Mechanism studies of coomassie blue and silver staining of proteins.

A relatively high complexation affinity has been found for coomassie blue G-250 and the following amino acids: arginine; tyrosine; lysine; and histidine. A linear relationship was observed between log molar absorptivity and log molecular weight of 52 of 69 proteins, polypeptides, and di- and tripeptides that were allowed to react with coomassie blue G-250 in solution. The solution complexation results were used in a study of the detection of the following model proteins: bovine serum albumin, lysozyme, recombinant DNA derived human insulin, and calmodulin. Interactions between coomassie blue stained gels and silver detection reagents were determined and used as the basis for studies of enhanced sensitivity of detection of electrophoretically developed proteins. Sensitivity enhancements of up to eight-fold were observed when various sulfonic acid dye complexed proteins were detected with silver reagents versus the use of silver reagents alone. A site-directed nucleation of silver caused by the protein complexed sulfonic acid dyes is proposed as a mechanism for the observed enhancements.