Discrete charge carrier transfer sites on proteins? A D.C. conductivity study on ultrathin protein films

D.C. electrical conduction in thin protein films (200 mg/cm2; approximately 2 mu in thickness) of bovine serum albumin and its dinitrophenylated derivatives with different stoichiometric composition was investigated at 17, 20 and 23% relative humidities and at room temperature. Statistically significant decrease in conductivity due to derivatization was observed even at protein-2,4-dinitrophenol stoichiometry as low as 1:2. A charge injection mechanism based upon discrete charge carrier transfer sites could account for the observations. Analogous events may operate in cellular signaling and coding.