Quenching of the triplet state of meso-substituted thiacarbocyanine dyes by nitroxyl radicals, iodide ions, and oxygen in solutions and in complexes with DNA

Using the flash photolysis method, the spectral and kinetic characteristics of triplet states of a number of meso-substituted thiacarbocyanine dyes (3,3′-diethyl-9-methoxythiacarbocyanine iodide, 3,3′,9-triethylthiacarbocyanine iodide, 3,3′-diethyl-9-methylthiacarbocyanine iodide, and 3,3′-diethyl-9-thiomethylthiacarbocyanine iodide) were studied, and the rate constants of triplet quenching by a stable nitroxyl radical, iodide ion, and oxygen were determined in solutions and in complexes with DNA. The results obtained show the formation of two types of dye-DNA complexes: formed by binding of the dye in the groove of a DNA molecule and by intercalation of the dye between base pairs. The complexation creates steric hindrances upon quenching of the triplet states of the ligands and causes great differences between the rate constants of the quenching processes.     

Infrared spectra of double-alkali silicate glasses

Infrared reflection spectra have been taken of bisilicate glasses in which one alkali oxide (Na₂O, K₂O) is gradually replaced by another while their total content is kept constant, and the electrical conductivity and density, of these glasses have been determined. The spectra of single-alkali glasses containing 16–20% of alkali and whose structure, according to some authors, is similar to that of bisilicate glasses, are also included. The main characteristic features of the spectra of double-alkali glasses do not confirm this assumption, but indicate that their structure approximates that of single-alkali glasses; nevertheless, the parts composing the microheterogeneous structure have an altered composition as compared with that of single-alkali glasses. Electrical conductivity passes through a minimum for all three combinations of the alkali oxides, while density passes through a weak maximum in the case of sodium-potassium glasses only.     

Temperature-concentration dependence of the electrical conductivity of glasses in the Zn(PO3)2-NaF system

Temperature-concentration dependence of the electrical conductivity in glasses of the Zn(PO₃)₂-NaF system was studied and compared with similar dependences for glasses of other systems. The extremal dependences log σ = f([Na⁺]) and {ie937-1} are interpreted from the standpoint of a macroscopically inhomogeneous structure of the glasses under study.     

Extraction Equilibria in the Fullerene C60-Fullerene C70-Solvent Systems

A new method was proposed for separation of light fullerenes C₆₀ and C₇₀ based on realization of two-phase extraction equilibria in multicomponent fullerene-containing systems C₆₀-C₇₀-solvent I-solvent II and C₆₀-C₇₀-solvent I-solvent II-inert component. The principal possibility and high efficiency of the extraction separation of light fullerenes were demonstrated.     

Effect of Lithium Sulfide on Electrical Properties of Li2S-LiPO3 Glasses

The temperature and concentration dependences of the electrical conductivity was studied in Li₂S-LiPO₃ glasses. The effect of lithium sulfide additions (22.5-25 mol %) to LiPO₃ on the electrical conductivity was studied. The nature of the conductivity was studied over the whole range of Li₂S concentrations using Tubandt's procedure, and the contribution of electronic component to the total electrical conductivity was examined by Liang-Wagner's polarization method.     

Spectral and kinetic investigation of interaction of 3,3′-diethyl-9-chlorothiacarbocyanine perchlorate with DNA

Interaction of the meso-substituted carbocyanine dye 3,3′-diethyl-9-chlorothiacarbocyanine (DCTC) perchlorate with DNA in phosphate buffer solutions (pH 7) was studied by spectral and kinetic methods. It was shown that the dye mainly exists in the cis-isomer form in water and aqueous-alcoholic solutions. The interaction with DNA leads to the formation of a trans-DCTC complex, which gradually (over a few tens of minutes) converts into the complex of the dye cis-isomer. It was revealed that the reactant concentration and ionic strength of solution have a considerable effect on the kinetic characteristics of trans-cis-reorganization of DCTC complexes, thus indicating a complex character of the process.     

Study of protein coatings cross-linked via the free-radical mechanism on magnetic nanoparticles by the method of spectral and fluorescent probes

Magnetite nanoparticles have been obtained with stable coatings formed from bovine and human serum albumins. The coatings are fixed by free-radical cross-linking of the proteins with the use of their ability to form interchain covalent bonds under the action of free radicals, which are generated with participation of transition metals present on nanoparticle surface. The method of spectral and fluorescent probes has been employed for the first time to describe the properties of coatings with the use of various dyes. It has been shown that, when studying the adsorption and free-radical cross-linking of proteins on nanoparticles, it is reasonable to use polymethine and squarylium dyes for estimating the functional properties of the proteins forming the coatings. It has been found that as many as 50% of molecules forming an albumin coating crosslinked via the free-radical mechanism retain their capability of bonding to a fluorescent dye. It has been concluded that the proteins occurring in the structure of the coatings retain their functional properties.     

The Study of <Emphasis Type="Italic">cis-trans</Emphasis> Equilibrium and Complexation with DNA of <Emphasis Type="Italic">meso</Emphasis>-Substituted Carbocyanine Dyes

The effect of DNA was studied on cis-trans equilibrium and spectral and fluorescent properties of a number of meso-substituted carbocyanine dyes: 3,3′-diethyl-9-thiomethylthiacarbocyanine iodide (K1), 3,3′-diethyl-9-methoxythiacarbocyanine iodide (K2), 3,3′-9-triethylthiacarbocyanine iodide (K3), 3,3′-dimethyl-9-ethyloxacarbocyanine iodide (K4), 3,3′-9-triethyl-5,5′-dimethyloxacarbocyanine iodide (K5), and 3,3′,9-triethyl-6,6′-dimethoxyoxacarbocyanine iodide (K6). Equilibrium between the cis and trans isomeric forms was detected for the thiacarbocyanine dyes in a number of organic solvents, with a shift of the equilibrium toward the cis-isomer caused by an increase in the solvent polarity. The oxacarbocyanines are present only in the form of trans-isomers in both polar and nonpolar solvents. Interaction of the dyes with DNA leads to the formation of stable noncovalent complexes. The complexation of the thiacarbocyanine dyes results in a shift of the isomeric equilibrium and occurs predominantly via the cis-form of the dye. The oxacarbocyanine dyes produce complexes with DNA in the initial trans-form.__________Translated from Khimiya Vysokikh Energii, Vol. 39, No. 4, 2005, pp. 280–286.Original Russian Text Copyright © 2005 by Pronkin, Tatikolov, Anikovskii, Kuz’min.