1112.3720 (Sharadwata Pan et al.)

Universal solvent quality crossover of the zero shear rate viscosity of
semidilute DNA solutions    [PDF]

Sharadwata Pan, Duc At Nguyen, P. Sunthar, T. Sridhar, J. Ravi Prakash

The radius of gyration and the hydrodynamic radius of a number of linear, double-stranded DNA molecules, ranging in length from 3 to 300 kilobase pairs, extracted from modified strains of E. coli and dissolved in the presence of excess salt in a commonly used solvent, have been obtained by static and dynamic light scattering measurements. Using scaling relations from polymer solution theory, the \theta-temperature for this solvent, and the crossover swelling of the two radii have been determined. It is shown that, as in the case of neutral synthetic polymer solutions, dilute DNA solutions exhibit universal swelling behaviour. Comparison of the universal swelling with previously obtained results of Brownian dynamics simulations enables an estimate of the solvent quality of a DNA solution at any temperature and molecular weight. The zero shear rate viscosity of semidilute unentangled DNA solutions, measured across a range of molecular weights and concentrations at a fixed value of solvent quality, is shown to obey power law scaling with concentration predicted by scaling theory, but with an effective exponent \nu_eff that depends on the solvent quality, in place of the Flory exponent \nu.

View original: http://arxiv.org/abs/1112.3720