Mason S F
Department of Chemistry, King's College London, UK.
Ciba Found Symp. 1991;162:3-10; discussion 10-5. doi: 10.1002/9780470514160.ch2.
Pasteur (1860) showed that many organic molecules form enantiomeric pairs with non-superposable mirror-image shapes, characterized by their oppositely signed optical rotation but otherwise apparently identical. Equal numbers of left-handed and right-handed molecules resulted from laboratory synthesis, whereas biosynthetic processes afforded only one of the two enantiomers, leading Pasteur to conclude that biosynthesis involves a chiral force. Fischer demonstrated (1890-1919) that functional biomolecules are composed specifically of the D-sugars and the L-amino acids and that the laboratory synthetic reactions of such molecules propagate with chiral stereoselectivity. Given a primordial enantiomer, biomolecular homochirality follows without the intervention of a chiral natural force, except prebiotically. Chiral forces known at the time were found to be even handed on a time and space average, exemplifying parity conservation (1927). The weak nuclear force, shown to violate parity (1956), was unified with electro-magnetism in the electroweak force (1970). Ab initio estimations including the chiral electroweak force indicate that the L-amino acids and the D-sugars are more stable than the corresponding enantiomers. The small energy difference between these enantiomeric pairs, with Darwinian reaction kinetics in a flow reactor, account for the choice of biomolecular handedness made when life began.
巴斯德（1860年）指出，许多有机分子形成具有不可重叠镜像形状的对映体对，其特征是旋光性符号相反，但在其他方面明显相同。实验室合成产生的左旋和右旋分子数量相等，而生物合成过程只产生两种对映体中的一种，这使巴斯德得出结论，生物合成涉及一种手性力。费歇尔证明（1890 - 1919年），功能性生物分子具体由D - 糖和L - 氨基酸组成，并且此类分子的实验室合成反应具有手性立体选择性。如果存在原始对映体，除了在生命起源前的情况外，生物分子的同手性无需手性自然力的干预即可产生。当时已知的手性力在时间和空间平均上是无偏向的，这体现了宇称守恒（1927年）。弱核力被证明违反宇称（1956年），并在电弱力中与电磁力统一（1970年）。包括手性电弱力在内的从头算估计表明，L - 氨基酸和D - 糖比相应的对映体更稳定。在流动反应器中，这些对映体对之间的小能量差异以及达尔文反应动力学，解释了生命起源时生物分子手性的选择。
