Simple electrochemical deposition techniques can produce highly defined metal nanostructures in templates. Electroless deposition (ELD) can be effectively used for depositing metals on insulators such as biological or plastic surfaces. With biomolecular templates, metallization methods are often restricted to mild reductions, and the deposition of copper at pH values above 12 is usually not applicable. We produced copper nanowires of 3 nm in diameter and up to 150 nm in length by electroless deposition within the 4 nm wide channel of tobacco mosaic virus (TMV) particles. We employed a low pH (similar to 7.5) copper electroless deposition solution that is compatible with biomolecules. The fabrication process of the nanowires is based on sensitization of tobacco mosaic virus with Pd(II) prior to the electroless deposition. We analyzed the chemical composition of the nanowires by energy-filtering transmission electron microscopy, and used the method also for nickel and cobalt nanowires deposited within the viral channel. (c) 2006 Elsevier Ltd. All rights reserved.