Homochirality is ubiquitous in living systems. For example, helical vines grow predominantly with a right handed twist. Geographically isolated populations of snails are always dominated by groups with the same twirl in their shells. On the molecular level, it is well known that the building blocks of biology are homochiral, with proteins composed of L-amino acids and oligonucleotides containing only D-sugars. This situation is in stark contrast with abiotic chemistry which always produces racemic mixtures in the absence of chirally enriched catalysts. Similarly, there is no obvious mechanical or physical reason why most vines twist to the right, or why most people have their heart on the left. The pervading presence of homochirality in life presents a long standing and unresolved problem relating to its origins, particularly at the molecular level. Put simply, how did homochirality evolve from a racemic start? Although many theories abound, one of the difficulties in addressing this problem is a lack of experimental data or suitable model systems. Surprisingly, this gap is being reduced by experiments on small molecular clusters utilizing mass spectrometry (MS).

Electrospray ionization (ESI) provides not only a facile means for introducing biomolecules into the gas phase, but also provides a robust source capable of transferring molecular clusters into the gas phase for examination by MS. The most notable cluster discovered to date is the protonated serine octamer [8Ser+H]⁺ (referred to hereafter as the serine octamer) originally discovered by Cooks and coworkers. When sampled by ESI or several related techniques, the serine octamer is an unusually abundant or magic number cluster. Further experiments, have illustrated that the serine octamer has a strong preference to be homochiral. This preference is strong enough to lead to partial spontaneous resolution of a racemic system, a phenomenon which is rarely observed and thought to be a prerequisite to the origin of life. Thus the serine octamer offers a model system that has a strong preference for homochirality, but which is not created through a biological process. We are studying the serine octamer and other interesting clusters to answer fundamental questions about homochirality.