Imaging the Substructures of Individual IgE Antibodies with Atomic Force Microscopy

The interactions between antibodies and substrates directly affect their conformations and thus their immune functions. Therefore, it is desirable to study the structures of antibodies at the single molecule level. Herein, the substructures of Immunoglobulin E (IgE) on solid surfaces were investigated. For this purpose, tapping-mode atomic force microscopy (AFM) was applied to observe individual IgE substructures adsorbed onto Mg²⁺ and Na⁺ modified mica substrates in air. As expected, the AFM images revealed that the IgE antibodies exhibited different conformations on the surface of mica substrate consisting of the four basic orientations: three domain, two equivalent domain, two unequal domain, and single domain morphologies. Moreover, the differences in the different orientations in single IgE antibodies were also identified clearly.