Imaging streptavidin 2D crystals on biotinylated lipid monolayers at high resolution with the atomic force microscope

Streptavidin crystals were grown on biotinylated lipid monolayers at an air /water interface and transferred onto highly oriented pyrolytic graphite (H OPG). These arrays could be imaged to a resolution below 1nm using the atom ic force microscope, The surface topographs obtained were compared with neg ative-stain electron microscopy images and the atomic model as determined b y X-ray crystallography. The streptavidin tetramer (60kDa) exposes two free biotin-binding sites to the buffer solution, while two are occupied by lin kage to the lipid monolayer. Therefore, the streptavidin 2D crystals can be used as nanoscale matrices for binding biotinylated compounds. Furthermore , this HOPG-based preparation method provides a general novel approach to s tudy the structure of protein arrays assembled on lipid monolayers with the AFM.