The peculiarities of sorbtion mechanism of phenole molecules by films of PVA‐PAAN interpolymer complex

The peculiarities of sorbtion mechanism of phenole molecules by poly(vinylalcohol) and poly(acrylamide) (PVA‐PAA_N) films are examined. An analytical model of absorbtion process based on diffusive character of penetration of phenole molecules in polymer film with the following spontaneous capturing by selftuning traps is proposed. The analytical results can be easy compared with experimental data obtained by spectrophotometry method. The comparison of theory and experiment gives the average value of resulting diffusion lenght of phenole molecule during «free» life‐time <l>∼10⁻⁶ cm.     

Interaction of cyanine dyes with nucleic acids. XVII. Towards an aggregation of cyanine dyes in solutions as a factor facilitating nucleic acid detection

Spectral properties of newly synthesized cyanine dyes, namely 1-[6-(4-[6-[2,6-dimethyl-4-(3-methyl-2,3-dihydro-1,3-benzothiazol- 2-ylidenmethyl)-1-pyridiniumyl]hexanoyl]piperazino)-6- oxohexyl]-2,6-dimethyl-4-(3-ethyl-2,3-dihydro-1,3-benzothiazol+ ++-2-ylidenmethyl)pyridinium (K-6) (bichromophoric dye) and 1-[5-di(3-[5-[2,6-dimethyl-4-(3-methyl-2,3-dihydro-1,3-benzothiazol++ +-2-ylidenmethyl)-1-pyridiniumyl]pentylcarboxamido]pro pyl) carbamoylpentyl]-2,6-dimethyl-4-(3-methyl-2,3-dihydro-1,3-benzo thiazol-2-ylidenmethyl) pyridinium (K-T) (trichromophoric dye) in solutions in the presence of and without deoxyribonucleic acid (DNA) were studied within a wide concentration range. It has been established that absorption, as well as fluorescence of investigated dye solutions, without DNA are mainly determined by H-aggregates of dye molecules. On the contrary, the fluorescence of dye solutions in the presence of DNA gives an intrinsic dye molecular fluorescence. H-aggregates are broken because of binding dye molecules with DNA. It has been suggested that both K-T and K-6 molecules bind mainly with DNA via the interaction of two chromophores. As the ratio of the number of dye molecules to that of DNA base pairs increases with an increase in dye concentration, a formation of dye molecule H-aggregates on DNA molecules are observed. Such aggregates have a different structure than those formed in the solutions without DNA. On the grounds of the data obtained, it is concluded that it is possible to use a dye aggregation capable of obtaining higher values for fluorescence enhancement of the DNA stains.     

Peculiarities of Raman spectra of polyurethane/carbon nanotube composite

We present a detailed analysis of the Raman spectra of polyurethane (PU)/single wall carbon nanotube (SWCNT) composites obtained at room temperature using 488 and 514.5 nm laser excitation. The spectra reveal a significant influence of the polymeric matrix on the carbon nanotube bundles. The nanocomposite Raman bands become broader and are shifted to higher frequencies in comparison to the corresponding bands of the pristine SWCNT bundles. Redistribution of intensity in the vicinity of a G-band and an increase of splitting of the radial breathing mode are also observed for the nanocomposites. Various spectral features of SWCNT clearly indicate the large interfacial interaction of the PU matrix and the SWCNT, possibly due to the π-π stacking between the PU chains and the SWCNT.     

Estimate of P-and P,T-odd effects in diatomic van der Waals molecules

The magnitudes of the possible P-and P, T-odd effects in diatomic van der Waals molecules are estimated. The estimates fall between the values corresponding to atoms and molecules/radicals. Arguments are presented showing that the loss of approximately two orders of magnitude in the strength of the effect for van der Waals molecules with an unpaired electron, such as CsXe, as compared with molecules/radicals can be partially compensated by a number of experimental advantages of working with van der Waals molecules. Pis’ma Zh. éksp. Teor. Fiz. 64, No. 10, 659–663 (25 November 1996)     

A laboratory search for variation of the fine-structure constant using atomic dysprosium

Electric-dipole transitions between nearly degenerate, opposite parity levels of atomic dysprosium (Dy) were monitored overan eight-month period to search for a variation in thefine-structure constant, α. The frequencies of thesetransitions are sensitive to variation of α due to largerelativistic corrections of opposite sign for the opposite-paritylevels. In this unique system, in contrast to atomic-clockcomparisons, the difference of the electronic energies of theopposite-parity levels can be monitored directly utilizing aradio-frequency (rf), electric-dipole transition between them. Ourmeasurements for the frequency variation of the 3.1-MHz transitionin ¹⁶³Dy and the 235-MHz transition in ¹⁶²Dy can beanalyzed for both a temporal variation and a gravitational-potentialdependence of α since, during the data acquisition period, the Earth is located at different values of the gravitationalpotential of the Sun. The data provide a rate of fractional temporalvariation of α of (-2.7±2.6)×10^-15 yr^-1 ora value of (-8.7 ±6.6) ×10^-6 for k_α, thelinear-variation coefficient for α in a changinggravitational potential. These results are independent ofassumptions regarding variation of other fundamental constants. Thelatter result can be combined with other experimental constraints toextract the first limits on k_e and k_q, which characterize thevariation of m_e/m_p and m_q/m_p in a changing gravitationalpotential, where m_e, m_p, and m_q are electron, proton, andquark masses. All results indicate the absence of significantvariation at the present level of sensitivity.     

Some peculiarities of spectral proprieties of leukocytes

This article presents the results of spectral investigations of white blood human cells including absorption, fluorescence and phosphorescence (using low-temperature measurements). For this research, the main optical centres were identified and local distribution of emitting and absorbing centres into white blood human cells was determined. In addition, the spectra of normal and pathological (B-cell chronic lymphocytic leukemia, B-CLL) cells were compared.     

Effect of Polyacrylamide and Dextran-Polyacrylamide Graft Polymers on Absorption and Fluorescence Spectra of Hematoporphyrin

Absorption and fluorescence spectra of hematoporphyrin (HP) solutions in distilled water and in the presence of polyacrylamide and three dextran-graft-polyacrylamide branched polymers are studied. HP is shown to interact with the studied polymers leading to the destruction of HP aggregates, which is positive for the use of porphyrin as a photosensitizer in the photodynamic therapy. For the concentrations of the polymers of 0.001%, the studied polymers demonstrated a similar impact on HP.     

Styryl Dyes as Two-Photon Excited Fluorescent Probes for DNA Detection and Two-Photon Laser Scanning Fluorescence Microscopy of Living Cells

Spectral-fluorescent properties of benzothiazole styryl monomer (Bos-3) and homodimer (DBos-21) dyes in presence of DNA were studied. The dyes enhance their fluorescence intensity in 2–3 orders of magnitude upon interaction with DNA. Studied styrylcyanines in DNA presence demonstrate rather high values of two-photon absorption (TPA) cross-section, which are comparable with the values of TPA cross section of the rhodamine dyes. An applicability of the styrylcyanines as probes for the fluorescence microscopy of living cells was studied. It was shown that both dyes are cell-permeable but homodimer dye DBos-21 produces noticeably brighter staining of HeLa cells comparing with monomer dye Bos-3. Molecules of DBos-21 initially bind to the nucleic acids- containing cell organelles (presumable mitochondria) and are able to penetrate into the cell nucleus. Thus, homodimer styryl DBos-21 dye is viewed as efficient stain for single-photon and two-photon excitation fluorescence imaging of living cells.     

Fluorescence of Styryl Dyes-DNA Complexes Induced by Single- and Two-Photon Excitation

The series of novel monomer and homodimer styryl dyes based on (p-dimethylaminostyryl) benzothiazolium residues were synthesized and studied as possible fluorescent probes for nucleic acids detection. Spectral-luminescent and spectral-photometric properties of obtained dyes in the unbound state and in DNA presence were studied. Fluorescence emission induced by two-photon excitation of dye-DNA complexes in aqueous buffer solution was registered. Two-photon absorption cross section values of the studied dyes in DNA presence were evaluated.     

Davydov Splitting in Spectra of Cyanine Dye J-Aggregates, Formed on the Polynucleotides

It was found in our previous work (T. Y. Ogul'chansky et al. (2001) Spectrochimica Acta Part A 57, 2705–2715) that the carbocyanine dye Cyan iPr forms J-aggregates in the groove of poly(dA)-poly(dT). In the present paper we study in detail the spectral properties and energy levels structure of the Cyan iPr J-aggregates by means of absorption and fluorescence spectroscopy and polarization measurements. The energy structure of an aggregate consists of at least two exciton zones, and dipole moments of the absorption transitions to these zones are oriented at an angle of about 90° one to another. It was supposed that the transition moment of the lower zone is parallel to the polynucleotide axis and the moment of the upper zone is perpendicular. The fluorescent transitions are possible only from the lower exciton zone, while the excitations of higher zone undergo nonradiative transitions to the lower one.