Specific fluorescent bands on chromosomes produced by acridine orange after prestaining with base specific non-fluorescent DNA ligands

Monomerizing effect of caffeine, o-phenanthroline, and tannin on cationic dyes: a model system to analyze spectral characteristics of the intercalative binding to nucleic acids

If used as co-solutes in concentrated solutions of cationic planar dyes, caffeine, o-phenanthroline, and tannin induce striking hyperchromic and bathochromic shifts in their absorption spectra. Likewise, the fluorescence of acridine orange at high concentration greatly increases in the presence of caffeine, the emission peak appearing at a shorter wave-length. These spectral changes, which are similar to those produced by organic solvents, detergents, and alpha-cyclodextrin, reflect the disaggregating (monomerizing) capacity of the co-solutes on stacked chromophores. After washing with saturated solutions of caffeine or o-phenanthroline, the chromatin fluorescence by intercalating fluorochromes is reduced or abolished, which suggests competition effects for intercalative binding modes. These results support the use of caffeine, o-phenanthroline, and tannin in spectroscopic and histochemical studies of dye-stuff interactions with DNA and chromatin.

Banding of Allium chromosomes protected against DNase digestion by DNA-binding drugs

Metaphase chromosome bands were induced in Allium flavum (Liliaceae) by protecting the chromosomal DNA with DNA-binding compounds of different base specificities against DNase digestion. The bands obtained represented different subsets of C-band heterochromatin.

Acridine orange-methyl green fluorescent staining of nucleoli

The staining of nucleoli with the fluorescent dye acridine orange following by counter-staining with methyl green differentially stained nucleoli in both plant and animal cells. The nucleoli fluoresced as bright structures highlighted against the quenched fluorescence of the chromatin. This technique provides a simple and highly reproducible method for differential staining of nucleoli.