Reaction of Amino Acids, Di- and Tripeptides with the Environmental Oxidant NO3.: A Laser Flash Photolysis and Computational Study.
Absolute rate coefficients for the reaction between the important environmental free radical oxidant NO3.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 1.8×106m-1s-1per abstractable hydrogen atom. The considerably faster reaction with phenylalanine [k=(1.1±0.1)×107m-1s-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.
School of Chemistry, Bio21 Institute, The University of Melbourne, Parkville, Victoria, 3010, Australia.
Joses G
JG
Nathanael
School of Chemistry, Bio21 Institute, The University of Melbourne, Parkville, Victoria, 3010, Australia.
Amber N
AN
Hancock
School of Chemistry, Bio21 Institute, The University of Melbourne, Parkville, Victoria, 3010, Australia.
Uta
http://orcid.org/0000-0003-1756-5449
U
Wille
D002563:Cerium / Q000737:chemistry; D039301:Computers, Molecular; D004151:Dipeptides / Q000737:chemistry*; D004579:Electron Transport; D006859:Hydrogen / Q000737:chemistry; D007700:Kinetics; D007834:Lasers; D009589:Nitrogen Oxides / Q000737:chemistry*; D009842:Oligopeptides / Q000737:chemistry*; D016877:Oxidants / Q000737:chemistry; D010649:Phenylalanine / Q000737:chemistry*; D010782:Photolysis / Q000528:radiation effects; D013816:Thermodynamics
D004151:Dipeptides; D009589:Nitrogen Oxides; D009842:Oligopeptides; D016877:Oxidants; C032786:cerium nitrate; D002563:Cerium; D010649:Phenylalanine; D006859:Hydrogen; C039900:nitroxyl
density functional calculations; kinetics; nitrate radical; oxidative damage; peptides; reaction mechanisms