Andrade Marco A R, Favarin Bruno, Derradi Rafael, Bolean Mayte, Simão Ana Maria S, Millán José Luis, Ciancaglini Pietro, Ramos Ana P
Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, 14040-901 Ribeirão Preto, São Paulo, Brazil.
Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92037, USA.
Colloids Surf A Physicochem Eng Asp. 2016 Sep 5;504:305-311. doi: 10.1016/j.colsurfa.2016.05.085. Epub 2016 May 27.
UV-vis spectroscopy is a powerful tool to investigate surface phenomena. Surface tension measurements coupled to spectroscopic techniques can help to elucidate how the interface organization influences the electronic properties of molecules. However, appreciable sample volumes are usually necessary to achieve strong signals during conduction of experiments. This study reports on the simultaneous acquisition of surface tension data and UV-vis spectra by axisymmetric drop shape analysis (ADSA) coupled to diffuse reflectance (DRUV) spectrophotometry using a pendant microliter-drop that requires small sample volumes and low analyte concentrations. Three example systems gave evidence of the applicability of this technique: (a) disaggregation of an organic dye driven by surfactant as a function of the surface tension and alterations in the UV-vis spectra, (b) activity of a glycosylphosphatidylinositol anchored enzyme estimated from formation of a colored product, and (c) interaction between this enzyme and biomimetic membrane systems consisting of dipalmitoylphosphaditylcholine and cholestenone. Apart from using smaller sample volume, this coupled technique allowed to investigate interfacial organization in the light of electronic spectra obtained within a shorter acquisition time. This procedure provided precise interfacial information about static and dynamic systems. This has been the first study describing the kinetic activity of an enzyme in the presence of phospholipid monolayers through simultaneous determination of the surface tension and UV-vis spectra.
紫外可见光谱法是研究表面现象的有力工具。将表面张力测量与光谱技术相结合，有助于阐明界面组织如何影响分子的电子性质。然而，在实验过程中，通常需要相当大的样品体积才能获得强信号。本研究报告了通过轴对称滴形分析（ADSA）与漫反射（DRUV）分光光度法联用，使用悬垂微升液滴同时采集表面张力数据和紫外可见光谱，该方法所需样品体积小且分析物浓度低。三个示例系统证明了该技术的适用性：（a）表面活性剂驱动的有机染料解聚，作为表面张力和紫外可见光谱变化的函数；（b）根据有色产物的形成估算糖基磷脂酰肌醇锚定酶的活性；（c）该酶与由二棕榈酰磷脂酰胆碱和胆甾烯酮组成的仿生膜系统之间的相互作用。除了使用更小的样品体积外，这种联用技术还能根据在更短采集时间内获得的电子光谱来研究界面组织。该方法提供了有关静态和动态系统的精确界面信息。这是第一项通过同时测定表面张力和紫外可见光谱来描述磷脂单层存在下酶的动力学活性的研究。
