Interaction of polyanions with basic fuchsin and formaldehyde.

Basic fuchsin and formaldehyde react readily with a number of polyanions in aqueous solutions. Deoxyribonucleic acid, ribonucleic acid, several synthetic polynucleotides and polyvinylsulfate all convert buffered solutions of basic fuchsin and formaldehyde from a magenta to a purple color at ambient temperature. The formation of product is maximal in about 20 min and the resulting complexes are stable enough to be isolated by gel filtration. Microgram amounts of polyanion suffice to produce the color changes and the spectral shifts vary with the type of polyanion. These results are interpreted to indicate that polymerization of basic fuchsin and formaldehyde is an essential aspect of color formation.