New estimates of asymmetric decomposition of racemic mixtures by natural beta-radiation sources.
The Vester-Ulbricht hypothesis suggests that the chirality of biological molecules originates from the beta-radiolysis of prebiotic racemic mixtures.  Despite the inconclusiveness of past investigations, recent calculations have shown that beta particles, because of their helicity, radiolyse L- and D-enantiomers at slightly different rates, the asymmetry, AR, being predicted to be 10(-11) (new experimental tests, give /AR/ < 2 x 10(-9)).  Before this, the size of the radiolysis-induced chiral polarization, eta R (eta triple bond (nL - nD)/(nL + nD) where nL and nD are the numbers of L and D molecules present), was estimated for different values of AR; according to Keszthelyi et al., if /AR/ approximately 10(-11), /eta R/ can never exceed the chiral polarization, /eta F/, produced by statistical fluctuations, thus invalidating the V-U hypothesis.  Here we re-examine the major assumptions on which these calculations were based and find that several overly restrictive conditions were imposed, which, when relaxed, allow the condition /eta R/ > /eta F/, in accordance with the V-U hypothesis.
Hegstrom
R A
RA
Department of Chemistry, Wake Forest University, Winston-Salem, North Carolina 27109, USA.
Rich
A
A
Van House
J
J
D000596:Amino Acids / Q000737:chemistry; D001610:Beta Particles; D019418:Evolution, Chemical; D008962:Models, Theoretical; D015394:Molecular Structure; D000069497:Origin of Life; D013237:Stereoisomerism; D013696:Temperature
D000596:Amino Acids