title: Significance of the amide functionality on DOPA-based monolayers on gold.
abstract: The adhesive proteins secreted by marine mussels contain an unusual amino acid, 3,4-dihydroxyphenylalanine (DOPA), that is responsible for the cohesive and adhesive strength of this natural glue and gives mussels the ability to attach themselves to rocks, metals, and plastics. Here we report a detailed structural and spectroscopic investigation of the interface between N-stearoyldopamine and a single-crystalline Au(111) model surface and an amide-absent molecule, 4-stearylcatechol, also on Au(111), with the aim of understanding the role of the amide functionality in the packing, orientation, and fundamental interaction between the substrate and the monolayer formed from an aqueous environment by the Langmuir-Blodgett technique. The organization of monolayers on gold was observed directly and studied in detail by X-ray photoelectron spectroscopy (XPS), contact angle measurements (CA), surface-enhanced Raman spectroscopy (SERS), infrared reflection-absorption spectroscopy (IRRAS), and atomic force microscopy (AFM). Our study shows that within the monolayer the catecholic oxygen atoms are coordinated to the gold surface, having a more perpendicular orientation with respect to the aromatic ring and the apparently tilted alkyl chains, whereas the amide functionality stabilizes the monolayer that is formed.
authors.affiliation: Laboratory of Materials and Interface Chemistry, Eindhoven University of Technology, P.O. Box 513, NL-5600 MB Eindhoven, The Netherlands.
authors.forename: Dina
authors.initials: D
authors.lastname: Rībena
authors.forename: Alexander
authors.initials: A
authors.lastname: Alekseev
authors.forename: Otto
authors.initials: O
authors.lastname: van Asselen
authors.forename: Gilbère J A
authors.initials: GJ
authors.lastname: Mannie
authors.forename: Marco M R M
authors.initials: MM
authors.lastname: Hendrix
authors.forename: Leendert G J
authors.initials: LG
authors.lastname: van der Ven
authors.forename: Nico A J M
authors.initials: NA
authors.lastname: Sommerdijk
authors.forename: Gijsbertus
authors.initials: G
authors.lastname: de With
mesh_terms: D000269:Adhesives / Q000737:chemistry; D000577:Amides / Q000737:chemistry*; D000818:Animals; D040761:Biomimetic Materials / Q000737:chemistry*; D049872:Bivalvia / Q000737:chemistry; D002396:Catechols / Q000737:chemistry*; D003460:Crystallization; D004295:Dihydroxyphenylalanine / Q000737:chemistry*; D004298:Dopamine / Q000031:analogs & derivatives* / Q000737:chemistry; D006046:Gold / Q000737:chemistry*; D018625:Microscopy, Atomic Force; D056951:Photoelectron Spectroscopy; D011506:Proteins / Q000737:chemistry; D013055:Spectrophotometry, Infrared; D013059:Spectrum Analysis, Raman; D013228:Stearates / Q000737:chemistry*; D013499:Surface Properties; D013816:Thermodynamics; D014867:Water / Q000737:chemistry
chemical_list: D000269:Adhesives; D000577:Amides; D002396:Catechols; C499798:N-stearoyl-dopamine; D011506:Proteins; D013228:Stearates; D014867:Water; D004295:Dihydroxyphenylalanine; D006046:Gold; D004298:Dopamine