Ultraviolet spectra of the complexes of acridine orange with deoxyribonucleic acid and polyphosphates

Summary

Two kinds of changes were found in ultraviolet spectrum of acridine orange bound to polyphosphate and native or denatured DNA: (a) changes similar to those caused by aggregation in the solutions of pure acridine orange (i.e. blue shifts of the bands at 37300 cm⁻¹ and 43670 cm⁻¹, a decrease of absorbance of the band at 34600 cm⁻¹ and an increase of absorbance of the band at 43670 cm⁻¹), which were observed at those ratiosP/D, when the dye formed aggregates on the surface of the polyanion; (b) a decrease of absorbance in the whole near ultraviolet region, which had high value even when isolated dye molecules were bound to the polyanion. While the first kind of changes is due to mutual interactions between the aggregated acridine orange molecules, the second kind can be explained as due to interaction of the dye molecules with adjacent chromophores of the polyanion and/or solvent. The maximum value of the hypochromic effect in the near ultraviolet maximum was higher for complexes of denatured DNA than for complexes of native DNA.