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  • 1
    ISSN: 1432-1432
    Keywords: Aqueous solutions ; Cyanides ; Ionizing radiation ; Peptides ; Infrared spectra ; Prebiotic molecules
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Oligomers formed by ionizing radiation in aqueous cyanide solutions, under various experimental conditions, have been characterized by infrared spectroscopy. IR bands appear in the region known to be characteristic for amides and peptides. The results are discussed in relation to radiation-induced formation of peptidic material and the potential role of ionizing radiation as an energy source for some processes in prebiotic molecular evolution.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1432
    Keywords: Aqueous solutions ; Hydrogen Cyanide ; Ionizing radiation ; Chemical evolution ; Amino acids ; Glycine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Oxygen-free aqueous solutions of hydrogen cyanide, 0.1 M and pH∼6, were exposed to gamma rays from a60Co source, the mixture of nonvolatile products was fractionated and the fractions were analysed. It has been found that the complex mixture contains oligomers and polymers with molecular weights up to 20,000 daltons, mainly polyamides with urea and peptidic fragments. Among the constituents are carbamyl glycinonitrile and carbamyl glycinamide that represent 6.4% and 3.1% of the total of unfractionated material respectively. Urea content is 2.6%, but the derivatives of urea are more abundant. Acid hydrolysis releases several amino acids. Glycine is the most abundant (75% or more of total amino acid content), and its concentration considerably increases in some fractions when the hydrolysis is carried out at 130°C. The role of free radicals in reactions leading to the formations of radiolytic products is considered. Some comparisons are made between findings in the present work, at initial pH∼6, and an earlier study of ammonium cyanide at pH 9.
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  • 3
    ISSN: 1432-1432
    Keywords: Aqueous solutions ; Nitriles ; Ionizing radiations ; Products fractionation ; Long-living nitroxide radical ; Additional oligomerization ; Chemical evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Oxygen-free aqueous solution of CH3CH2CN (0.1 M, pH 6) were exposed to gamma rays from a60Co source and the mixture of radiolytic products fractionated. The separated fractions were analysed by magnetic resoncance methods (EPR, NMR), spectrophotometry (UV-VIS-IR), gas chromatography and amino acids analysis. About 70% of radiolytic products consist of non volatile material. A large variety of compounds was detected: propionaldehyde, acetaldeyde, sixteen carboxylic acids and, in the hydrolysate, eleven protein and nonprotein amino acids. About 20% of the nonvolatile radiolytic products have a hydrophobic character and can be extracted with chloroform. Among them is a long-living nitroxide free radical which is stable for months at room temperature. It has been suggested that the nitroso compounds are formed as radiolytic products, and that they act as spin-traps by converting some of the short living radicals to the observed nitroxide radical. This and other experimental findings are discussed in the light of free radical reactions induced by ionizing radiation.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular evolution 15 (1980), S. 239-260 
    ISSN: 1432-1432
    Keywords: Aqueous solutions ; Cyanides ; Ionizing radiation ; Fractionation of products ; Chemical evolution ; Additional oligomerization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Oxygen-free aqueous solutions of NH4CN (0.1 M, pH 9) were exposed to gamma rays from a60Co source, the mixture of nonvolatile products was fractionated, and the fractions were analyzed. The procedures were chosen to make effective investigations of radiolytic products, and to minimize the contributions of chemical changes which are known to occur in aqueous solution in the absence of ionizing radiation. It has been found that the main constituents are: urea, 25.9%; an oligomer, very likely oligoimine (18.4%); and several fractions (about 50%) which release amino acids on hydrolysis. These fractions differ considerably, as shown by amino acid assay, enzymatic digestion, IR spectra, and biuret reaction. All these tests were found to be positive for two fractions; in two further fractions the enzymatic cleavage was absent, but other tests were positive. Negative enzymatic and biuret tests, and no bands characteristic of amide or peptide, were found for a fraction whose hydrolysate consisted of 55% glycine. Although most of the isolated materials were found to be composite, the results of the analyses were sufficient for getting a reliable over-all picture of the chemical action of the ionizing radiation. The role of free radicals in reactions leading to the formations of radiolytic products was considered.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular evolution 15 (1980), S. 261-275 
    ISSN: 1432-1432
    Keywords: Aqueous solutions ; Nitriles ; Ionizing radiation ; Products fractionation ; Chemical evolution ; Additional oligomerization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Oxygen-free aqueous solutions of CH3CN (0.1 M, pH 6) were exposed to gamma rays from a60Co source, the mixture of nonvolatile radiolytic products was fractionated and the fractions were analysed. Succinic, maleic, fumaric, malonic and pyruvic acids were identified. Glycol aldehyde, glucose and probably ribose were observed in the hydrolysate of fractionated material. It has been suggested that an oligomer is formed which has a fragment with the polyhydroxy structure and on hydrolysis releases the carbohydrates. Radiolytic products which release amino acids on hydrolysis were found in several fractions. The amino acid contents of the hydrolysates were up to about 2.8% of the fraction mass. The presence of several protein and nonprotein amino acids suggests that their origin should be in a peptidic structure, which is probably a fragment of an oligomer radiolytically produced. A direct analysis of the irradiated solution shows the presence of acetaldehyde, propionaldehyde, glyoxal and of biacetyl. Experimental findings are discussed and a free-radical mechanism is proposed to account for the chemical changes observed.
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  • 6
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Recently, a new charge percolation mechanism (CPM) of the Ziegler-Natta (ZN)polymerization of olefins by supported transition metal (Mt) complexes has been presented: amacromolecular chain is formed by polymerization of the monomer cluster (nM) adsorbed on thesupport (S) between two immobilized Mt ions, some in the higher (Mtn+1, i.e. acceptors) and theother in the lower (Mtn-1, i.e. donors) oxidation state:(Mtn-1...nM...Mtn+1)/S → (Mtn Mtn)/S + polymer.A special computer program «Lattice» has been developed to simulate olefin polymerization basedon CPM using a Monte Carlo procedure. The effects of reaction conditions (Mt concentration, Mt/Sratio, sequence of chemical components addition and time) of ethylene and propylenepolymerization by various Mt precursors (TiCl4/MgCl2, CrOx) and supports (MgCl2, SiO2) onmolecular mass and molecular mass distribution can be predicted by simulation and confirmed bypublished experimental results
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Radiation Physics and Chemistry 22 (1983), S. 771-778 
    ISSN: 0146-5724
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering , Physics
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Radiation Physics and Chemistry 22 (1983), S. 765-770 
    ISSN: 0146-5724
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering , Physics
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Earth and Planetary Science Letters 16 (1972), S. 257-262 
    ISSN: 0012-821X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Geosciences , Physics
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Earth and Planetary Science Letters 6 (1969), S. 316-320 
    ISSN: 0012-821X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Geosciences , Physics
    Type of Medium: Electronic Resource
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