Simulation of Atomic Force Microscopy Images of Collagen Molecules on Graphite Surface

Based on the all-atom empirical force field model, we investigated the force distance curves and the corresponding atomic force microscopy (AFM) images for the single collagen molecule adsorbed on the graphite surface, both in UHV and in water, assuming the (10,0) capped carbon nanotube tip. We found that in UHV the height difference between the proline and glycine amino residues can be clearly resolved in the images, whether the molecule assumes the triple helix structure or its deformed structure which is energetically more favorable. In water, the amplitude of the oscillatory solvation force is found to be different between on top of the collagen molecule and on top of the graphite surface. It indicates that the collagen molecule would be observed to be lower in water than the molecule observed in UHV environment.