光谱学与光谱分析, 2014, 34 (12): 3281, 网络出版: 2014-12-08  

荧光、紫外和红外光谱分析人乳和牛乳β-酪蛋白的功能和构象差异

Comparison of the Function and Conformation of Human β-Casein and Bovine β-Casein by Spectroscopic Study
刘微 1,2,3,*李萌 1,2任皓威 1,2刘宁 1,2,3
作者单位
1 国家乳业工程技术研究中心, 黑龙江省乳品工业技术开发中心, 黑龙江 哈尔滨150028
2 乳品科学教育部重点实验室(东北农业大学), 黑龙江 哈尔滨150030
3 东北农业大学食品学院, 黑龙江 哈尔滨150030
摘要
β-酪蛋白是人乳酪蛋白的主要成分, 但它在牛乳中的含量却很小。 β-酪蛋白在两者中含量的差异, 是人乳比牛乳更易消化的原因之一, 研究人乳与牛乳β-酪蛋白结构和功能的差异, 对研制出更适合婴儿肠道的, 新型人乳模拟型婴儿配方奶粉具有指导性的意义。 用紫外分光光度法研究人乳β-酪蛋白和牛乳β-酪蛋白的溶解性、 巯基含量、 乳化性等功能性质, 用荧光光谱和红外光谱分析比较两种蛋白的结构特点。 两种蛋白等电点十分接近(pH 4.0~5.0), 在等电点附近时, 人乳β-酪蛋白的溶解性(10.83%)低于牛乳β-酪蛋白(11.83%), 而偏离等电点时人乳β-酪蛋白具有更高的溶解性, 人乳β-酪蛋白的乳化活性指数(110~140 m2·g-1)高于牛乳β-酪蛋白(70~130 m2·g-1), 两种蛋白的表面巯基(SH)相似[(18.47±0.08)和(18.67±0.17) μmol·g-1], 而牛乳β-酪蛋白总巯基的含量[(47.46±0.23) μmol·g-1]大于人乳β-酪蛋白[(26.17±0.12) μmol·g-1], 两种蛋白官能团相似, 均含有β-折叠结构, 人乳β-酪蛋白的氢键数量和内部的疏水性均小于牛乳β-酪蛋白。 结果表明, 人乳β-酪蛋白比牛乳β-酪蛋白具有更少的α-螺旋和β-折叠等二级结构, 具有更疏松灵活的三级结构, 同时也具有更高的分子的表面活性。
Abstract
β-casein was the main component of human milk casein, but the content of β-casein in the bovine milk was less. The difference in β-casein content of the two samples was one of the reasons why human milk is more digestible than bovine milk. Studying the differences of structure and function in human and bovine milk β-casein can help us develop a new human milk simulated infant formula which will be more suitable for the infant gut. The UV spectrophotometer was used to study the solubility, sulfhydryl and emulsification of human milk β-casein and bovine milk β-casein, Fluorescence spectroscopy and the infrared spectroscopy were used to study the structural characteristics of human milk β-casein and bovine milk β-casein. The two samples shared a similar isoelectric point (pH 4.0~5.0), the solubility of human milk β-casein (10.83%) was lower than which in bovine milk β-casein (11.83%) near the pI, while it was higher when it deviated the pI. The emulsion ability (110~140 m2·g-1) of human milk β-casein was higher than that in bovine milk β-casein (70~130 m2·g-1) and surface sulfhydryl group (SH) of two kinds of milk protein were similar [(18.47±0.08) μmol·g-1 and (18.67±0.17) μmol·g-1]. The total sulfhydryl group [(47.46±0.23) μmol·g-1] in bovine milk β-casein was more than that in human milk β-casein [(26.17±0.12) μmol·g-1]. Functional groups in two samples were similar and they both contained beta sheet, human milk β-casein had less H-bond and internal hydrophobic than bovine milk β-casein. The results showed that the two samples had similar functional groups, while human milk β-casein had much less secondary structure such as α-helix and β-sheet, a looser tertiary structure and a better interfacial activity.

刘微, 李萌, 任皓威, 刘宁. 荧光、紫外和红外光谱分析人乳和牛乳β-酪蛋白的功能和构象差异[J]. 光谱学与光谱分析, 2014, 34(12): 3281. LIU Wei, LI Meng, REN Hao-wei, LIU Ning. Comparison of the Function and Conformation of Human β-Casein and Bovine β-Casein by Spectroscopic Study[J]. Spectroscopy and Spectral Analysis, 2014, 34(12): 3281.

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