Protein crystals as templates for materials chemistry

This work describes the first use of macromolecular biological crystals as templates for materials synthesis. The macromolecular crystal itself offers unique micro- and mesoporous structure with specific binding sites for molecules. This work utilizes this porous structure for the design of polymer and metal loaded nanocomposites. The crystals are first strengthened with intermolecular covalent cross-links. The sturdy crystals then serve as scaffolds for the infusion of polymers or the growth of metallic nanoparticles. Polymer infused and encased Hen Egg White Lysozyme (HEWL) crystals show reproducible diffraction for many months to a resolution of 4A. Metal nanoparticles can be grown in HEWL crystals using an electroless plating technique in which palladium ions bound to amino acids are subsequently reduced and form a catalytic surface for the deposition of platinum metal. If these nanoparticles are grown in a macromolecular crystal with larger pores, such as Cowpea Mosaic Virus, then the protein structure effectively guides the growth of the nanoparticles resulting in monolithic, highly ordered nanocomposites. These novel patterned materials could find use as x-ray optics, sensors, or x-ray diffraction standards