Interaction of nucleic acid segments as a result of modification of the network of hydrogen bonds of the solvent

It is shown that experimental results on the influence of various factors i n the formation efficiency and structure of cholesteric liquid-crystal disp ersions of nucleic acids cannot be consistently described using conventiona l theories of liquid crystal formation. A new model is proposed for the int eraction of nucleic acid segments which allows for a change in the particul ar structure of the solvent hydrogen bonds in the presence of nucleic acid molecules. The conclusions of the model agree with existing spectroscopic a nd structural investigations of DNA dispersions. According to our model, in teraction between nucleic acid molecules and solvent modifies proton tunnel ing processes in the latter, leading to effective interaction between the n ucleic acids. A theoretical analysis of the model is made using a pseudospi n formalism in which the effective interaction potential of the nucleic aci d segments is calculated. It is shown that this potential may lead to nemat ic ordering for small distances between the nucleic acid molecules (R less than or equal to 30 Angstrom) and cholesteric ordering for large distances. (C) 2000 MAIK "Nauka/Interperiodica".