Polyelectrolytes conformational probes: Auramine O and ethidium bromide interactions with hypercoiling maleic acid–olefin copolymers

Two cationic dyes—auramine O (AuO) and ethidium bromide (EBr)—have been tested for their ability to respond to conformational states of maleic acid–olefin copolymers in aqueous solution. The fraction of bound dye and the intensity of fluorescence of AuO are extremely sensitive to the presence of polyelectrolyte compact coils and to changes in ionic strength and counterion species. A related behavior is shown by the shift in the absorption visible spectrum of EBr, whereas its fluorescence seems to depend somewhat on the “structure” of the compact coils. These properties of the two dyes, which find a convincing correlation with viscosity and equilibrium thermodynamic data for the copolymers considered, are thus proved to be useful in probing the degree of compactness of polyelectrolyte coiled conformations in dilute aqueous solutions.