Time-Resolved CIDNP Study of Intramolecular Charge Transfer in the Dipeptide Tryptophan-Tyrosine

• DOI: 10.1021/jp011858t
• Publication Date: 2002-07-26T04:47:33Z
• Authors: Olga B. Morozova; Alexandra V. Yurk...; Yuri P. Tsentalovich; Malcolm D. E. Forbes; Renad Z. Sagdeev
• Keywords: CIDNP

Time-resolved chemically induced dynamic nuclear polarization (CIDNP) and laser flash photolysis (LFP) techniques have been used to study the kinetics mechanism of photochemical reaction between 2,2'-dipyridyl (DP) dipeptide l-tryptophan-l-tyrosine (TrpH-TyrOH) in acidic aqueous solution (pH = 3.8). Analysis geminate CIDNP pattern reveals that quenching protonated triplet dipyridyl TDPH+ results formation both tryptophan tyrosine radicals from with comparative efficiency. The total rate constant by TrpH-TyrOH was found be (2.5 ± 0.3) × 109 M-1 s-1. radical transformation TrpH+•→TyrO• via intramolecular electron transfer (IET) leads an increasing tyrosyl concentration, growth signals, fast decay signal TrpH, inversion sign emission enhanced absorption for DP. spin−lattice relaxation times formed reactions IET (5 105s-1) were determined quantitative analysis at different concentrations D2O. A significant isotope effect (kH/kD 1.5) LFP measurements. In presence efficient IET, degenerate exchange TrpH•+ diamagnetic molecule makes a negligible contribution signal.