Spin-dependent electron scattering from optically active molecules

The origin of the isomeric purity of biomolecules has been extensively discussed1. In particular, it has been suggested that spin-polarized electrons or positrons emerging in the β-decay of radio-active nuclei may have led to a preferential destruction of one of the two isomers at an early stage of evolution and that this process tipped the initial balance of abundance of the two self-replicating isomers2. As experimental tests of this hypothesis have remained largely inconclusive3,4, it seemed useful to investigate the spin dependence of electron scattering from optically active molecules under the simplest possible conditions. Here we describe an experiment which indicates that spin-polarized electrons, like polarized light, when scattered from optically active molecules, can ‘distinguish’ between right-handed and left-handed isomers.