Quantitation of stained proteins in SDS polyacrylamide gels with lysozyme as internal standard.

A simple method for the quantitation of proteins on SDS-polyacrylamide gels, with lysozyme as an internal standard, has been designed. Gels containing known weight ratios of standard proteins to lysozyme were electrophoresed, stained with Coomassie blue R250, and scanned at 550 nm. Peak areas corresponding to individual proteins were determined and the area ratios of proteins to lysozyme were calculated. Plots of area ratio vs weight ratio were linear over a limited range and were reproducible from gel to gel and thus suffice as a standard curve. We have used this method to determine accurately and precisely the amount of rhodopsin in the photoreceptor membranes of rat retinas.