Structure of peptides on metal oxide surfaces probed by NMR.

Peptides that bind inorganic surfaces and template the formation of nanometer-sized inorganic particles are of great interest for the self- or directed assembly of nanomaterials for sensors and diagnostic applications. These surface-recognizing peptides can be identified from combinatorial phage-display peptide libraries, but little experimental information is available for understanding the relationship between the peptide sequence, structure at the nanoparticle surface, and function. We have developed NMR methods to determine the structures of peptides bound to inorganic nanoparticles and report on the structure of three peptides bound to silica and titania surfaces. Samples were prepared under conditions leading to rapid peptide exchange at the surface such that solution-based nuclear Overhauser experiments can be used to determine the three-dimensional structure of the bound peptide. The binding motif is defined by a compact "C"-shaped structure for the first six amino acids in the 12-mer. The orientation of the peptide on the nanoparticle surface was determined by magnetization transfer from the nanoparticle surface to the nearby peptide protons. These methods can be applied to a wide variety of abiotic interfaces to provide an insight into the relationship between the primary sequence of peptides and their functionality at the interface.