DNA - a Molecular Wire or an Insulator

6 DNA - a Molecular Wire or an Insulator - The rate, as well as the extent, of electron and hole migration within DNA had been a topic of intense experimental and theoretical interest and dispute.60 ESR studies have made significant contributions to the understanding of these important phenomenon. 

For example, Debije et al.61 presented yields of crystalline oligonucleotides and 

Debije and Bernhard investigated free radical yields in crystalline X-irradiated duplex DNA at 4 K.52 Thirteen different oligodeoxynucleotides were investigated using ESR spectroscopy in order to assess the extent to which structural factors 

At loadings lower than 1 MX per 20 DNA bp, the fraction of the electrons captured by the intercalator was found to follow the relation D(t) = l/pln/c0t this assumes random MX intercalation in the DNA and an increase electron transfer to intercalator with ln(f) as expected for a single-step tunnelling process. The electron-transfer distances, after 1 min at 77 K, were about 8-10 bps for the most electron affinic intercalators MX and NPa. For these intercalators tunnelling decay constants p of 0.8 - 0.9 A, were reported with a /c0 = 1 x 10 s 1 in the standard relation for fall off of p with tunnelling distance, k = k0e bD. These 

4 The Effects of Complexing Agents. Cai et al.66 replaced the sodium counterion of MX-DNA with various aliphatic amine cations, e.g. spermine cation, and alkyltrimethylammonium cation as well as polymeric amine cations, such as poly-L-lysine and polyethylenimine to vary the separation between DNA duplexes. The radiation-produced electrons from the complexing agents readily transfer to the more electron affinic DNA. 

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