Binding of dyes to polycations I. Biebrich scarlet and histone interaction parameters

Spectroscopic studies indicate that the anionic dye Biebrich scarlet binds and stacks to polycations in an analogous way to cationic dyes on polyanions. Both exciton and dispersion interactions are needed to account for the spectral shifts and intensity changes. The low stacking coefficients are suggestive but not strong evidence for helical structure in the polycations examined. Calculations based on exciton theory using the observed spectral shifts, show that the dyes lie on the outside of the polymers, probably in a radial orientation.