Study of the chemical structures of the photo-cross-linking products between Tyr and the 5-azido-2-nitrobenzoyl residue

Irradiation of N-(tyrosyl)-N'-(5-azido-2-nitrobenzoyl)-1,2-diaminoethane (I ) initiates chemical reactions that lead to different products depending on the experimental conditions. All of these products are attributed to the r eactions of triplet 4-nitrobenzoyl nitrene (4NBN). The reactions of triplet 4NBN with the tyrosyl residue result in the formation of two distinct prod ucts: compound II, which is unstable in aqueous solution, and the stable co mpound cyclo-[1-(4'-nitro-3'-benzoyl)-2-(aminotyrosyl)-N,N'-ethylenediamine ] (III). The formation of II is detected only in aerobic conditions. The un stable photoproduct II converts almost completely into compound III when it s solution is concentrated. The photoproducts II and III have absorption sp ectra that are close to those of the photolabelled peptides. This finding i s important for speculating about the chemical nature of the photomodificat ion products of protein tyrosyl residues by the arylazide group. (C)2000 El sevier Science S.A. All rights reserved.