Structure of immunoglobulin G by scanning tunnelling microscopy

Scanning tunnelling microscopy (STM) has been used to examine the shape of individual immunoglobulin G (IgG) molecules deposited onto a graphite surface. IgG was chosen for this study as it has a well-characterized and distinctive three-dimensional structure. The micrographs clearly reveal the IgG molecule as trilobed, corresponding with the known structural organization of IgG. Comparison of these images with the structure of IgG determined by X-ray crystallography shows that the STM images are consistent with the crystal structure. This illustrates that STM is a valuable technique for examining protein structure, allowing rapid determination of the overall molecular shape that is consistent with more established techniques.