A monomethine cyanine dye Cyan 40 for two-photon-excited fluorescence detection of nucleic acids and their visualization in live cells

Monomethine cyanine dye 4-((1-methylbenzothiazolyliliden-2)methyl)-1,2,6-trimethylpyridinium perchlorate (Cyan 40) was investigated as a two-photon-excited fluorescence probe for nucleic acids (NA). Cyan 40 has been shown to demonstrate efficient two-photon-excited fluorescence in the presence of NA in vitro in contrast to solutions without NA. Two-photon confocal laser scanning microscopy (TPCLSM) and two-photon laser scanning microspectrofluorometry were used to check the possibility of using Cyan 40 as two-photon-excited fluorescence label for NA in living cells. Study of dye effect on viability of cells was also carried out. We ascertained that Cyan 40 is a cell-permeant dye, manifesting efficient two-photon-excited fluorescence when bound to NA in living cells, without any significant influence on viability of cells. TPCLSM images obtained from stained cells indicate preferential RNA staining by Cyan 40 compared with DNA.     

Electronic–Rotational Coupling and c 1 Σ – u –b 1 Σ + g Transition Probability in the Oxygen Molecule

A theory was proposed for the formation of intensity of the forbidden singlet–singlet c ¹ _u ^– b ¹ _g ⁺ transition in the oxygen molecule. The dipole moments of transitions that contribute to the formation of the intensity of the c–b transition in the range of internuclear distances of 1.2–2.0 Å were calculated using the configuration interaction method with a valence triple-zeta basis set. Based on these results, the electric dipole moment for the c ¹ _u ^– b ¹ _g ⁺ transition was calculated.     

Effect of Fullerene C60 and Other Antioxidants on High-Temperature Oxidative Degradation of Poly(methyl methacrylate) and Methyl Methacrylate Copolymers with Methacrylic Acid

Fullerene C_{6 0} inhibits high-temperature oxitative degradation of poly(methyl methacrylate) and methyl methacrylate copolymers with methacrylic acid.     

Analysis of the latent structure of luminescence and absorption spectra of thallium complexes

Comprehensive investigations of luminescence, excitation, and absorption spectra as well as of the luminescence kinetics of a frozen LiCl-Tl⁺ solution are carried out. It is established that the luminescence spectrum consists of four components. One component is caused by luminescence of the matrix and the remainder by luminescence of one luminescence center, namely, by the saturated complex of thallium TlCl₂(H₂O)Cl₄. The absorption spectrum consists of three components. Their parameters have been evaluated. Each component of the luminescence spectrum is excited in several components of the absorption spectrum. It is found that the luminescence spectrum components and their intrinsic absorption bands are located differently on the frequency axis. These data are similar to those obtained for other activated solutions of electrolytes. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 1, pp. 75–78, January–February, 2000.     

Femto-picosecond relaxation of triazole-bridged bis(zinc porphyrin)

The femtosecond dynamics of excitation relaxation has been revealed for the zinc porphyrin dimer using the pump-probe technique. The data obtained have been analyzed with the use of quantum-chemical calculations. The excitation relaxation dynamics shows that systems of this kind hold promise as models for investigation of photosystems and development of artificial analogues of natural photosynthetic centers. A model has been proposed to explain the found coherent dynamics of exciton bands.     

Effect of stimulated raman scattering on the formation of the random lasing spectrum of dyes

The nature of the line structure of the random lasing spectrum of vesicular films activated by dyes (rhodamine 6G, pyrromethene 597) has been analyzed. The spectral lines appear above the random lasing threshold and are manifested only within the spectrum of the amplified spontaneous radiation of dye molecules against the continuous-pedestal background. Their intensities are proportional to the product of the intensities of the pump and continuous spectrum at the frequencies of these lines, and the frequencies are exactly reproduced from pulse to pulse. The shifts of the lines are strongly correlated with the pump frequency and the frequencies of these lines coincide with the frequencies of the Raman scattering lines of dye molecules. Using these properties, it has been shown that the observed lines are due to stimulated resonant Raman scattering by dye molecules, which occurs simultaneously with the stimulated emission of these molecules. These two processes affect each other and jointly form a united nonlinear process where all of the oscillations active in Raman scattering are manifested.     

Fluorescence and host-guest energy transfer in polymeric chains

Intrachain singlet electronic excitation energy transfer from host polyvinylcarbazole (PVCa) to guest vinylbenzocarbazole (VBCa) units has been studied through measurements of the quenching effect on PVCa fluorescence and observation of the sensitized guest VBCa emission in solutions at 293 and 77K for different intramolecular concentrations of guest VBCa units. A method of taking into account intrinsic traps of singlet excitons (excimer forming sites, EFS), ordinarily present in an impurity free polymer macromolecule, has been elaborated. The comparison of the experimental data with theory shows that the one-dimensional singlet excitation energy transfer in a polymeric chain involves motion of incoherent excitons randomly hopping to a nearest neighbor along the line under conditions when capturing occurs upon the first visit of a trap and trapping centers of different origin become indistinguishable as regards their capturing capability.     

Excimer formation and charge carrier photogeneration in solid polymers

Data are presented on excitonic photogeneration processes in solid polymers similar to those observed in molecular-crystal photoconductivity. It is shown that excimeric states responsible for the intrinsic photogeneration are preferably of intramolecular origin.     

Luminescence of poly-N-epoxypropylcarbazole

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 53, No. 1, pp. 41–49, July, 1990.