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Scaling Relations of Multicomponent Phase Coexistence Boundaries

Daoyuan Qian1, Julia Acker2, Rob M. Scrutton1, Charlotte M. Fischer1, Seema Qamar1, Tomas Sneideris1, Alexander Borodavka2, and Tuomas P. J. Knowles1,*

  • 1Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom
  • 2Department of Chemical Engineering and Biotechnology, University of Cambridge, Philippa Fawcett Drive, Cambridge CB3 0AS, United Kingdom

  • *Contact author: tpjk2@cam.ac.uk
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PRX Life 4, 013026 – Published 2 March, 2026

DOI: https://doi.org/10.1103/t2v5-49k4

Abstract

Multicomponent phase-separating molecular systems play a key role as membraneless organelles in living cells. Phase diagrams are indispensable for probing the concentration-dependent behavior of these condensates, yet their interpretation has remained largely qualitative due to challenges of modeling complex, multicomponent interactions. Here, we present a generic framework for quantitative analysis and interpretation of phase diagrams. We derive an analytical expression for the phase boundary normal vector, which reveals two distinct scaling regimes: one for associative phase separation, characterized by a power-law scaling analogous to mass-action kinetics that allows for direct extraction of dense phase solute molar ratios, and another for condensate dissolution, where an exponential scaling quantifies three-body repulsion effects triggered by the addition of a new component. We analyze a wide range of experimentally measured phase diagrams, covering proteins NSP5, NSP2, FUS, Whi3, G3BP1, and antimicrobial peptides, and we demonstrate that the additional quantitative insights can aid the mechanistic interpretation of their phase behavior.

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This article appears in the following collection:

Collection on Physics of Biomolecular Condensates

From the fundamentals of phase separation, dynamics and structure of condensates in biological settings, to advanced imaging methods, this special collection presented by PRX Life showcases exciting and timely work on the physics of biomolecular condensates.

This Invited Collection is coordinated by PRX Life Associate Editor Christoph Weber, in consultation with Jerelle Joseph, Simon Alberti, and Tanja Mittag. Every article published in this collection underwent a rigorous peer review process, adhering to the same high standards applied to all papers handled by the journal. The PRX Life editorial team managed the peer review and made all editorial decisions.

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PRX Life 4, 013026– Published 2 March, 2026
  • Received 17 November 2024
  • Accepted 3 September 2025
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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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