Programme

P.53 -- Poster, VCTP-47

Date: Thursday, 4 August 2022

Time: 08:30 - 10:00

Can DNA form twisted bundles in toroidal condensates?

Nhung T. T. Nguyen and Trinh Xuan Hoang

Institute of Physics, Vietnam Academy of Science and Technology

Toroidal structures are the most frequently observed morphology of DNA condensates. While the packing of DNAs inside the toroids can be essentially revealed by experiment, it is much less clear about the global conformations adopted by DNAs in the condensates. In this study, we consider a model of toroidal condensate that corresponds to a twisted bundle arrangement of the chain conformation and compare it to other models which are akin to a spool-like and a constant-curvature wrapping, respectively. It is shown that for the toroid energy consisting of a bending energy and a surface energy term, the twisted bundle model always yields optimal conformations of lower energies than the other models. For the ranges of polymer length and surface tension relevant to DNA condensates, the twist number k* of the optimal twisted bundle toroid is found to vary between 0.84 and 1. To find support for the analytical results, we carried out replica-exchange molecular dynamics (REMD) simulations of stiff polymers with self-attraction. Interestingly, the simulations show that twisted bundle toroids can be obtained in the collapse of these polymers. The twisted bundle conformations, however, are limited to relatively short chains due to the polymeric constraint. For longer chains, the viable toroidal conformations appear to be largely spool-like with some disordered parts.

Presenter: Nguyễn Thị Thùy Nhung