Europhys. Lett.
Volume 67, Number 3, August 2004
Page(s) 418 - 424
Section Condensed matter: structure, mechanical and thermal properties
Published online 01 July 2004
Europhys. Lett., 67 (3), pp. 418-424 (2004)
DOI: 10.1209/epl/i2004-10076-x

Twist-bend instability for toroidal DNA condensates

I. M. Kulic, D. Andrienko and M. Deserno

Max-Planck-Institut für Polymerforschung - Ackermannweg 10, 55128 Mainz, Germany

(Received 17 March 2004; accepted in final form 19 May 2004)

We propose that semiflexible polymers in poor solvent collapse in two stages. The first stage is the well-known formation of a dense toroidal aggregate. However, if the solvent is sufficiently poor, the condensate will undergo a second structural transition to a twisted entangled state, in which individual filaments lower their bending energy by additionally orbiting around the mean path along which they wind. This "topological ripening" is consistent with known simulations and experimental results. It connects and rationalizes various experimental observations ranging from strong DNA entanglement in viral capsids to the unusually short pitch of the cholesteric phase of DNA in sperm heads. We propose that topological ripening of DNA toroids could improve the efficiency and stability of gene delivery.

64.70.Nd - Structural transitions in nanoscale materials.
87.15.He - Dynamics and conformational changes.
61.30.Pq - Microconfined liquid crystals: droplets, cylinders, randomly confined liquid crystals, polymer dispersed liquid crystals, and porous systems.

© EDP Sciences 2004