Year: 2025
Type: article
Abstract: Phase separation is fundamental to cellular organization, yet early events driving this process remain poorly characterized. ATP is highly concentrated in platelet dense granules, where it coexists with divalent cations. Here, we reconstitute ATP phase separation and use nuclear magnetic resonance (NMR) to discover a 1:2 stoichiometric complex between Mg2+ and ATP. Using a modified NMR pulse sequence of diffusion-ordered spectroscopy (DOSY), we accurately evaluate the size of Mg2+–ATP nanoclusters, and identify them as pre-transitional intermediates that grow in hydrodynamic radius at increasing Mg2+ concentration. Excess Mg2+ beyond the specific ratio promotes hydration and charge neutralization of the nanoclusters, resulting in the formation of a system-spanning network. The process is characteristic of phase separation coupled to percolation, a mechanism further validated by complementary techniques. Our work reveals how stoichiometric imbalance between interacting components regulates phase transition kinetics and dictates the physical properties of the resulting condensate. Studying the phase separation of small molecule systems provides a simplified framework for elucidating assembly pathways that may be obscured in macromolecular systems, but most studies focus on protein- or RNA-based condensates. Here, using nuclear magnetic resonance, the authors reveal that ATP, in the presence of Mg²⁺, undergoes phase separation coupled to percolation (PSCP), where the formation of 1:2 Mg²⁺–ATP nanoclusters precedes system-spanning networks and macroscopic condensation.
Source: Communications Chemistry
Authors: Zihan Li, Tairan Yuwen, Chun Tang
Language: English
Subfield: Organic Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $3,690
Awards: G4243641284, G8742973581
OpenAlex ID: W4416535512