Optico-hydrodynamic properties of high molecular weight DNA from steady-state flow birefringence and viscosity at extremely low velocity gradients.

Abstract

AbstractThe flow birefringence, extinction angles, and shear‐dependent viscosity over a velocity gradient range of approximately 0.1–3 sec−1 have been obtained for T2 bacteriophage DNA at low concentration in neutral aqueous buffer. The data are found to be interpretable and self‐consistent in terms of subchain dynamical theory, including hydrodynamic, interactions and excluded volume, and the parameters characterizing these phenomena are in good agreement with the results of other hydrodynamic experiments and theoretical calculations. No necessity for modification of the subchain model in terms of limited extensibility or internal viscosity is found for high molecular weight DNA at the velocity gradients studied, although the latter cannot be ruled out on the basis of the present data. The Kuhn statistical segment length is determined from the intrinsic optical anisotropy and is estimated as 930 Å. Implications of these findings and their relation to appropriate dynamical models for DNA are discussed.