The interaction of the anionic dye, Biebrich scarlet, with histone, poly-l-lysine, and polyvinyl-pyridinium has been studied. A marked decrease in the major absorption peak at 505 mµ, with a small shift to a longer wave-length, was observed as chromotrope concentration was raised to about molar equivalence with the dye. A minor absorption maximum at 545 mµ showed little or no hypochromic effect but a similar shift toward the red. A second small peak at 420 mµ revealed little if any hypochromic change and no shift in the position of the peak. At great chromotrope excess the spectrum returned toward that of the free dye. No spectral changes occurred when monomers or an anionic polymer were mixed with the dye. The specific conductance of dye-chromotrope mixtures was measured, and Δmhos and %Δ were determined as measures of electrostatic interaction. There was maximal %Δ at about molar equivalence with histone, poly-l-lysine and spermidine that correlated with the spectral changes. It is proposed that a metachromatic effect was produced from the electrostatic interaction between the anionic dye, Biebrich scarlet, and cationic chromotropes analogous to the interaction of metachromatic cationic dyes with anionic chromotropes.
