Whence Homochirality?

Just as left and right hands cannot be superimposed in space, so the carbon centers in biologically derived amino acids and sugars are locked in a single specific orientation, or chiral sense, distinct from its mirror image. An enduring question is how this circumstance came about. This month, a collection of nine papers organized by Pizzarello and Lahav explores this question from a variety of angles. Among the contributions, Green and Jain review several theories put forward over the past half-century; they emphasize that chiral selectivity is a natural consequence of the evolution of enzymes toward maximum catalytic efficiency, and they further suggest that life may have begun on both sides of the mirror, so to speak, with organisms of the presently unfavored symmetry tripped up by an early random event...

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