-Glu-Gly- Asp-Lys-His25-Lys-Leu27 Fluorescence lifetimes were measured at the emission maximum and in the red edge of the spectrum. At wavelengths greater than 320 nm, the data was best fit with three exponentials. The third exponential gave lifetimes of 13.1 ns and 15.9 ns when the peptide was dissolved in the solvents propane-2-ol and propane-1,2-diol, respectively (lambda EX = 275 nm, lambda EM = 350 nm). These fluorescence lifetimes are similar to that observed for a decay component of native S-100b in the red edge of the emission, suggesting that the 1 degrees and 2 degrees features of a heptadecapeptide from S-100b protein has enough structural information when dissolved in solvents of intermediate polarity provide appropriate conditions for long-lived fluorescence from a tyrosine/tyrosinate species to occur.