Department of Chemical, Paper, and Biomedical Engineering, Miami University, Oxford, Ohio 45056, United States.
Langmuir. 2022 Apr 5;38(13):4090-4101. doi: 10.1021/acs.langmuir.2c00172. Epub 2022 Mar 24.
Understanding the interactions between surfactants and proteins is important for the formulation of consumer products as surfactant binding can alter protein activity and stability. Additionally, the structure of the protein-surfactant complex can influence surface activity, which is important for emulsion and foam development. ,-Dimethyldodecylamine N-oxide (DDAO) is an amphoteric surfactant that is nonionic at high pH. It is often used as a foam booster in detergent formulations and for the extraction of membrane proteins. In this study, a variety of biophysical characterization methods was used to investigate the impact of DDAO at pH 8 on the structure of the globular protein β-lactoglobulin (βLG). Pyrene fluorescence and surface tension studies show that βLG had minimal impact on the critical micelle concentration (CMC) of DDAO, while fluorescence and circular dichroism spectroscopy found unfolding of βLG at concentrations of DDAO greater than the CMC. Small-angle X-ray scattering results confirm changes in the structure of βLG at DDAO concentrations above the CMC. Taken together, DDAO behaves like nonionic and zwitterionic surfactants below its CMC with limited interaction with βLG, while it induces protein unfolding at concentrations higher than the CMC, resulting in a protein-surfactant complex structure that resembles a protein-decorated micelle.
了解表面活性剂和蛋白质之间的相互作用对于消费品的配方很重要，因为表面活性剂的结合可以改变蛋白质的活性和稳定性。此外，蛋白质-表面活性剂复合物的结构可以影响表面活性，这对于乳液和泡沫的形成很重要。-二甲基十二烷基氧化胺（DDAO）是一种两性表面活性剂，在高 pH 值下是非离子的。它通常用作洗涤剂配方中的泡沫增强剂和膜蛋白的提取剂。在这项研究中，使用了多种生物物理特性描述方法来研究 DDAO 在 pH 8 下对球状蛋白β-乳球蛋白（βLG）结构的影响。芘荧光和表面张力研究表明，βLG 对 DDAO 的临界胶束浓度（CMC）几乎没有影响，而荧光和圆二色性光谱研究发现，在 DDAO 浓度大于 CMC 时，βLG 发生了展开。小角 X 射线散射结果证实，在 CMC 以上的 DDAO 浓度下，βLG 的结构发生了变化。综上所述，DDAO 在低于 CMC 时表现为非离子型和两性离子型表面活性剂，与βLG 的相互作用有限，而在高于 CMC 的浓度下会诱导蛋白质展开，导致类似于蛋白质修饰胶束的蛋白质-表面活性剂复合物结构。
