Pressure effects on tryptophan and its derivatives

The high pressure effects on fluorescence of free tryptophan (Trp) and its derivatives, N-acetyl-tryptophan (AT), N-acetyl-tryptophanamide (NATA), try ptophanamide (TA), and tryptophan, containing 6-polypeptides in aqueous sol ution, were investigated in a pressure range from 0.1 to 650 MPa, It was fo und by analyzing the center of spectral mass in the wave length range from 300 to 450 nm that high pressure shifted the fluorescence spectra of all th ese species to red direction: 421 cm(-1) for Trp, 305 cm(-1) for AT, 310 cm (-1) for NATA, 265 cm(-1) for TA, and 220 cm(-1) for single tryptophan cont aining 6-polypeptides. All the fluorescence efficiencies (i.e., quantum yie ld) of the compounds were reduced with pressure except free tryptophan wher e its fluorescence efficiency was enhanced with pressure. Glycerol, ethanol , and pH obviously influenced the pressure effects on their fluorescence ch aracteristics. Since the tryptophan fluorescence is usually used as a probe for protein structural investigation, these findings suggested that the in trinsic pressure effect on tryptophan (or its derivatives) must be taken in consideration to explain the phenomenon observed in high pressure study on biomolecules when using the usual fluorospectroscopic approaches. In the p resent investigation, the mechanisms involved for pressure effects on trypt ophan and its derivatives were explored and discussed. (C) 2000 Academic Pr ess.