Dr. Davide Michieletto (University of Edinburgh)

Abstract

Polymer physics successfully describes most of the polymeric materials that we encounter everyday. In spite of this, it heavily relies on the assumption that polymers do not change topology (or architecture) in time or that, if they do alter their morphology, they do so in equilibrium. This assumption spectacularly fails for DNA in vivo, which is constantly topologically re-arranged by ATP-consuming proteins within the cell nucleus. Inspired by this, here I propose to study entangled systems of DNA which can selectively alter their topology and architecture in time and may expend energy to do so. I argue that solutions of topologically active (living) polymers can display unconventional viscoelastic behaviours and can be conveniently realised using solutions of DNA functionalised by certain families of vitally important proteins. In this talk I will present some results on the microrheology of entangled DNA undergoing digestion by restriction enzymes and ligation by T4 ligase.  I will present theories, simulations and experiments using particle tracking microrheology showing that we can harness this non-equilibrium process to yield time-varying viscoelastic behaviours.