Montmorillonite-catalysed formation of RNA oligomers: the possible role of catalysis in the origins of life
http://rstb.royalsocietypublishing.org/content/361/1474/1777.full
Abstract
Large deposits of montmorillonite are present on the Earth today and it is believed to have been present at the time of the origin of life and has recently been detected on Mars. It is formed by aqueous weathering of volcanic ash. It catalyses the formation of oligomers of RNA that contain monomer units from 2 to 30–50. Oligomers of this length are formed because this catalyst controls the structure of the oligomers formed and does not generate all possible isomers. Evidence of sequence-, regio- and homochiral selectivity in these oligomers has been obtained. Postulates on the role of selective versus specific catalysts on the origins of life are discussed. An introduction to the origin of life is given with an emphasis on reaction conditions based on the recent data obtained from zircons 4.0–4.5 Ga.
Take the clay used in the Ferris et al. experiments, for instance. Montmorillonite (often used in cat litter) is a layered clay "rich in silicate and aluminum oxide bonds" (Shapiro 2006, 108). But the montmorillonite employed in the Ferris et al. experiments is not a naturally-occuring material, as Ertem (2004) explains in detail. Natural or native clays don't work, because they contain metal cations that interfere with phosphorylation reactions:
(Shapiro 2006, 108)
This handicap was overcome in the synthetic experiments by titrating the clays to a monoionic form, generally sodium, before they were used. Even after this step, the activity of the montmorillionite depended strongly on its physical source, with samples from Wyoming yielding the best results....Eventually the experimenters settled on Volclay, a commercially processed Wyoming montmorillonite provided by the American Colloid Company. Further purification steps were applied to obtain the catalyst used for the "prebiotic" formation of RNA.
Several years ago, a prominent origin of life researcher complained to me in private correspondence that 'you ID guys won't be satisfied until we put a spark through elemental gases, and a cell crawls out of the reaction vessel.'
But this is not an unreasonable demand that ID theorists make of the abiogenesis research community. It is, rather, what that community claims to be able to show -- namely, that functional complexity arises without intelligent intervention, strictly from physical precursors via natural regularities and chance events.
Thus, pointing out where intelligent intervention (design) is required for any product is hardly unfair sniping. It is simply realism: similar criticisms apply to the other steps in the Ferris et al. RNA experiments, such as the source of the activated mononucleotides employed, a point Ferris himself acknowledges:
A problem with the RNA world scenario is the absence of a plausible prebiotic synthesis of the requisite activated mononucleotides. (Huang and Ferris 2006, 8918) -
http://rstb.royalsocietypublishing.org/content/361/1474/1777.full
Abstract
Large deposits of montmorillonite are present on the Earth today and it is believed to have been present at the time of the origin of life and has recently been detected on Mars. It is formed by aqueous weathering of volcanic ash. It catalyses the formation of oligomers of RNA that contain monomer units from 2 to 30–50. Oligomers of this length are formed because this catalyst controls the structure of the oligomers formed and does not generate all possible isomers. Evidence of sequence-, regio- and homochiral selectivity in these oligomers has been obtained. Postulates on the role of selective versus specific catalysts on the origins of life are discussed. An introduction to the origin of life is given with an emphasis on reaction conditions based on the recent data obtained from zircons 4.0–4.5 Ga.
Take the clay used in the Ferris et al. experiments, for instance. Montmorillonite (often used in cat litter) is a layered clay "rich in silicate and aluminum oxide bonds" (Shapiro 2006, 108). But the montmorillonite employed in the Ferris et al. experiments is not a naturally-occuring material, as Ertem (2004) explains in detail. Natural or native clays don't work, because they contain metal cations that interfere with phosphorylation reactions:
(Shapiro 2006, 108)
This handicap was overcome in the synthetic experiments by titrating the clays to a monoionic form, generally sodium, before they were used. Even after this step, the activity of the montmorillionite depended strongly on its physical source, with samples from Wyoming yielding the best results....Eventually the experimenters settled on Volclay, a commercially processed Wyoming montmorillonite provided by the American Colloid Company. Further purification steps were applied to obtain the catalyst used for the "prebiotic" formation of RNA.
Several years ago, a prominent origin of life researcher complained to me in private correspondence that 'you ID guys won't be satisfied until we put a spark through elemental gases, and a cell crawls out of the reaction vessel.'
But this is not an unreasonable demand that ID theorists make of the abiogenesis research community. It is, rather, what that community claims to be able to show -- namely, that functional complexity arises without intelligent intervention, strictly from physical precursors via natural regularities and chance events.
Thus, pointing out where intelligent intervention (design) is required for any product is hardly unfair sniping. It is simply realism: similar criticisms apply to the other steps in the Ferris et al. RNA experiments, such as the source of the activated mononucleotides employed, a point Ferris himself acknowledges:
A problem with the RNA world scenario is the absence of a plausible prebiotic synthesis of the requisite activated mononucleotides. (Huang and Ferris 2006, 8918) -
