(502c) Characterization of the Structure of Oligopeptide Kinase Substrates Immobilized On Solid Surfaces

This presentation addresses two methods for characterization of the structure of oligopeptides immobilized at interfaces. Although many methods exist to measure the functional properties of biomolecules at interfaces (e.g., enzymatic activity), few approaches enable characterization of the structure of the biomolecules. A particular focus is directed to oligopeptides that are substrates of the epidermal growth factor receptor (EGFR). The EGFR is a tyrosine kinase which phosphorylates the oligopeptides, and inhibitors of the tyrosine kinase activity of the EGFR represent an important class of emerging anti-cancer agents. The first method of characterization to be described is based on Near Edge X-ray Absorption Fine Structure Spectroscopy (NEXAFS). We have used NEXAFS to characterize the chemistry of immobilization of the oligopeptides. We have also explored the hypothesis that phosphorylation of the oligopeptides can lead to conformational changes that can be measured by NEXAFS. The second method of characterization involves measurements of the orientational ordering of liquid crystals supported on oligopeptide-decorated surfaces. Our measurements define the sensitivity of the orientational ordering of liquid crystals to the density and structure of the EGFR peptide substrates. We will conclude this presentation by comparing and contrasting the information obtained from these two methods for characterizing the structure and density of biomolecules at surfaces.