The problem on the origin of homochirality in nature

Abstract

The property of chirality is non-superimposable forms that are mirror images of one another, as are left and right hands. The chirality and symmetry breaking in nature are important phenomenon. From fundamental particle and molecule to matter and universal system, there are chirality and symmetry breaking at different level. To explore their unification is an interesting scientific problem. A substance is said to be homochiral if all the constituent units are the same chiral form. In life, homochirality is a common property of amino acids and sugars. The homochirality of L -amino acids as well as D -sugars is a necessity for the origin of life and biosystems. While the origin of this phenomenon is not clearly understood, many different mechanisms for the emergence of homochirality are proposed. The mechanism ensuring the preservation of homochirality in a prebiotic state is needed. In this paper, the question “what is the origin of homochirality in nature”, that was one of 125 scientific problems selected and published in Science , was interpreted. Specially, the relation between the homochirality and the origin of life was focused on, and these related hypothesis, theory and progress were introduced and discussed. So far, there are the following major hypotheses on the origin of homochirality: (1) the Vester-Ulbricht Mechanism and Yamagata Mechanism based on parity violation; (2) the natural circularly polarized light caused the origin of homochirality; (3) the liquid solid chemical reaction caused the homochiral selection; (4) the statistical selection; (5) the vitality mechanism; (6) the Earth’s magnetic field theory; (7) the dissipative theory. There are new researches indicated that the noise, self catalysis and self replication, and nonconservation of parity gravity may induce the origin of homochirality, i.e. symmetry breaking. These hypotheses can explain some experimental data on the homochirality, but each one is not able to get the inevitable result: only L -amino acids and D -sugar are selected in origin of life. In the research field on homochirality origin, Chinese scholars also put forward some hypotheses: (1) the unbalanced radiolysis and low temperature phase transition; (2) the Earth’s orbital chirality theory; (3) the biomolecular chiral synthesis induced by electron-spin, and so on.