title: Characterization of surfaces presenting covalently immobilized oligopeptides using near-edge X-ray absorption fine structure spectroscopy.
abstract: This study addresses the need for methods that validate the surface chemistry leading to the immobilization of biomolecules and provide information about the resulting structural configurations. We report on the use of near-edge X-ray absorption fine structure spectroscopy (NEXAFS) to characterize a widely employed immobilization chemistry that leads to the covalent attachment of a biologically relevant oligopeptide to a surface. The oligopeptide used in this study is a kinase substrate of the epidermal growth factor receptor (EGFR), a protein that is a common target for cancer therapeutics. By observing changes in the pi* and sigma* orbitals of specific nitrogen and carbon atoms (amide, imide, carbonyl), we are able to follow the sequential reactions leading to immobilization of the oligopeptide. We also show that it is possible to use NEXAFS to extend this characterization method to submonolayer densities that are relevant to biological assays. Such an element-specific chemical characterization of small peptides on surfaces fills an unmet need and establishes NEXAFS as useful technique for characterizing the immobilization of small biomolecules on surfaces.
authors.affiliation: Department of Chemical and Biological Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, Wisconsin 53706, USA.
authors.forename: Yiqun
authors.initials: Y
authors.lastname: Bai
authors.forename: Xiaosong
authors.initials: X
authors.lastname: Liu
authors.forename: Peter
authors.initials: P
authors.lastname: Cook
authors.forename: Nicholas L
authors.initials: NL
authors.lastname: Abbott
authors.forename: F J
authors.initials: FJ
authors.lastname: Himpsel
mesh_terms: D000595:Amino Acid Sequence; D055767:Immobilized Proteins / Q000737:chemistry*; D009842:Oligopeptides / Q000737:chemistry*; D017785:Photons; D013499:Surface Properties; D056928:X-Ray Absorption Spectroscopy
chemical_list: D055767:Immobilized Proteins; D009842:Oligopeptides
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