论文标题
三价阳离子对$β$ - 乳糖球蛋白吸附层的结构和充电状态的特定离子效应
Specific Ion Effects of Trivalent Cations on the Structure and Charging State of $β$-Lactoglobulin Adsorption Layers
论文作者
论文摘要
在这项工作中，我们解决了y $^{3+} $和nd $^{3+} $阳离子对乳清蛋白$β$β$ -lactoglobolin（blg）在空气水界面上的吸附，这是电解质浓度的函数。两种阳离子在界面和大体解决方案中都引起了非常相似但急剧的变化。在此，应用了电泳迁移率和振动和频率产生光谱法（SFG）的测量，并始终显示出BLG净电荷的反转，以明显的低离子浓度为30（bumb）和40（交易界面）$ m $ $ m $ $^{3+} $^{3+} $或nd $或nd $^$^$^{3+} $ a的$ 15;来自ASP或界面BLG的ASP或GLU残基的羧酸盐拉伸振动的SFG光谱显示出羧酸盐拉伸频率的显着变化，我们将其与Y $^{3+} $或ND $^{3+} $ y $^{3+} $ y $^{3+} $ ions的特定有效结合结合在一起。在零净电荷的点附近发现了具有结合三价离子的BLG部分的特征重入凝结。发现BLG的最高胶体稳定性是离子浓度<20 $μ$ m和> 50 $ $ $ m的最高胶体稳定性。对BLG溶液的宏观泡沫的调查揭示了界面充电状态与泡沫稳定性之间存在结构 - 特性关系。实际上，当界面净电荷可忽略不计时，发现泡沫稳定性在20 $ $ $ $ $ $ $的浓度中的最低限度。我们的结果提供了有关蛋白质/离子分散液的液体气体界面电荷反转的新信息。因此，我们认为我们的发现是阐明接口处的重进入连接效应及其与泡沫稳定性的重要一步。
In this work, we addressed the effects of Y$^{3+}$ and Nd$^{3+}$ cations on the adsorption of the whey protein $β$-lactoglobulin (BLG) at air-water interfaces as a function of electrolyte concentration. Both cations caused very similar but dramatic changes at the interface and in the bulk solution. Here, measurements of the electropho-retic mobility and vibrational sum-frequency generation spectroscopy (SFG) were applied and consistently showed a reversal of the BLG net charge at remarkably low ion concentrations of 30 (bulk) and 40 (interface) $μ$M of Y$^{3+}$ or Nd$^{3+}$ for a BLG concentration of 15 $μ$M. SFG spectra of carboxylate stretching vibrations from Asp or Glu residues of interfacial BLG showed significant changes in the carboxylate stretching frequency, which we associate to specific and efficient bind-ing of Y$^{3+}$ or Nd$^{3+}$ ions to the proteins carboxylate groups. Characteristic reentrant condensation for BLG moieties with bound trivalent ions was found in a broad concentration range around the point of zero net charge. The highest colloidal stability of BLG was found for ion concentrations <20$μ$M and >50$μ$M. Investigations on macroscopic foams from BLG solutions, revealed the existence of structure-property relations between the interfacial charging state and the foam stability. In fact, a minimum in foam stability at 20$μ$M ion concentration was found when the interfacial net charge was negligible. Our results provide new information on the charge reversal at the liquid-gas interface of protein/ion dispersions. Therefore, we see our findings as an important step in the clarification of reentrant con-densation effects at interfaces and their relevance to foam stability.
