Aggregation of cation-anionic and related polymethine dyes

Absorption, fluorescence, and fluorescence excitation spectra were studied for a number of cation-anionic and related anionic polymethine dyes in weakly polarand nonpolarsolvents, as well as in binary mixtures of solvents of different polarity. For some dyes, aggregation is observed in toluene or acetonitrile-toluene mixtures with low amounts of acetonitrile, which is revealed as appearance of new absorption bands and/or broadening of the initial bands of a monomeric dye. Solvent mixtures butyronitrilehexane with low butyronitrile content were found to greatly stimulate the formation of dye aggregates for most of the dyes studied. The absorption spectra of the aggregates are often blue-shifted with respect to the corresponding absorption spectra of parent monomeric dyes and/or represent broad continuums located both in the blue and red regions. For one of the cation-anionic dyes studied, which consists of 3,3′-diethylthiamonomethinecyanine cation and trimethinebenzoxanine anion, fluorescent aggregates were observed; their broad fluorescence band is located in the long-wavelength region. For this dye, gradual transition from nonfluorescent aggregates to fluorescent ones and then to monomeric ion pairs and dissociated ions was observed in butyronitrile-hexane mixtures with growing butyronitrile content

Protein-Coated Magnetic Nanoparticles: Creation and Investigation

A novel universal approach to cross-linking of protein macromolecules on the surface of magnetite na-noparticles has been developed. The approach is based on protein liability to free radical modification, leading to the formation of intermolecular covalent cross links. Free radicals are locally generated on the surface of nanoparticles. Using a set of physicochemical methods, it has been proven that stable coatings composed of protein macromolecules are formed around individual nanoparticles. The proteins fixed on nanoparticles do not lose their activity as a result of adsorption and free radical modification. Fluorescent probe approach for evaluation of the native functional properties of serum albumin as a part of coating is suggested. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3537

The content of lutein and its oxidized forms in human eye tissues in prenatal development

ABSTRACT Purpose. To study the presence of carotenoids in the tissues of prenatal human eye in the course of its development. Material and methods. The eyes were obtained from abortive human fetuses of 12-28 weeks of pregnancy. The fetuses were brought to the Kulakov Research Center of Obstetrics, Gynecology, and Perinatology, the Russian Academy of Medical Sciences, from licensed institutions of the Ministry of Public Health, working under the Russian Federation legislation on citizen health protection, and in accordance with the approved list of medical indications. The ages of the fetuses were determined by an obstetrician. Totally, 49 samples of eye tissues from human fetuses at different pregnancy ages were used. The content of carotenoids and their oxidized forms was measured by high-performance liquid chromatography (HPLC) technique. Results. The presence of lutein and/or its oxidized forms was estimated by HPLC in the tissues of prenatal human eyes (cornea, sclera, optic nerve, retinal pigment epithelium with choroid, ciliary body with iris, vitreous body). Conclusion. The finding of lutein or oxidized forms of lutein in tissues of the human eye in the course of prenatal development is of essential interests for understanding physiology of the prenatal and postnatal eye

Photonics of Some Monomethine Cyanine Dyes in Solutions and in Complexes with Biomolecules

In search of new probes for biomolecules, the spectral fluorescent study of four monomethine cyanine dyes (MCD), both unsymmetrical and symmetrical, has been carried out in different organic solvents, in aqueous buffer solutions, and in the presence of DNA and HSA. The complexation of MCD with biomacromolecules leads to a steep growth of the fluorescence intensity. Complexes of MCD with dsDNA and HSA of various types were modeled in silico by molecular docking. Experiments on thermal dissociation of dsDNA in the presence of MCD showed the formation of intercalative complexes of MCD with DNA. Quenching of intrinsic fluorescence of HSA by MCD occurred with rate constants much higher than the diffusion limit, that is, in dye–HSA complexes. Effective constants of MCD complexation with the biomacromolecules were estimated. MCD 1 has the best characteristics as a possible fluorescent probe for dsDNA and can serve as a sensitive and selective probe for dsDNA in the presence of HSA. Photochemical properties of MCD complexed with DNA have been also studied. An increase in the quantum yield of the triplet states of MCD in complexes with DNA has been found, which may be important for using these dyes as potential candidates in photodynamic therapy

Complex formation between 3;3´-diethylthiacarbocyanine iodide and DNA and its investigation in aqueous solution

The binding of 3;3′-diethylthiacarbocyanine iodide (DTCC) with molecules of DNA was investigated by different photochemical methods. Absorption spectra were investigated under various concentration of DNA. Isosbestic points observed in these spectra are attributable to existence of two different complexes DTCC with DNA. Equilibrium constants of the formation of complexes I and II were determined (K1≈106M−1, K2≈5×104M−1 accordingly). Differential absorption spectra of two photoisomers of DTCC were obtained by flash photolysis method; it was found that the quantum yield of the short-lived photoisomer decreases and the quantum yield of the second long-lived photoisomer builds up with the increase in the DNA concentration. Kinetics of interaction between the triplet state of the dye and oxygen were investigated under various concentration of DNA. The growth of the quantum yield of fluorescence and intersystem crossing was observed with the increase in the DNA concentration

Ion pairs of indobenzimidazolo cyanines: a structural study based on conductivity, absorption, fluorescence and H-1-NMR

Asymmetric benzimidazolo carbo, di- and tricarbocyanines form ion pairs of the solvent-separated and contact types with different counterions in tetrahydrofuran, toluene and toluene-nitrile mixtures. The dissociation constants of the ion pairs in tetrahydrofuran, evaluated from conductivity data, do not depend on the length of the polymethine chain and show only a small decrease with decreasing counterion size. The absorption and fluorescence excitation spectra of the contact ion pairs exhibit a pronounced hypsochromic shift with respect to the solvated ions and the solvent-separated ion pairs. H-1-NMR experiments have provided information about the electronic structures of the ions of both the asymmetric dyes and the corresponding symmetric carbocyanines. They have also revealed different preferred anion locations in the contact ion pairs of the symmetric indocarbocyanine on one hand, and of the benzimidazolo carbocyanine and the asymmetric dyes on the other. This structural difference is suggested to be a cause of the observed opposite effects of ion pairing on the isomerization kinetics of the two groups of dyes. (C) 1998 Elsevier Science B.V. All rights reserved