DNA Puts New Spin On Electron Transfer

In addition to applied magnetic fields and ferromagnetic films, monolayers of tightly packed double-stranded DNA now occupy a spot on the list of materials and forces that can manipulate electron spins for possible use in electronics (Science, DOI: 10.1126/science.1199339). An international team led by Helmut Zacharias of Germany’s University of Münster and Ron Naaman of Israel’s Weizmann Institute of Science reports an exceptionally high 60% selectivity for left-handed spin in electrons ejected by UV light from a gold substrate coated with a DNA layer. This spin polarization, achieved with 78-base-pair DNA, far exceeds selectivities of about 25% that scientists have attained in the past with ferromagnetic films. The spin selection phenomenon likely stems from DNA’s chirality, the researchers say, and the results suggest that spin could have a more important role in biomolecular electron transfer than originally thought. But “the jury is still out” on whether this discovery will translate into a spintronic filtration device that advances information technology, says materials scientist Samuel D. Bader of Argonne National Laboratory. The data are “intriguing,” Bader adds, but further work is needed to “dissect the problem.”