Metachromasy of Nucleic Acids

Abstract

If nucleic acids and a metachromatic dye are mixed in amounts giving a low nucleic acid: dye ratio a ‘positive’ metachromatic effect occurs similar to that observed with truly chromotropic substances: for instance, thionine or toluidine blue become red or reddish-violet. This may be observed in test-tubes with pure solutions of the substances. In microscopical preparations this occurs when the staining, is strong. If the amount of N.A. is such that the ratio N.A.: dye is high, a ‘negative’ metachromasy occurs, that is, shades of colour are produced that are greener than those obtained in pure water solutions. In microscopical preparations this occurs when the staining of nuclei is very light. Both ‘positive’ and ‘negative’ metachromasy have the characteristics of truly metachromatic phenomena--specific absorption curves and suppression by heat.