Network of hydrogen bonds as a medium for DNA interaction in solvents

We suggest that the DNA molecules could form the cholesteric phase owing to an interaction mediated by the network of the hydrogen bonds (H-network) i n the solvent. The model admits of the dependence of the optical activity o f the solution on the concentration of the PEG, and the change in the sense of the cholesteric twist due to the intercalation by the daunomicyn. Using the experimental data for the cholesteric phase of the DNA dispersion, we obtain a rough estimate for the energy given by our model, and show that it should be taken into account as well as the energy due to the steric repul sion, van der Waals and electrostatic forces, generally used for studying t he DNA molecules. The elastic constant of the H-network generating the inte raction between the DNA molecules is determined by the energy due to the pr oton vibration in the hydrogen bonds. (C) 2001 Elsevier Science B.V. All ri ghts reserved.