A new reaction of vicinal sulfonyliminocarboxylates with phosphites

The reaction of alkyl trifluoro(organylsulfonylimino)propionates with phosphites occurs with NC transfer of the RSO₂ group and leads to sulfonyl-substituted trifluoroalanine derivatives. The novel rearrangement is interpreted as cheletropic 1,4-cycloaddition of the phosphite and subsequent 1,2-shift of the sulfonyl group in the intermediate cyclic phosphorane.     

A catalyst-free one-step synthesis of N-pyrimidinyl amidines from endocyclic enamines and 4-azidopyrimidines

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Control of Protonated Schiff Base Excited State Decay within Visual Protein Mimics: A Unified Model for Retinal Chromophores

Artificial biomimetic chromophore-protein complexes inspired by natural visual pigments can feature color tunability across the full visible spectrum. However, control of excited state dynamics of the retinal chromophore, which is of paramount importance for technological applications, is lacking due to its complex and subtle photophysics/photochemistry. Here, ultrafast transient absorption spectroscopy and quantum mechanics/molecular mechanics simulations are combined for the study of highly tunable rhodopsin mimics, as compared to retinal chromophores in solution. Conical intersections and transient fluorescent intermediates are identified with atomistic resolution, providing unambiguous assignment of their ultrafast excited state absorption features. The results point out that the electrostatic environment of the chromophore, modified by protein point mutations, affects its excited state properties allowing control of its photophysics with same power of chemical modifications of the chromophore. The complex nature of such fine control is a fundamental knowledge for the design of bio-mimetic opto-electronic and photonic devices.     

Block copolymers containing polyacrylamide and polyacrylic acid: Bulk structure and hydrogen bonds system

Asymmetric block copolymers PAAc-b-PAAm (DBCs) and PAAm-b-PAAc-b-PAAm (TBCs) comprised poly(acrylic acid) blocks of constant chain length and polyacrylamide blocks of variable chain length were synthesized using RAFT/MADIX technique. Their properties in a bulk state were studied by differential scanning calorimetry and the hydrogen bond system was investigated by Fourier transform infrared spectroscopy. It was found that DBCs and TBCs possess a homogeneous amorphous structure, whose temperatures of glass transition and destruction beginning increased with growth of PAAm block length. The H-bond system between PAAc and PAAm blocks was most developed in TBC sample and formed manly by the mixed cyclic dimmers of carboxyl and amide groups.     

Interfacial behavior of water bound to nitrocellulose containing residual nitric and sulfuric acids

To prepare nitrocellulose (NC), microcrystalline cellulose was treated in a mixture of nitric and sulfuric acids. Prepared NC containing a small amount of acids was studied at a different hydration degree (h = 10–1000 mg g^?1) in different dispersion media (chloroform-d, acetone-d₆ or their mixtures) using low-temperature ¹H NMR spectroscopy. The hydration degree and the presence of residual acids affected the temperature dependence of the chemical shifts of proton resonance of water bound to NC. The Gibbs free energy of bound water became less negative with increasing hydration rate. The chloroform and acetone media affect the behavior of bound-to-NC water unfrozen at T<273 K differently. Quantum chemical calculations were performed using ab initio (HF/6-31G(d,p)), DFT (B3LYP/6-31G(d,p)) and semiempirical PM7 methods to analyze the interfacial behavior of water interacting with NC containing residual amounts of nitric and sulfuric acids.      

Investigation of Excitation of $${K}$$ Isomers $${}^{{179m2}}$$ Hf and $${}^{{180m}}$$ Hf in ( $${\gamma,\gamma^{\prime}}$$ ) Reactions

Physics of Atomic Nuclei - The weighted-average cross sections for $${}^{179m2}$$ Hf and $${}^{180m}$$ Hf population in ( $$\gamma,\gamma^{\prime}$$ ) reactions induced by gamma rays of...     

Behavior of poly(ε-caprolactone)-based diblock copolymers in a bulk state and in solution

Abstract

A series of amphiphilic MOPEO-b-PCL copolymers (DBCs), based on biocompatible methoxypoly(ethylene oxide) with M_n=4.5?kDa and poly(ε-caprolactone) of a variable chain length, was synthesized by an anionic ring-opening block copolymerization. The structural investigations, performed by DSC and WAXS methods, revealed the microphase separation in DBC bulk structure and the existence of separate amorphous regions and microcrystalline domains of MOPEO and PCL blocks. Spectrophotometry and SLS were used to study the self-assembling of DBC macromolecules in selective dioxane/aqueous solution and to determine the main micellization parameters (CMC and -ΔG°). The DBC micelles morphology and their specific aggregation in mixed solvent were shown.     

Activity study of graphite from the chernobyl NPP reactor

The content of the isotopes ³H, ¹⁴C, ³⁶Cl, ⁵⁵Fe, ⁵⁹Ni, ⁶³Ni, ⁶⁰Co, ⁹⁰Sr, ^93m Nb, ¹⁰⁸Ag, ¹³³Ba, ¹³⁴Cs, ¹³⁷Cs, ¹⁵⁴Eu, and ¹⁵⁵Eu in the GRP-2-125 graphite from the reactor of Power Unit 2 at the Chernobyl Nuclear Power Plant was measured. The results were compared with the calculations and literature data. Some regularities and correlations were revealed in the content of various radionuclides in graphite. Graphite porosity and desorption of radionuclides from graphite were studied. Original Russian Text ? M.D. Bondar’kov, D.M. Bondar’kov, A.M. Maksimenko, V.A. Zheltonozhskii, M.V. Zheltonozhskaya, V.V. Petrov, A.I. Savin, 2009, published in Izvestiya Rossiiskoi Akademii Nauk. Seriya Fizicheskaya, 2009, Vol. 73, No. 2, pp. 274–278.