HO - initiated oxidation of isoleucine amino acid in the aqueous phase

The results showed that the overall diffusioncontrolled rate constant is equal to 4.82×109 M-1 s -1 at 298.15K. The zwitterionic form is the main existing form that plays an essential role in the HO - initiated oxidation of Ile (99.98%). The most preponderant reactions are found at C6-H (36.19%) and C8-H (37.77%) positions. Finally, the influence of temperature on the overall rate is also evaluated.
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HO - initiated oxidation of isoleucine amino acid in the aqueous phaseCite this paper: Vietnam J. Chem., 2023, 61(S1), 37-44 Research articleDOI: 10.1002/vjch.202200210 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; AcceptedAbstract Protein damage by the direct oxidative attack on amino acid side chains is considered the main cause of human agingand diseases. Therefore, a better understanding of the oxidation process is necessary for screening and designing newdrugs. In this work, the oxidation of L-isoleucine (Ile) by HO● radical was mechanistically and kinetically studied usingM05-2X/6-311++G(3df,3pd)//M05-2X/6-311++G(d,p) level of theory. All possible hydrogen transfer (HT) and singleelectron transfer (SET) reactions are considered in the aqueous phase. The results showed that the overall diffusion-controlled rate constant is equal to 4.82×109 M-1s-1 at 298.15K. The zwitterionic form is the main existing form that playsan essential role in the HO● - initiated oxidation of Ile (99.98%). The most preponderant reactions are found at C6-H(36.19%) and C8-H (37.77%) 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 radicalAmino acids contain the amino (-NH2/NH3+) and or anion (HO• or HO−) that damages biomolecules. Forcarboxylic (-COOH/COO–) groups.[1] They are example, Schöneich[14] studied the reaction mechanismnaturally abundant in humans, animals, plants, and of methionine (Met) oxidation by ROS. The resultsmicroorganisms. Currently, approximately 500 illustrated that Met donates one or two electronsnatural amino acids have been identified.[2] Among depending on the ROS nature to form Met radicalthem, only 20 α-amino acids play the role of building cation or Met sulfoxide, respectively. Galano et al.blocks of proteins and are necessary for the normal computationally studied the HO•-initiated oxidation ofphysiological functions of cells.[3] All amino acids, asparagine (Asn)[15] and serine (Ser)[16] in the gas phaseexcept for glycine, have the L-configuration in free at the B3LYP/6-311G(d,p) level of theory. Theform.[4] Essential and non-essential amino acids are hydrogen transfer (HT) was identified to occurtwo main types of natural α-amino acids,[5] which exclusively from the beta site, and the overallplay an important role in metabolism, temperature-dependent rate constants (koverall) areneurotransmitters, and intercellular signaling.[6] (5.50±0.25)×107 exp[(1482±13)/T] (Asn), and Oxidative damage of biomolecules like DNA, (3.91±0.17) × 108 exp[(1446±12)/T] (Ser) (Lmol-1s-1).lipids, and protein by reactive oxygen species (ROS) Another study by Galano et al.[17] showed that thehas generally been involved in the pathogenesis of oxidation of Met by HO• radicals arises almost via HTseveral diseases, such as cancer, allergies, viral reaction at the gamma (γ) site. The overallinfections, inflammation, atherosclerosis, and temperature-dependent rate constant at theneurodegeneration,[7,8] as well as certain physiological BHandHLYP/6-311G(d,p) level was k =processes (i.e., aging, ischemia-reperfusion injury, and (2.12±0.26)×107 exp[(2047±34)/T], (in Lmol-1 s-1).protein turnover).[9] The oxidation mechanism of α- Medina et al have thermo-chemically and kineticallyamino acids has been attracting the attention of several investigated the reaction of a leucine derivative withworks for decades.[10-14] The modification of free biological radicals, in both aqueous and lipid media.[18]amino acids and proteins might be related to ionizing Their results illustrate that the γ site of leucine was theradiation in the presence of oxygen or metal ion- most favorable for the reactions with •N3, •OOCCl3,ca ...