Linear Viscoelastic Moduli of Concentrated DNA Solutions

Abstract

We present mechanical measurements of the frequency-dependent linear viscoelastic storage and loss moduli, G‘(ω) and G‘‘(ω), for calf 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, Ce, we observe a dominant plateau elasticity, for large ω. As ω decreases, G‘ falls until it is equal to G‘‘ at the crossover frequency, ωc, below which G‘‘ dominates. These measurements are consistent with a model of entangled semiflexible polymer coils in a good solvent, which predicts ∼ C2.3 and ωc ∼ C-2.4.