Département de chimie moléculaire

The photoreaction mechanism of [Ru(TAP)2(phen)]2+ and [Ru(TAP)3]2+ (TAP = 1,4,5,8-tetraazaphenanthrene) with tryptophan (Trp), N-acetyl-Trp, and Lys-Trp-Lys is examd. The existence of a photoelectron-transfer process from the amino acid unit is demonstrated by laser flash photolysis expts. The back electron transfer (BET) from the reduced complex to the oxidized amino acid, occurring at the microsecond time scale, corresponds approx. to an equimol.-bimol. process; however, it is disturbed by another reaction, originating from the oxidized Trp. Moreover, in competition with the BET, the reduced and oxidized intermediates give rise to an adduct. The latter is clearly detected by gel electrophoresis expts. in denaturing conditions, with a system composed of an oligonucleotide derivatized at the 3' end by the RuIITAP complex and hybridized with the complementary sequence functionalized at the 5' end by the tripeptide Lys-Trp-Lys. Thus, upon illumination, a crosslinking between the two strands is obsd., which originates from the presence of a Trp residue. [on SciFinder(R)]