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.

No abstract

The electrocatalytic hydrogen-evolution at the pyrolytic graphite electrode has been studied by cyclic voltammetry. This reaction has been achieved for solutions containing the redox protein Desulfovibrio vulgaris (Hildenborough) hydrogenase and a polycationic species poly-L-lysine. The effect of several parameters (concentrations, molecular weight of poly-L-lysine) on the electrocatalytic reaction has been investigated. Using small-overpotential conditions it has been shown that this electrode has the hydrogen-electrode function. Its stability has been examined using cyclic voltammetry and impedance measurements.