All-fiber Kerr cell

An all-fiber nanosecond Kerr light gate is described that was constructed using microstructured fibers. The switching voltage for a 20?cm long device is as low as Vπ～85 V at a 1.06?μm wavelength. The device is fully spliced. The active element is a three-hole fiber provided with internal electrodes in the side-holes and a liquid core of nitrobenzene, which is fully enclosed. This work allows the exploiting of electrically driven liquid-core fibers and demonstrated the removal of the major limitations of Kerr cells in the past, allowing for integration, safe use, and relatively low switching voltage.     

Quantification of local hydration at the surface of biomolecules using dual-fluorescence labels

By using four labels of the 3-hydroxyflavone family displaying selective sensitivity to hydrogen bond (HB) donors and poor response to other polar molecules, we developed an approach for measuring local water concentration [H(2)O](L) (or partial volume of water: W(A) = [H(2)O](L)/55.6) in the label surrounding both in solvent mixtures and in biomolecules by the intensity ratio of two emissive forms of the label, N*/T*. Using a series of binary water/solvent mixtures with limited preferential solvation effects, a linear dependence of log(N*/T*) on the local concentration of HB donor was obtained and then used as a calibration curve for estimating the W(A) values in the surroundings of the probes conjugated to biomolecules. By this approach, we estimated the hydration of the labels in different peptides and their complexes with DNAs. We found that W(A) values for the label at the peptide N-terminus are lower (0.63-0.91) than for free labels and depend strongly on the nature of the N-terminal amino acid. When complexed with different DNAs, the estimated hydration of the labels conjugated to the labeled peptides was much lower (W(A) = 0-0.47) and depended on the DNA nature and linker-label structure. Thus, the elaborated method allows a site-specific evaluation of hydration at the surface of a biomolecule through the determination of the partial volume of water. We believe the developed procedure can be successfully applied for monitoring hydration at the surface of any biomolecule or nanostructure.     

Recyclizations of 3-formylchromones with binucleophiles

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Synthesis of a novel Boc-protected cyclopropane-modified proline analogue

The synthesis of the Boc derivative of a novel member of the cyclopropane-modified proline library, Boc-protected 5-azaspiro[2.4]heptane-6-carboxylic acid, is reported. The synthesis was performed in six steps starting from (2S,4R)-4-hydroxyproline using a modified Simmons-Smith reaction as the key step. The reaction conditions for all the steps were carefully selected to avoid racemization at the chiral centers in the intermediates and the final product.     

1-Alkyl-5-((di)alkylamino) tetrazoles: building blocks for peptide surrogates

An approach to the synthesis of 1-alkyl-5-((di)alkylamino)tetrazoles by nucleophilic substitution in 1-alkyl-5-sulfonyltetrazoles with anions generated from the primary or secondary amines was developed. Tolerance of the method to the presence of some functional groups (i.e., protected amine) in both components of the reaction was demonstrated. Obtained tetrazoles are promising building blocks for the design of peptide surrogates, in particular, for replacement approaches of alkyl urea derivatives.     

Micro-Mesoporous Carbon Materials Prepared from the Hogweed (Heracleum) Stalks as Electrode Materials for Supercapacitors

Russian Journal of Electrochemistry - The data on carbonization and surface activation of raw hogweed (Heracleum) are presented. The structural and electrochemical properties of thus synthesized...     

Temperature-Dependent Photoluminescence of Silver-Indium-Sulfide Nanocrystals in Aqueous Colloidal Solutions

The temperature dependence of the photoluminescence (PL) intensity of colloidal semiconductor nanocrystals (NCs) makes them an appealing option in bio-sensing applications. Here, we probed the temperature-dependent PL behavior of aqueous glutathione (GSH)-capped Ag−In−S (AIS) NCs and their core/shell AIS/ZnS heterostructures. We show that both core and core-shell materials reveal strong PL quenching upon heating from 10 to 80 °C, which is completely reversible upon cooling. The PL quenching is assigned to the thermally activated dissociation of complexes formed by ligands with the metal cations on the NC surface and the introduction of water into the NC coordination sphere. This unique mechanism of the thermal PL quenching results in a much higher temperature sensitivity of the aqueous colloidal AIS (AIS/ZnS) NCs as compared with previously reported analogs capped by covalently bound ligands. Our results are expected to stimulate further studies on aqueous ternary NCs as colloidal luminescent nano-thermometers applicable for ratiometric temperature sensing.     

Giant thermodynamical optical effect near ferroelastic phase transition point in Cs3Bi2I9 layered crystal

For the first time we have found a new giant thermodynamical optical effect near the ferroelastic phase transition point in Cs₃Bi₂I₉ layered crystal. The effect is appeared as periodical oscillations in time of the reflection coefficient. This phenomenon is caused by the small temperature deviations in thermodynamical system the appearance of which in the reflection spectra is strongly amplified in the ferroelastic phase transition point. The optical oscillations are explained on the base of a model that takes into account the temperature dependence of the refractive index through the order parameter (spontaneous strain) of the crystal.     

Synthesis and crystal structure of 7,7,10-trimethyl-7-silabenzo[a]anthrone

Skeletal isomerization of arylsilanes that occurs under conditions of catalytic dehydrocyclization and is accompanied by migration of the triorganosilyl group was additionally confirmed by dehydrocyclization of dimethyl(2,4-dimethylphenyl)(1-naphthyl)silane on chromium-containing oxide catalysts. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2236–2239, December, 1997.