Role of transition metals in sclerotization of biological tissue.

Biomimetics seeks to elucidate the biochemical and structural principles governing functionality in biological systems and exploit them in the design of synthetic materials. Although the lure has been great, breakthroughs have been rare. The overwhelming complexity of chemical compositions and structural motifs in biology renders the task of "reverse engineering" a formidable challenge. The challenge is amplified by the inherent limitations in probing the effects of a single test variable, keeping others fixed. Here a novel methodology is presented for probing the effects of various transition metals on the hardness and stiffness of a single biological system, notably the jaws of the marine polychaete annelid Nereis virens. Not only is the exceptionally high efficacy of Zn, Cu, and Mn in hardening demonstrated, but also that metal selection is not restricted to that which occurs naturally in the targeted system.