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Computational study of molecular structures and antioxidant mechanism of ovothiols

In this paper, the molecular structure and antioxidant activity of ovothiols (OSH) have been studied by using four DFT functionals, namely B3LYP, B3PW91, X3LYP, M06 with the basis set of 6-311++G(2df,2p). | Journal of Science and Technology 54 (2C) (2016) 328-333 COMPUTATIONAL STUDY OF MOLECULAR STRUCTURES AND ANTIOXIDANT MECHANISM OF OVOTHIOLS Le Tien Dung1, Pham Thi Thanh Xuan1, Dinh Tuan2, Pham Le Minh Thong3, Pham Cam Nam1, * 1 University of Danang - University of Science and Technology, Faculty of Chemistry, 54 Nguyen Luong Bang, Da Nang and VN-UK, Institute for Research & Executive Education 2 3 Hue University’s College of Sciences, Department of Chemistry, 77 Nguyen Hue, Hue Duy Tan University, Institute of Research and Development, 03 Quang Trung, Da Nang * Email: pcnam@dut.udn.vn; camnamp@yahoo.com Received: 15 June 2016; Accepted for publication: 23 October 2016 ABSTRACT In this paper, the molecular structure and antioxidant activity of ovothiols (OSH) have been studied by using four DFT functionals, namely B3LYP, B3PW91, X3LYP, M06 with the basis set of 6-311++G(2df,2p). Two major antioxidant mechanisms, namely, hydrogen atom transfer (HAT) and stepwise electron transfer-proton transfer (SET-PT) have been investigated and applied on three optimized conformations of ovothiols. Bond dissociation enthalpy (BDE), vertical ionization energy (IE), proton dissociation enthalpy (PDE), chemical potential (µ), chemical hardness (η) and global electrophilicity (ω), have been calculated and discussed in the gas phase. Keywords: ovothiols, antioxidant, HAT, SET-PT, BDE, IE, PDE, density functional theory. 1. INTRODUCTION Sulfur containing functional groups have been found to play an important in both primary and secondary metabolites [1]. The maintenance of cellular redox homeostasis, the maintenance of protein thiol-disulfide ratios and the protection of cells from reactive oxygen species occur under the presence of thiols in living systems. Ovothiols (1-methyl-4-mercaptohistidines) are present in millimolar concentrations in sea urchin eggs [2]. Such high concentrations of these heterothiols might be needed to protect the fertilized sea-urchin egg from free .