Molecular resolution atomic force microscopy of soluble proteins in solution.

We introduce a simple specimen preparatory method for atomic force microscopy of soluble proteins in aqueous solutions. It is demonstrated that the mica surface is suitable for direct adsorption of macromolecules that are sufficiently stable to withstand the disturbance of the probe for reproducible imaging at high resolution. It is also shown that the main problem impeding successful imaging is the excessive adsorption of macromolecules, as loosely bound macromolecules readily stick to the tip and produce various imaging artifacts.