Determination of Viscosity of Biomolecular Condensates

Biomolecular condensates produced by liquid-liquid phase separation (LLPS) have become a central player in many cellular processes. Viscosity, one of the material properties of biomolecular condensates, is used to describe mobility and can reflect the resistance to fluid flow. The viscosity of these in vivo is typically quantified by measuring the diffusion coefficients of fluorescently labeled components and correlating them with viscosity using the Stokes-Einstein equation. Recent studies have shown that progressive increases in the viscosity of biomolecular cohesions are often associated with the protofibrils that form the basis of diseases associated with aging. Thus, quantitative studies of cohesive material denaturation are expected to reveal these mechanisms and facilitate therapeutic advances in these diseases.

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Viscosity reflects the macroscopic nature of biomolecular condensates, where liquid condensates are less viscous and gel-like condensates are more viscous. Our team of experts is dedicated to the quantitative study and direct measurement of the viscosity of biomolecular condensates. Here, CD BioSciences offers classical particle tracking technique to measure the viscosity of biomolecular condensates.

We provide detailed procedures to measure the mean square displacement of tracer microspheres in biomolecular condensates and to detect the apparent viscosity of the condensates.

(1) Sample preparation. Samples are prepared by adding passivated polystyrene beads to the buffer and then adding protein/RNA to form the condensate. The beads used for particle tracking must be coated with a passive/inert polymer that prevents non-specific interactions between the tracer particles and the molecules in the condensate.

(2) Sample imaging. We provide video microscopy to track exogenous spherical particles diffusing in biomolecular condensates and to image the motion of the particles for a set duration.

(3) Analytical imaging. We use particle tracking software or custom programs implementing tracking algorithms to analyze the imaging series. The mean square displacement of the trajectory calculation is calculated and plotted based on the position of the output particles as a function of time.

Advantages of Particle Tracking Technique

• A simple, useful and reliable technique for estimating condensate viscosity.
• No special instrument setup or fluorescent markers are required.
• Provides unbiased information about viscosity of condensates.
• Can be used to track nanoparticles and individual molecules in living cells using advanced labeling techniques and super-resolution microscopy.
• Combined with agglomeration analysis that measures the inverse capillary velocity, the surface tension of condensates can be inferred.

We provide robust single-particle tracking experiments to measure the apparent viscosity of the condensate, further reflecting the mobility of the biomolecular condensate. It constitutes an imaging of the diffusion of beads in the condensate in a limited time. In addition, our team of experts is developing unique techniques to quantify the viscosity of biomolecular condensates without the effect of surface wetting effects. 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.