Determination of Interfacial Tension of Biomolecular Condensates

Surface tension is defined as a measure of the collective intermolecular forces that drive the minimisation of surface area to reduce the interfacial energy between two liquids. At the liquid-liquid interface, the interfacial tension determines many of the properties of biomolecular coalescents. For example, liquid-like coalescers adopt a spherical shape to minimise the surface area under the influence of interfacial tension and to minimise the overall free energy of the system. In addition, interfacial tension promotes the agglomeration of two meeting liquid-like condensates. Other effects, such as Ostwald ripening, are also controlled by interfacial tension. Following in vitro and in vivo induction of liquid-liquid phase separation (LLPS), the growth/coarsening of bioagglomerates is controlled by Ostwald maturation and agglomeration. Interfacial tension also controls the interaction between immiscible biocondensates.

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In addition to viscosity, the surface tension of biomolecular condensates can play a key physiological role and is another important parameter for characterising the strength of molecular interactions in fluids. The measurement of surface tension relies heavily on the kinetics of fusion between the two condensates. Here, CD BioSciences offers the following two strategies to measure the surface tension of biomolecular condensates.

• Measurement of the Surface Tension/Viscosity Ratio

The ratio of viscosity to surface tension is known as the inverse capillary velocity. Our team of experts develop various types of manipulation, including the use of light traps and shear stress to increase the frequency of organelle or droplet encounters to improve statistical events for quantitative fusion analysis. We offer improved optical tweezers and fluorescence recovery after photobleaching (FRAP) methods to measure the viscosity of biomolecular condensates and further calculate surface tension based on inverse capillary velocity.

It should to be noted that this strategy does not provide information about viscosity or surface tension, only the ratio between these two quantities.

• Direct Measurement of Surface Tension

We offer a right-angle imaging method to quantify the change in height of a class of liquids over time due to gravity. This method is widely used to determine the surface tension of liquid-like droplets and nucleoli in raw foams in vitro. In addition, we are also develop micro pipette aspiration (MPA) to quantify the surface tension of biomolecular condensates.

The advantages of using optical tweezers to quantify the surface tension of biomolecular condensates are as follows:

• Elimination of surface adhesion effects present when using microscopy to analyse fusion events at the coalescent surface.
• Allow fast and efficient collection of data from multiple fusion events for statistical analysis.
• Provide higher temporal resolution of the process.
• Do not require fluorescent labelling of molecules.

CD BioSciences has an advanced optical tweezers method to measure the fusion relaxation time and inverse capillary velocity of biomolecular condensates in vitro, which is a powerful tool for assessing their material properties. This method provides higher process time resolution and allows practical and efficient collection of large numbers of fusion events. If you have any special requirements for our services, please feel free to contact us. We are looking forward to working together with your attractive projects.