Rheology and scaling of concentrated linear DNA solutions

We have studied the flow and entanglement behavior of concentrated monodisperse linear lambda DNA, M_W ~ 3.2x10⁷ g/mol in solution. Dynamic tests on solutions of having concentrations from 0.47 to 3.75 mg/ml DNA in an aqueous buffer showed a rubbery plateau modulus, G_N⁰ that scales with concentration as C^2.24. Two distinct zones in the behavior of the relaxation time, τ_D against concentration are observed: scaling as C^~0.88 and C^~3.55 in low and high concentration regimes, respectively. The Cox-Merz rule and the time concentration superposition were established to follow in the range of concentrations studied. The damping function was obtained for different concentrations following stress relaxation experiments. The samples showed an increase in softening with strain as concentration increases. The entanglement behavior was found to be similar to that of synthetic melts and solutions.