(187c) Quantifying Nucleation in and of Biomolecular Condensates

Keywords: Biophysics, Thermodynamics, Phase separation, Nucleation, Diffusion, Modeling

Main body

Various biomolecules including proteins, peptides, and nucleic acids are known to undergo phase separation both in vivo and in vitro. In phase separation, a solution demixes into two phases: the first phase is enriched in the biomolecule, the constituents of which are known as condensates, and the second one is depleted in it. Understanding and predicting the biophysical properties of condensates represents a topic of immediate scientific interest.

While the literature focuses on the thermodynamics of phase separation, little is known about the associated kinetics, i.e., the nucleation and growth of condensates. This is largely because nucleation is too fast to be measured by conventional means, necessitating the development of advanced monitoring techniques [1].

Here we propose a novel approach of quantifying the nucleation of condensates by leveraging the inverse phenomenon, i.e., the nucleation of dilute phase (of voids) in sufficiently large condensates upon temperature change. This phenomenon has previously been studied experimentally [2], and we here introduce a mechanistic diffusion-nucleation model to quantify the nucleation of voids [3]. Building on Classical Nucleation Theory (CNT), we show how to obtain the nucleation kinetics of condensates from the measured kinetics of the voids. We further compared the predicted nucleation behavior of condensates with experiments in microdroplets and observed a close agreement. This indicates that the nucleation of voids in condensates can be used as a proxy to quantify the nucleation of condensates, hence opening up a pathway for future studies of condensate dynamics.

References

[1] SF Shimobayashi et al.: Nucleation landscape of biomolecular condensates. Nature (2021), 599, 503–506.

[2] NA Erkamp et al.: Spatially non-uniform condensates emerge from dynamically arrested phase separation. Nat. Commun. (2023), 14, 684.

[2] LT Deck, NA Erkamp, TPJ Knowles: Quantifying nucleation in and of biomolecular condensates, manuscript in preparation.