Tritium/protium fractionation near and inside DNA

The fractionation factor of tritium between water and DNA as well as betwee n water and the first hydration shell of DNA is determined. For this purpos e the sublimation kinetics of water from DNA dissolved in water were determ ined at -200 degreesC and tritium was measured in the remaining water free DNA. The last sublimating water fractions showed a tritium level of about 1 .4, the residual water free DNA about 1.9 units above the bulk, water. The tritium accumulation inside and near DNA is attributed to the thermodynamic triton-proton exchange isotope effect existing between the strong hydrogen bridges of water and weaker hydrogen bridges as well as inside DNA as betw een the first hydration shell and DNA.