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采用紫外光谱、荧光光谱及红外光谱分析技术,研究了微生物转谷氨酰胺酶(MTGase)聚合酪蛋白酸钠(Na-CN)生物聚合物的空间结构特征,并探讨了MTGase改善Na-CN乳化性能的作用机理。紫外光谱显示,MTGase聚合Na-CN生物聚合物的多肽链的Trp和Tyr残基的紫外吸收峰的强度明显低于Na-CN,说明生物聚合物的“空间结构效应”占较重要的地位。荧光发射光谱显示,Na-CN生物聚合物的Trp和Tyr残基的荧光强度比Na-CN有显著的增强,表明生物聚合物的疏水性区域更加暴露。然而,MTGase长时间催化(12h)得到的生物聚合物的荧光强度反而有所下降(与4h的场合相比),这反映了“空间位阻效应”。红外光谱显示,Na-CN与其生物聚合物的酰胺特征峰相差不大,说明两者的二级结构基本上相近。此外,MTGase改善Na-CN乳化性能的机理是:MTGase催化导致Na-CN的空间结构发生了变化,进而改变了蛋白表面的表面疏水性质,最终达到改善Na-CN乳化性质的效果。
The spatial structure characteristics of microbial transmethylase (MTGase) polymerized sodium caseinate (Na-CN) biopolymer were studied by UV spectroscopy, fluorescence spectroscopy and infrared spectroscopy. The effects of MTGase on the emulsification of Na-CN The mechanism of performance. The UV spectra showed that the intensity of the UV absorption peaks of Trp and Tyr residues in the MTGase-polymerized Na-CN biopolymer polypeptide chain was significantly lower than that of Na-CN, indicating that the “spatial structure effect” of biopolymers occupies a more important position. Fluorescence emission spectra showed that the fluorescent intensities of Trp and Tyr residues of Na-CN biopolymer were significantly enhanced compared to that of Na-CN, indicating that the hydrophobic region of the biopolymer is more exposed. However, the fluorescence intensity of the biopolymer obtained after a long period of MTGase catalysis (12 h) decreased somewhat (compared with 4 h), reflecting the “steric hindrance effect”. Infrared spectroscopy showed that the difference between the amide peaks of Na-CN and its biopolymer was similar, indicating that the secondary structures of the two were similar. In addition, the mechanism of MTGase to improve the emulsifying properties of Na-CN is: MTGase catalyzed changes in the spatial structure of Na-CN, thereby changing the surface hydrophobic properties of the protein surface, and ultimately achieve the effect of improving the emulsifying properties of Na-CN.