分别运用生物酶法和化学碱法,研究不同质量浓度花青素与大豆分离蛋白(soy protein isolate,SPI)发生共价相互作用后对蛋白结构的影响。采用共价结合率测定和游离巯基含量测定方法对花青素和SPI在不同共价交联方式下的结合强度进行比较,后采用傅里叶变换红外光谱、紫外-可见吸收光谱和荧光光谱对不同共价交联方式下的花青素-SPI共价聚合物的结构及构象进行解析。结果表明:随着花青素添加量的升高,花青素与SPI的结合率逐渐提升,游离巯基含量持续下降。光谱测定显示花青素对SPI的共价交联可以改变蛋白的二级结构,使蛋白多肽链解折叠,并且改变蛋白芳香族氨基酸残基所处的微环境,进而使蛋白的构象发生改变。此外,相较于化学碱法,生物酶法共价交联的花青素-SPI聚合物结合率更高,巯基含量下降更显著,结构及构象的变化更为明显,这表明花青素与SPI在生物酶法处理下,共价结合能力强于化学碱法处理。
In this paper, we studied the effects of the covalent interaction of soy protein isolate (SPI) and different concentrations of anthocyanin on protein structure under enzymatic and alkaline conditions. The covalent bonding rate and free sulfhydryl content were used to compare the degree of bonding between anthocyanin and SPI in different covalent cross-linking modes. Fourier transform infrared (FT-IR) spectrocopy, UV-Vis absorption spectroscopy and fluorescence spectroscopy were used to analyze the structure and conformation of the anthocyanin-SPI conjugates. The results showed that the bonding rate of anthocyanin-SPI conjugates increased and its content of free sulfhydryl decreased with the increase of anthocyanin concentration. The secondary structure of SPI was changed and the protein was unfolded after anthocyanin was linked covalently to it. And the microenvironment around the aromatic amino acid residues in the protein was also changed, thereby resulting in its conformational change. Furthermore, the anthocyanin-SPI conjugates had a higher bonding rate, a lower content of free sulfhydryl and more obvious structural and conformation changes in under enzymatic conditions than alkaline conditions. This indicated that anthocyanin has a stronger covalent binding ability to SPI under enzymatic conditions than alkaline conditions.
soybean protein isolate (SPI)
第一作者:刘英杰(1994—)(ORCID: 0000-0002-6874-2903),女,硕士研究生,研究方向为粮食、油脂及植物蛋白工程。E-mail: firstname.lastname@example.org;通信作者:江连洲(1960-)(ORCID: 0000-0002-4749-2001),男,教授,博士,研究方向为粮食、油脂及植物蛋白工程。E-mail: email@example.com.