Adsorption of ribonuclease A and lysozyme at the mercury/solution interface

The adsorption of lysozyme and RNase A at a dropping mercury electrode from 0.1 M Tris-HCl + 1 mM EDTA + 0.2 M KCl buffer solution (pH 8.8) was invest igated by applying phase-sensitive alternating current polarography. Both p roteins are strongly adsorbed over a wide range of electrode potential arou nd the zero charge potential. The adsorption of the protein resulted in a d ecrease in the double-layer capacitance component to the capacitance of the supporting electrolyte/mercury double layer. Changes in capacitance allowe d Frumkin adsorption isotherms and thermodynamic adsorption parameters to b e obtained. Apart from the capacity current components, the faradaic curren t components were also monitored to test the accessibility of protein -S-S- bonds to redox processes at the mercury surface. (C) 1999 Academic Press.