Thursday, 17 May 2018

Magnetic fields could fish out enantiomers

When chemists need to separate one chiral molecule from a mixture of enantiomers—for instance, when synthesizing potential drug molecules—they often turn to high-performance liquid chromatography (HPLC). A new study suggests an alternative to this approach. The authors report that magnetic fields could separate enantiomers in a racemic mixture.

This effect is possible because electrons don’t behave the same way in one enantiomer as they do in another. Electrons and other elementary particles have an intrinsic property called spin. In the case of electrons, the particles are either spin up or spin down. In a chiral molecule, these spin states affect electron motion. Electrons in one spin state will move more easily than those in the other state. 

If the surface is magnetized, the spin states of the material’s electrons will align parallel to the magnetic field. Electrons with like spin states repel each other. A chiral molecule approaching the surface will either be attracted or repelled depending on the spin state of the electrons that concentrated at the end facing the surface. As a result, the researchers say, one enantiomer will preferentially adsorb to a magnetized surface, while the other chiral molecule will not.



The effect with silicon dioxide nanoparticles decorated with enantiomers of a polyalanine oligomer and a magnetized, gold-coated surface. Through scanning electron microscope images, l-alanine oligomer nanoparticles adsorbed eight times as well as the d-alanine particles when the magnetic field pointed up from the surface, and the d-alanine nanoparticles adsorbed four times as well when the field pointed down. 

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Magnetic fields could fish out enantiomers

When chemists need to separate one chiral molecule from a mixture of enantiomers—for instance, when synthesizing potential drug molecules—...