LINEAR VISCOELASTIC MODULI OF CONCENTRATED DNA SOLUTIONS

We present mechanical measurements of the frequency-dependent linear v iscoelastic storage and loss moduli, G'(omega) and G ''(omega), for ca lf thymus DNA (13 kbp) in a saline buffer over a range of mitotically relevant mass concentrations from C = 1 to 10 mg/mL. For C exceeding a critical entanglement concentration, C-e, we observe a dominant plate au elasticity, G'(p), for large omega. As omega decreases, G' falls un til it is equal to G '' at the crossover frequency, omega(c), below wh ich G '' dominates. These measurements are consistent with a model of entangled semiflexible polymer coils in a good solvent, which predicts G'(p) similar to C-2.3 and omega(c) similar to C-2.4.