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  • 1
    Publication Date: 1970-11-14
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Springer Nature
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  • 2
    Publication Date: 1967-05-01
    Print ISSN: 0005-2795
    Electronic ISSN: 1879-2952
    Topics: Biology
    Published by Elsevier
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  • 3
    Publication Date: 2006-02-14
    Description: When the polycondensation of amino acid acylates was catalyzed with Na-montmorillonite, the polypeptides were consistently found to exhibit a distribution of discrete molecular weights, for as yet undiscovered reasons. One possible explanation was connected to the stepwise mode of monomer addition. New experiments have eliminated this possibility, so that there is the general assumption that this discreteness is the result of a preference of shorter oligomers to add to others of the same length, a feature that could be attributed to some structure of the platelet aggregates of the montmorillonite. The production of optical stereoisomers is anticipated when D,L-amino acids are polymerized on montmorillonite. Having used an optically active surface, the essence of the results lies not only in the occurrence of optically active oligomers and polymers, but also in the fact that the latter exhibit the same molecular weight characteristics as the D,L-polymers. Preparatory to work contemplated on a parallel synthesis of amino acid and nucleotide oligomers, studies were continued on the co-adsorption of amino acids, nucleotides, and amino acid-nucleotides on montmorillonite.
    Keywords: SPACE BIOLOGY
    Type: NASA, Washington Second Symposium on Chemical Evolution and the Origin and Evolution of Life; p 66
    Format: text
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  • 4
    Publication Date: 2019-06-27
    Description: Alanine, starting from alanine-adenylate, has been polymerized in the presence of non-swelling Al-montmorillonite. The yield of polymerization is much lower than that obtained in the presence of swelling Na-montmorillonite. The possibility that the changing interlayer spacing in Na-montmorillonite might be responsible for its catalytic properties, is discussed.
    Keywords: CHEMISTRY AND MATERIALS (GENERAL)
    Type: Journal of Molecular Evolution; 10; Sept. 20
    Format: text
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  • 5
    Publication Date: 2019-06-27
    Description: From the point of view of prebiotic synthesis, clays might have performed functions of concentration, catalysis, and protection of molecules. The degrees of polymerization obtained, when amino acid adenylates are added to montmorillonite suspensions in water, are much higher than those obtained by polymerization in the absence of such a clay. In addition, they are of a discrete spectrum, usually multiples of 6 or 7, and reach values of up to 40 mers. In the absence of clay a continuous spectrum of degrees of polymerization is obtained, and usually up to 4-6 mers only. Copolymerization in the absence of clays yields mostly random copolymers, in their presence mostly block copolymers are obtained. Optical density measurements show that after adsorption has taken place on the clay, stacking of its layers occurs. Polymerization starts only after these stacked layers have been formed
    Keywords: SPACE BIOLOGY
    Type: Origins of Life; 7; Dec. 197
    Format: text
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  • 6
    Publication Date: 2019-07-13
    Description: The adsorption and polymerization of alanine adenylate on montmorillonite at pH 7 when either its interspacial faces or its edger are blocked by an excess of histidine or sodium hexametaphosphate was investigated. Results indicate that alanine adenylate can be adsorbed any place on the interspacial spaces of the clay; however, adsorption of its phosphate part, which is limited to the edges of the clay, is necessary for polymerization to occur. As a result, polymerization takes place only at sites on the interspacial faces bordering the edges.
    Keywords: CHEMISTRY AND MATERIALS (GENERAL)
    Type: Origin of life; Second ISSOL Meeting and Fifth ICOL Meeting; Apr 05, 1977 - Apr 10, 1977; Kyoto; Japan
    Format: text
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  • 7
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    Unknown
    In:  Other Sources
    Publication Date: 2019-06-28
    Description: Clays and other minerals have been investigated in context with prebiotic processes, mainly in polymerization of amino acids. It was found that peptides adsorbed on the clay, prior to polymerization, influence the reaction. The ratio between the amount of the peptides adsorbed and that of the clay is important for the yield as well as for the degrees of polymerization obtained. Adsorption prior to reaction produces a certain order in the aggregates of the clay particles which might induce better reaction results. Excess of added peptides disturbs this order and causes lesser degrees of polymerization. In addition to adsorption, clays are also able to occlude between their layers substances out of the environment, up to very high concentrations.
    Keywords: CHEMISTRY AND MATERIALS (GENERAL)
    Type: Origins of Life (ISSN 0302-1688); 14; 1-4
    Format: text
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  • 8
    Publication Date: 2019-06-27
    Description: The polymerization of alanine adenylate in the presence of the sodium form of various clays was studied, and hectorite was found to cause more polymerization than nontronite and montmorillonite (in that order) although the differences were not great. The effect on polymerization of presaturating montmorillonite with different cations was determined. Hectorite, with increased basicity of the interspatial planes, allows polymerization of lysine, which montmorillonite does not. The general trend is that, for the same amino acid, higher degrees of polymerization are obtained when the cation in the octahedral lattice of the clay is divalent rather than trivalent. With the exchangeable cations the order is reversed, for a reason that is explained. The main role of clays in the polymerization mechanism of amino acids is concentration and neutralization of charges.
    Keywords: CHEMISTRY AND MATERIALS (GENERAL)
    Type: Journal of Molecular Evolution; 11; June 20
    Format: text
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  • 9
    Publication Date: 2019-07-13
    Description: Serine guanylate was prepared and its polymerization studied in the presence of montmorillonite and in its absence. In water, without clay, serine guanylate polymerizes in the same way as does serine adenylate. In the presence of montmorillonite, serine guanylate polymerizes to a lesser extent and produces also lower degrees of polymerization than does serine adenylate. It is postulated that the reason for this difference in behavior might lie in the fact that guanylic acid is much more acidic than adenylic acid; hence would bind much more strongly to the edges of montmorillonite and thus, by blocking these sites, would inhibit the catalytic activity of the clay.
    Keywords: SPACE BIOLOGY
    Type: Origin of life; Jun 22, 1980 - Jun 27, 1980; Jerusalem; Israel
    Format: text
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular evolution 10 (1977), S. 73-76 
    ISSN: 1432-1432
    Keywords: Prebiotic peptide synthesis ; Alanine adenylate ; Non-swelling montmorillonite ; Heterogeneous catalysis ; Polymerization templates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Alanine, starting from alanine-adenylate, has been polymerized in the presence of non-swelling Al-montmorillonite. The yield of polymerization is much lower than that obtained in the presence of swelling Na-montmorillonite. The possibility that the changing interlayer spacing in Na-montmorillonite might be responsible for its catalytic properties, is discussed.
    Type of Medium: Electronic Resource
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