Showing papers on "Xanthene published in 1989"

Xanthene-dye-labelled phosphatidylethanolamines as probes of interfacial pH. Studies in phospholipid vesicles

Abstract: We have been developing the use of plasma-membrane-bound fluorescent probes to measure the pH values at the surfaces of living chondrocytes. For this purpose, three lipophilic pH indicators were made by covalently binding the xanthene dyes fluorescein, eosin or dichlorofluorescein to the amino group of phosphatidylethanolamine. The probes were incorporated into phospholipid vesicles and the effect of pH on the fluorescence was characterized. Fluorescence was measured at a single emission wavelength during excitation at two wavelengths, and the ratio of the intensities was calculated. The experimentally observed pKobs. values were determined by fitting the fluorescence ratios to the Henderson-Hasselbalch equation. All three probes acted as pH indicators, and the eosinyl-, dichlorofluoresceinyl- and fluoresceinylphosphatidylethanolamines had pKobs. values of 3.5, 6.3 and 7.5 respectively. At physiological salt concentrations, changes in the composition of the vesicle membrane had little effect on these values. We concluded that these probes were promising candidates for the measurement of pH values at cell surfaces.

N-phenylglycine-(thio)xanthene dye photoinitiating system and application to photopolymer for visible laser exposure

Abstract: It was found that the bimolecular type photoinitiators consisting of N-phenylglycine and (thio)xanthene dyes exhibited high initiating efficiency on irradiation of visible light. From the time-resolved spectroscopic study, the free radical is formed by the sensitized decarboxylation of N-phenylglycine in the presence of (thio)xanthene dye. By using these initiating systems, the visible laser sensitive photopolymer was prepared and the imaging characteristics were evaluated.

Benzo[k, l], xanthene–3, 4–dicarboximides and benzimidazoxanthenoisoquinolinones – yellow and orange dyes for synthetic–polymer fibres

Abstract: Condensation of 4–chloro–l, 8–naphthalic anhydride with 2–nitrophenol afforded 4–(2–nitrophenoxy)–l, 8–naphthalic anhydride, which on reduction followed by Pschorr intramolecular cyclisation gave benzo[k, l]xanthene–3, 4–dicarboxylic acid anhydride. The identity of the product was confirmed by its alternative synthesis from 5–amino–4–phenoxy–l, 8–naphthalic anhydride. Benzo[k, l]xanthene–3, 4–dicarbox–ylic acid anhydride condensed with alkylamines or arylamines and with o–phenylenediamines to yield the corresponding imides and imidazole derivatives, which coloured polyester in fluorescent greenish–yellow to orange hues, respectively, of good fastness to light and sublimation. The colour of the dyes is discussed with respect to analogous ring–closed sulphur– containing heterocycles.

Effect of magnetic field on radical yields during the photoreduction of xanthene dyes in viscous media

Abstract: The effect of an external magnetic field (H⩽ 0.18 T) on the yield of semiquinone radicals during photoreduction of xanthene dyes (fluorescein, ethyleosine, erithrosine and rose bengal) in a viscous ternary mixture of glycerol, p-cresol and ethanol has been studied by the flash-photolysis technique. The effect of the magnetic field depends upon field strength and solvent viscosity. Magnetic enhancement (an increase of radical yield up to 2.5 times) was observed for dyes in solvents of moderate viscosity [3 ⩽(η/T)/cP K–1⩽ 8]. The influence of internal and external heavy atoms on magnetic field effect in the above-mentioned reactions has been investigated. In the case of fluorescein and erithrosine the existence of an external heavy atom (KI, 0.1 mol dm–3 leads to a decrease in magnetic field effect in contrast to the behaviour of rose bengal. The effect of external heavy atoms on the e.s.r. spectrum of fluorescein-semiquinone radical (HDH˙) has been also studied. Peak broadening and poorer resolution were found in the presence of CsCl for the spectrum of HDH˙. The influence of external heavy atom on the g-factor of free radicals as well as the role of spin–orbit coupling in a magnetic field are discussed.

Effect of Solvent Polarity on Nonradiative Processes in Xanthene Dyes: Rhodamine B in Normal Alcohols

Abstract: The fluorescence lifetime of rhodamine B in a series of normal alcohols (C/sub n/H/sub 2n-1/OH, n = 1-6) was measured as a function of temperature. The nonradiative rate constants were calculated from the fluorescence lifetimes and quantum yields. Activation energies were obtained from Arrhenius plots of the nonradiative rate constant. The variation of the nonradiative rate constant with solvent polarity and temperature was consistent with a photophysical mechanism that involves equilibrium between the planar and twisted configurations of the diethylamino groups on the xanthene ring of rhodamine B and internal conversion from the twisted configuration. The activation energy is equal to the free energy difference between the twisted and planar configurations. The solvent polarity dependence of the free energy difference and of the rate constant for internal conversion from the twisted configuration determines the variation of the nonradiative rate constant with solvent. When solvent polarity effects are taken into account by using the parameter E/sub T/(30), the nonradiative rate constant shows weak or no dependence on the solvent viscosity.

Effects of organic solvents on charge separation in photo-induced electron transfer from xanthene dyes to methyl viologen

Abstract: Efficiencies of charge separation in eosin Y- and erythrosine-sensitized reduction of methyl viologen (MV2+) were determined in water-organic solvent mixtures by laser flash photolysis. The MV+• yield increased with increasing fraction of organic solvents, and depended on the type of solvent, increasing in the order of acetonitrile > acetone > dioxane > ethanol > DMSO. The hydrophobic nature of solvents plays an important role in the charge separation.

Conjugate from medical compound and diphosphonic acid derivative

Abstract: NEW MATERIAL:A compound of formula I (A-CO-is residue of the medical compound; R is -NH- or -O-; m is 0, 1; n is 1-10). EXAMPLE: Disodium salt of {α-(3',6'-dihydroxy-3-oxo-spiro[phthalane-1,9'- xanthene]-6-carbonyloxy)acetamidemethylene}bis(sulfonic acid). USE: Anti-inflammatory drugs. PREPARATION: A compound of formula A-COOH is reacted with a compound of formula II (OR 1 is protected OH; Y is halogen) to form a compound of formu la III. This compound is then put to elimination of the protective group contained to obtain a compound of formula IV. COPYRIGHT: (C)1990,JPO&Japio

Highly soluble xanthene and method for its preparation

Abstract: The solubility of Xanthan is improved by the addition of water-soluble carboxylic acids or hydrogen phosphates.

Novel xanthene dyes

Abstract: Novel xanthene dyes are disclosed which, excite in the range of 450-650 nm and which will emit to the red of fluoroscein. These dyes may be coupled to tagging agents, such as monoclonal antibodies, and used to detect cells in a sample.

Photochemical Hydrogen Abstraction Reactions of 9,10-Dihydro-9,10-o-benzenoanthracene-1,4-dione Derivatives with Xanthene: Intramolecular Charge Transfer Quenching

Abstract: Intramolecular charge transfer interaction in triptycene system was investigated. 9,10-Dihydro-9,10-o-benzenoanthracene-1,4-dione (triptycenequinone) and its analogs were readily photoreduced with xanthene to give the corresponding hydroquinones and the adducts with two xanthenyl radicals. The chemically induced dynamic nuclear polarization examination and the corresponding thermal reaction proved the adducts to be originated from free radical coupling of xanthenyl radicals and quinones. The quantum yield for disappearance of the quinones depended upon both the substituents and solvents. Kinetic analysis by applying Stern–Volmer plot, using anthracene as a quencher, revealed that the quantum yield of intersystem crossing and the lifetime of the triplet state decreased with increasing electron-donating power of the aromatic rings in triptycenequinones. These solvent and substituent effects suggest that intramolecular charge transfer quenching of both the singlet and the triplet excited states of quinones b...

Study Of The Specificity Of Xanthene Dye Binding To Mitochondria

Abstract: The binding of Rhodamine 123 (Rh123), Rhodamine 6G (R6G), and Rhodamine B (RhB) (from the cationic xanthene series) to isolated rat liver mitochondria maintained in State IV respiration in the presence of rotenone (NADH oxidase inhibitor) was monitored by following changes in the fluorescence signal of the dyes. Rh123 and Rh6G bind strongly with quenching, to 0.25 and 0.20, respectively, and red shift of emission maxima by 10 nm. RhB binds much less potently with slight emission enhancement of 1.2. For Rh123 added to 0.5 mg/ml mitochondria' protein, a sigmoidal relationship is obtained between percentage fluorescence quenching and log of Rh123 concentration with a 50% inflection point of 3.5x10-6M, estimating an apparent association constant of 2.9x 105M-1 for Rh123 binding. Addition of 7 uM RhB during Rh123 titration moves the sigmoidal inflection point to higher Rh123 concentrations, suggesting either RhB enhancement of binding of Rh123 fluorescence quenching by energy transfer to RhB bound. These results suggest that, to a great degree, the binding of the xanthene dyes to mitochondrial sites is specific, competitive, and probably cooperative.

Fotochemische Primärprozesse von Xanthenfarbstoffen. X. Zum Einfluß ionischer Mizellen auf die Löschung der Fluoreszenz von Xanthenfarbstoffen durch Diazoniumionen

Abstract: Photochemical Primary Processes of Xanthene Dyes. X. The Influence of Ionic Micelles on the Fluorescence Quenching of Xanthene Dyes with Diazonium Ions The steady-state and the time-resolved fluorescence quenching of xanthene dyes by diazonium salts is investigated. The fluorescence of anionic dyes is more efficiently quenched than that of cationic dyes, due to the opposite charge. In the presence of anionic micelles the fluorescence quenching of cationic dyes by diazonium ions is more effective than in water, because the dye and diazonium ions are solubilized in the Stern region of the micelles. In the presence of cationic micelles the fluorescence of anionic dyes is effectively quenched by p-dodecyloxybenzene-diazonium salt solubilized in the micelles like a tensid ion. The equilibrium constants for the distribution of the diazonium ions between the micelles and the water phase are determined. The importance of the singlet state for the sensitized photolysis of diazonium salts is discussed.

Free-radical mechanism of photodecomposition of dyes in solution

Abstract: 1. The contribution of the free-radical mechanism to photodecomposition in deoxygenated solutions of rhodamine 6G and azo dyes was determined quantitatively. 2. In the presence and absence of oxygen, the azo dyes studied are photoinitiators of free radical transformations of repeated effect with a high initiation coefficient. 3. The rate constants of the chemical reaction of alkyl and peroxide radicals of the solvent with a number of azo, anthraquinone, and xanthene dyes were obtained.

Synthesis and Mass Fragmentation Pattern of Fluorinated Spiro(3H-indole-3,9′-(9H)xanthene)-1′,2,8′(1H,2′H,5′H)-triones.

Abstract: Some new fluorine containing spiro-xanthenes and spiro-acridines have been synthesized. Spiro-xanthenes were obtained by the reaction of fluorinated indole-2,3-diones with 1,3-cyclohexanedione by three different routes. Further, spiro-xanthenes were treated with ammonium acetate or fluorinated anilines in acidic medium resulting in corresponding spiro-acridines. All synthesized compounds have been characterized on the basis of elemental analyses, IR, 1 H and 19 F NMR and Mass spectral studies.

Unusual Reductions Induced by Formic Acid.

Abstract: Treatment of xanthene carbinol 1a or xanthenylidene derivative 2a with refluxing formic acid unexpectedly gave dihydro compound 3a . Thioxanthene and acridine carbinols 1b and 1c and acridinylidene derivative 2c were also partially reduced when treated with formic acid.