Damage of amino acids by aliphatic peroxyl radicals: a kinetic and computational study

Abstract

Absolute second-order rate coefficients for the reaction of the N- and C-protected amino acids tyrosine (Tyr), tryptophan (Trp), methionine (Met) and proline (Pro) with triethylamine-derived aliphatic peroxyl radical TEAOO˙, which was used as a model for lipid peroxyl radicals, were determined using laser flash photolysis. For Ac-Tyr-OMe a rate coefficient of 1.4 × 104 M−1 s−1 was obtained, whereas the reactions with Ac-Trp-OMe and Ac-Met-OMe were slower by a factor of 4 and 6, respectively. For the reaction with Ac-Pro-OMe only an upper value of 103 M−1 s−1 could be determined, suggesting that Pro residues are not effective traps for lipid peroxyl radicals. Density functional theory (DFT) c..