Electrochemical study of the interaction between cytochrome c and DNA at a modified gold electrode

The direct electron transfer of surface-confined horse heart cytochrome c (Cyt c) was achieved using COOH-terminated alkanethiolate-modified gold electrode. Later DNA was immobilized on the two-layer modified electrode. The quantitative determination of DNA was explored and the interaction between cytochrome c and DNA was studied. The binding site sizes were determined to be 15 bp per Cyt c molecule with double-stranded (ds) DNA and 30 nucleotides binding one Cyt c molecule with single-stranded (ss) DNA. At the dsDNA/Cyt c/MUA/Au electrode, the rate constant of oxidation electron transfer k(s,ox) = 1.59 x 10(-3) cm s(-1) was obtained, at the ssDNA/Cyt c/MUA/Au electrode, the value was 2.43 x 10(-3) m s(-1) when the scan rate was 1.0 V/s. The different electrodes were characterized with electrochemical quartz crystal microbalance and atomic force microscope. (c) 2004 Elsevier Inc. All rights reserved.