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Chiral Induced Spin Selectivity

Final Report Summary - CISS (Chiral Induced Spin Selectivity)

The basic molecular building blocks of life, e.g. DNA and proteins, lack mirror symmetry and all organisms, plants, animals and of course human beings are made from molecules that have “helical” symmetry, like a screw shape. In principle the molecules can be like right handed or left handed screws. Each type of screw is called enantiomer. Electrons that carry charge have another property- the spin, which is the angular momentum of the electron. The spin can have two values many times related to as UP and DOWN. In our research we established that the transfer of electrons through chiral molecules depends on the spin. One spin is preferred in transmission through "left handed" enantiomer while the other through "right handed". This findings open new research field in which chiral molecules can serve in a novel type of electronics- the spintronics. The effect also explains why evolution preferred proteins as an electron transfer medium and not other molecules. In addition, the research result in developing a new method for separating enantiomers. In nature, the components from which proteins are made, the amino acids, and the sugars are are enantiomerically pure in all organisms and this purity is preserved with extremely high fidelity. Such enantiomeric selectivity is very difficult to achieve when one tries to synthesize these molecules artificially in the laboratory. Moreover, the enantiopurity of drug medications is known to be essential to their efficacy and for eliminating side effects, some of which can be deadly. The same is true for pesticides that should be of specific enantiomer.
Since typically in chemical reactions both enantiomers are produced in equal amount, separating the two enantiomers of chiral molecules is a central process in the pharmaceutical and chemical industries. Today, the separation process is specific and a special process has to be developed for each type of molecule. The separation is difficult and expensive.
Our novel method is based on the enantio-selective affinity of chiral molecules to magnetic surfaces. Our method is generic and therefore does not require specific adaption to each molecule. Our studies demonstrated our ability to separate of amino acids, peptides and sugars.