CYTOCHROME-C DYNAMICS AT GOLD AND GLASSY-CARBON SURFACES MONITORED BYIN-SITU SCANNING TUNNEL MICROSCOPY

We have investigated the absorption of cytochrome c on gold and glassy carbon substrates by in situ scanning tunnel microscopy under potenti ostatic control of both substrate and tip. Low ionic strength and pote ntial ranges where no Faradaic current flows were used. Cyt c aggregat es into flat composite structures of about 50 nm lateral extension at gold surfaces. The aggregates evolve in time, and structures resemblin g individual cyt c molecules can be distinguished in the space between the 50 nm structures. Cyt c aggregates also form at glassy carbon but have a different, unbroken character where cyt c both sticks well to the surface and exhibits notable mobility. The observations suggest th at characteristic surface specific, internally mobile protein aggregat es are formed at both surfaces and that in situ molecular resolution o f the STM pictures may have been achieved.