INTERFACIAL BEHAVIOR OF GLOBULAR-PROTEINS AT A PLATINUM-ELECTRODE

The surface adsorption behavior of the globular proteins, bovine β-lactoglobulin A, hen egg white lysozyme, and bovine pancreatic ribonuclease A have been investigated at a platinum electrode using cyclic voltammetry. A good correlation over the temperature range 273-343 K was obtained between the charge density due to protein adsorption and the accessibility of free sulfhydryl groups, which is an indication of the amount of conformational changes and/or dissociation of dimeric units of the protein. The surface charge density was attributed to a flattening or denaturing of the protein at the electrode surface to allow adsorption of carboxyl groups, accompanied by electron transfer at these anodic potentials. The calculated surface concentrations, Γ (mg m-2), based on the number of carboxyl groups and two-electron transfer processes/carboxyl group give good agreement with calculated values obtained by others using such techniques as radioactive labeling and ellipsometry. The present technique which measures the charge density due to adsorption of proteins at platinum electrode surfaces appears to be very sensitive to structural changes of the protein both in the bulk solution and at the metal/solution interface. © 1992.