Almonte Lisa, Lopez-Elvira Elena, Baró Arturo M
Department of Surfaces and Coatings, Instituto de Ciencia de Materiales de Madrid (CSIC), C/Sor Juana Inés de la Cruz 3, Campus de Cantoblanco (Spain), Fax: (+) 913720623.
Chemphyschem. 2014 Sep 15;15(13):2768-73. doi: 10.1002/cphc.201402234. Epub 2014 Jul 2.
Chemical information can be obtained by using atomic force microscopy (AFM) and force spectroscopy (FS) with atomic or molecular resolution, even in liquid media. The aim of this paper is to demonstrate that single molecules of avidin and streptavidin anchored to a biotinylated bilayer can be differentiated by using AFM, even though AFM topographical images of the two proteins are remarkably alike. At physiological pH, the basic glycoprotein avidin is positively charged, whereas streptavidin is a neutral protein. This charge difference can be determined with AFM, which can probe electrostatic double-layer forces by using FS. The force curves, owing to the electrostatic interaction, show major differences when measured on top of each protein as well as on the lipid substrate. FS data show that the two proteins are negatively charged. Nevertheless, avidin and streptavidin can be clearly distinguished, thus demonstrating the sensitivity of AFM to detect small changes in the charge state of macromolecules.
即使在液体介质中，也可以通过使用具有原子或分子分辨率的原子力显微镜（AFM）和力谱（FS）来获取化学信息。本文的目的是证明，即使两种蛋白质的AFM形貌图像非常相似，但固定在生物素化双层膜上的抗生物素蛋白和链霉抗生物素蛋白的单分子仍可以通过AFM进行区分。在生理pH值下，碱性糖蛋白抗生物素蛋白带正电荷，而链霉抗生物素蛋白是中性蛋白。这种电荷差异可以通过AFM来确定，AFM可以通过FS探测静电双层力。由于静电相互作用，在每种蛋白质顶部以及脂质底物上测量时，力曲线显示出主要差异。FS数据表明这两种蛋白质带负电荷。然而，抗生物素蛋白和链霉抗生物素蛋白可以被清楚地区分，从而证明了AFM检测大分子电荷状态微小变化的灵敏度。
