IMAGING OF PROTEINS ADSORBED ON SELF-ASSEMBLED MONOLAYERS BY ATOMIC-FORCE MICROSCOPY IN LIQUID

Atomic force microscopy (AFM) imaging of proteins adsorbed on Au(111) substrates was examined. When Au(111) was modified with 4-mercaptopyri dine self-assembled monolayers (SAM), uniformly adsorbed hemoglobin mo lecules were observed on the substrate in a physiological buffer solut ion. In contrast, very few molecules were observed on octadecanethiol SAM. When the bare Au(111) was used without surface modification, uncl ear AFM images were obtained although protein molecules might have bee n adsorbed. The results suggested that the adsorption phenomenon of me talloproteins is strongly affected by surface modification of the gold substrate. In addition, our data indicated that the adsorbed metallop roteins on SAM could be successfully observed by tapping mode AFM in p hysiological solution without chemical fixation of protein molecules.