Selenium-chelating corn oligopeptide as a potential antioxidant supplement: investigation of the protein conformational changes and identification of the antioxidant fragment composition
2020
Qin, Xiu-Yuan | Zhang, Jiang-Tao | Li, Guo-Ming | Cai, Mu-Yi | Lu, Jun | Gu, Rui-Zeng | Liu, Wenying
A selenium-chelating corn oligopeptide (Se-COP) with high protein and low molecular weight was prepared as a selenium supplement. We utilized infrared (IR), ultraviolet (UV), and circular dichroism (CD) spectroscopy, 1-anilinonaphthalene-8-sulfonate (ANS)-binding fluorescence spectra, and isothermal titration calorimetry (ITC) to analyze and describe Se-COP and its reactions. It was concluded that the chelation reaction was a spontaneous process driven by enthalpy and entropy, with ΔH=3.79 × 10⁴ ± 4075 cal/mol, ΔS = 146 cal/mol, ΔG = –23356.30 ± 126.94 cal/mol, binding constant Kₐ = 1.18 × 10⁴ ± 855 M–¹, and binding site number n = 0.13 ± 0.0126, and described as coordination bonds forming and hydrophobic interaction, as well as protein conformational changes including secondary and tertiary hydrophobic structure. Se-COP had strong antioxidant capacity, and mass spectrometry (MS) was used to identify the antioxidant peptide fragment, which was characterized as LLPPY and quantified at 428.95 ng/mg. This study indicated that Se-COP prepared by chelation may be a Se supplement with antioxidant capacity that can be applied in functional foods or ingredients.
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