The results showed that the overall diffusioncontrolled rate constant is equal to ×109 M-1 s -1 at . The zwitterionic form is the main existing form that plays an essential role in the HO - initiated oxidation of Ile (). The most preponderant reactions are found at C6-H () and C8-H () positions. Finally, the influence of temperature on the overall rate is also evaluated. | Cite this paper Vietnam J. Chem. 2023 61 S1 37-44 Research article DOI HO - initiated oxidation of isoleucine amino acid in the aqueous phase Nguyen Thi Huong Lan1 Truong Dinh Hieu1 2 Ngo Thi Chinh1 2 Nguyen Thi Le Anh1 2 Pham Thi Yen Nhi2 Dao Duy Quang1 2 1 Faculty of Pharmacy Duy Tan University Da Nang 55000 Viet Nam 2 Institute of Research and Development Duy Tan University Da Nang 55000 Viet Nam Submitted Revised Accepted Abstract Protein damage by the direct oxidative attack on amino acid side chains is considered the main cause of human aging and diseases. Therefore a better understanding of the oxidation process is necessary for screening and designing new drugs. In this work the oxidation of L-isoleucine Ile by HO radical was mechanistically and kinetically studied using M05-2X 6-311 G 3df 3pd M05-2X 6-311 G d p level of theory. All possible hydrogen transfer HT and single electron transfer SET reactions are considered in the aqueous phase. The results showed that the overall diffusion- controlled rate constant is equal to 109 M-1s-1 at . The zwitterionic form is the main existing form that plays an essential role in the HO - initiated oxidation of Ile . The most preponderant reactions are found at C6-H and C8-H positions. Finally the influence of temperature on the overall rate is also evaluated. Keywords. Amino acid oxidation free radical kinetics DFT hydrogen transfer SET. 1. INTRODUCTION or a carboxylic acid whereas the latter leads to the Fenton reaction-based production of hydroxyl radical Amino acids contain the amino -NH2 NH3 and or anion HO or HO that damages biomolecules. For carboxylic -COOH COO groups. 1 They are example Schöneich 14 studied the reaction mechanism naturally abundant in humans animals plants and of methionine Met oxidation by ROS. The results microorganisms. Currently approximately 500 illustrated that Met donates one or two electrons natural amino acids have been identified.
