Abstract
A general method has been developed to make the smallest gold-conjugated antibody label yet developed for electron microscopy. It should have wide application in domainal mapping of single molecules or in pinpointing specific molecules, sites, or sequences in supramolecular complexes. It permits electron microscopic visualization of single antigen-binding antibody fragments (Fab') by covalently linking an 11-atom gold cluster to a specific residue on each Fab' such that the antigenic specificity and capacity are preserved. The distance of the gold cluster from the antigen is a maximum of 5.0 nanometers when the undecagold-Fab' probe is used as an immunolabel.