Surface properties of monomolecular films of oxidized and reduced cytochrome c and f

The surface properties of monomolecular films of oxidized and reduced cytochromes f and c were measured at an air-water interface. Area/molecular (A) and surface potential (deltaV) for oxidized and reduced forms of the cytochromes were measured as a function of pH. Oxidized cyt f has a maximum for both A and deltaV at pH 7.5. At a surface pressure of 6 dyn/cm the maximum A equals 2600 plus or minus 50 A2 and the maximum deltaV equals 200 plus or minus 10 mV. Reduced cyt f as a function of pH has a minimum value for both A (2200 A2) and deltaV (95 mV). Oxidized cyt c as a function of pH has minima for A (140 A2) and deltaV (188 mV) at pH 7.0 and 7.3, respectively. On the other hand, reduced cyt has maximum values for A (220 A2) and deltaV (260 mV) at pH 7.0 and 7.3, respectively.