December 4, 2000, Volume 78, Number 49, p. 63
SCIENCE/TECHNOLOGY CONCENTRATES

Electrocatalytic activation of biological redox reactions can be switched on or off via a magnetic assembly developed by researchers in Israel [J. Am. Chem. Soc. ,122, 12053 (2000)]. Itamar Willner, a professor of chemistry at Hebrew University of Jerusalem, along with colleagues Ronit Hirsch and Eugenii Katz, covalently attached electron relay ligands containing a redox component to magnetite particles. The functionalized iron oxide magnetic particles were placed in a solution containing an electrode, a redox enzyme, and its substrate. An external magnet placed next to the electrode attracts the magnetite particles to the electrode, where the ligand's redox component, depending on its nature, is either oxidized or reduced. This event activates the redox enzyme, turning catalysis "on." Catalysis is turned "off" by repositioning the magnet away from the electrode to draw the magnetite particles away. The team used the approach to control both enzymatic oxidation of glucose and reduction of nitrate, exploiting ferrocene- and bipyridinium-functionalized magnetite particles, respectively. Future applications might include external control of catalysis in bioreactors or activation of biofuel cells, the researchers say.