Metastable intermediates in the condensation of semiflexible polymers.
Motivated by results from an earlier Brownian dynamics simulation for the collapse of a single, stiff polymer in a poor solvent [B. Schnurr, F. C. MacKintosh, and D. R. M. Williams, Europhys. Lett. 51, 279 (2000)] we calculate the conformational energies of the intermediate (racquet) states suggested by the simulations. In the absence of thermal fluctuations (at zero temperature) the annealed shapes of these intermediates are well-defined in certain limits, with their major structural elements given by a particular case of Euler's elastica. In appropriate units, a diagram emerges that displays the relative stability of all states, tori, and racquets. We conclude that, in marked contrast to the collapse of flexible polymers, the condensation of semiflexible or stiff polymers generically proceeds via a cascade through metastable intermediates, the racquets, towards a ground state, the torus or ring, as seen in the dynamical simulations.
Department of Physics and Biophysics Research Division, University of Michigan, Ann Arbor, Michigan 48109-1120, USA. bernhard.schnurr@wiezmann.ac.il
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