Pyrvinium is a polymethine cation which shows interesting fluorescence emission and DNA binding properties. In diluted aqueous solution, pyrvinium pamoate induced a bright yellow fluorescence in kinetoplast DNA from Trypanosoma cruzi epimastigotes as well as in chicken erythrocyte nuclei under a wide range of excitations. No fading was observed after mounting in suitable media. Spectroscopic studies on pyrvinium solutions revealed bathochromic and hypochromic shifts in the absorption spectrum of its complex with DNA. A striking enhancement of pyrvinium fluorescence was found in solvents of high viscosity or after binding to DNA. Experimental results and the chemical structure of pyrvinium allow us to suggest that the minor groove of adenine-thymine DNA regions could be the specific binding site for this new DNA fluorochrome.
We describe the fluorescence properties and cytochemical applications of the aromatic diamidine M&B 938. Treatment of cell smears (chicken blood, Ehrlich ascites tumor, rat bone marrow, mouse mast cells, and Trypanosoma cruzi epimastigotes) with aqueous solutions of M&B 938 (0.5-1 microgram/ml at pH 6-7; UV excitation) induced bright bluish-white fluorescence in DNA-containing structures (interphase and mitotic chromatin, AT-rich kinetoplast DNA of T. cruzi), which was abolished by previous DNA extraction. DNA was the unique fluorescent polyanion after staining with M&B 938 at neutral or alkaline pH, other polyanions such as RNA and heparin showing no emission. M&B 938-stained mouse metaphase chromosomes revealed high fluorescence of the AT-rich centromeric heterochromatin, and strong emission of heterochromatin in human chromosomes 1, 9, 15, 16, and Y was found after distamycin A counterstaining. On agarose gel electrophoresis, M&B 938-stained DNA markers appeared as fluorescent bands. The 1.635-KBP fragment from DNA ladder revealed a higher emission value than that expected from linear regression analysis. Spectroscopic studies showed bathochromic and hyperchromic shifts in the absorption spectrum of M&B 938 complexed with DNA, as well as strong enhancement of fluorescence at 420 nm. In the presence of poly(dA)-poly(dT), the emission of M&B 938 was 4.25-fold higher than with DNA; no fluorescence was observed with poly(dG)-poly(dC). Experimental results and considerations of the chemical structure suggest that the minor groove of AT regions of DNA could be the specific binding site for M&B 938, which shows interesting properties and useful applications as a new DNA fluorochrome.
We describe the use of tris (2,2'-bipyridine) ruthenium (n) (Rubipy) as a cationic fluorochrome for cytochemical and histochemical studies. After staining with Rubipy, mast cell granules (MCGs) and lymphocyte nuclei (LN) from mouse peritoneal cavity and human breast carcinoma showed intense orange fluorescence and no fading under blue or blueviolet exciting light. Staining at low pH (a) or pre-treatment with A13+ ions strongly diminished the fluorescence of LN, whereas that of MCG was less affected. Ca2 + and Ba2 + ions only diminished MCG fluorescence. Blots of DNA, pectic acid, heparin, and other sulfated polysaahrides stained with Rubipy showed high emission, which was reduced in DNA and pectic acid staining at low pH. Studies with chemically
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