Living Helices in Fluctuating Polymer Chains: Cooperative Nucleation, Dynamics, and Lifetime
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arXiv
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| Format: | Preprint |
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2026
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| _version_ | 1866916064464470016 |
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| author | Bagchi, Biman |
| author_facet | Bagchi, Biman |
| contents | Helical segments in polymer chains are often transient, finite, and dynamically evolving, yet their origin and stability remain incompletely understood. Here we develop a minimal coarse-grained statistical-mechanical theory that explains how such living helices emerge in fluctuating polymer systems. Using a three-state model with cooperative interactions, we show that helix formation proceeds through a multistep nucleation mechanism. An initial constrained pre-nucleus forms first, followed by cooperative stabilization that promotes the growth of finite helical segments. The resulting free-energy landscape naturally favors marginally stable helices whose size is determined by a competition between cooperative gains and nonlinear penalties arising from stiffness, torsional strain, and solvent fluctuations. By formulating the dynamics as a stochastic process in segment size, we derive analytical expressions for both formation times and lifetimes within a mean first-passage framework. For representative parameters relevant to flexible polymers and peptide segments, the theory predicts characteristic timescales in the nanosecond to sub-microsecond range. The present analysis supports a view of living helices as finite, mobile excitations whose stability is controlled by cooperativity, boundary motion, and solvent-induced fluctuations. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2605_30868 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Living Helices in Fluctuating Polymer Chains: Cooperative Nucleation, Dynamics, and Lifetime Bagchi, Biman Soft Condensed Matter Helical segments in polymer chains are often transient, finite, and dynamically evolving, yet their origin and stability remain incompletely understood. Here we develop a minimal coarse-grained statistical-mechanical theory that explains how such living helices emerge in fluctuating polymer systems. Using a three-state model with cooperative interactions, we show that helix formation proceeds through a multistep nucleation mechanism. An initial constrained pre-nucleus forms first, followed by cooperative stabilization that promotes the growth of finite helical segments. The resulting free-energy landscape naturally favors marginally stable helices whose size is determined by a competition between cooperative gains and nonlinear penalties arising from stiffness, torsional strain, and solvent fluctuations. By formulating the dynamics as a stochastic process in segment size, we derive analytical expressions for both formation times and lifetimes within a mean first-passage framework. For representative parameters relevant to flexible polymers and peptide segments, the theory predicts characteristic timescales in the nanosecond to sub-microsecond range. The present analysis supports a view of living helices as finite, mobile excitations whose stability is controlled by cooperativity, boundary motion, and solvent-induced fluctuations. |
| title | Living Helices in Fluctuating Polymer Chains: Cooperative Nucleation, Dynamics, and Lifetime |
| topic | Soft Condensed Matter |
| url | https://arxiv.org/abs/2605.30868 |