A mechanism for reversible mesoscopic aggregation in liquid solutions

• Published in: Nature communications 2019-05, Vol.10 (1), p.2381-2381, Article 2381
• Main Authors: Chan, Ho Yin, Lubchenko, Vassiliy
• Format: Article
• Language: English
• Subjects: 119/118; 631/57/2266; 639/301/1034/1036; Droplets; Humanities and Social Sciences; Inclusions; Internal pressure; multidisciplinary; Ostwald ripening; Proteins; Science; Science (multidisciplinary); Variation
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-019-10270-5

Solutions of proteins and other molecules exhibit puzzling, mesoscopically sized inclusions of a solute-rich liquid, well outside the region of stability of the solute-rich phase. This mesoscopic size is in conflict with existing views on heterophase fluctuations. Here we systematically work out a microscopic mechanism by which a metastable solute-rich phase can readily nucleate in a liquid solution. A requisite component of the mechanism is that the solute form long-lived complexes with itself or other molecules. After nucleated in this non-classical fashion, individual droplets grow until becoming mechanically unstable because of a concomitant drop in the internal pressure, the drop caused by the metastability of the solute-rich phase. The ensemble of the droplets is steady-state. In a freshly prepared solution, the ensemble is predicted to evolve in a way similar to the conventional Ostwald ripening, during which larger droplets grow at the expense of smaller droplets. Solutions of proteins and other molecules can host puzzling, solute-rich inclusions of mesoscopic dimensions. Here the authors report a mechanism by which mesoscopic clusters can nucleate and ripen, requiring that the solute form long-lived complexes, with implications for biologically and industrially relevant systems.