Thermodynamics and Structural Consequences of Metal Binding Peptides

Metal binding peptides are the focus of considerable research given that they can template the formation of nanostructures with precisely defined shapes and sizes¹. The resulting peptide-coated nanostructures can be used for catalysis¹, sensing heavy metals in contaminated water sources, or for clean energy harvesting. Schwerdersky demonstrated that the interaction between the metal and the peptide arises by coordination at either the carboxylic or the amine terminus followed by slow deprotonation and coordination of the amide nitrogens from the peptide backbone³. However, the binding affinities between the metal and the peptide remains poorly understood, the binding parameters between the peptides and the metals has not been quantitatively determined and determining the strength of the interaction between the peptides and the metals is critical for applications related to sensing, catalysis, and nanostructure synthesis. The goals of this research are (1) develop a method to quantify the binding strength (DG°) between the flgA3 peptide and metals, (2) compare the DG° between different metals and flgA3, and (3) determine how DG affects the structure of the resulting peptide-nanoparticle structure. The FlgA3 peptide (DYKDDDKPAYSSGAPPMPPF) will be studied in the context of this research, because it was found to have strong binding affinity to metals and has been found to template the formation of different sizes of Au nanoparticles. To quantify the thermodynamic binding parameters (DH°, DS°, DG°), we will use variable temperature fluorescence spectroscopy. The FlgA3 peptide fluoresces due to two tyrosine groups in the peptide chain, and it has an emission at 303 nm that should be quenched following binding to a heavy metal such as Au. Using Stern-Volmer binding analysis, we will determine the association constant of FlgA3 to Au at different temperatures by performing quantitative detection. A van Hoff analysis of these data will directly provide DH and DS which we will use to find DG. We will then repeat the Stern-Vollmer analysis between FlgA3 and different heavy metals, including Pt (II), Pd (II), Hg (II), Ir(II) to see if there is any bonding selectivity. Following the determination of binding parameters, we will use the FlgA3 peptide to make bimetallic nanoparticles at different temperatures. We hypothesize that at different temperatures, the selectivity of the peptide will change and this may affect the structure of the resulting bimetallic nanoparticle. In conclusion, as part of this competition; I hope to develop new skills as a researcher and address challenging scientific problems. References: 1. Beverly D. Briggs, Marc R. Knecht.  Peptide based methods for the fabrication of functional materials. Physical Chemistry Letters,2012, 405-414. 2. Slocik, J.M.; Stone, M.O.; Naik, R.R. Small 2005, 1, 1048. 3. Sovago, I.; Osz, K. Dalton Transactions 2006, 3841. Schwederski, B.E.; Lee, H.D. Margerum, D.W. Inorganic Chemistry 1990, 29,359