Stretching Response of Discrete Semiflexible Polymers
Bibliographic record
Abstract
We demonstrate that semiflexible polymer chains (characterized by a persistence length 𝓁 ) made up of discrete segments or bonds of length b show at large stretching forces a crossover from the standard wormlike chain (WLC) behavior to a discrete-chain (DC) behavior. In the DC regime, the stretching response is independent of the persistence length and shows a different force dependence than in the WLC regime. We perform extensive transfer-matrix calculations for the force-response of a freely rotating chain (FRC) model as a function of varying bond angle γ (and thus varying persistence length) and chain length. The FRC model is a first step toward the understanding of the stretching behavior of synthetic polymers, denatured proteins, and single-stranded DNA under large tensile forces. We also present scaling results for the force response of the elastically jointed chain (EJC) model, that is, a chain made up of freely jointed bonds that are connected by joints with some bending stiffness; this is the discretized version of the continuum WLC model. The EJC model might be applicable to stiff biopolymers such as double-stranded DNA or Actin. Both models show a similar crossover from the WLC to the DC behavior, which occurs at a force f / k B T ∼ 𝓁 / b 2 and is thus (for polymers with a moderately large persistence length) in the piconewton range probed in many AFM experiments. We also give a heuristic simple function for the force−distance relation of a FRC, valid in the global force range, which can be used to fit experimental data. Our findings might help to resolve the discrepancies encountered when trying to fit experimental data for the stretching response of polymers in a broad force range with a single effective persistence length.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".