大豆分离蛋白与低浓度尿素相互作用的红外光谱分析

Determination of Interaction of Urea and Soybean Protein Isolate by Fourier Transform Infrared Spectroscopy

大豆蛋白在食品工业中有很重要的应用,随着地球可再生资源的日益匮乏,大豆蛋白在非食品工业中的应用也越来越受到人们的关注,尿素是常用的化学变性剂,在蛋白质变性中有广泛的应用。为研究尿素变性对大豆蛋白结构的影响,对大豆分离蛋白(SPI)与低浓度尿素溶液相互作用的红外光谱进行了酰胺Ⅲ带研究。结果表明,溶解在不同浓度尿素溶液中的大豆分离蛋白的二级结构与大豆分离蛋白的水溶液相比发生了很大的变化,在0.1molL-1尿素溶液中大豆分离蛋白中的β-折叠的含量最小,随着尿素浓度的增加,β-折叠的含量增加,无规卷曲的含量在0.1molL-1尿素溶液中达到最大,之后随尿素浓度增加而降低,α-螺旋和β-转角随着尿素浓度的增加,其含量都是呈现先增加后下降的趋势,在1molL-1尿素溶液中两者的含量与大豆分离蛋白水溶液中的含量相比变化不大。因此,低浓度尿素可以明显影响大豆分离蛋白的二级结构。

Soy protein is attractive because they are environmentally friendly, biodegradable and renewable. Thus, more and more attention has been given to the development of soy protein＇s application in non-food industry. Urea is a common chemical denaturant, which is used widely to denature protein. To study the effect of urea modification on soy protein, FTIR spectroscopy was applied to investigate the interaction of urea and soybean protein isolates（SPI）. Amide band Ⅲ of SPI was analyzed to obtain the change in secondary structure of SPI when different concentrations of urea were added. At 0. 1 mol L^-1 concentration of urea ,the content of β-sheet decreased and the content of random coil increased. With the increasing of urea concentration, the β- sheet increased and the random coil decreased. The contents of α- helix and β- turn increased at first and then decreased with the increment of urea concentration. These results indicated that lower concentration of urea has obvious effects on the secondary structure of soy protein isolates.