C-10 amino acid derivatives of colchicine

The synthesis has been effected of C-10 N-acylated amino acid derivatives of colchicine by condensing (-aminoethylamino) colchicide with N-acylated amino acids. The structures of the compounds obtained have been confirmed by their UV and PMR spectra and by thin-layer chromatography.M. A. Aidkhozhin Institute of Molecular Biology and Biochemistry, Kazakhstan Academy of Sciences, Alma-Ata. V. A. Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow. Translated from Khimiya Prirodnykh Soedinenii, Nos. 3,4, pp. 372–375, May–August, 1992.     

Chemical transformations of lignin during the biodegradation and organosolv pulping of deciduous wood

The lignins from the liquors in the organosolv pulping of aspen wood treated with wood-destroying fungi have been investigated using quantitative¹H and¹³C NMR spectroscopy and exclusion liquid chromatography. It has been shown that the biodegradation of lignin takes place in different ways according to the complex of enzymes produced by the fungi. Phanerochaete sanguinea causes degradation through predominant cleavage at alkyl-phenyl bonds, and Trametes villosus at the C-C bonds of the aliphatic chain. In addition to degradation reactions, polymerization (condensation) reactions also take place with the appearance of new C_ar-O-C and C_ar-C bonds. It has been established that the biological pretreatment of aspen wood ensuring partial degradation of the lignin leads to its more ready extraction in the process of organosolv pulping.Wood Chemistry Division of the Irkutsk Institute of Organic Chemistry, Siberian Branch of the Russian Academy of Sciences. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 603–610, July–August, 1995. Original article submitted May 23, 1994.     

Analyse de metaux rares et de materiaux semi-conducteurs a l'aide de l'activation aux helions-3 et aux neutrons thermiques

Résumé On a présenté les méthodes de détermination de O et C dans quelques métaux réfractaires et matériaux semi-conducteurs. On a porté une attention particulière au procédé de traitement de la surface avant et après irradiation et aux méthodes pour séparer du fluor et du carbone radiochimiquement purs. Pour la détermination de Cu, Mn, Co, Ni, Cu et Zn, on concentre les impuretés et on les sépare par la méthode de chromatographie d'extraction. On a discuté des perspectives d'utilisation de la chromatographie d'extraction en analyse par activation des matériaux de haute pureté.     

Nanobiocomposites of noble metals based on arabinogalactan: Preparation and properties

A simple general method employing arabinogalactan hemicellulose as a reducing and stabilizing agent is used to synthesize hydrophilic nanoparticles of noble metals. The prepared organic-inorganic nanobiocomposites are characterized by electronic spectroscopy, powder X-ray diffraction, and scanning electron microscopy. The sizes of coherent scattering regions of the metal phase of the prepared nanocomposites are determined, and their surface morphology and grain size are demonstrated to be controlled by the nature of the nanosized metal.     

Reaction of the Na salts of 2-amino-6-methyl-4-hydroxypyrimidine with bis(bromomethyl)phosphinic acid

The reaction of the Na salts of 2-amino-6-methyl-4-hydroxypyrimidine and bis(bromomethyl)phosphinic acid gave 3,5-dioxo-1,2,3,4,5,8-hexahydro-7-methyl-1,8-diaza-4a-azonia-3-phosphanaphthalene-3-olate, whose structure was determined by X-ray diffraction study. The molecule has a bipolar structure, in which a positive charge is delocalized on the guanidine fragment and a negative charge is on the phosphinic acid fragment.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1125–1128, June, 1995.     

Synthesis of difurazanyl ethers from 4,4′‐dinitroazoxyfurazan

Nonselective attacks at the carbon bonded to a nitro group and carbon bonded to the N(O) atom of the azoxy group were observed in the reactions of 4,4′‐dinitroazoxyfurazan with bases and nucleophiles. A mechanism is presented to account for both of the pathways to products. A series of new difurazanyl ether derivatives was synthesized. © 2000 John Wiley & Sons, Inc. Heteroatom Chem 11:48–56, 2000     

Photosensitivity of polyimides and polyquinazolones based on aromatic and heteroaromatic diamines

Soluble polyimides containing triphenylamine residues as substituents at the imide nitrogen atom and polyquinazolones with diphenyl oxide, diphenylpropane, benzimidazole, benzoxazole, benzothiazole, oxadiazole, and triphenylamine moieties in the diamine component of the repeating unit have been synthesized. The spectroscopic study of polyquinazolones indicates their capability for donor-acceptor interactions. Emission bands of the polymers are of the exciplex nature. The photogeneration of current carriers in the polymers under study has been examined by the method of surface potential photoinduced decay. It has been shown that the intrinsic photosenitivity of polyquinazolones is nearly the same as (or somewhat higher than) that of the corresponding polyimides, but the former polymers are characterized by a less efficient spectral sensitization by dyes and donor-acceptor additives.     

Monitoring of initial stages of the biodamage of construction materials used in aerospace equipment using electron microscopy

The biocorrosion activity of microorganisms extracted from the Mir Space Station and the Russian segment of the International Space Station was estimated with respect to the aluminum-magnesium alloy AMg-6 used in space equipment. Thirty-six cultures belonging to 28 species were analyzed. As test objects, 180 AMg-6 samples with mechanically treated, anodized, and chemically polished surfaces were used. Almost all the studied microorganism species were technophiles capable of causing corrosion changes in the surface even protected by anodizing or chemical polishing. Mechanically treated samples were biocorroded to a greater extent. The most aggressive technophilic microorganisms caused stronger surface changes in comparison with chemical corrosion: surface oxidation, pitting, and cracking were observed.     

Creation of a diagnostic complex for the characterization of cryogenic laser-fusion targets using the tomography method with probing irradiation in the visible spectrum

We present our results on developing a diagnostic complex for high-precision characterization of the parameters of laser-fusion microobjects, such as microspheres and cryogenic targets (the microobject size is 1–2 mm). The complex operates based on the principle of tomography. The complex consists of (a) the scanning system providing a set of shadow projections of a microobject in the visible range of radiation and (b) specially developed software for 3D reconstruction of the microobject from the set of projections. The spatial resolution of the optical system is 1 μm for a probing-radiation wavelength of 490 nm. The distinctive features of the diagnostic complex are (1) operation with both free-standing and mounted targets and (2) the possibility of scanning the targets from room to cryogenic temperatures. The operation of the complex was demonstrated in the reconstruction of polystyrene microspheres by a large set (80–90) of shadow projections at room and cryogenic temperatures.     

Luminescent and photosensitive properties of nanocomposites based on tris(diimine) Ru<Superscript>2+</Superscript> complexes chemically bound to a silica matrix

The photosensitive and luminescent properties of composites in the system organic Ru²⁺ complex-SiO₂ are studied. The effect exerted by specific interactions of Ru²⁺ complexes with the silica matrix and by different ligands on the spectral characteristics of the complexes is studied.