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The interactions between the B3 (catechin-4 R,8-catechin) red wine tannin and the human salivary protein fragment IB714 (SPPGKPQGPPPQGG) were monitored by H magic angle spinning NMR, circular dichroism, electrospray ionization mass spectrometry, and molecular modeling. It is found that the secondary structure of IB7(下标14)  is made of a type II helix (collagen helix) and random coil. The central glycine 8 appears to act as a flexible rotula separating two helix II regions. Three tannin molecules tightly complex
the peptide, without modifying its secondary structure, but seem to reduce its conformational dynamics. The binding dissociation constant is in the millimolar range. B3 tannins with a “tweezers” conformation bind to the hydrophilic side of the saliva peptide, suggesting that the principal driving forces toward association are governed by hydrogen bonding between the carbonyl functions of proline residues and both the phenol and catechol OH groups. These findings are further discussed in the frame of an astringency
phenomenon.
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在B3(儿茶素4 R,8-儿茶素)红葡萄酒的单宁和人类唾液蛋白片段IB714(SPPGKPQGPPPQGG)之间的相互作用被用H魔角旋转核磁共振,圆二色性,电喷雾电离质谱法,和分子模拟监测。可知IB7(下标14)的二级结构是由II型螺旋(胶原螺旋)和无规卷曲的。中央甘氨酸8似乎充当柔性rotula分隔两个螺旋II区域。三单宁分子紧紧复杂
肽,而​​不需要修改它的二级结构,但似乎降低其构象动力学。的结合解离常数是在毫摩尔范围内。 B3丹宁带有“镊子”构象结合到唾液肽的亲水性侧,这表明主要驱动力朝向相关联地由脯氨酸残基和两个酚和儿茶酚的OH基的羰基的功能之间的氢键的约束。这些发现在涩味的帧进一步讨论
现象。
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2楼2015-07-06 09:25:50
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