Bonner W A, Rubenstein E, Brown G S
Department of Chemistry, Stanford University, CA 94305, USA.
Orig Life Evol Biosph. 1999 May;29(3):329-32. doi: 10.1023/a:1006511115735.
Recent investigations of stable isotope ratios of amino acids from the Murchison meteorite have shown them to be of unambiguous extraterrestrial origin, and examinations of their enantiomeric compositions, where terrestrial contamination can be excluded, have found a consistent excess of L-enantiomers. One explanation for this observation has been the asymmetric photolysis of racemic extraterrestrial amino acids by circularly polarized light (CPL) in the synchrotron radiation from orbiting electrons around the pulsar remnants of supernovae. Mason (1997) has attempted to discredit this mechanism on the grounds that circular dichroism (CD) bands for optically active molecules alternate in sign and sum to zero over the entire spectrum, and hence enantioselective photochemical reactions cannot be induced by broad band CPL. We submit arguments disputing this conclusion and present reasons for expecting that broad band CPL synchrotron radiation would be quite capable of inducing asymmetric photolysis, particularly in aliphatic amino acids.
近期对默奇森陨石中氨基酸稳定同位素比率的研究表明，它们具有明确无误的外星起源。在排除地球污染的情况下，对其对映体组成的研究发现，L-对映体始终过量。对于这一观察结果的一种解释是，超新星脉冲星遗迹周围轨道电子产生的同步辐射中的圆偏振光（CPL）使外消旋外星氨基酸发生不对称光解。梅森（1997年）试图质疑这一机制，理由是光学活性分子的圆二色性（CD）谱带在符号上交替出现，且在整个光谱范围内总和为零，因此宽带CPL无法诱导对映选择性光化学反应。我们提出了反驳这一结论的论据，并给出了预期宽带CPL同步辐射能够诱导不对称光解的理由，尤其是在脂肪族氨基酸中。
