Yuan Yong J, Velev Orlin D, Chen Ken, Campbell Bruce E, Kaler Eric W, Lenhoff Abraham M
Department of Chemical Engineering, University of Delaware, Newark, Delaware 19716, USA.
J Agric Food Chem. 2002 Aug 14;50(17):4953-8. doi: 10.1021/jf025582d.
An experimental procedure was developed to characterize the solubility of the soybean protein fractions close to the isoelectric point. The results show that the 7S fraction is precipitated in a much narrower range of pH values than the 11S fraction. Surprisingly, the addition of salt to the solutions leads to increased solubility of proteins, unlike the common "salting out" effect generally expected for proteins in solution in this range of salt concentrations. The precipitation equilibria of both soybean fractions in the presence of calcium ions and electrolyte were characterized. The amount of calcium ions required to precipitate a mole of the 7S fraction is much larger than that required for the 11S fractions. The precipitation pattern can be correlated to the charge density per surface area of the proteins.
开发了一种实验程序来表征接近等电点的大豆蛋白组分的溶解度。结果表明，7S组分在比11S组分窄得多的pH值范围内沉淀。令人惊讶的是，向溶液中添加盐会导致蛋白质溶解度增加，这与在此盐浓度范围内溶液中蛋白质通常预期的“盐析”效应不同。表征了在钙离子和电解质存在下两种大豆组分的沉淀平衡。沉淀一摩尔7S组分所需的钙离子量远大于11S组分所需的量。沉淀模式可以与蛋白质每表面积的电荷密度相关联。
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