Concentrated DNA rheology and microrheology

T. G. Mason, A. Dhople, D. Wirtz

Research output: Contribution to journalConference articlepeer-review

Abstract

We present mechanical measurements of the frequency-dependent linear viscoelastic storage and loss moduli, G′(ω) and G″(ω), and the yield stress, τy, and yield strain, γy, for calf thymus DNA (13 kbp) over a range of mitotically relevant concentrations from CDNA = 1 to 10 mg/ml. For large CDNA, we find a dominant plateau elasticity, G′p, at high ω. As ω decreases, G′ falls until it is equal to G″ at the crossover frequency, ω-c$/, below which G″ dominates. We measure G′p approx. CDNA2.25 and ω-c$/ approx. CDNA-2.4, consistent with scaling exponents for classical polymer solutions. The mechanical |G*(ω)| agree well with those measured using a new microrheological technique based on video tracking microscopy of thermally-driven fluorescent colloidal spheres and a frequency-dependent Stokes-Einstein equation. We have developed this technique to probe how enzymes, typically available in small quantities, can affect the rheology of the DNA. Using it, we report preliminary measurements of a higher ω-c$/ for a DNA network in which the ATP-powered enzyme Topoisomerase II transiently cuts and rebinds the DNA, thereby relaxing entanglements.

Original languageEnglish (US)
Pages (from-to)153-158
Number of pages6
JournalMaterials Research Society Symposium - Proceedings
Volume463
StatePublished - Jan 1 1997
EventProceedings of the 1996 MRS Fall Meeting - Boston, MA, USA
Duration: Dec 2 1996Dec 6 1996

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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