“Effect of the Electrostatic Microenvironment on the Observed Oxidation-Reduction Potential of Electroactive Supramolecular Bioconjugates”

O. AZZARONI; B. YAMEEN; W. KNOLL

PHYSICAL CHEMISTRY CHEMICAL PHYSICS

ROYAL SOC CHEMISTRY

Año: 2008 vol. 10 p. 7031 - 7038

1463-9076

The present work describes our studies of the influence of the electrostatic microenvironment onthe observed oxidation–reduction potential of redox-labeled supramolecular bioconjugates. Ourexperimental results show that the charge of the protein (streptavidin), determined by the pH,strongly influences the redox potential of the incorporated ferrocene centers. This is due to theelectrostatic contributions from the fixed charges in the protein that affect the relative stability ofthe redox species involved in the electroactive label. In addition, the ionic strength plays a centralrole in screening the stabilizing or repulsive interactions, thus further influencing the magnitude ofthe apparent redox potential. This dependence of the redox potential on pH and ionic strengthwas described in quantitative terms by following a similar approach to that previously used forinterpreting the behaviour of electron transfer proteins. This work provides a framework tounderstand, rationalize and predict variations in redox potentials of electroactive centersincorporated into different soft matter-based complex environments, like supramolecularbio-architectures. The potential of the approach was demonstrated through creation of apH-tunable bioelectrochemical interface with switchable behavior based entirely on redox-activesupramolecular bioconjugates.