Observing interactions between the IgG antigen and anti-IgG antibody with AFM

Abstract

Spatially specific interactions between the immonoglobulin G (IgG) antigen and anti-IgG monoclonal antibody (McAb) have been studied in detail by tapping-mode AFM. The binding numbers and binding sites of the antigen molecules with antibody molecules, as well as the conformational changes during the binding process have been revealed. Results showed that: (1) there are spatially specific interactions between IgG and McAb molecules; (2) the binding sites of IgG with McAb molecules are located at four quadrants on the surface of IgG molecules; (3) the binding number of an IgG molecule with McAb may be four; (4) significant morphological changes occurred during reaction of IgG with McAb molecules suggesting that the binding process is accompanied by a conformational change of the proteins involved.