A kelp-like forest of DNA strands, rooted in sulphur on a bed of gold, turns out to be just the job for filtering electrons according to their spin state. When the strands are long – up to 80 base pairs - the technique is more efficient than magnet-based filters yielding spin polarization of 60 per cent at room temperature.
Developed by German and Israeli scientists, the filter could be useful in the emerging field of spintronics, but it could also shed light on the role spin plays in biology.
The researchers then shone a laser on to the gold, which liberates electrons via the photoelectric effect. Some of these electrons travel through the DNA forest and are fed into a device that measures their spin polarization. The team performed the experiment using linearly polarized laser light, which liberates unpolarized electrons. However, after travelling through the DNA, the electrons became polarized by as much as 60%.
Ron Naaman and colleagues at the Weizmann Institute in Israel and the University of Münster in Germany suggest the effect is caused by the electrons’ interactions with the lattice of strands, rather than individual strands, since a straggly forest doesn't filter the electrons at all. They suspect the chirality of the DNA strands plays a part, too, but the exact mechanism remains unclear.
The work, which is described in much more detail at PhysicsWorld, is published in the February 18th issue of the journal Science.