title: Tethering hydrophobic peptides to functionalized self-assembled monolayers on gold through two chemical linkers using the Huisgen cycloaddition.
abstract: Gold surfaces functionalized with an α-helical peptide have been generated by reacting an azide-terminated self-assembled monolayer with structured peptides containing two cyanophenylalanines through a Huisgen cycloaddition. Mixed monolayers of a reactive bromine-terminated thiol and inert alkane thiol were prepared at various concentrations of the Br-terminated moiety. These were reacted with sodium azide to form azide-terminated monolayers with controlled concentration of the reactive azide. These surfaces were studied through ellipsometry and X-ray photoelectron spectroscopy, which demonstrated that the concentration of the reactive azide group on the surface is controlled by the chemical conditions under which the monolayer is prepared. Grazing incident angle surface infrared spectroscopy (GRAS-IR) of the azide-terminated surface demonstrated that the azide is approximately perpendicular to the plane of the surface, as expected. These surfaces were then exposed to an α-helical peptide composed of alternating leucine and lysine residues, with two residues replaced with cyanophenylalanine to react with two neighboring surface-bound azide groups to bind the peptide to the surface through two covalent bonds. The yield of this reaction was quantified through monitoring the absorption of the azide group by GRAS-IR. Despite damage to the monolayer during the reaction, reaction yields of 80-98% were determined for optimized reaction conditions. Although the peptide retains its α-helical configuration under the reaction conditions, GRAS-IR analysis of the amide I and II modes of the surface-bound peptide showed that it is probably randomly oriented on the surface.
authors.affiliation: Department of Chemistry and Biochemistry, Center for Nano- and Molecular Science and Technology, and Institute for Cell and Molecular Biology, 1 University Station A5300, The University of Texas at Austin, Austin, Texas 78712, United States.
authors.forename: Ignacio F
authors.initials: IF
authors.lastname: Gallardo
authors.forename: Lauren J
authors.initials: LJ
authors.lastname: Webb
mesh_terms: D000595:Amino Acid Sequence; D001386:Azides / Q000737:chemistry; D001966:Bromine / Q000737:chemistry; D057930:Click Chemistry; D006046:Gold / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D008969:Molecular Sequence Data; D009570:Nitriles / Q000737:chemistry; D010455:Peptides / Q000737:chemistry*; D056951:Photoelectron Spectroscopy; D017433:Protein Structure, Secondary; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties
chemical_list: D001386:Azides; D009570:Nitriles; D010455:Peptides; D006046:Gold; D001966:Bromine