Why does Coomassie Brilliant Blue R interact differently with different proteins? A partial answer

Dimethyl sulfoxide was found to be effective for extraction of Coomassie Brilliant Blue R-250 (Coomassie R) from stained proteins on polyacrylamide gel slices. A good correlation was found between the ability of different proteins to bind Coomassie R and their capacity for interaction with Coomassie Brilliant Blue G-250 (Coomassie G) in solution. Scatchard analysis showed that the number of Coomassie R ligands bound to each protein molecule is approximately proportional to the number of positive charges on the protein, about 1.5-3 dye molecules/charge.