The use of colloidal metal particles in protein blotting

Abstract Two procedures are described for staining the overall protein pattern on transfer membranes. Both methods involve the use of colloidal metal particles. AuroDye staining is based on the interaction of anionic colloidal gold particles with cationic proteins at low pH. The method is highly sensitive, but limited to nitrocellulose and polyvinylidene difluoride membranes. FerriDye comprises an incubation in a cationic iron (hydrous) oxide sol and subsequent intensification with potassium hexacyanoferrate in acidic medium. FerriDye is of intermediate sensitivity, but there are no limitations concerning membranes. It can be used on nitrocellulose‐, nylon‐and polyvinylidene difluoride‐based membranes. An immunodetection procedure is described which uses colloidal gold‐labelled secondary antibodies to visualize antigen‐antibody interactions. This signal can be significantly enhanced by silver. The procedure explained uses a new light‐insensitive and user‐friendly silver enhancement system.