SynopsisThe binding constants for the complex formation of more than twenty ring nitrogenand amino-substituted acridine derivatives with calf thymus DNA were measured by a fluorescence method. DNA quenches the fluorescence of the aminoacridine dyes so long &s both amino hydrogens are not substituted. These dyes show an enhancement of their fluorescence intensity in the presence of DNA. Typical representatives of both are proflavine and acridine orange derivatives, respectively. A discussion of steric and electronic influences of various substituents attached to the ring nitrogen and amino groups on the binding led to the concept of different conformations for intercalated acridines without amino groups and the aminoacridines. The electrostatic binding site of the former seems to be the positively charged ring nitrogen, while the binding sites in the aminoacridines are so located that the amino groups are directed towards the negatively charged DXA phosphates.The biological action of a chemical compound is very often related to its physicochemical interaction with biological materials, especially with biopolymers. The observed effects are in some cases highly specific, so that small changes in the dye structure lead to marked changes in the biological activity. The cationic forms of the acridines, which will be discussed here only, interact mainly with polyanions such as the nucleic acids. The mutations produced by acridines are considered one result of such complex formations and; the influence of the dye structure has been discussed by Pullman and Weissbluth.' It is therefore not surprising that much work has been directed towards obtaining thermodynamical data on and the structure of the complex formed by the interaction of dyestuffs with deoxyribonucleic acids.The ability of most of the dyes to aggregate gives rise to the possibility for binding of the dyes in the polymerics as well as in the monomeric form.g Binding in the polymeric form appears to occur a t higher dye to DNAphosphate ratios, where the dyes are stacked on the outside of the DNA helix.s On the other hand, many authors who have discussed the problem of monomer binding consider that the dyes interact not only with the charged phosphates, but also with the DNA bases. This includes the possibility that the dyes are inserted to some extent between the base pairs 595 * Part I-VI see references 1-6.

2016-11-15T19:38:30

No abstract