DNA Electrochemistry as a Probe of Base Pair Stacking in A-, B-, and Z-Form DNA
DNA-mediated charge transport (CT) chemistry is sensitive to DNA structure and base pair stacking. In an electrochemical assay based upon DNA CT, DNA-modified electrode surfaces are used to examine the electrochemical reduction of methylene blue (MB), a small molecule that binds to the DNA film by intercalation. Here electrochemically we probe CT in the three primary conformations of double-stranded nucleic acids, A-, B-, and Z-form DNA. The A-form is examined in the context of a DNA/RNA hybrid duplex and Z-DNA, in duplexes containing d(^(m)CG)_8 sequences at high Mg^(2+) concentrations. We find that both A- and B-DNA support efficient DNA CT as measured by MB reduction in the DNA film; a lower level of reduction is evident with the Z-form film. Furthermore, mismatches incorporated into A-form duplexes, as in B-form duplexes, disrupt MB reduction, thus providing a strategy for mutation detection through testing of RNA transcripts at DNA electrodes.
© 2003 American Chemical Society. Received August 5, 2003; Revised Manuscript Received September 11, 2003; Publication Date (Web): October 24, 2003. We are grateful to the National Institutes of Health (GM61077) for their financial support of this research and to Melanie O'Neill for assistance with DNA figures.