Zhao Yu, Liang Rong, Yang Yiying, Lin Songyi
National Engineering Research Center of Seafood, School of Food Science and Technology, Dalian Polytechnic University, Dalian 116034, No. 1 Qinggongyuan, Ganjingzi District, PR China.
College of Agriculture, Liaocheng University, Liaocheng 252000, PR China.
J Theor Biol. 2020 May 7;492:110195. doi: 10.1016/j.jtbi.2020.110195. Epub 2020 Feb 14.
In this study, the pine nut peptides, Lys-Asp-His-Cyc-His (KDHCH), was used as the molecule dynamics (MD) simulations subject, which has been proved that the antioxidant activity was improved after pulse electric field (PEF) treatment and the secondary structure was changed as the circular dichroism (CD) results showed. In the present study, we applied the MD simulation to discover the mechanism of the antioxidant activity improvement. The MD results showed that with the PEF treatment of 15 kV/cm, the oxygen atoms of KDHCH changed a lot, especially the atoms No.32 and No.63, of which the distance difference value was -3.02 nm, compared with the 0 kV/cm PEF treatment. The result showed an approach trend between residues Lys-and His-and the α-C atom of Lys, Cys-and His-all got closer after the PEF treatment, which means the structure became tight after the PEF treatment. However, the results of 45 kV/cm PEF treatment presented more effects on the change of KDHCH. The calculations of oxygen atoms show an approach trend between residues Lys, Asp-and His. The α-C atom of Lys, Cys-and His-all got closer after the PEF treatment, which means the structure became tight after the PEF treatment and proved the results of the calculations of the oxygen atoms. The structures of PEF treated and untreated peptide samples were measured by 1D and 2D nuclear magnetic resonance (NMR) in order to verify the results of the molecular dynamics simulations. The 8.37-8.40 ppm (-NH- in chain) and 8.84-8.88 ppm (-NH- in chain) appeared left shift, while at the 8.45-8.47 ppm (-NH- in chain) occurred a right shift. The 7.82 ppm (-NH- in imidazole ring) on His-shifted left after PEF treatment, which reached 7.84 ppm by the 1D-H NMR spectroscopy. Moreover, the long-range connectivity between -NH (8.78 ppm) on 2H-ASP and -CH (2.72 ppm) on 1H-LYS; -SH (2.50 ppm) on 4H-CYS and -OH (3.53 ppm) on 5H-HIS all appeared in spectra of the PEF treatment sample. This study will also be helpful to further mechanism exploration.
在本研究中，将松仁肽Lys-Asp-His-Cyc-His（KDHCH）用作分子动力学（MD）模拟对象，脉冲电场（PEF）处理后其抗氧化活性得到提高，且圆二色性（CD）结果表明其二级结构发生了变化。在本研究中，我们应用MD模拟来探究抗氧化活性提高的机制。MD结果显示，在15 kV/cm的PEF处理下，KDHCH的氧原子变化很大，尤其是32号和63号原子，与0 kV/cm的PEF处理相比，其距离差值为-3.02 nm。结果表明，Lys和His残基与Lys的α-C原子之间呈现靠近趋势，PEF处理后Cys和His的α-C原子也都更靠近，这意味着PEF处理后结构变得紧密。然而，45 kV/cm的PEF处理对KDHCH的变化影响更大。氧原子的计算结果显示Lys、Asp和His残基之间呈现靠近趋势。PEF处理后Lys、Cys和His的α-C原子都更靠近，这意味着PEF处理后结构变得紧密，证实了氧原子的计算结果。为了验证分子动力学模拟的结果，采用一维和二维核磁共振（NMR）对PEF处理和未处理的肽样品结构进行了测定。8.37 - 8.40 ppm（链中-NH-）和8.84 - 8.88 ppm（链中-NH-）出现左移，而在8.45 - 8.47 ppm（链中-NH-）出现右移。His上7.82 ppm（咪唑环中-NH-）在PEF处理后左移，一维氢核磁共振波谱显示其变为7.84 ppm。此外，2H-ASP上的-NH（8.78 ppm）与1H-LYS上的-CH（2.72 ppm）之间的远程连接；4H-CYS上的-SH（2.50 ppm）与5H-HIS上的-OH（3.53 ppm）之间的远程连接均出现在PEF处理样品的光谱中。本研究也将有助于进一步探索其机制。
