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bioRxiv · 10.64898/2025.12.09.693115

Compaction and swelling of single stretched DNAs driven by molecular crowding

Gupta, P.·Marko, J. F.·Scolari, V. F.
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Abstract

We present a theory for the effects of osmotic pressure exerted by macromolecular crowders, on a double-stranded DNA or other semiflexible polymer extended by tension. Our results predict the force and crowder-density dependence of the polymer extension. The lowest-order effect is a crowder-dependent compression that counteracts the external stretching force, which can collapse the polymer at a crowder-dependent critical force f*. This compression is dependent on crowder radius r and density{phi} , with higher densities and smaller radii having greater effects on the force-extension curve. At first order in perturbation theory we also find a fluctuation-dependent correction to the depletion volume, which can overwhelm the simple compression effect for large crowders, leading to expansion of the polymer.

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Gupta, P., Marko, J. F., Scolari, V. F.. 2025-12-10. Compaction and swelling of single stretched DNAs driven by molecular crowding. https://doi.org/10.64898/2025.12.09.693115

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