Ma C Y, Rout M K, Mock W Y
Food Science Laboratory, Department of Botany, The University of Hong Kong, Hong Kong.
J Agric Food Chem. 2001 Jul;49(7):3328-34. doi: 10.1021/jf010053f.
The conformation of oat globulin dispersions (10% in D2O) under the influence of pH, chaotropic salts, protein structure perturbants, and heating conditions was studied by Fourier transform infrared (FTIR) spectroscopy. The FTIR spectrum of oat globulin showed major bands from 1670 to 1634 cm(-1), corresponding to the four major types of secondary structures, that is, beta-turns, beta-sheets, alpha-helices, and random coils. At extreme acidic and alkaline pH conditions, there were changes in intensity in the bands attributed to beta-sheet structures (1626, 1634, and 1682 cm(-1)), and shifts of the bands to higher or lower wavenumbers, indicating changes in conformation. In the presence of some chaotropic salts, the 1626 and 1634 cm(-1) bands were shifted upward, with a marked decrease in the intensity of the 1634 cm(-1) peak. The addition of several protein structure perturbants led to a slight shift in the alpha-helix/random coil bands and a marked reduction in the beta-sheet peaks, suggesting protein unfolding. Heating under aggregating conditions led to slight shifts in all of the major bands and progressive changes in the intensity of the alpha-helix, beta-sheet, and beta-turn peaks, suggesting protein denaturation. This was accompanied by marked increases in intensity of the two intermolecular beta-sheet bands (1682 and 1624-1626 cm(-1)) associated with the formation of aggregated strands. The IR spectra of soluble and insoluble aggregates showed a redistribution of native and extensively denatured proteins in the two fractions.
通过傅里叶变换红外（FTIR）光谱研究了燕麦球蛋白分散体（在D2O中为10%）在pH值、离液盐、蛋白质结构扰动剂和加热条件影响下的构象。燕麦球蛋白的FTIR光谱显示出1670至1634 cm(-1)的主要谱带，对应于四种主要的二级结构类型，即β-转角、β-折叠、α-螺旋和无规卷曲。在极端酸性和碱性pH条件下，归属于β-折叠结构（1626、1634和1682 cm(-1)）的谱带强度发生变化，且谱带向更高或更低波数移动，表明构象发生了变化。在一些离液盐存在的情况下，1626和1634 cm(-1)的谱带向上移动，1634 cm(-1)峰的强度显著降低。添加几种蛋白质结构扰动剂导致α-螺旋/无规卷曲谱带略有移动，β-折叠峰显著降低，表明蛋白质发生了去折叠。在聚集条件下加热导致所有主要谱带略有移动，α-螺旋、β-折叠和β-转角峰的强度逐渐变化，表明蛋白质发生了变性。这伴随着与聚集链形成相关的两个分子间β-折叠谱带（1682和1624 - 1626 cm(-1)）强度的显著增加。可溶性和不溶性聚集体的红外光谱显示了天然和广泛变性蛋白质在这两个部分中的重新分布。
