Effects of pH on the molecular binding between β-lactoglobulin and bixin.
Effects of pH on the molecular binding between β-lactoglobulin and bixin.
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DOI：
10.1021/jf303844w
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发表时间：
2013-01
影响因子：
6.1
通讯作者：
Yue Zhang;E. Wright;Q. Zhong
中科院分区：
文献类型：
--
作者：
Yue Zhang;E. Wright;Q. Zhong
在pH 3.0-10.0范围内研究了胭脂树红中主要的乳清蛋白β-乳球蛋白（β-Lg）和主要的类胡萝卜素胭脂树红之间的结合。傅立叶变换红外光谱和紫外-可见吸收光谱的结果表明，结合涉及复合物的形成。色氨酸荧光猝灭和分析超离心数据表明，存在两个特异性结合位点，且结合亲和力随pH值的增加而显著增加。在较高的pH值下，色氨酸荧光向胭脂树橙的能量转移效率较高。热力学参数和等温滴定量热法和分析超离心法得到的特异性结合位点数表明，结合主要涉及两个特异性结合位点的疏水相互作用。pH对结合的影响与β-Lg的构象有关，其疏水口袋在较高的pH和离子强度下变得更可用。
Binding between β-lactoglobulin (β-Lg), the major whey protein, and bixin, the major carotenoid in annatto, was studied at pH 3.0-10.0. The Fourier transform infrared spectroscopy and UV-vis absorption spectroscopy results showed that the binding involved a complex formation. The tryptophan quenching fluorescence and analytical ultracentrifugation data showed that there were two specific binding sites and that the binding affinity increased significantly with an increase in pH. A higher efficiency of energy transfer from tryptophan fluorescence to bixin was observed at higher pH. Thermodynamic parameters and the number of specific binding sites obtained from isothermal titration calorimetry and analytical ultracentrifugation suggested that binding involved mostly hydrophobic interactions for the two specific binding sites. The impacts of pH on binding were correlated to the conformation of β-Lg, the hydrophobic pocket of which becomes more available at higher pH and ionic strength.