Model cyclic peptides to investigate the Trp-mediated photo reduction of disulfide bonds in proteins

摘要

Irradiation with ultraviolet light may reduce or even abolish the biological activity of proteins,The damage is initiated through photon absorption of the chromophore amino acids,for example the indole part of tryptophan.The structure of goat alpha-lactalbumin(GLA)is stabilized by four S-S bridges and some are in close contact with Trp-residues.Upon irradiation at 280 nm we observed structural modification of native GLA.Spectroscopic data presented evidence that these conformational changes are caused by cleavage of disulfide bonds,probably due to a direct e transfer from the excited indole part to the disulfide bond.To clarify the role of Trp and of other less specific groups,,cyclic peptides containing a single Trp-residue and one ring closing S-S bridge are studied in photolysis experiments.In a number of variants Trp was changed to Phe and Val.Here we report the synthesis and spectroscopic investigation of cyclic peptides chosen from molecular modelling.