No abstract

Liquid‐Liquid phase separation has emerged as fundamental process underlying the formation of biomolecular condensates. Insights into the composition and structure of biomolecular condensates is, however, complicated by their molecular complexity and dynamics. Here, we introduce an improved spatially‐resolved NMR experiment that enables quantitative analysis of the physico‐chemical composition of multi‐component biomolecular condensates in equilibrium and label‐free. Application of spatially‐resolved NMR to condensates formed by the Alzheimer's disease‐associated protein Tau demonstrates decreased water content, exclusion of the molecular crowding agent dextran, presence of a specific chemical environment of the small molecule DSS, and ≈150‐fold increased concentration of Tau inside the condensate. The results suggest that spatially‐resolved NMR can have a major impact in understanding the composition and physical chemistry of biomolecular condensates.

Biomolecular phase separation plays a key role in spatial organization of cellular activities. Dynamic formation and rapid component exchange between phase separated cellular bodies and their environment are crucial for...

Nuclear magnetic resonance (NMR) spectroscopy can also be used for the measurement of the Fick diffusion coefficient.

We introduce a new approach for resolving the NMR spectra of mixtures that relies on the mutual diffusion of dissolved species when a concentration gradient is established within the NMR tube. This is achieved by cooling down a biphasic mixture of triethylamine and deuterated water below its mixing temperature, where a single phase is expected. Until equilibrium is reached, a gradient of concentration, from 'pure' triethylamine to 'pure' water, establishes within the tube. The amount of time required to reach this equilibrium is controlled by the mutual diffusion coefficient of both species. Moreover, a gradient of concentration exists for each additional compound dissolved in this system, related to the partition coefficient for that compound in the original biphasic state. Using slice selective experiments, it was possible to measure these concentration gradients and use them to separate signals from all the present species. We show the results acquired for a mixture composed of n-octanol, methanol, acetonitrile and benzene and compare them with those obtained by pulse field gradient NMR. Copyright © 2016 John Wiley & Sons, Ltd.