大豆蛋白肽-酪蛋白非磷酸肽组装产物的荧光光谱分析及抗氧化性研究

对不同p H值条件下制备的大豆蛋白肽-酪蛋白非磷酸肽组装产物(casein non-phosphopeptides-soybean peptide complex,CNPSPC)的荧光光谱及抗氧化性进行分析。结果表明,随着p H值增加,CNPSPC埋藏在疏水环境中的Trp残基暴露到分子表面的强度逐渐低于组装前的原料蛋白,且Trp残基所处的微环境极性有所降低。硫磺素T荧光光谱分析表明,p H 6.0的制备条件下,CNPSPC荧光强度最大,此时CNPSPC的β-折叠结构含量可能最多。组装改变了CNPSPC的Trp残基在空间结构中所处的微环境,使CNPSPC的分子构象发生改变。与酪蛋白非磷酸肽(casein non-phosphopeptides,CNPP)和大豆蛋白肽(soybean peptide,SP)相比,CNPSPC的抗氧化能力有所提高,在p H 6.0时其清除1,1-二苯基-2-三硝基苯肼自由基、O_2~-·、·OH能力达到最大,分别提高到组装前大豆蛋白的3.34、1.12倍和1.08倍。

Fluorescence Spectral Analysis and Antioxidant Effect of Soybean Ploypeptide-Casein Non-Phosphorylated Peptide Assembly

The fluorescence spectra and antioxidant properties of casein non-phosphopeptides-soybean peptide complex (CNPSPC) prepared under different pH conditions were analyzed. The results showed that with the increase of pH, the content of surface-exposed Trp residues buried in hydrophobic environment in CNPSPC was became lower than in the raw protein, and the microenvironment polarity of Trp residues was decreased. The results of thioflavin T (ThT) fluorescence assay showed that the fluorescence intensity of CNPSPC was maximum at pH 6.0, which represented β-sheet was the dominant secondary structure of CNPSPC. The microenvironment of Trp residues was changed by the assembly, thereby changing the molecular conformation of CNPSPC. Compared with casein non-phosphopeptides (CNPP) and soybean peptide (SP), the antioxidant capacity of CNPSPC was improved. The scavenging activities of CNPSPC against 1,1-diphenyl-2-picrylhydrazyl (DPPH), superoxide anion and hydrolxyl radicals were maximum at pH 6.0, which increased by 3.34, 1.12 and 1.08 times compared to soybean protein respectively.