JBeukema
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Did clay mould life's origins?Clay was suggested by the crystallographer John Bernal as a means of concentrating primitive biomolecules onto its surface so as to be available for further reactions. Clays again became the focus of studies more recently when James Ferris showed that they can act as catalysts for the formation of long strands of RNA, which with proteins and DNA are major compounds essential for the origin of life.
In a second paper, also published in Physical Chemistry Chemical Physics, Professor Fraser has extended these ideas to consider amino acids and to try to understand why all amino acids used to make proteins are left-handed.
With colleagues Professor Neal Skipper from UCL, Dr Martin Smalley from York University and Dr Chris Greenwell from Durham University he replaced the cations between the layers making up natural clay molecules with weakly bound organic cations, causing the clay layers to drift apart.
That created an extremely sensitive clay system with sufficient space to insert both left-handed and right-handed forms of the amino acid histidine between the layers.
"We found that the R- and S-histidine molecules interact differently with the clay surfaces. These clays are abiotically able to select for chirality left- or right-handedness as well as being implicated in the abiotic synthesis of RNA," Professor Fraser says. "Our experiments were the first to show that clay molecules could do that.
"We also found that the tiny interlayer space some 5nm wide was a very important dynamic region for studying prebiotic chemistry and that the reactions of simple chemicals there leads to the formation both of RNA oligomers and the selection of left-handed amino acids.
Clays have also been shown by Jack Szostak and others to enable fatty acids to form primitive cells and, interestingly, clays show similar selective behaviour in space, as reported recently by the NASA scientists Glavin and Dworkin.