Some features of formation and dissolution of a series of Pu(IV) and Zr alkyl and butyl alkyl phosphates in the system tBP — N-dodecane — Nitric acid — Water

The formation and composition of salts produced on interaction of a series of alkyl- and butylalkylphosphoric acids having alkyl radical chain lengths from C₄ to C₁₀ with Pu(IV) and Zr in organic and aqueous phases of the system TBP — n-dodecane — nitric acid — water have been studied. The composition of compounds was found to depend on the conditions of their formation, being defined first of all by the HNO₃ concentration in aqueous and organic phases.     

A New Predictive Equation for the Depression in Freezing Points of Multicomponent Aqueous Solutions Conforming to the Linear Isopiestic Relation

The linear isopiestic relation has been used together with a well-known thermodynamic equation to establish a new predictive equation for freezing point depression. This equation can provide predictions for multicomponent solutions conforming to the linear isopiestic relation using only information on the corresponding binary subsystems. The predictive capability of the equation has been tested by comparing with the experimental data at 25°C reported in the literature and particularly those of Pathwardhan and Kumar. The systems used are NaCl—MgCl₂—H₂O, NaCl—BaCl₂—H₂O, NaCl—CaCl₂—H₂O, LiCl—NaCl—H₂O, LiCl—KCl—H₂O, LiCl—CsCl—H₂O, NaCl—KCl—H₂O, and NaBr—KBr—H₂O. The predictions of the two equations agree well with the experimental data although our new equation is, in general, better.     

A Quantum Chemical Study of N14 Cluster

Ab initio molecular orbital theory and density functional theory have been employed to study N₁₄ cluster with low spin at the HF/6-31G*, B3LYP/6-31G*, B3PW91/6-31G*, BP86/6-31G*, and BHLYP/6-31G* levels of theory. Twelve isomers were studied, including one previously investigated cage molecule. The most stable isomer of N₁₄ is a C _2h -symmetric molecule that contains two separated five-membered nitrogen rings connected by a —N=N—N=N— bridge. The second, third, and fifth most stable isomers each have one five-membered nitrogen ring. The theoretical results suggest that the five-membered nitrogen ring gives rise to a particularly stable structural unit, and the more side chains that the five-membered nitrogen ring links with, the less stable the structure will become.     

Ionization constants of a number of alkaloids used in medicine

The pK_a values of a number of alkaloids in water or in aqueous ethanol have been measured by the potentiometric titration method: nuphleine — 4.59, 6.98; brevicolline — 5.17, 8.02; chelidonine — 6.40; sanguinarine — 7.32; chelerythrine — 7.53; stepharine — 8.48; d-pseudoephedrine — 9.49. For nuphleine and brevicolline, each of which has two nitrogen atoms capable of protonation, assignments have been made of pK_a values to the corresponding atoms on the basis of the results of UV spectroscopy.All-Union Scientific-Research Institute of Medicinal Plants, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 337–341, May–June, 1984.     

Investigations into the formation and characterization of microemulsions. I. Phase diagrams of the ternary system water—sodium alkyl benzene sulfonate—hexanol and the quaternary system water—xylene—sodium alkyl benzene sulfonate—hexanol

The phase diagrams of the ternary system water—sodium alkylbenzene sulfonate (NaDBS)-hexanol and the quaternary system water—xylene—NADBS—hexanol have been established at three different temperatures, namely 25, 37, and 50°C. The different phases formed have been qualitatively examined using optical (phase contrast and polarizing) microscopy. The textures of the various liquid crystalline phases in the ternary system have been identified, by comparison with previous studies in the literature. Some of the liquid crystalline phases have been quantitatively assessed using low angle X-ray diffraction. The latter measurements were also used to determine the unit cell dimensions in the various phases studied. With the quaternary system, particular attention was paid to the transparent region which consisted of an L₂ (inverse micellar) phase extending into another transparent region which has a blue “tinge” in some cases, namely the microemulsion (M) region. The amount of water solubilized in the L₂ (reverse micelle) or M + L₂ phase was calculated from the phase diagrams. With the ternary system the results showed a maximum in moles of water solubilized per mole total surfactant (NaDBS + hexanol) at a concentration of 0.3 mole surfactant, at an optimum molar ratio of n-hexanol to NaDBS of 4.5:1. This maximum was about twice with the quaternary system, when compared with that of the ternary system, indicating the importance of the role of xylene in solubilization of water by the surfactants. The present investigation has also shown that the extent of the microemulsion region is significantly reduced by increases of temperature when the NaDBS is lower than 15 wt%.     

Quantum calculations on the adsorption of halide ions on the noble metals

The interaction of halide ions with the three noble metals has been investigated using the B3LYP density functional method and the cluster model approximation. The results of calculations for the M—X⁻ and M₁₂—X⁻ (M = Cu, Ag, Au; X = F, Cl, Br, I) systems are presented. At the (100) surface, modeled in the present work by the M₁₂ cluster, all halide ions have been found to adsorb preferentially at the hollow site, followed by the bridge and by the top positions. The adsorption energy has been found to decrease when going from fluoride to iodide in both atom—ion and cluster—ion cases. The opposite trend is observed for the estimates of the charge transfer from the ions to the surface. When different metals are compared, the M₁₂—X⁻ interaction energies decrease in the order Au > Ag > Cu, but for the smaller ions some deviations from this line do appear. The relative values of the calculated harmonic vibrational frequencies do agree with those found experimentally, but their magnitude is much smaller as a result of the effect of the lower surface coverage.     

Polysiloxane-Diamine Modified Gel as Precursor to Crystalline/Amorphous Si3N4

New hybrid organic-inorganic materials are prepared by reaction of polymethylhydrosiloxane (PMHS) with aniline (An) or 4,4-diamino,diphenyl methane (APM) through a condensation between NH₂-terminated amines and Si—H groups. The obtained modified-polysiloxane is a liquid polymer (PS-An) in the first case and a cross-linked gel (PS-APM) in the second one. The chemical structures of PS-An and PS-APM were investigated by ²⁹Si nuclear magnetic resonance and were proved to be formed of created (Si—O)₂(Me)Si—N(H)— and unreacted (Si—O)₂(Me)Si—H sites. The pyrolysis of the diamine-based gel has been carried out in N₂ atmosphere up to 1450°C. FTIR, ²⁹Si MAS NMR and X-ray diffraction have shown that Si—O and Si—C bonds are totally broken during pyrolysis and that the final product is formed of crystalline and amorphous silicon nitride in the presence of a free carbon phase.     

Elaboration and Characterisation of Hybrid Materials of Polymethylhydrosiloxane Modified by Diamines of Various Lengths

The polymethylhydrosiloxane (PMHS) modified by bifunctional organic compounds (diamines), offer the possibility of producing organic-inorganic hybrid materials. These materials present excellent opto-electronic properties and find numerous applications such as the manufacture of electroluminescent diodes and ion or radiation sensors.This work shows that monolithic and transparent hybrid gels were obtained by reaction at room temperature of PMHS with diamines in tetrahydrofuran, using hexachloroplatinic acid (H₂PtCl₆·6H₂O) as catalyst. The products have been characterized by infrared and ²⁹Si MAS-NMR spectroscopy. The results show that the diamines have reacted with the PMHS leading to the monolithic and transparent gels in which both organic-inorganic —Si—(H)N—(CH₂) _n —N(H)—Si— bridges are formed (n = 3, 4 and 6). The thermal analysis of the xerogels was determined by TGA and DTA. The structure and texture of the obtained materials, were studied by Chemical Analysis and the Brunauer-Emmett-Teller (BET) method.     

Electrocatalysis of metalloporphyrins: Part 12. Chemically modified electrodes with porphyrin-incorporated Nafion coatings

The electrocatalytic behaviour of cobalt(III) tetrakis(4-trimethylammoniumphenyl)porphyrin (CoTMAP) and the electroreduction mechanisms of dioxygen and dithiodipropionic acid (PSSP) at glassy carbon electrodes (GCEs) modified with Nafion coatings incorporating CoTMAP and Ru(NH₃)₆³⁺ have been studied. The experimental results indicate that the catalytic electroreduction of dioxygen using CoTMAP as a catalyst and Ru(NH ₃)₆³⁺ as a mediator could proceed at the Nafion coating—solution interface regardless of the state of the electrode surface. The catalytic electroreduction of dithiodipropionic acid could not proceed at the Nafion coating—solution interface but only at the GCE—solution interface, suggesting the importance of the adsorption of Co(I)TMAP on the GCE to the catalytic electroreduction of PSSP.     

Extractive substances of the bark of Picea obovata

The chemical composition of a petroleum ether extract of the bark of the Siberian spruce has been studied. Extracts included saturated aliphatic alcohols and C₁₆-C₂₄ acids — abietic, dehydroabietic, isopimaric, oleic, lineolic, and linolenic — alkyl ferulates, ketones, and alcohols of the serratene type, and also ⁴-stigmasten-3-one. Onoceradienedione and onoceradienediol — precursors of the serratene triterpenoids — and also a saturated vicinal diol — triacontane-10,11-diol — have been isolated from the extractive substances of conifer in the native form for the first time.Novosibirsk Institute of Organic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 654–662, November–December, 1992.     

Permselectivities and ion-exchange properties of organically modified sol—gel electrodes

Sol—gel films prepared from organosilanes containing acidic/basic sites have been investigated as permselective and ion-exchange coatings for electroanalytical and bioanalytical investigations. When a glassy carbon electrode was modified with a sol—gel film fabricated from 3-aminopropyl-methyl-diethoxysilane (silane—NH₂), excellent permselectivity and anion-exchange properties were obtained. For a pH 7.4, 1 mM potassium ferricyanide solution, an eight-fold increase in current was observed after the electrode was immersed in solution for 10min whereas complete suppression of the electrochemical response for ruthenium hexaamine and methyl viologen was observed. Sol—gel films fabricated from trimethoxysilylpropyl ethylenediamine triacetic acid (silane—(COOH)₃) exhibited nearly complementary behavior. An approximately 10-fold increase in current was observed for pH 7.4, 1 mM ruthenium hexaammine solutions and complete suppression of the potassium ferricyanide response was observed. These ion-exchange properties can be attributed to the strong electrostatic interactions between the acid/basic functional group in the matrix and the highly charged analyte molecules. When glassy carbon electrodes were modified with diethyl-(triethoxysilypropyl) malonate (silane—(COOEt)₂), the films did not exhibit distinct ion-exchange properties but rather suppressed the reduction of potassium ferricyanide. The observed permselectivity results from the electron dense carbonyl group and/or hydrolyzed ester functionalities in the film.     

A study of the acid-base transformations of oxodihydrothiochrome

The acid-base properties of oxodihydrothiochrome — the product of the redox disproportionation of the vitamin B₁ catabolite thiochrome (pH=10.7, 4.5, and 0.5) — have been studied in the pH interval of 0–12 by PMR spectroscopy. It has been established that in acid medium (pH 0–1) the formation of a doubly charged ion is accompanied by a further structural transformation of the molecule of (I) with the formation of a vitamin B₁ analogue — oxothiamine (II). A possible mechanism of the action of (I) as an inhibitor of thiamine-dependent enzymes is discussed in the light of the results obtained. Details of the PMR spectra of (I) and (II) are given.Institute of Biochemistry, Academy of Sciences of the BSSR, Grodno. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 497–501, July–August, 1986.     

Isolierung und Strukturaufklärung eines hämolytisch wirkenden Polypeptides aus dem Abwehrsekret europäischer Unken

Zusammenfassung Ein aus 24 Aminosäuren bestehendes Polypeptid wurde aus dem Abwehrsekret europäischer Unken isoliert. Abbauversuche machen folgende Primärstruktur wahrscheinlich:H₂N—Gly—Ile—Gly—Ala—Leu—Ser—Ala—Lys—Gly—Ala—Leu—Lys—Gly—Leu—Ala—Lys—Gly—Leu—Ala—GluX—His—Phe—Ala—Asp(NH₂)₂.Das Polypeptid (Bombinin) wird durch die proteolytischen Enzyme des Unkengiftes rasch abgebaut. Es wirkt hämolytisch und zeigt gewisse strukturelle Analogien zu Melittin.

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Isolation and structure of an hemolytic polypeptide from the defensive secretion of european bombina species

A tetracosapeptide has been isolated from the defensive secretion of European unks. The following primary structure is proposed:H₂N—Gly—Ile—Gly—Ala—Leu—Ser—Ala—Lys—Gly—Ala—Leu—Lys—Gly—Leu—Ala—Lys—Gly—Leu—Ala—GluX—His—Phe—Ala—Asp(NH₂)₂.The polypeptide (bombinin) is quickly hydrolyzed by the proteolytic enzymes of the unk toxin. Bombinin shows hemolytic activity. Its structure resembles somewhat that of melittin.

     

Isolation,purification, and study of some properties of the extracellular lignin peroxidases of the wood-destroying fungusPleurotus ostreatus

Abstact Two bands with lignin peroxidase activity have been detected by isoelectric focusing in a total enzyme preparation obtained from a 15-day filtrate of the culture liquid of the fungusPleurotus ostreatus by fractionation with ammonium sulfate. Two homogeneous forms of the enzymes — LGP-I and LGP-II — have been obtained by gel filtration on Sephadex G-100, ion-exchange chromatography on DEAF-Toyopearl 650 M gel, and rechromatography on Sephadex G-75, and also by electrophoresis in PAAG. The specific activities of the purified lignin peroxidases LGP-I and LGP-H amounted to 36.5 and 54.3 units/mg, their degrees of purification being 8.7 and 12.9, respectively. The molecular masses of LGP-I and LGP-II, determined by electrophoresis in PAAG in the presence of Na-DS and by gel filtration on TSK HW–65 gel were 42–44 and 61–63 kDa. The isoelectric points of LGP-I and LGP-II were 3.4 and 4.1, their pH optima 2.7 and 3.4, and the, temperatures of their optimum enzymatic action 28 and 34°C, respectively. The isoenzymes differed from one another substantially with respect to pH stability and resistance to heat. The values of K_M determined from the rates of hydrolysis of the substrate by the enzymes in the presence of H₂O₂ at pH 3.7 were 0.09 mM for LGP-I and 0.07 mM for LGP-II. The values of K_M with respect to veratryl alcohol, determined by the Lineweaver—Burk method, were 0.117 mM for LGP-II and 0.132 mM for LGP-II.Institute of Microbiology, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (3712) 41 71 29. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 394–402, May–June, 1996. Original article submitted November 11, 1994.     

Effect of the potential of an external electron donor on C<Subscript>2</Subscript>H<Subscript>2</Subscript> reduction catalyzed by the nitrogenase active center (FeMoco) isolated from the enzyme

The effect of potential value and chemical properties of an external electron donor on C₂H₂ reduction catalyzed by nitrogenase active center (cluster [(₆-N)Fe₇MoS₉·homocitrate] FeMoco isolated from the enzyme) has been investigated in the presence of proton donors of different acidity. The temperature—reaction rate dependences of these reactions have been studied. It has been shown that the rate-limiting steps of the reactions differ depending on the proton donor used. When thiophenol or water are used as proton donors, and electrochemical step — the electron transfer from cathode to adsorbed catalytic cluster — has been found to be a rate-limiting one. The effective activation energy of ethane formation as a product of four-electron C₂H₂ reduction is found to be 1.5 times lower than that of ethylene, namely, 13 kcal mol^–1. When stronger acid, pentafluorothiophenol, is used as a proton donor, the chemical step of intramolecular rearrangement of the catalyst—substrate complex taking place in solution becomes a rate-limiting one. The effective activation energies of both ethylene and ethane become equal to 32 kcal mol^–1.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1583–1591, August, 2004.     

Use of high-performance liquid chromatography to quantitative thymine-containing pyrimidine dimers in DNA

We have developed two high-performance liquid chromatographic systems for the measurement of pyrimidine dimers in hydrolysates of DNA. Normal-phase chromatography on an NH₂ column in methanol—ethyl acetate (3:97) at an elution rate of 2.0 ml/min allowed quantitaion of thymine-containing (thymine-thymine plus thymine-uracil) pyrimidine dimers at levels as low as 0.1% of the total radioactivity as thymine in DNA. This system was unaffected by the presence of up to 1 mg of contaminating protein (bovine serum albumin) or 40 μg of DNA in hydrolysates prepared for chromatography. Reversed-phase chromatography on a μBondapak C₁₈ column allowed measurement of thymine-thymine dimers at concentrations as low as 0.02% of the total radioactivity. With 0.1% tetrahydrofuran in wateras the solvent at a flow-rate of up to 0.6 ml/min, thymine—thymine, thymine—uracil, and uracil—uracil dimers were completely resolved. We were not able to quantitate the latter two dimeric forms, however, owing to the presence of other radioactive components of undefined origin that eluted concomitantly with the uracil-containing dimers.     

Berberis alkaloids. XXI. Intebrine — A new N-benzylisoquinoline alkaloid from Berberis integerrima

A new N-benzylisoquinoline alkaloid — intebrine, with the composition C₂₀H₁₉NO₇ — has been isolated fromBerberis integerrima Bunge. The spatial structure of intebrine has been reliably determined by the x-ray structural method (diffractometer, CuK radiation, 972 reflections, direct method, R=0.048). Its chemical behavior, spectral characteristics, and mass-spectrometric fragmentation under electrom impact have been studied.Andizhan State Medical Institute. Institute of the Chemistry of Plant Substances, Uzbekistan Republic Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedeninii, No. 1, pp. 65–70, January–February, 1993.     

Molecular Structure of 1,3,5-Tris (Trimethylstannyl) Benzene: An Electron Diffraction Study

The molecular structure of 1,3,5-tris (trimethylstannyl) benzene has been determined by gas-phase electron diffraction. The C — C bond length is in good agreement with that in benzene. In agreement with the somewhat electron-releasing character of the substituents, the endocyclic bond angles at the substituents are somewhat smaller than 120°. The mean value of Sn — C bond lengths is greater than that in tetraphenyltin and tetramethyltin. The SnMe₃ groups appear freely rotating around the C_aryl — Sn bonds. The following bond lengths (r _g) and bond angles were determined: (Sn — C)_mean 2.150 ± 0.007 Å, C — C 1.399 ± 0.005 Å, (C — H)_mean 1.105 ± 0.006 Å, < C — C(Sn) — C 117.7 ± 1.7º, < C_aryl — Sn — C_methyl 106.7 ± 0.7º < Sn — C — H 111.5 ± 0.9º.     

New multifunctional materials obtained by the intercalation of anionic dyes into layered zinc hydroxide nitrate followed by dispersion into poly(vinyl alcohol) (PVA)

Different anionic blue and orange dyes have been immobilized on a zinc hydroxide nitrate (Zn₅(OH)₈(NO₃)₂nH₂O — Zn–OH–NO₃) by anion exchange with interlayer and/or outer surface nitrate ions of the layered matrix. Orange G (OG) was totally intercalated, orange II (OII) was partially intercalated, while Niagara blue 3B (NB) and Evans blue (EV) were only adsorbed at the outer surface. Several composite films of poly(vinyl alcohol) — PVA were prepared by casting through the dispersion of the hybrid material (Zn–OH–OG) into a PVA aqueous solution and evaporation of water in a vacuum oven. The obtained composite films were transparent, colored, and capable of absorbing UV radiation. Improved mechanical properties were also obtained in relation to the nonfilled PVA films. These results demonstrate the onset of a new range of potential applications for layered hydroxide salts in the preparation of polymer composite multifunctional materials.     

Development of a method for determining bornyl acetate in the products of the processing of Abies sibirica

Summary The conditions for the reaction of esters—bornyl acetate—with an alkaline solution of hydroxylamine have been studied by the method of steepest ascent. A method has been developed for determining esters in a CO₂ extract ofAbies sibirica.Krasnodar Scientific-Research Institute of the Food Industry. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 303–306, May–June, 1976.