The fluorescence of quinacrine mustard with nucleic acids

Mechanisms of quinacrine binding and fluorescence in nuclei and chromosomes

The mechanisms has been investigated whereby quinacrine binds to the DNA of nuclei and chromosomes in cytological preparations fixed in methanol-acetic acid. A variety of evidence is consistent with the idea that the quinacrine binds by intercalation. This is supported by a high value for the affinity of quinacrine for DNA, together with a saturation value of 0.2 quinacrine molecules/nucleotide; binding in the presence of strong salt solutions; and inhibition of fluorescence and banding by denaturation or depurination of DNA. At high quinacrine concentrations, weak binding of quinacrine to nuclei and chromosomes also occurs, but this is not relevant to the production of strong fluorescence or Q-banding patterns. A number of factors were tested which might have affected quinacrine fluorescence and banding. These included: pH; blocking protein amino groups by acetylation or benzoylation; introduction of hydrophobic groups by benzoylation; and dephosphorylation. All these treatments were without effect. However, comparison of the quinacrine fluorescence of human and onion nuclei, which differ substantially in the base composition of their DNA, shows that quinacrine fluorescence can be enhanced in cytological preparations by AT-rich DNA.

Hoechst 33258 banding of Drosophila nasutoides metaphase chromosomes

Hoechst 33258 banding of D. nasutoides metaphase chromosomes is described and compared with Q and C bands. The C band positive regions of the euchromatic autosomes, the X and the Y fluoresce brightly, as is typical of Drosophila and other species. The fluorescence pattern of the large heterochromatic chromosome is atypical, however. Contrary to the observations on other species, the C negative bands of the large heterochromatic chromosome are brightly fluorescent with both Hoechst 33258 and quinacrine. Based on differences in the various banding patterns, four classes of heterochromatin are described in the large heterochromatic chromosome and it is suggested that each class may correspond to an AT-rich DNA satellite.

Q-banding of human chromosomes after BUdR and BCdR treatment

Two different Q patterns were found in BUdR and BCdR treated chromosomes of human lymphocyte cultures: X-type pattern, in which Giemsa and quinacrine banding both are reversed; Y-type pattern, in which Q-banding remains conventional in spite of reverse G-banding. Possible mechanisms of these findings are discussed.

Molecular basis of chromosome banding. II. The effect of silver and mercury ions on the fluorescence intensity of acranil-DNA complexes

Silver and mercury ions are known to react with the bases of nucleic acids in solution. At low cation/base ratios Ag+ has an affinity for GC pairs in DNA, whereas Hg++ is preferentially bound to AT-rich nucleic acids. We have used fluorometry to measure the effect of these cations on the fluorescence intensity of preformed complexes of acranil and DNA in solution. The results are: 1) Ag+ enhances the fluorescence intensity presumably by affecting the dye intercalated in the vicinity of GC-pairs. 2) The addition of Hg++ leads to a quenching of the fluorescence intensity of the complex at low ion/base ratios, suggesting an effect on the dye molecules bound to AT pairs. At high GC-content of the nucleic acid, slight enhancement of the fluorescence intensity occurs with Hg++. 3) With both metals there is a correlation between base content of DNA and effect on the intensity of fluorescence indicating base specificity of the dye-polymer interaction.

Molecular basis of chromosome banding. I. The effect of mouse DNA fractions on two fluorescent dyes in vitro

The effects of mouse satellite, main band and total DNA on the fluorescence intensity of quinacrine and of the bibenzimidazole derivative Hoechst 33258 were tested in solution. No significant differences were noticed between the double-stranded DNAs in spite of the 5% difference in AT-content between satellite and main band DNA. Single-stranded DNAs enhanced the fluorescence intensity of Hoechst 33258 far less than double-stranded DNAs. Having been denaturated and then reassociated the DNA fractions were intermediate in their enhancing effects on the fluorescence intensity of Hoechst 33258, the differences presumably being due to different degrees of reassociation. The effect of denatured and subsequently reassociated satellite DNA on the fluorescence intensity of quinacrine was similar to that of the native DNAs. Main band and total DNA quenched the fluorescence intensity of quinacrine more after denaturation-reassociation than it did when native. In the discussion the results are related to known cytological data.