CAN BIOLOGICAL HOMOCHIRALITY RESULT FROM A PHASE-TRANSITION

The problem of chiral purity in living organisms is still one of the p rominent difficulties in the study of the origins of life. In particul ar the parity non-conservation known to occur in weak interactions cou ld not be related to this lack of symmetry: these physical forces, tho ugh universal, are very weak and up to now no amplification process ha d been proposed. In 1991, A. Salam remarked that, due to the attractiv e character of the parity violating force in electro-weak interactions , a phase transition at low temperature should exist, leading eventual ly to enantiomeric purity. We undertook then a series of experimental tests, looking for a sizeable change in the optical activity of cystin e molecules. We found no evidence for the phase transition down to 0.0 1 K. The interpretation of these negative results will be discussed, a nd future experiments proposed.