Electrochemistry of catechol terminated monolayers with Cu(II), Ni(II) and Fe(III) cations: a model for the marine adhesive interface.
The redox electrochemistry of hydroquinone and Cu2+-, Ni2+-, and Fe3+-hydroquinone complexes immobilized at the SAM interface has been studied in aqueous solutions with pH 5 to 12 using cyclic voltammetry. Self-assembled monolayers were constructed with terminal hydroquinone residues designed to model marine adhesive proteins that use the DOPA (3,4-dihydroxyphenylalanine) moiety. Coordination of metal to the hydroquinone group results in a shift to the ligand oxidation potential, with the value for Delta E p,a dependent on the solution pH and identity of the metal. Cu2+ shifts the hydroquinone oxidation by -285 mV (pH 8.8), and Ni2+ by -194 mV (pH 9.16). The hydroquinone oxidation was shifted by -440 mV at pH 5 for Fe3+ solutions examined up to pH 7. By contrast, reduction of the quinone is unperturbed by the presence of Cu2+, Ni2+, and Fe3+ ions. Implications of these results to the mechanism of marine adhesion are discussed.
Brooksby
Paula A
PA
Department of Chemistry, University of Canterbury, Private Bag 4800, Christchurch, New Zealand. paula.brooksby@canterbury.ac.nz
Schiel
David R
DR
Abell
Andrew D
AD
D000269:Adhesives; D000473:Alkanes / Q000737:chemistry; D002396:Catechols / Q000737:chemistry*; D002412:Cations / Q000737:chemistry; D003300:Copper / Q000737:chemistry*; D004563:Electrochemistry; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000737:chemistry*; D008956:Models, Chemical; D015394:Molecular Structure; D009532:Nickel / Q000737:chemistry*; D009792:Oceans and Seas; D010084:Oxidation-Reduction; D013438:Sulfhydryl Compounds / Q000737:chemistry; D013499:Surface Properties
D000269:Adhesives; D000473:Alkanes; D002396:Catechols; D002412:Cations; D013438:Sulfhydryl Compounds; D003300:Copper; D009532:Nickel; D007501:Iron; C034221:catechol