Proteinases immobilized on poly(vinyl alcohol) cryogel: novel biocatalysts for peptide synthesis in organic media

Covalent immobilization of subtilisin and thermolysin on cryogel of poly(vinyl alcohol) was carried out. The biocatalysts obtained are characterized by high stability in water and in DMF—MeCN mixtures of various compositions. The synthetic efficiency of immobilized subtilisin in the multiple iterative synthesis of the peptide Z—Ala—Ala—Leu—Phe—pNA was examined in organic mixtures of different solvent compositions. Immobilized subtilisin exhibits high synthetic activity in organic media. A series of N-acylated p-nitroanilides of tetrapeptides of the general formula Z—Ala—Ala—Xaa—Yaa—pNA (Z is benzyloxycarbonyl, Xaa = Leu, Lys, or Glu; Yaa = Phe or Asp; pNA = 4-NO₂—C₆H₄NH-) were synthesized in 70—98% yields using immobilized subtilisin as a biocatalyst without activation and protection of the ionogenic groups of polyfunctional amino acids. Immobilized thermolysin in a DMF—MeCN mixture catalyzed the formation of the peptide Z—Ala—Ala—Leu—pNA, which was obtained in 90% yield (during 1 h). It was demonstrated that the biocatalyst can be used repeatedly and that it retained activity after storage in an aqueous buffer during 6 months.     

Structure of Polycrystalline CeNi3-Based Intermetallic Hydrides at 293 and 5 K

Crystallography Reports - The structure of polycrystalline CeNi3Н3.0 hydride samples at 5 and 293 K has been studied by neutron diffraction. The hydrides have a rhombic lattice (sp. gr. Pmcn,...     

Investigation of gold nanotubes of chiralities (4, 3) and (5, 3) in the Hubbard model

The quantum systems of gold nanotubes of chiralities (4, 3) and (5, 3) have been studied in the framework of the Hubbard model for arbitrary values of the Coulomb interaction and electron concentration. The anticommutator Green’s functions of nanosystems, the energy spectra, and the ground state, ionization, and electron affinity energies have been calculated. The obtained data have been used for comparative analysis of nanosystems.     

Contact Interactions between Polymeric Particles

The adhesion interaction between the particles of various amorphous glassy polymers and crystallizing poly(ethylene glycol) is investigated in the air and in the argon atmosphere. A strong effect of adsorption phenomena on the molecular attraction of polymers is disclosed.     

Electronic structure of π-systems. Studies of electronic structures and tautomeric transformations of a series of 4-methyl-8-(R-phenylazo)dihydrofuro[2,3-<Emphasis Type="Italic">h</Emphasis>]coumarin-9-ones

Tautomeric transformations of a series of 4-methyl-8-(R-phenylazo)dihydrofuro[2,3-h]-coumarin-9-ones were studied by ¹H NMR, IR, electronic absorption spectroscopy, mass spectrometry, and quantum chemistry methods. The obtained results suggest that (p-R-phenyl)-derivatives exist in the quinone hydrazone form, while (o-R-phenyl)derivatives exist as a mixture of quinone hydrazone and azo enol tautomers with domination of the former. The anti-quinone hydrazone tautomers with a strong intramolecular hydrogen bond are more favorable than the syn-quinone hydrazone tautomers.     

Dynamic Surface Tension and Adsorption/Desorption Kinetics for Mixtures on Planar Surfaces: I. Under Nonflow Conditions

The adsorption/desorption kinetics for individual polymers and polymer mixtures of the water-soluble associative polymers with molecular weights of 12, 62, and 100 kg/mol onto SiO2 planar substrate have been studied by ellipsometry at room temperature under nonflow conditions. Equations were derived to predict behaviors of the adsorption/desorption kinetics and dynamic surface tension onto planar surfaces for any times. It is shown that the desorption kinetics of the water-soluble associative polymers onto planar SiO2 surface is an irreversible process due to strong interaction between polymer molecules and an interface. Copyright 1999 Academic Press.     

Adsorption Kinetics of Polyelectrolytes on Planar Surfaces under Flow Conditions

The focus of our work has been to develop a theory of adsorption kinetics for polyelectrolytes in a flow cell onto planar surfaces in the framework of the two-dimensional model and to study adsorption processes of polyelectrolytes on a planar surface by ellipsometry. We have studied the adsorption kinetics of water-soluble cationic poly(vinylamine) hydrochloride homopolymer from aqueous solution onto both silicon wafers and polystyrene films by ellipsometry. Equations were derived to calculate (a) the equilibrium adsorption, (b) the thickness of the adsorbed layer, (c) the activation energy of adsorption for water-soluble polyelectrolytes, (d) the rate constant for the water-soluble polyelectrolytes, (e) the effective coefficients of diffusion in the adsorbed layer, and (f) the time needed to attain the equilibrium state for the adsorption of the water-soluble polyelectrolytes in a flow cell. Copyright 1999 Academic Press.     

C5-homologization of ubiquinone-9 and ubiquinone-10 using sulfur-containing synthons

Conclusions A seven-stage method has been developed for the transformation of ubiquinone-9 to ubiquinone-10 using sulfur-containing synthons as the key step; the most effective synthon was found to be prenyl phenyl sulfide. The analogous homologization of solanesol and decaprenol using an isoprenyl trans-C₅-hydroxysulfone was also examined.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 695–701, March, 1988.     

Two-Dimensional Coordination Polymer {[Zn(Pht)(4.4′-Bipy)(H2O)2] · 2H2O} n : Synthesis and Structure

The coordination polymer {[Zn(Pht)(4,4-Bipy)(H₂O)₂] · 2H₂O} _n (where Pht is a doubly deprotonated phthalic acid residue and 4,4-Bipy is 4,4-bipyridine) was synthesized and studied by X-ray diffraction. It was shown that both ligands perform a bridging function and unite the Zn atoms into a two-dimensional network with a periodicity of 11.302(2) Å (with 4,4-Bipy as the bridge) or 7.627(2) Å (with Pht as the bridge). The coordination polyhedron of Zn is a distorted octahedron with C ₂ symmetry. The Zn–N distances in the coordination polyhedron are 2.117(3) and 2.131(3) Å; the Zn–O_carb distance is 2.171(2) Å and the Zn–O(w) distance is 2.129(2) Å. The O–H···O hydrogen bonds involving the outer-sphere water molecules combine the polymer layers into a framework.