Radical polymerization inside living cells.

Polymerization reactions conducted inside cells must be compatible with the complex intracellular environment, which contains numerous molecules and functional groups that could potentially prevent or quench polymerization reactions. Here we report a strategy for directly synthesizing unnatural polymers in cells through free radical photopolymerization using a number of biocompatible acrylic and methacrylic monomers. This offers a platform to manipulate, track and control cellular behaviour by the in cellulo generation of macromolecules that have the ability to alter cellular motility, label cells by the generation of fluorescent polymers for long-term tracking studies, as well as generate a variety of nanostructures within cells. It is remarkable that free radical polymerization chemistry can take place within such complex cellular environments. This demonstration opens up a multitude of new possibilities for how chemists can modulate cellular function and behaviour and for understanding cellular behaviour in response to the generation of free radicals.

Spectral-luminescent and photochemical characteristics of homodimers of the styrylcyanine dye Sbt in solutions.

The influence of concentration, solvent nature on the intermolecular interaction and its spectroscopic manifestations in solutions of styrylcyanine dye Sbt ((E)-2-(4-(dimethylamino)styryl)-3-methylbenzo[d]thiazol-3-ium iodide) and its homodimers, i.e. dyes with two interconnected chromophores, was studied. It was found out that, depending on the concentration, the structure of dye molecules, the nature of the solvent various forms of associated molecules are forms; each of these forms is manifested in the spectra of absorption and fluorescence in its own way. It is shown that the intensity of the main absorption band of the studied dyes in aqueous solutions and in a mixture of water+ethanol decreases in the process of light irradiation and a new band is observed in the region of shorter wavelengths; the intensity of the new band increases with increase of radiation exposure of solutions.

Optical gain in DNA-DCM for lasing in photonic materials.

We present a detailed study of the gain length in an active medium obtained by doping of DNA strands with 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran dye molecules. The superior thermal stability of the composite and its low quenching permit one to obtain an optical gain coefficient larger than 300 cm(-1). We also demonstrate that such an active material is feasible for the infiltration into photonic nanostructures, allowing one to obtain fluorescent photonic crystals and promising lasing properties.

Substituent and solvent effects on the beta-heterolysis reaction of beta-hydroxy arylethyl radicals.

Time-resolved conversion of a series of beta-hydroxy arylethyl radicals with electron-donating and -withdrawing aromatic substituents to their corresponding styrene radical cation via heterolytic loss of the beta-hydroxy leaving group was examined with nanosecond laser flash photolysis. In all cases, the reaction was catalyzed by added perchloric acid. Radicals 2a-d reacted via a pre-equilibrium protonation mechanism in acidic 1,1,1,3,3,3-hexafluoroisopropanol (HFIP), and measuring rate constants for radical cation formation as a function of acid content allowed for the determination of absolute rate constants ranging from 3.6 x 10(6) to 3.8 x 10(7) s(-1) for the loss of water from the protonated beta-hydroxy arylethyl radicals 2a-d, as well as the acidity constants, pKa approximately 1.5 (in HFIP), for the protonated radicals. The 4-methoxy-substituted beta-hydroxy arylethyl radical 2e reacted by rate determining protonation in HFIP with a second-order rate constant of k(H+) = 7.8 x 10(8) M(-1) s(-1). However, in acetonitrile, 2,2,2-trifluoroethanol, and mixtures of these two solvents, 2e reacted by pre-equilibrium protonation, allowing for solvent effects on the rate constant for loss of water from the protonated radical 2e to be determined. With use of these data, substituent electronic effects on the kinetics of the beta-heterolysis reaction are discussed. Differences in the effect of solvent on the rate constant for loss of water from the protonated beta-hydroxy arylethyl radicals and other beta-substituted arylethyl radicals are also discussed.

Controlling photochemical geometric isomerization of a stilbene and dimerization of a styrene using a confined reaction cavity in water.

Utility of a water-soluble deep cavity cavitand, octa acid, as a reaction medium is illustrated by carrying out photochemical reactions of a stilbene and a styrene included within the octa acid in water. Geometric isomerization of trans-4,4'-dimethyl stilbene is restricted while dimerization of 4-methyl styrene is facilitated within the octa acid cavity. The excited-state chemistry of both systems is different in this medium from that in organic solvents. The change in chemistry is attributed to the supramolecular effects provided by the host cavity.

[Catalysis of 'dark' stage of cis-trans-isomerization of betaine stilbazole by myoglobin]. / Kataliz "temnovoi" stadii reaktsii tsis-trans-izomerizatsii betaina stil'bazola mioglobinom.

The back thermal cis-trans isomerization reaction of stilbazole betaine in the presence of metmyoglobin was studied. The catalytic effect of metmyoglobin heme on the back thermal cis-trans isomerization reaction of stilbazole betaine was observed.

Characterization of p-bis(O-methylstyryl)benzene as a lifetime and anisotropy decay standard for two-photon induced fluorescence.

We describe the fluorescence spectral properties of p-bis(O-methylstyryl)benzene (bis-MSB) as a standard for time-resolved measurements of two-photon induced fluorescence. Bis-MSB displays the same single exponential intensity decay in several solvents for one- and two-photon excitation. The anisotropy decay displays the same single correlation time of one- and two-photon excitation. The amplitudes of the anisotropy decay are distinct for one- and two-photon excitation. At some excitation wavelengths the anisotropy amplitude appears to be solely the result of one- and two-photon photoselection, but at shorter wavelengths the anisotropy amplitudes are not related by single constant factor. The absorption range of bis-MSB makes it a suitable standard for one- and two-photon excitation of intrinsic protein fluorescence and extrinsic fluorophores.

[Graft polymerization onto poly(methylvinylsiloxane)-bonded silica gel by gamma-ray irradiation].

Poly(methylvinylsiloxane)-bonded silica gel was synthesized by condensation reaction between silica gel and the hydrolysis product of methylvinyldichlorosilane. Graft polymerization of styrene or indene onto poly(methylvinylsiloxane)-bonded silica gel was carried out by gamma-ray irradiation and compared with that onto silica gel. Homopolymer was found to be formed through a radical mechanism concurrently with an ionic mechanism in the graft polymerization. Probably genuine graft polymers are formed in the graft polymerization onto poly(methylvinylsiloxane)-bonded silica gel, while the product formed in the graft polymerization onto silica gel may be apparent graft polymers.