title: Buildup of polyelectrolyte-protein multilayer assemblies on gold electrodes. Role of the hydrophobic effect.
abstract: The buildup of layer-by-layer assemblies onto gold surfaces from water-soluble charged polyelectrolytes and proteins is examined using quartz crystal microgravimetry (QCM) and electrochemical techniques. Polyelectrolytes such as poly(styrenesulfonate) and poly(ester sulfonic acid) (Eastman AQ-29D polymer) adsorb spontaneously onto gold, contrary to poly(ethyleneimine). From the modification of the gold surface with a thiol and specific adsorption of polymers under polarization conditions, it is concluded that the hydrophobicity of the gold surface seems to be a determining factor in the adsorption process. Alternate adsorption onto gold resonators first coated with AQ-29D polymer gives stable multilayer films in the case of positively charged lysozyme (pI = 11) or polyheme Desulfovibrio vulgaris Hildenborough cytochrome c3 (pI = 10.5). QCM frequency changes with the number of adsorption steps suggest that a linear increase in film mass occurs. Desulfomicrobium norvegicum polyheme cytochrome c3 (pI = 7), which has a null global charge at neutral pH, is shown to give also stable multilayer AQ-29D/cytochrome c3 films, suggesting that several types of interactions, especially the hydrophobic effect, are involved in the buildup process.
authors.affiliation: Unité de Bioénergétique et Ingénierie des Protéines, Institut de Biologie Structurale et Microbiologie--CNRS, 31 chemin Joseph Aiguier, 13402 Marseille Cedex 20, France.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Lojou
authors.forename: Pierre
authors.initials: P
authors.lastname: Bianco
mesh_terms: D000327:Adsorption; D003574:Cytochrome c Group / Q000737:chemistry; D004563:Electrochemistry; D004566:Electrodes; D004573:Electrolytes / Q000737:chemistry*; D006046:Gold / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D007526:Isoelectric Point; D009113:Muramidase / Q000737:chemistry; D011091:Polyesters / Q000737:chemistry; D011094:Polyethyleneimine / Q000737:chemistry; D011137:Polystyrenes / Q000737:chemistry; D011487:Protein Conformation; D011506:Proteins / Q000737:chemistry*; D013451:Sulfonic Acids / Q000737:chemistry
chemical_list: D003574:Cytochrome c Group; D004573:Electrolytes; D011091:Polyesters; D011137:Polystyrenes; D011506:Proteins; D013451:Sulfonic Acids; C476201:poly(ester sulfonic acid); C003321:polystyrene sulfonic acid; D006046:Gold; D011094:Polyethyleneimine; C017165:cytochrome c(3); D009113:Muramidase