Imsook Kim and Juhyoun Kwak , "Investigation of the electrode Reaction of Cytochrome c and Pyrroloquinoline quinone on Self-Assembled Monolayers of Amino Acids," J. Korean Electrochem. Soc., 2 (1), 27 - 30 (1999.02.__.)

Abstract
Self-Assembled monolayers of carboxyl-terminated alkanethiols, which is negatively charged in pH 7.0, were usually used to facilitate the electron transfer between the positively charged protein and the electrode. In case of L-cysteine, as it has both positive and negative group, it can be a candidate for a new modifier to facilitate positively charged protein or negatively charged protein. Our investigation of L-cystein shows that the electron transfer occurs successfully to both cytochrome c (cyt. c) and pyrroloquinoline quinone (PQQ). By using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC), we made a covalent bond between cyt. c and monolayer. Then PQQ was electrostatically adsorbed to the same monolayer. Cyclic voltammograms show that both molecules do not interfere each other and electron transfer is appreciable.

Keywords : Self-Assembled Monolayer, Cytochrome c, Pyrroloquinoline quinone, L-Cystein, Cyclic voltammetry