A Computational Chemistry Investigation into Amino Acid Catalyzed Water Oxidation in the Presence of Singlet Oxygen
Mentor:Emily Jarvis, Assistant Professor of Chemistry, loyola marymount university
Singlet molecular oxygen can be found in biological systems because of photosensitizers and UV/visible light and has been implicated in pathologies such as cataracts, ageing, sunburn and a number of other skin diseases. Several biological molecules, such as the amino acids tryptophan and histidine, react with singlet oxygen to produce changes in protein structure resulting in protein dysfunction. These photo-oxidized molecules not only lose their function, but can continue this chain of biological damage by the production of reactive oxygen species, such as peroxide or trioxidane species. Using computational chemistry techniques, we investigate oxidation of water catalyzed by photo-oxidized amino acids and amino acid derivatives. We investigate plausible reaction mechanisms using B3LYP density functional theory calculations within Gaussian 09 software employing the 6-311G basis for optimization of the molecular structures and pKa calculations for the amino acids and their derivatives. We employ the higher level cc-pVTZ basis for calculating energetics along the reaction coordinate. Calculations were done in the gas phase as well as in aqueous solutions using IEFPCM to account for implicit solvent effects. We report our energetics for competing reaction pathways and local bonding characteristics of the key O-O bond forming step.