New estimates of asymmetric decomposition of racemic mixtures by natural β-radiation sources

Abstract

The Vester–Ulbricht hypothesis suggests that the chirality of biological molecules originates from the β-radiolysis of prebiotic racemic mixtures¹. Despite the inconclusiveness of past investigations^2–4, recent calculations^5,6 have shown that β particles, because of their helicity, radiolyse L- and D-enantiomers at slightly different rates, the asymmetry, A_R, being predicted to be 10⁻¹¹ (new experimental tests^7,8 give |A_R|<2×10⁻⁹). Before this, the size of the radiolysis-induced chiral polarization, η_R (η ≡ (n_L − n_D)/(n_L + n_D) where n_L and n_D are the numbers of L and D molecules present), was estimated^9–12 for different values of A_R; according to Keszthelyi et al.^9–11, if |A_R|∼10⁻¹¹ |η_R| can never exceed the chiral polarization, |η_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 |η_R|>|η_F|, in accordance with the V–U hypothesis.