AFM and STM studies of the interaction of antibodies with the S-layer sheath of the archaeobacterium Methanospirillum hungatei

Abstract

We have investigated the problems of measuring the attachment of antibodies to biological surfaces by studying IgG antibodies on the S-layer sheath of the archaeobacterium Methanospirillum hungatei. The antibodies were labelled with ∼10 nm diameter colloidal gold particles. A comparison of electron microscopic, STM, and AFM images was made. Estimates of the binding energy of the label to the antibody were made by displacing the labels with various AFM imaging forces. Our binding energies were larger than the typical energies obtained from reaction-rate experiments. The antibody-sheath bond was stronger than the antibody-label bond.