Transient helix formation in charged semiflexible polymers without confinement effects

Abstract

Switching on generic interactions e.g. the Coulomb potential or other long ranged spherically symmetric repulsive interactions between monomers of bead-spring model of a semi-flexible polymer induce instabilities in a semiflexible polymer chain to form transient helical structures. Our proposed mechanism could explain the spontaneous emergence of helical order in stiff (bio-) polymers as a chain gets charged from a neutral state. But since the obtained helical structures dissolve away with time, hydrogen bonding (or other additional mechanisms), would be required to form stabilized helical structures as observed in nature (such as in biological macro-molecules). The emergence of the helix is independent of the molecular details of the monomer constituent. The key factors which control the emergence of the helical structure is the persistence length and the charge density. We have avoided using torsional potentials to obtain the transient helical structures. Moreover, we can drive the semiflexible polymer to form helices in a recurring manner by periodically increasing and decreasing the effective charge of the monomers. If the two polymer ends are tethered to two surfaces separated by a distance equal to the contour length of the polymeric chain, which could be in the range 10 nm–μ, the life time of the helical structures formed is increased.

Rigidity Dictates Spontaneous Helix Formation of Thermoresponsive Colloidal Chains in Poor Solvent

“…Hence, we use H2 to identify local helical order. 52,53 A semiflexible polymeric chain, with Δ cl = 0, is without helical order and has significantly lower values of both H2 and H4 as compared to a chain with helical order (refer SI III-B Figure S13).…”

“…However, if the handedness varies along the chain - for example, if half of the chain is right handed, and the other half is left-handed, H 4 will have values close to zero but H 2 will remain nonzero. Hence, we use H 2 to identify local helical order. , A semiflexible polymeric chain, with Δ cl = 0, is without helical order and has significantly lower values of both H 2 and H 4 as compared to a chain with helical order (refer SI III-B Figure S13).…”

Soft matter research in India

“…In their study of the morphologies and interactions in semiflexible polymeric systems, Mitra and Chatterji [11] use a bead-spring model to demonstrate the emergence of transient helical structures under the combined influence of spherically symmetric long-range repulsions between the constituent monomers and the ubiquitous thermal fluctuations. While the aforementioned helix formation depends strongly on persistence length and charge density, it is insensitive to the molecular details of the monomers.…”