Structural and mechanistic features of genetically engineered polypeptides for non-biological inorganic materials

Technological advances have facilitated the generation of genetically engineered peptides and proteins that possess the capabilities of recognizing and binding to inorganic solids and/or controlling nucleation processes that form inorgnaic solids. However, very little is known regarding the structure of these interesting polypeptides and how structure contributes to functionality. This thesis presents studies done on three different genetically engineered peptides. First is a gold binding polypeptide (14 amino acids) that was selected to specifically bind gold {111} surfaces but has also been shown to nucleate gold crystals. Results show that the sequence binds two gold ions, one specifically in the -KTQATS motif and another nonspecifically at the C-terminal. Conformationally, the peptide possesses an open extended conformation available to adapt to the gold surface (at neutral pH). Next is an examination of a single-wall nanohorn binding peptide (12 amino acids). The conformation of this peptide, at neutral pH, is also in an open labile conformation that allows for adsorption onto the nanohorn surface. Repeats of these two peptides have shown to have a higher affinity for their respective surfaces and are also examined. The repeats show similarly unstructured states at neutral pH. Lastly is a genetically engineered protein p288 (116 amino acids), which catalyzes dendritic structures from both inorganic (NaCl, KCl, and CuSO4) and organic (sucrose) substrates. Again, this protein has a unstructured conformation at neutral pH. Studies of all three sequences (and some repeats) show that in the presence of trifluorethanol, a structure stabilizing solvent, that alpha-helical secondary structures are formed. This stabilization could play an important role in molecular assembly applications of these species. From a small genetically engineered peptide (12 amino acids) to a large genetically engineered protein (116 amino acids) there are conformationally similar features that must be owed to inherent ability to bind to and/or control the nucleation of inorganics.