Showing papers on "Xanthene published in 1977"

Picosecond Fluorescence Studies of Xanthene Dyes

Abstract: Subnanosecond lifetime measurements using picosecond pulses from a mode locked Nd3+/glass laser together with conventional absorption and fluorescence yield methods have been used to study the photophysics of fluorescein and three of its halogenated derivatives (eosin, erythrosin, and rose bengal) in aqueous and simple alcoholic solvents. For each of the dye molecules absorption and fluorescence maxima move towards higher energy ("blue shift") as the solvent changes from i-PrOH to HlO. Fluorescence lifetimes and quantum yields are found to decrease markedly with this solvent change and also with in- creased halogenation ("heavy-atom effect") of the fluorescein parent. Published triplet yield data confirm that the variations observed in the nonradiative part of the decay rate can be attributed almost wholly to variations in the rate of SI-TI intersys- tem crossing. A simple and reasonable explanation of the observed effects can be found if for these particular solvent-solute combinations stabilization energies lie in the order AE(TI) < AE(S1) < AE(S0). This idea is consistent with both the increased SI-S0 spectral "blue shifts" and the enhanced intersystem crossing rate, arising from a smaller SI-TI energy gap, when these dye molecules are placed in a more aqueous solvent environment. The studies are relevant to the use of these dyes as fluorescent probes in biologically important molecules. I. Introduction The fluorescence properties of the xanthene dyes have both theoretical and practical interest. The advent of the dye laser' has sparked off renewed interest in the correlation between molecular structure and fluorescence properties, while the use of fluorescent dye probes in structural studies of molecules of biological significance has become an area of considerable a~tivity.~,~ The usefulness of a fluorescent probe relies on variations in the dye's fluorescent properties with alterations in its environment, solvent polarity being an example. Despite a considerable amount of work, no detailed theory explaining the often very dramatic effects of environment and structure on fluorescence has emerged. For example, the effect of solvent and macromolecular environment on the fluorescence lifetime and quantum yield of perhaps the most widely used fluorescent probe, ANS- ( 1 -anilinonaphthalene-8-sulfonate), not well understood although various mechanisms for the fluorescence quenching in polar solvents have been pr~posed.~-~ Until a better understanding of the environmental factors affecting the fluorescence of dye molecules has been achieved, detailed conclusions based on fluorescent probe studies must be treated with caution. Fluorescein and its halogenated derivatives provide an ex- cellent model series for studies of this kind, for not only do the degree and type of halogenation greatly alter the fluorescence yield, but the photophysical properties of these dyes are also very dependent on the nature of the solvent. We have studied absorption and emission spectra, fluorescence lifetimes, and fluorescence yields of eosin, erythrosin, and rose bengal (Figure 1 j in a series of alcohols and in aqueous solution. The data provide a clear picture of the changes in nonradiative decay rate that occur in these molecules as a result of changes in the solvent environment. 11. Experimental Section (a) Chemicals. Eosin (BDH) was purified by recrystallization from acidic solution and rose bengal (BDH) was purified by chromatog- raphy on an alumina-talc column. The erythrosin sample (BDH) was used as supplied. Spectroscopic grade (Merck) methanol, ethanol, 2-propano1, and triply distilled water were used as solvents. All the aqueous solutions were buffered to pH 9.2. Dye concentrations of

Photoinitiators for photopolymerizable coating compositions

Abstract: Photopolymerizable coating compositions contain, as the binder, olefinically unsaturated compounds having a boiling point above 50° C, together with from 0.5 to 15% by weight of photoinitiators, based on the binder. The photoinitiators are a mixture of an aromatic carbonyl compound A, which is a derivative of benzoin or benzil, which has at least one carbon-oxygen single bond in the α-position relative to the carbonyl group, an aromatic carbonyl compound B which is derived from benzophenone, fluorenone, anthraquinone, xanthene, thioxanthone or acridone, and an amine C of the general formula ##STR1## where R', R" and R"' are H, alkyl of 1 to 10 carbon atoms, cycloalkyl of 3 to 10 carbon atoms, aryl, hydroxyalkyl of 1 to 8 carbon atoms or alkoxyalkyl of 2 to 4 carbon atoms, but at most 2 substituents are H and at most 2 substituents are aromatic. These coating compositions may be used for finishing various substrates, as fillers or as printing inks.

Effect of pH on dye‐laser output power

Abstract: Experiments have been performed to measure the output power of stimulated emission from acidified or basified solutions of xanthene dyes pumped by a N2 laser. The results showed the laser output power was improved for rhodamine 6G, rhodamine B, pyronin B, fluorescein disodium salt, and fluorescein dipotassium salt by factors of 2.2, 2.8, 1.7, 26.7, and 8.6, respectively.

Photo-CIDNP in the tyrosyl unit: a new tool in high resolution nuclear magnetic resonance studies of peptides

Abstract: Photo-CIDNP in the ring and in the methylene protons of the tyrosyl unit in tyrosine, in its derivatives, and in peptides dissolved in D2O is induced by the reversible hydrogen abstraction by excited triplet xanthene dyes.

Derivation and interpretation of the spectra of aggregates. Part 5.—Dimers of some xanthene dyes

Abstract: Characteristic visible spectra of the monomeric and dimeric species of Pyronine B in aqueous solution have been obtained. The spectra of the dimeric species of the xanthene dyes Rhodamine B, Pyronine Y and Pyronine B were fitted to, and compared with, theoretical spectra calculated from two excition interaction theories. The existence of a weak coupling arising from the nuclear momenta and predicted by an adiabatic theory of exciton interactions in dimers is confirmed.

Relationship Between in vitro Intestinal Absorbability and Partition Coefficients of Xanthene Derivatives

Abstract: Four xanthene derivatives, namely, 8-chlorotheophylline, caffeine, theophylline and 1-methyl-3-sisobutylxanthene (SC-2964) were studied to ascertain their in vitro intestinal absorbability and partitioning property in an octyl alcohol/pH 7.4 buffer system. Absorbability in vitro was estimated as the cumulative transfer rate (μglmin.) of the test compounds transfering across everted rat intestine sacs. The results demonstrated a dependency of the cumulative transfer rates on the partition coefficients. A logarithmic correlation between cumulative transfer rates and partition coefficients of the test compounds was observed. It is concluded that this predictive methodology could be adopted to screen potentially active compounds and optimize the selection of compounds to be developed into orally bioavailable dosage forms.

Polarized Absorption Spectra and Configuration Analyses of Xanthene and Xanthone

Abstract: The polarized absorption sepctra of xanthene and xanthone were measured in stretched poly (vinyl alcohol) films, and the polarization direction of each electronic transition was determined. It was confirmed that xanthone has the short molecular-axis polarized bands (1A1←1A1) at 343, 260, and 226 nm, and the long molecular-axis polarized ones (1BA2←1A1) at 290, 266, and 242 nm. The electronic transitions of xanthone are discussed in connection with those of xanthene by use of the configuration analysis. For the 266 and 260 nm bands, the contributions of the intramolecular charge transfer character from the xanthene skeleton to the carbonyl group are considerable.

Phosphorescence and orbital nature of triplet state of xanthene dyes

Abstract: 7. 8. 9: R. A. Bell and J. K. Sanders, Can. J. Chem., 48, No. 7, 1114 (1970). R. E. Schirmer, J. H. Noggle, J. P. Davis, and P. A. Hart, J. Amer. Chem,, 92, 3266 (1970). R. E. Schirmer and J. H. Noggle, J. Amer. Chem. Soc., 94, 2947 (1972). M. Ya. Karpeiskii and G. I. Yakovlev, Bioorgan. Khim., ~, 1221 (1976). K. H. Drexhage, Laser Focus, 9, 35 (1973). S. S. Anufrik, V. A. Mostovnikov, A. N. Rubinov, V. F. Voronin, and G. R. Ginevich, Quantum Electronics and Laser Spectroscopy [in Russian], Nauka i Tekhnika, Minsk (1974), p. 5.

Xanthene-9-carboxylates

Abstract: The invention relates to xanthene-9-carboxylates of the formula ##STR1## wherein R1 and R3 may be the same or different and represent a lower alkyl group, n and m each are integers of 2 to 5, or pharmaceutically-effective salts thereof The compounds according to the invention possess cholinolytic and bronchospasmolytic effects and are completely devoid of harmful side-effects Thus these compounds can be used to great advantage in therapy

1'-Substituted xanthene-9-spiro-4'-piperidine derivatives

Abstract: The disclosure relates to xanthene derivatives which possess analgesic activity, to processes for the manufacture of said derivatives and to pharmaceutical compositions containing them. Typical of the xanthene derivatives disclosed is 6-chloro-4-hydroxy-1'-methylxanthene-9-spiro-4'-piperidine.

Electricallyyconductive high polymeric compound

Abstract: PURPOSE:An electrically-conductive high polymeric compound comprising a charge-transfer complex obtained from a polymer containing xanthene groups and an electron acceptor.

Preparation of xanthene derivatives

Abstract: PURPOSE:Xathene derivatives useful as antiallergic and antiasthmatic agents are prepared in good yields from salicylaldehydes or salicylic acids through simple steps.

The photochemical reaction of 1,1,4,4-tetramethyl-2,3-tetralindione with hydrogen donors

Abstract: The photochemical reaction of 1,1,4,4-tetramethyl-2,3-tetralindione, 1, with hydrogen donors, such as xanthene and aldehyde, in the liquid phase has been investigated. When xanthene was selected as the hydrogen donor, the main products were the “1,2-adduct,” photo-reduced α-keto alcohol, and 9,9′-bixanthenyl. The photolysis of 1 and an aldehyde gave the mixture of the “1,2-adduct” and the “1,4-adduct.” However, in the reaction with isobutyraldehyde another type of “1,2-adduct” was obtained, i.e., a combination product between the semidione radical and the isopropyl radical resulting from the decarbonylation of the isobutyryl radical, together with propene and carbon monoxide. The usual type of “1,2-adduct,” the “1,4-adduct,” and the photo-reduced product (α-keto alcohol) were the minor products in the reaction. It was also confirmed that the original “1,4-adduct” obtained from 1 and acetaldehyde rearranged photochemically to a different type of “1,2-adduct,” but no reverse rearrangement was observed under...

Action of Food Dyes on Digestive Enzymes (I)

Abstract: Inactivation of chymotrypsinogen in the presence of xanthene dyes such as rose bengale, phloxine, erythrosine and eosine was observed through the irradiation of light, but not in the dark. The extent of inhibition was in the following order; rose bengale>phloxine>erythrosine>eosine.Interaction of xanthene dyes with chymotrypsinogen were also examined by the spectrophotometric methods. In the presence of chymotrypsinogen, the absorption maxima of the dyes did not shift at pH 6.97, 7.99 and 10.0, but shifted to longer wavelength at pH 4.73 and 5.78.The binding numbers and the binding free energies were calculated from the difference spectra for the mixtures of the dyes and chymotrypsinogen which were incubated at 37°C for 15min. In comparison the both indexes of rose bengale to chymotrypsinogen in the dark with those in the light, they were not so increased in proportion to the inactivation of chymotrypsinogen. The order of binding capacities and affinities was rose bengale>phloxine>erythrosine>eosine at pH 4.77, regardless of the conditions with and without the irradiation.It was assumed that chymotrypsinogen would be inactivated in the presence of xanthene dyes by the photo-effect, not by the binding capacities and/or the affinities.