[The effect of acridine dyes on the molecular structure of DNA]

DNA--acriflavin complexes have been investigated by the methods of flow birefringence and viscometry. The intrinsic viscosity and the optic anysotropy of the complex increase with the increasing quantities of binding dye. Experimental data are treated on the basis of different models of binding. At high ionic strength (mu = 0,1) one type of binding takes place which is described by the intercalation model. In this case the thermodynamic rigidity of DNA-molecule within the complex is proportional to "r". In solutions of low ionic strength (mu = 0,001), two types of DNA-acriflavin binding occur: intercalation and external binding. At low ionic strength, the spectrophotometric titration technique is shown to give a reduced value of "r".