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Coil-helix transition in macromolecules. II. Changes in chain size
Karthik C Sinha1, Alexey A Gavrilov1, Artem M Rumyantsev1
1Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27606, USA.
The Journal of Chemical Physics
|August 12, 2026
Summary
Macromolecular coil-to-helix transitions alter chain dimensions by changing local geometry and stiffness. Our study reveals six regimes governing chain size based on helicity and fragment length, confirmed by molecular dynamics simulations.
Area of Science:
- Polymer Physics
- Biophysics
- Computational Biology
Background:
- Macromolecular transitions from coil to helix significantly impact chain dimensions.
- Understanding these transitions is crucial for predicting polymer behavior.
Purpose of the Study:
- To develop a theoretical framework predicting macromolecular dimensions during coil-to-helix transitions.
- To investigate the influence of helicity degree and helical fragment length on chain size.
Main Methods:
- Application of the wormlike (persistent) chain model.
- Development of a minimal coarse-grained molecular dynamics model.
- Analysis of scaling arguments to construct a conformational diagram.
Main Results:
- A conformational diagram with six distinct regimes for end-to-end distance was established.
- Molecular dynamics simulations quantitatively validated the theoretical framework.
- Non-monotonic behavior of end-to-end distance was observed due to competing effects.
Conclusions:
- The developed framework accurately captures how helix geometry and stiffness control macromolecular dimensions.
- The approach demonstrates generality across different helical structures (α, π, 1-7 helices).
- Competition between local compactization and increased stiffness dictates chain behavior.
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