Single‐Molecular Imaging of Anticoagulation Factor I from Snake Venom by Atomic Force Microscopy

Abstract

AbstractAnticoagulation factor I (ACF I) from the venom of Agkistrodon acutus is a binding protein to activated coagulation factor X (FXa) and possesses marked anticoagulant activity. Single ACF I molecule has been successfully imaged in air by tapping mode atomic force microscopy (AFM) with high‐resolution using glutaraldehyde as a coupling agent. The physical adsorption and covalent binding of ACF I onto the mica show very different surface topographies. The former exhibits the characteristic strand‐like structure with much less reproducibility, the latter displays a elliptic granular structure with better reproducibility, which suggests that the stability of ACF I molecules on the mica is enhanced by covalent bonding in the presence of glutaraldehyde. A small‐scale AFM amplitude‐mode image clearly shows that the covalently bonded ACF I molecule by glutaraldehyde has olive shape structure with an average size of 7.4 nm × 3.6 nm × 3.1 nm, which is very similar to the size determined from the crystal structure of ACF I.