Abstract
Solutions of denatured DNA obtained by lysing Bacillus subtilis bacteria at pH 12.5 exhibited time-dependent increases in viscosity, recoil, and retardation time (rheopexy), as measured by a Cartesian-diver rotating-cylinder viscoelastometer. The degree of rheopexy depended on DNA concentration, solvent viscosity and shear stress, but was relatively insensitive to temperature. Of the three viscoelastic parameters measured, recoil was the most sensitive indicator of rheopexy, viscosity moderately sensitive and retardation time the least sensitive. The rheopectic transitions were attributed to temporary, reversible, shear-induced aggregation of single-stranded DNA molecules.
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