Spinning off DNA

Biological molecules and quantum systems are not just apples and oranges – they’re more like apple trees and cans of frozen orange juice. The two exist in completely different conditions, on completely different scales. Yet research by Prof. Ron Naaman of the Chemical Physics Department (Faculty of Chemistry), conducted together with scientists at the Weizmann Institute and in Germany, definitively shows that a biological molecule – DNA – can discern between the quantum states known as spin in such subatomic particles as electrons.

Biological molecules are chiral: They exist in either “left-” or “right-handed” forms that can’t be superimposed on one another. Double-stranded DNA molecules are doubly chiral – both in the arrangement of the individual strands and in the direction of their helical twists. Naaman, together with Prof. Zeev Vager of the Particle Physics and Astrophysics Department, research student Tal Markus, and Prof. Helmut Zacharias and his research team at the University of Münster, Germany, thought that this chirality might imbue DNA with spin-selective properties. Their findings appeared in Science.

The researchers exposed DNA to groups of electrons with both directions of spin. Indeed, the team’s results surpassed expectations: The biological molecules reacted strongly with the electrons carrying one of those spins, and hardly at all with the others. Their findings imply that the chiral nature of the DNA molecule somehow “sets the preference” for the spin of electrons moving through it.

The team’s findings could have relevance for both biomedical research and the field of spintronics. For instance, if further studies bear out the finding that DNA sustains damage only from spins pointing in one direction, then medical radiation exposure might be reduced and devices designed accordingly. On the other hand, DNA and other biological molecules could become a central feature of new types of spintronic devices that will work on particle spin rather than electric charge, as they do today.