Physics

Viscosity

Wetting

Nanotechnology

Organic chemistry

Biological system

Membrane

Biomolecule

Biology

Physical chemistry

Pipette

Composite material

Fluorescence recovery after photobleaching

Aqueous solution

Chemistry

Materials science

Phase (matter)

Chromatography

Biochemistry

Surface tension

Thermodynamics

Biophysical Reports

The material properties of biomolecular condensates have been suggested to play important biological and pathological roles. Despite the rapid increase in the number of biomolecules identified that undergo liquid-liquid phase separation, quantitative studies and direct measurements of the material properties of the resulting condensates have been severely lagging behind. Here, we develop a micropipette-based technique that uniquely, to our knowledge, allows quantifications of both the surface tension and viscosity of biomolecular condensates, independent of labeling and surface-wetting effects. We demonstrate the accuracy and versatility of this technique by measuring condensates of LAF-1 RGG domains and a polymer-based aqueous two-phase system. We further confirm our measurements using established condensate fusion and fluorescence recovery after photobleaching assays. We anticipate the micropipette-based technique will be widely applicable to biomolecular condensates and will resolve several limitations regarding current approaches.

Surface tension and viscosity of protein condensates quantified by micropipette aspiration