Origin of Chirality in the Molecules of Life
J. A. Cowan, R. J. Furnstahl
Abstract
Molecular chirality is inherent to biology and cellular chemistry. In this report, the origin of enantiomeric selectivity is analyzed from the viewpoint of the “RNA World” model, based on the autocatalytic turnover of glyceraldehyde as a precursor for simple sugars, and in particular ribose, as promoted by the formose reaction. Coupling of formaldehyde and glycolaldehyde produces glyceraldehyde, which contains a chiral carbon center that is carried through in formation of the ribose ring. The parity non-conserving weak nuclear interaction is the only inherently handed property in nature and is herein shown to be sufficient to differentiate between two enantiomeric forms in an autocatalytic reaction performed over geologically relevant time scales, but only in the presence of catalytic metal ions such as divalent calcium or higher Z alkaline earth elements. This work details calculations of the magnitude of the effect, the impact of various geologically available metal ions, the effect of time and temperature, and their influence on chiral selection in the molecules of life. Alternative mechanisms are also considered, and a method of resolving these is proposed.