Qi Phoebe X, Wickham Edward D, Garcia Rafael A
Dairy and Functional Foods Research Unit and ‡Biobased and Other Animal Co-products Research Unit, Eastern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture , Wyndmoor, Pennsylvania 19038, United States.
J Agric Food Chem. 2014 Jul 30;62(30):7567-76. doi: 10.1021/jf502699g. Epub 2014 Jul 15.
Changes in the structural and thermal stability of β-lactoglobulin (β-LG) induced by interacting with sugar beet pectin (SBP) have been studied by circular dichroism (CD), Fourier transform infrared, and steady-state as well as time-resolved fluorescence spectroscopic techniques. It has been demonstrated that SBP not only is capable of binding to native β-LG but also causes a significant loss in antiparallel β-sheet, ∼10%, accompanied by an increase in either random coil or turn structures. In addition, the interaction also disrupted the environments of all aromatic residues including Trp, Phe, and Tyr of β-LG as evidenced by near-UV CD and fluorescence. When preheated β-LG was combined with SBP, the secondary structure of β-LG was partially recovered, ∼4% gain in antiparallel β-sheet, and Trp19 fluorescence was recovered slightly. Although forming complexes with SBP did not significantly impact the thermal stability of individual secondary structural elements of β-LG, the environment of Trp19 was protected considerably.
通过圆二色性（CD）、傅里叶变换红外光谱以及稳态和时间分辨荧光光谱技术，研究了与甜菜果胶（SBP）相互作用引起的β-乳球蛋白（β-LG）结构和热稳定性的变化。结果表明，SBP不仅能够与天然β-LG结合，还会导致反平行β-折叠显著损失约10%，同时无规卷曲或转角结构增加。此外，近紫外CD和荧光表明，这种相互作用还破坏了β-LG中包括色氨酸（Trp）、苯丙氨酸（Phe）和酪氨酸（Tyr）在内的所有芳香族残基的环境。当预热的β-LG与SBP结合时，β-LG的二级结构部分恢复，反平行β-折叠增加约4%，Trp19荧光略有恢复。虽然与SBP形成复合物对β-LG单个二级结构元件的热稳定性没有显著影响，但Trp19的环境得到了相当程度的保护。
