arXiv subjects

D. Marenduzzo

Publications and source records attributed to D. Marenduzzo.

93 records · Page 6Linked to original sources

arXiv2002

Force-induced unfolding of a homopolymer on fractal lattice: exact results vs. mean field predictions

We study the force-induced unfolding of a homopolymer on the three dimensional Sierpinski gasket. The polymer is subject to a contact energy between nearest neighbour sites not consecutive along the chain and to a stretching force. The hierarchical nature of the lattice we consider allows for an exact treatment which yields the phase diagram and the critical behaviour. We show that for this model mean field predictions are not correct, in particular in the exact phase diagram there is {\em not} a low temperature reentrance and we find that the force induced unfolding transition below the theta temperature is second order.

cond-mat.stat-mech↗

arXiv2001

Phase diagram of force-induced DNA unzipping in exactly solvable models

The mechanical separation of the double helical DNA structure induced by forces pulling apart the two DNA strands (``unzipping'') has been the subject of recent experiments. Analytical results are obtained within various models of interacting pairs of directed walks in the (1,1,...,1) direction on the hypercubic lattice, and the phase diagram in the force-temperature plane is studied for a variety of cases. The scaling behaviour is determined at both the unzipping and the melting transition. We confirm the existence of a cold denaturation transition recently observed in numerical simulations: for a finite range of forces the system gets unzipped by {\it decreasing} the temperature. The existence of this transition is rigorously established for generic lattice and continuum space models.

cond-mat.stat-mech↗

arXiv2001

Dynamical scaling of the DNA unzipping transition

We report studies of the equilibrium and the dynamics of a general set of lattice models which capture the essence of the force-induced or mechanical DNA unzipping transition. Besides yielding the whole equilibrium phase diagram in the force vs temperature plane, which reveals the presence of an interesting re-entrant unzipping transition for low T, these models enable us to characterize the dynamics of the process starting from a non-equilibrium initial condition. The thermal melting of the DNA strands displays a model dependent time evolution. On the contrary, our results suggest that the dynamical mechanism for the unzipping by force is very robust and the scaling behaviour does not depend on the details of the description we adopt.

cond-mat.soft↗