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Active transport as a mechanism of microphase selection in biomolecular condensates

Le Qiao1,*, Peter Gispert1, Lukas S. Stelzl2,3, and Friederike Schmid1,†

  • *Contact author: le.qiao@uni-mainz.de
  • †Contact author: friederike.schmid@uni-mainz.de
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Phys. Rev. Research 8, 033345 – Published 21 September, 2026

DOI: https://doi.org/10.1103/wk2j-3bz9

Abstract

The size and organization of biomolecular condensates formed by liquid-liquid phase separation are set by multiple cellular mechanisms that are not yet fully understood. Here, we identify a transport-driven mechanism: Stochastic binding of phase-separating proteins to cytoskeletal motor proteins, followed by active redistribution along filament networks, generates an effective long-range repulsion that arrests coarsening and selects a finite condensate size. A minimal diffusion-transport model, analyzed by linear stability theory and three-dimensional simulations, reveals a transition from macroscopic to microphase separation at remarkably low binding/release fractions, corresponding to minute motor-bound populations. Tuning motor binding rates b or transport velocities enables sublinear control of condensate sizes (L∼b−1/4) from a few hundred nanometers up to the micron scale. The selected length scale is robust to the intrinsic shot noise of the binding-release reactions. In anisotropic cytoskeletal environments, transport asymmetry drives morphological transitions from spherical to cylindrical condensates, independently of the thermodynamic parameters. This mechanism provides a versatile, spatiotemporally programmable route to condensate organization and informs the design of synthetic active emulsions with tunable architectures.

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Phys. Rev. Research 8, 033345– Published 21 September, 2026
  • Received 29 October 2025
  • Accepted 27 August 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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