A scanning tunnelling microscopic study of site-specifically immobilized immunoglobulin G on gold.

A convenient and efficient method for the site-specific incorporation of foreign cysteine residues at the C-termini of immunoglobulin G (IgG) using carboxypeptidase-Y-catalyzed transpeptidation is explored as a means of ensuring oriented immobilization of IgG on gold. A scanning tunnelling microscopic study of the immobilization of the modified IgG molecules on gold surfaces is reported. The results show not only that some globular features are observed to form striking surface patterns with a geometric size close to that of the fragments of IgG but also that the conformation of the bound IgG molecules appears more stable when adsorbed on gold. The effect of the immobilization method on these topographic features is discussed.