  Positions of protons in DNA hydrogen bonds are fundamental for the fidelity
of the replication process. Because the hydrogen bond is partially covalent the
electronic structure of DNA plays an important role in the replication process.
Current studies of electron transfer in DNA have shown that simple pictures
based on independent electron physics are not sufficient to account for the
experimental data. In this paper we propose a model for electron-proton
interaction in DNA and its relationship to mutagenesis. We argue that mutations
will be more frequent in DNA sequences where electron delocalization occurs. To
test our theory we calculate the heat capacity of DNA at low temperatures and
compare with the available experimental data in hydrated DNA. We find that our
model is in good agreement with the data. We also propose new measurements of
infrared absorption which would further test our ideas.
