Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Prebiotic clays

Quartz and other minerals, e.g., clays, have chiral sites on the surface. It was attempted to separate chiral compounds selectively. A very small chiral selection effect by clay minerals was reported. It was argued that the chiral sites of these minerals would arise from the adsorption of optically active biomolecules. This means that prebiotic clays would then have had no chiral sites. [Pg.428]

A combination of SIPS with the stabilising and synthesis-favouring properties of clay minerals was studied by Rode et al. (1999) in experiments involving dry/wet cycles. The simultaneous use of both SIPS and clay minerals as catalytically active surfaces led to peptides up to and including the hexamer (Gly)6. The question as to whether this technique fulfils prebiotic conditions can (within certain limitations) be answered positively, since periodic evaporation phases in limited areas (lagoons, ponds) are conceivable. The container material could have consisted of clay minerals. Further progress in the area of peptide synthesis under conditions which could have been present on the primeval Earth can be expected. [Pg.137]

Four billion years ago, the Earth s thin crust consisted of geochemicals (i.e., compounds containing the elements Si, O, Al, Fe, Mg, Ca, K and Na, as well as traces of other elements). Thus, some biogenesis researchers believed that the first replicating material consisted of geochemical material rather than substances containing carbon and other bioelements. Clay minerals in particular were included in experimental and theoretical studies. The most important are kaolinite and montmorillonite the latter was, and still is, used in many experiments carried out to simulate prebiotic reactions. [Pg.181]

The clay mineral montmorillonite, which is often used in different prebiotic syntheses, is probably now the most important mineral for experiments on prebiotic chemistry. It has shown its abilities in the area of simulation experiments on the formation of primitive cellular compartments montmorillonite accelerates the spontaneous conversion of fatty acid micelles to vesicles. Clay particles are often incorporated into the vesicle, just as is RNA, which is adsorbed at such clay particles. If the vesicles have been formed, they can continue to grow if fatty acids are fed to them via micelles. If the vesicles are pressed through 100 nm pore filters, they divide without dilution of their contents. [Pg.271]

Luke, B. T., A. G. Gupta, G. H. Loew, J. G. Lawless, and D. H. White. 1984. Theoretical Investigation of the Role of Clay Edges in Prebiotic Peptide Bond Formation. I. Structures of Acetic Acid, Glycine, H2S04, H3P04, Si(OH)4, and Al(OH)4. Int. I. Quantum Chem. Quantum Biol. Symp. 11, 117-135. [Pg.145]

Franchi, M., Ferris, J. R, and Gallori, E. (2003). Cations as mediators of the adsorption of nucleic acids on clay surfaces in prebiotic environments. Orig. Life Evol Biosph., 33, 1-16. [Pg.279]

Perhaps one of the most important roles of clays and coordination complexes in the synthesis of prebiotic compounds, apart from their catalytic influences, is one of protection. Mention has... [Pg.872]

Among activated forms of amino acids, mixed anhydrides with inorganic phosphate or phosphate esters require a special discussion because they are universally involved in peptide biosynthesis through the ribosomal and non-ribosomal pathways. These mixed anhydrides have stimulated studies in prebiotic chemistry very early in the history of this field. Amino acyl adenylates 18c have been shown to polymerize in solution [159,160] and in the presence of clays [139]. However, their participation as major activated amino acid species to the prebiotic formation of peptides from amino acids is unlikely for at least two reasons. Firstly, amino acid adenylates that have a significant lifetime in aqueous solution become very unstable as soon as either CO2 or bicarbonate is present at millimolar concentration [137]. Lacey and coworkers [161] were therefore conduced to consider that CO2 was absent in the primitive atmosphere for aminoacyl adenylate to have a sufficient lifetime and then to allow for the emergence of the modern process of amino acid activation and of the translation apparatus. But this proposition is unlikely, as shown by the analysis of geological records in favor of CO2 contents in the atmosphere higher than present levels [128]. It is also in contradiction with most studies of the evolution of the atmosphere of telluric planets [30,32], Secondly, there is no prebiotic pathway available for adenylate formation and ATP proved to be inefficient in this reaction [162]. [Pg.100]

Concentration of the organic reactants on surfaces or in the pores of clay materials prior to reaction has been suggested by Bernal [219] and Cairns-Smith [220]. Pores of different sizes might have operated as prebiotic reactors for asymmetric synthesis, since within their confined environment one may find chiral catalytic sites as well as chiral surfaces. One could envisage that such pores might have provided a plausible environment for the formation of diastereoisomeric self-assemblies of the types described in this review and as required for the stochastic mirror symmetry breaking scenarios. In addition, within such pores the chiral material once formed would be protected from racemization that could have been induced by impact with heavy bodies or by intense cosmic radiation. [Pg.158]

First, the question of where nucleotide monomers may have come from is critical. Given that the formose reaction is the most likely candidate for the synthesis of prebiotic ribose, but yields very little pure material, the role of stereoselective catalysts (clays, amino acids, or lipid aggregates) in directing the reaction should be fully explored. In this respect, Wachters-hauser16 has advanced a scheme for nucleotide synthesis based on pyrite catalysis than can be readily tested. [Pg.661]

Lahav, N. White, D. Chang, S. Peptide formation in the prebiotic era Thermal condensation of glycine in fluctuating clay enviromnents. Science 1978,201, 67-69. [Pg.13]


See other pages where Prebiotic clays is mentioned: [Pg.100]    [Pg.176]    [Pg.194]    [Pg.64]    [Pg.72]    [Pg.73]    [Pg.336]    [Pg.872]    [Pg.872]    [Pg.873]    [Pg.284]    [Pg.41]    [Pg.44]    [Pg.53]    [Pg.83]    [Pg.24]    [Pg.76]    [Pg.66]    [Pg.138]    [Pg.155]    [Pg.1383]    [Pg.1384]    [Pg.1384]    [Pg.1386]    [Pg.682]    [Pg.872]    [Pg.872]    [Pg.873]    [Pg.227]    [Pg.98]    [Pg.173]    [Pg.42]    [Pg.109]    [Pg.42]   
See also in sourсe #XX -- [ Pg.428 ]




SEARCH



Prebiotics

© 2024 chempedia.info