Tunneling spectroscopic study of hydrogenase Langmuir-Blodgett film

Hydrogenase Langmuir-Blodgett films from Thiocapsa roseopersicina were prep ared on gold-coated mica substrates using 20 mer of poly-L-lysine, which st abilizes the enzyme and improves the protein transfer. Scanning tunneling m icroscopy and intermittent contact mode atomic force microscopy were used t o observe the films and to determine that the single hydrogenase-hexagonal complex was laid horizontally to the gold surface. Tunneling spectroscopy o f the hydrogenase complex demonstrated the diodelike current-voltage charac teristics. The rectification of the tunneling current might be ascribed to the alignment of cofactors, a nickel atom and iron sulfur clusters of the h ydrogenase. (C) 1998 Elsevier Science Limited. All rights reserved.