CHEMICAL STUDIES ON AN ACRIFLAVINE-PHOSPHOTUNGSTATE COMPLEX; STAINING OF PHAGE DEOXYRIBONUCLEIC ACID MOLECULES FOR THE ELECTRON MICROSCOPE

Electrophoretic studies showed that the acriflavine-phosphotungstate (A-PTA) complex, which was formed by the reaction of acriflavine with phosphotungstic acid (PTA), contained a lower net positive charge than neutral acriflavine alone. Spectral studies from the titrations of specified aliquots of acriflavine with increasing volumes of PTA showed that the formation of A-PTA was characterized by a shift of the absorption peak of acriflavine from 452 mµ to a lower wavelength, at 446 mµ. The saturation of PTA binding sites on the acriflavine occurred when 3 molecules of dye reacted with 1 molecule of PTA. Binding curves of both neutral acriflavine and of A-PTA with "native" and with heat-denatured DNA showed shifts of λ max to longer wavelengths. A-PTA bound less native and less denatured DNA than the dye alone. The coupling of acriflavine with PTA caused a decrease in the net ability of the A-PTA complex to bind DNA. Double stranded DNA molecules from T3 bacteriophage were stained with the A-PTA complex for the electron microscope.