Surface Electrostatics Govern the Emulsion Stability of Biomolecular Condensates

Timothy J. Welsh, Georg Krainer, Jorge R. Espinosa, Jerelle A. Joseph, Akshay Sridhar, Marcus Jahnel, William E. Arter, Kadi L. Saar, Simon Alberti, Rosana Collepardo-Guevara, Tuomas P.J. Knowles

Research output: Contribution to journalArticlepeer-review

36 Scopus citations


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 (US)
Pages (from-to)612-621
Number of pages10
JournalNano Letters
Issue number2
StatePublished - Jan 26 2022
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • General Chemistry
  • Condensed Matter Physics
  • Mechanical Engineering
  • Bioengineering
  • General Materials Science


  • FUS
  • Liquid−liquid phase separation
  • colloid stability
  • microfluidics
  • zeta potential


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