"Golden blot"--detection of polyclonal and monoclonal antibodies bound to antigens on nitrocellulose by protein A-gold complexes.

Protein A bound to particles of colloidal gold is widely used for cytochemical localization of antigens. A method for detecting immune complexes on "Western blots" with protein A-gold has been developed. It involved the following steps: (i) electrophoretic separation of proteins, (ii) transfer to nitrocellulose, (iii) incubation with antibodies, and (iv) staining with protein A-gold. The amount of antigen detectable was 10-50 ng. The sensitivity could be improved by subsequent photochemical silver staining (1-10 ng detected), and was then comparable to autoradiograms using iodinated protein A.