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Reaction of Amino Acids, Di‐ and Tripeptides with the Environmental Oxidant NO 3 . : A Laser Flash Photolysis and Computational Study
Author(s) -
Nathanael Joses G.,
Hancock Amber N.,
Wille Uta
Publication year - 2016
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.201600994
Subject(s) - tripeptide , flash photolysis , flash (photography) , chemistry , laser , photodissociation , photochemistry , amino acid , physics , optics , biochemistry , reaction rate constant , kinetics , quantum mechanics
Absolute rate coefficients for the reaction between the important environmental free radical oxidant NO 3 . and a series of N ‐ and C ‐protected amino acids, di‐ and tripeptides were determined using 355 nm laser flash photolysis of cerium(IV) ammonium nitrate in the presence of the respective substrates in acetonitrile at 298±1 K. Through combination with computational studies it was revealed that the reaction with acyclic aliphatic amino acids proceeds through hydrogen abstraction from the α‐carbon, which is associated with a rate coefficient of about 1.8×10 6 m −1 s −1 per abstractable hydrogen atom. The considerably faster reaction with phenylalanine [ k =(1.1±0.1)×10 7 m −1 s −1 ] is indicative for a mechanism involving electron transfer. An unprecedented amplification of the rate coefficient by a factor of 7–20 was found with di‐ and tripeptides that contain more than one phenylalanine residue. This suggests a synergistic effect between two aromatic rings in close vicinity, which makes such peptide sequences highly vulnerable to oxidative damage by this major environmental pollutant.