Nonspecific binding of p-phenylenediamine-pyrocatechol peroxidase substrate to electrofocused proteins

Nonspecific staining of electrofocused protein bands was found with the peroxidase product of Hanker-Yates reagent (a mixture of p-phenylenediamine and pyrocatechol). No difficulty was encountered with diaminobenzidine as peroxidase substrate.