本研究以前期研究所得的Met-Met-Cys-Thr-Asp（MMCTD）抗氧化肽为研究载体，以DPPH自由基清除能力为抗氧化活性衡量指标，借助中红外光谱（Mid-infrared spectroscopy，MIR）、圆二色谱（Circular dichroism spectrum，CD）、Zeta电位以及核磁共振（Nuclear magnetic resonance，NMR）技术，深入探究高压脉冲电场（pulsed electric field, PEF）技术对MMCTD抗氧化肽活性的影响。研究表明在电场强度为5 kV/cm、电场频率为2400 Hz时，MMCTD的自由基清除能力达到最大值94.27%±0.03%且MMCTD的Zeta电位值下降到10.85±0.98 mV。MIR和NMR结果表明经PEF处理后MMCTD的官能团并未发生改变但所含的H质子所处的化学环境有所改变。经CD分析，其二级结构中的β-折叠的含量从13.70%下降至0.00%，β-转角以及无规则卷曲的含量都有着明显的增加。这些变化不仅初步揭示了PEF可以通过改变MMCTD的二级结构以及表面电荷分布来提高它抗氧化活性，更为进一步探究PEF提高抗氧化肽活性的机理奠定基础。

The antioxidant peptide Met-Met-Cys-Thr-Asp (MMCTD) obtained in the previous study was analyzed in this work, and 2,2-diphenyl-1-picrylhydrazyl (DPPH?) radical-scavenging capacity served as an indicator of antioxidant activity. Mid-infrared spectroscopy (MIR), circular dichroism (CD) spectroscopy, zeta-potential, and nuclear magnetic resonance (NMR) were used for an in-depth analysis of the effects of a pulsed electric field (PEF) on the antioxidant activities of peptide MMCTD. The results showed that when the electric field intensity was 5 kV/cm and pulse frequency was 2400 Hz, the DPPH radical-scavenging capacity reached a peak value (94.27%±0.03%, mean±SD) and the zeta-potential of peptide MMCTD being treated was reduced to 10.85±0.98 mV. The MIR and NMR results revealed that after the PEF treatment, the functional groups of peptide MMCTD were not changed, but the chemical environment of the hydrogen ion (proton) was changed. The CD analysis indicated that the proportion of the β-sheet in the secondary structure decreased from 13.7% to 0%, and the relative amounts of the β-turn and random coil increased significantly. These changes not only preliminarily reveal that PEF can enhance the antioxidant activity of peptide MMCTD by changing the secondary structure and surface charge distribution but also lay the foundation for identification of the mechanism underlying the enhancement of antioxidant activity by PEF.

“十二五”国家科技支撑计划项目（2012BAD33B03）