Direct visualization of heterogeneous molecular diffusion and interfacial barriers during condensate ripening
Year: 2026
Type: preprint
Abstract: Ripening processes are ubiquitous in various multiphase systems, such as emulsions, crystals, alloys, and biomolecular condensates. This phenomenon significantly affects the morphology of a system and its resulting properties through the growth of dispersed domains at the expense of others without direct contact. Though ripening has been studied for centuries, a molecule-level visualization of this process has never been captured, significantly hindering our fundamental understanding. Here, we use single-molecule tracking techniques to visualize and quantify the diffusion dynamics of poly-L-lysine (PLL) during a rapid ripening process, where ATP droplet condensates transform into fibrillar crystals. We successfully observe preferential motion of PLL within both the dilute and condensate phases toward growing crystals and uncover previously unknown molecular dynamics near interfaces. At condensate interfaces, PLL molecules encounter energetic barriers that trap their motions and restrict their escape from condensates. Near crystal fibers, we discover clear heterogeneity in molecular dynamics, which can be classified into Brownian, confined, and superdiffusive motions. To explain this result, simulations and a physical model reveal the formation of water lubrication layers on crystal fibers, which enables PLL molecules to slide along fibers with superdiffusive motion before crossing the layer and becoming immobilized on fibers with confined motion. These results provide molecular-level insight for understanding the fundamental ripening process and answering open questions across diverse nonequilibrium systems.
Source: ChemRxiv
Institution: Northwestern University
Language: English
Subfield: Physical and Theoretical Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7213926441