Surface Electrostatics Govern the Emulsion Stability of Biomolecular Condensates

Research output: Contribution to journalResearch articleContributedpeer-review


  • Timothy J Welsh - , University of Cambridge (Author)
  • Georg Krainer - , University of Cambridge (Author)
  • Jorge R Espinosa - , University of Cambridge (Author)
  • Jerelle A Joseph - , University of Cambridge (Author)
  • Akshay Sridhar - , University of Cambridge (Author)
  • Marcus Jahnel - , Dynamics of Biomolecules (Research Group), Biotechnology Center, Max Planck Institute of Molecular Cell Biology and Genetics (Author)
  • William E Arter - , University of Cambridge (Author)
  • Kadi L Saar - , University of Cambridge (Author)
  • Simon Alberti - , Chair of Cellular Biochemistry, Biotechnology Center (Author)
  • Rosana Collepardo-Guevara - , University of Cambridge (Author)
  • Tuomas P J Knowles - , University of Cambridge (Author)


Liquid-liquid phase separation underlies the formation of biological condensates. Physically, such systems are microemulsions that in general have a propensity to fuse and coalesce; however, many condensates persist as independent droplets in the test tube and inside cells. This stability is crucial for their function, but the physicochemical mechanisms that control the emulsion stability of condensates remain poorly understood. Here, by combining single-condensate zeta potential measurements, optical microscopy, tweezer experiments, and multiscale molecular modeling, we investigate how the nanoscale forces that sustain condensates impact their stability against fusion. By comparing peptide-RNA (PR25:PolyU) and proteinaceous (FUS) condensates, we show that a higher condensate surface charge correlates with a lower fusion propensity. Moreover, measurements of single condensate zeta potentials reveal that such systems can constitute classically stable emulsions. Taken together, these results highlight the role of passive stabilization mechanisms in protecting biomolecular condensates against coalescence.


Original languageEnglish
Pages (from-to)612-621
Number of pages10
JournalNano letters
Issue number2
Publication statusPublished - 10 Jan 2022

External IDs

Scopus 85123385700
WOS 000745242500001
Mendeley de0c9c6c-7fd4-3408-ad0a-326babfb1262


Research priority areas of TU Dresden

DFG Classification of Subject Areas according to Review Boards


  • Biomolecular Condensates, Emulsions, Proteins/chemistry, RNA/chemistry, Static Electricity, FUS, zeta potential, Liquid-liquid phase separation, colloid stability, microfluidics, Liquid−liquid phase separation, Fus, Zeta potential, Colloid stability, Microfluidics