Summary: | We examine the effects of the external force, torque, temperature, confinement, and excluded volume interactions (EVIs) on the stability of the helical configuration of an intrinsically straight semiflexible biopolymer inside a cylindrical cell. We find that to stabilize a helix, the confinement from both ends of the cell is more effective than a uniaxial force. We show that under a uniaxial force and in absence of confinement from bottom of the cell, a stable helix is very short. Our results reveal that to maintain a low pitch helix, a torque acting at both ends of the filament is a necessity, and the confinement can reduce the required torque to less than half making it much easier to form a stable helix. Moreover, we find that thermal fluctuations and EVIs have little impact on the stability of a helix. Our results can help understand the existence of the helix and ring configurations of some semiflexible biopolymers, such as MreB homologs, inside a rod-shaped bacteria.
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