Biotinylated proteins as molecular weight standards on Western blots.

Protein molecular weight standards were biotinylated by reaction with biotinyl-N-hydroxysuccinimide ester. The biotinylated proteins were resolved by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and electrophoretically transferred to nitrocellulose paper. The resolved protein bands were detected by formation of a streptavidin-biotin/horseradish peroxidase complex and reaction with 4-chloro-1-naphthol and hydrogen peroxide. The biotinylated proteins are easy to prepare and are useful as molecular weight standards with most procedures employing immunodetection of proteins following transfer to nitrocellulose paper.