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  • 1
    Electronic Resource
    Electronic Resource
    The effect of reaction conditions on montmorillonite-catalysed peptide formation (1996)
    Springer
    Catalysis letters 37 (1996), S. 267-272 
    Details
    ISSN: 1572-879X
    Keywords: catalysis ; chemical evolution ; montmorillonite ; prebiotic peptide formation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Oligomerization of glycine (gly) and diglycine (gly2) on montmorillonite was performed as cyclic, drying-wetting process at temperatures below 100°C, under varying reaction conditions. The influence of substrate/clay ratio, temperature and pH was found to be different for amino acid (AA) dimerization, cyclic anhydride (CA) formation and peptide chain elongation. High temperatures and neutral pH favour CA formation over diglycine production. An AA/catalyst ratio of 0.2 mmol/g leads to optimal yields. This supports the assumption that amino acid dimerization and CA formation take place at the edges of clay particles. Peptide chain elongation, starting from gly2, produces higher yields at higher temperatures and neutral pH.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00807765
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  • 2
    Electronic Resource
    Electronic Resource
    Silica, Alumina, and Clay-Catalyzed Alanine Peptide Bond Formation (1997)
    Springer
    Journal of molecular evolution 45 (1997), S. 457-466 
    Details
    ISSN: 1432-1432
    Keywords: Key words: Alanine — Glycine — Prebiotic peptide formation — Silica — Alumina — Clays — Catalysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. The peptide bond formation of alanine (ala), ala + glycine (gly), ala + diglycine (gly2), and ala + gly cyclic anhydride (cyc-gly2) in drying/wetting cycles at 80°C was studied. Silica, alumina, and representative smectites—montmorillonite and hectorite—were used as catalysts, and the dependence of reaction yields on the available amount of water in the reaction systems was evaluated. Silica and alumina catalyze the formation of oligopeptide mainly in temperature fluctuation experiments, whereas higher amounts of water in the reaction system support clay-catalyzed reactions. Silica and alumina are much more efficient for amino acid dimerization than clays. Whereas only 0.1% of ala oligomerized on hectorite and no reaction proceeded on montmorillonite, about 0.9 and 3.8% alanine converted into its dimer and cyclic anhydride on silica and alumina, respectively. Clay minerals, on the other hand, seem to more efficiently catalyze peptide chain elongation than amino acid dimerization. The reaction yields of ala-gly-gly and gly-gly-ala from ala + gly2 and ala + cyc-gly2 reached about 0.3% on montmorillonite and 1.0% on hectorite. The possible mechanisms of these reactions and the relevance of the results for prebiotic chemistry are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00006250
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  • 3
    Electronic Resource
    Electronic Resource
    The Effect of Smectite Composition on the Catalysis of Peptide Bond Formation (1996)
    Springer
    Journal of molecular evolution 43 (1996), S. 326-333 
    Details
    ISSN: 1432-1432
    Keywords: Key words: Clay catalysis — Glycine oligomerization — Molecular evolution — Prebiotic peptide formation — Smectite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Clay-catalyzed glycine and diglycine oligomerizations were performed as drying/wetting cycles at 80°C. Two trioctahedral smectites (hectorite and saponite), three pure montmorillonites, a ferruginous smectite, an Fe(II)-rich smectite, and three smectites containing goethite admixture were used as catalysts. Highest peptide bond formation was found with trioctahedral smectites. About 7% of glycine was converted to diglycine and diketopiperazine on hectorite after 7 days. In the case of dioctahedral smectites, highest yields were achieved using clays with a negative-layer charge localized in the octahedral sheets (up to 2% of converted glycine after 7 days). The presence of Fe(II) in clay is reflected in a higher efficiency in catalyzing amino acid dimerization (about 3.5% of converted glycine after 7 days). The possible significance of the results for prebiotic chemistry is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00006092
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  • 4
    Electronic Resource
    Electronic Resource
    The effect of smectite composition on the catalysis of peptide bond formation (1996)
    Springer
    Journal of molecular evolution 43 (1996), S. 326-333 
    Details
    ISSN: 1432-1432
    Keywords: Clay catalysis ; Glycine oligomerization ; Molecular evolution ; Prebiotic peptide formation ; Smectite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Clay-catalyzed glycine and diglycine oligomerizations were performed as drying/wetting cycles at 80°C. Two trioctahedral smectites (hectorite and saponite), three pure montmorillonites, a ferruginous smectite, an Fe(II)-rich smectite, and three smectites containing goethite admixture were used as catalysts. Highest peptide bond formation was found with trioctahedral smectites. About 7% of glycine was converted to diglycine and diketopiperazine on hectorite after 7 days. In the case of dioctahedral smectites, highest yields were achieved using clays with a negative-layer charge localized in the octahedral sheets (up to 2% of converted glycine after 7 days). The presence of Fe(II) in clay is reflected in a higher efficiency in catalyzing amino acid dimerization (about 3.5% of converted glycine after 7 days). The possible significance of the results for prebiotic chemistry is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02339007
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  • 5
    Electronic Resource
    Electronic Resource
    Peptide chain elongation: A possible role of montmorillonite in prebiotic synthesis of protein precursors (1995)
    Springer
    Origins of life and evolution of the biospheres 25 (1995), S. 431-441 
    Details
    ISSN: 1573-0875
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Several studies have proven the ability of montmorillonite to catalyse amino acid condensation under assumed prebiotic conditions, simulating wetting-drying cycles. In this work, the oligomerization of short peptides gly2, gly3, gly4 and ala2 on Ca-and Cu-montmorillonite in drying-wetting cycles at 80 °C was studied. The catalytic effect of montmorillonite was found to be much higher than in the case of glycine oligomerization. From gly2 after 3 weeks, 10% oligomers (up to gly6, with gly3 as main products) are formed. Gly3 and gly4 give higher oligomers even after 1 cycle. Ala2 produces both ala3 and ala4, whereas ala does not produce any oligomers under these conditions. Heteroologomerization was observed: ala-gly-gly is formed from ala and gly2. Much higher yields are obtained using Ca-montmorillonite, because copper (II) oxidizes organic molecules. The influence of the reaction mechanism on the preferential oligomerization of oligopeptides is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01581994
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  • 6
    Electronic Resource
    Electronic Resource
    The Combination of Salt Induced Peptide Formation Reaction and Clay Catalysis: A Way to Higher Peptides under Primitive Earth Conditions (1999)
    Springer
    Origins of life and evolution of the biospheres 29 (1999), S. 273-286 
    Details
    ISSN: 1573-0875
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Two reactions with suggested prebiotic relevance for peptide evolution, the saltinduced peptide formation reaction and the peptide chain elongation/stabilization on clay minerals have been combined in experimental series starting from dipeptides and dipeptide/amino acid mixtures. The results show that both reactions can take place simultaneously in the same reaction environment and that the presence of mineral catalysts favours the formation of higher oligopeptides. These findings lend further support to the relevance of these reactions for peptide evolution on the primitive earth. The detailed effects of the specific clay mineral depend both on the nature of the mineral and the reactants in solution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006540101290
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  • 7
    Electronic Resource
    Electronic Resource
    Silica, Alumina and Clay Catalyzed Peptide Bond Formation: Enhanced Efficiency of Alumina Catalyst (1999)
    Springer
    Origins of life and evolution of the biospheres 29 (1999), S. 451-461 
    Details
    ISSN: 1573-0875
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Catalytic efficiencies of clay (hectorite), silica and alumina were tested in peptide bond formation reactions of glycine (Gly), alanine (Ala), proline (Pro), valine (Val) and leucine (Leu). The reactions were performed as drying/wetting (hectorite) and temperature fluctuation (silica and alumina) experiments at 85 °C. The reactivity of amino acids decreased in order Gly 〉 Ala 〉 Pro ≈ Val ≈ Leu. The highest catalytic efficiency was observed for alumina, the only catalyst producing oligopeptides in all investigated reaction systems. The peptide bond formation on alumina is probably catalyzed by the same sites and via similar reaction mechanisms as some alumina-catalyzed dehydration reactions used in industrial chemistry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006524703513
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  • 8
    Electronic Resource
    Electronic Resource
    Glycine oligomerization on silica and alumina (1997)
    Springer
    Reaction kinetics and catalysis letters 62 (1997), S. 281-286 
    Details
    ISSN: 1588-2837
    Keywords: catalysis ; silica ; alumina ; prebiotic peptide formation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Oligomerization of glycine (gly) and diglycine (gly2) on silica and alumina was observed in experiments simulating wetting-drying cycles at 80°C. Glycine produces less than 1% total yield of gly2 and diketopiperazine (DKP) after one week. In experiments starting from gly2, more than 10% DKP is formed. Formation of higher oligomers (gly3–gly6) proceeded as well, with 3.8% and 5.1% total yields on silica and alumina surfaces respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02475464
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  • 9
    Electronic Resource
    Electronic Resource
    IR Spectra of octadecylammonium-montmorillonite in the range of the Si-O Vibrations (1992)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 13 (1992), S. 267-272 
    Details
    ISSN: 1573-1111
    Keywords: Clay ; smectites ; montmorillonite ; octadecylammonium-montmorillonite ; IR spectra ; Si-O vibrations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The bonding of octadecylammonium on the internal surface of montmorillonite influences the arrangement of the SiO4 tetrahedra in the structure of montmorillonite. The effect can be observed in smectites with a relatively well-ordered structure as seen in the IR spectra of octadecylammonium-montmorillonite in the range of Si-O vibrations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01042785
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  • 10
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    Resonance Energy Transfer between Rhodamine Molecules Adsorbed on Layered Silicate Particles (2009)
    American Chemical Society
    Details
    Publication Date: 2009-12-18
    Print ISSN: 1932-7447
    Electronic ISSN: 1932-7455
    Topics: Chemistry and Pharmacology
    Published by American Chemical Society
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