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  • Title: Effect of deuterium substitution on electron transfer at cytochrome c/SAM interfaces.
    Author: Davis KL, Waldeck DH.
    Journal: J Phys Chem B; 2008 Oct 02; 112(39):12498-507. PubMed ID: 18781714.
    Abstract:
    The involvement of protons in the heterogeneous electron transfer between cytochrome c and a gold electrode to which it is attached was studied by comparing the electron transfer rate constants for H2O and D2O solutions. Rate constants were measured as a function of the electrochemical cell solution and the protein incubant solution, i.e., k (0)(incubant, cell). Two separate isotope effects exist: a cell "isotope effect", KIE cell = k (0)(H2O, H2O): k (0)(H2O, D2O), which is manifest at short time scales (<30 s) and arises from the viscosity difference between H2O and D2O, and an incubant isotope effect, KIE inc= k (0)(H2O, H2O): k (0)(D2O, H2O), which is manifest at longer times (>2 h) and results from H/D exchange. The two isotope effects are approximately equal ( approximately 1.2) and a total isotope effect KIE total = k (0)(H2O, H2O): k (0)(D2O, D2O) can be constructed that is the product of KIE cell and KIE inc. The nature of the electron transfer process, possible coupling to a proton transfer process, and the involvement of specific hydrogens in the transfer mechanism are discussed.
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