Flow properties of high‐molecular‐weight DNA solutions: Viscosity, recoil, and longest retardation time

Viscosity η, recoil Γ, and longest retardation time τ 1R were measured for buffered aqueous solution of T2 DNA ( M = 1.3 × 10 8 ) and cell lysattes of Bacillus subtiles W 23 (DNA M = 2 × 10 9 ) as a function of concetration, shear stress σ, and time of shear t , using a cartesian‐diver‐suspended couette flow system. For the T2 solution, η decreased with increasing σ, Γ( t ) going through a maximum with t . For the B. subtiles lysates, the preponderant rheological component of which is chromatin DNA, above a critical σ, the η, Γ( t ), and τ 1R increased t over 15 to 45 minutes duration to values up to several times larger, indicating the formation of intermolecular aggregates. The onset of such effects and their significance in th e measurement of molecular properties by hydrodynamic means is disscussed.