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Electron Transport via Cytochrome C on Si–H Surfaces: Roles of Fe and Heme

Amdursky, Nadav, Pecht, Israel, Sheves, Mordechai, Cahen, David
Journal of the American Chemical Society 2013 v.135 no.16 pp. 6300-6306
ambient temperature, electrodes, electron transfer, heme, iron, proteins, silicon
Monolayers of the redox protein Cytochrome C (CytC) can be electrostatically formed on an H-terminated Si substrate, if the protein- and Si-surface are prepared so as to carry opposite charges. With such monolayers we study electron transport (ETp) via CytC, using a solid-state approach with macroscopic electrodes. We have revealed that currents via holo-CytC are almost 3 orders of magnitude higher than via the heme-depleted protein (→ apo-CytC). This large difference in currents is attributed to loss of the proteins’ secondary structure upon heme removal. While removal of only the Fe ion (→ porphyrin-CytC) does not significantly change the currents via this protein at room temperature, the 30–335 K temperature dependence suggests opening of a new ETp pathway, which dominates at high temperatures (>285 K). These results suggest that the cofactor plays a major role in determining the ETp pathway(s) within CytC.