Nonspecific protein adsorption at the single molecule level studied by atomic force microscopy

Liquid tapping atomic force microscopy was used to study the nonspecific adsorption of horse spleen ferritin at a bare gold surface at single molecule resolution. The majority of ferritin molecules adsorbed irreversible on gold surfaces in accordance with the random sequential adsorption (RSA) mechanism frequently used to describe irreversible adsorption processes. However, the time-resolved data also reveal events that go beyond the RSA model, i.e., lateral mobility and fragility of some molecules, resulting in desorption, chain formation, and subunit dissociation. Scanning effects of the AFM tip were observed, resulting in diminished protein coverage in the scanned area.