title: Formation of oriented polypeptides on Au(111) surface depends on the secondary structure controlled by peptide length.
abstract: We synthesized three different lengths of poly(L-lysine) containing an -SH group at the terminal (PLL(n)-SH, n (polymerization degree) = 4, 10, 30) and adsorbed them on an Au(111) surface. To analyze the formation process and the structure of self-assembled monolayers (SAMs), we used atomic force microscopy (AFM) and Fourier transform infrared reflection absorption spectra (FT-IR RAS). At the initial stage of SAM growth, formation of nanosize domains was confirmed by AFM imaging. The alpha-helical PLL(30)-SH exhibited a well-defined SAM structure after adsorption reached equilibrium. The alpha-helical PLL(30)-SH was almost perpendicular to the gold surface and exhibited interesting molecular packing due to the secondary structure of PLL(30)-SH and the underlying Au(111) array. The tilt angle of the helix axis from the substrate normal was estimated to be about 50 degrees (AFM) and 44 degrees (FT-IR RAS) respectively. On the other hand, PLL(4)-SH and PLL(10)-SH formed beta-sheet-type SAMs on the Au(111) surface based on the structure determined by FT-IR RAS spectrum.
authors.affiliation: Department of Biotechnology, Faculty of Engineering, Tottori University, Tottori 680-8552, Japan. sakurai@bio.tottori-u.ac.jp
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Sakurai
authors.forename: Sayaka
authors.initials: S
authors.lastname: Oka
authors.forename: Atsushi
authors.initials: A
authors.lastname: Kubo
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Nishiyama
authors.forename: Isao
authors.initials: I
authors.lastname: Taniguchi
mesh_terms: D000327:Adsorption; D002942:Circular Dichroism; D006046:Gold / Q000737:chemistry*; D018625:Microscopy, Atomic Force; D008970:Molecular Weight; D010455:Peptides / Q000138:chemical synthesis* / Q000737:chemistry; D011107:Polylysine / Q000737:chemistry*; D017433:Protein Structure, Secondary; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties
chemical_list: D010455:Peptides; D011107:Polylysine; D006046:Gold