High-resolution AFM imaging of the CA125 protein and its aptamer-based complexes.

An approach to evaluate the efficiency of aptamer/antigen complexation based on high-resolution AFM imaging data is proposed. The formation of specific complexes is the basis of diagnostic systems in medicine. It is shown that a comprehensive evaluation of the height and volume of objects sorbed on the surface of freshly cleaved mica from the solution of proteins and their complexes allows us to assess the success of complex formation in solution. The applicability of the approach is demonstrated using two variants of the CA125 antigen (containing seven or one full-length SEA domain) and two aptamers. The SEA domain is the binding contact in the antibody- or aptamer-mediated biorecognition system.