{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,6]],"date-time":"2026-05-06T20:35:43Z","timestamp":1778099743866,"version":"3.51.4"},"reference-count":61,"publisher":"MDPI AG","issue":"22","license":[{"start":{"date-parts":[[2022,11,19]],"date-time":"2022-11-19T00:00:00Z","timestamp":1668816000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"University of Aveiro, CICECO-Aveiro Institute of Materials","award":["UIDB\/5011\/2020"],"award-info":[{"award-number":["UIDB\/5011\/2020"]}]},{"name":"University of Aveiro, CICECO-Aveiro Institute of Materials","award":["UIDP\/50011\/2020"],"award-info":[{"award-number":["UIDP\/50011\/2020"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["IJMS"],"abstract":"<jats:p>Liquid-liquid phase separation underlies the formation of membrane-less organelles inside living cells. The mechanism of this process can be examined using simple aqueous mixtures of two or more solutes, which are able to phase separate at specific concentration thresholds. This work presents the first experimental evidence that mesoscopic changes precede visually detected macroscopic phase separation in aqueous mixtures of two polymers and a single polymer and salt. Dynamic light scattering (DLS) analysis indicates the formation of mesoscopic polymer agglomerates in these systems. These agglomerates increase in size with increasing polymer concentrations prior to visual phase separation. Such mesoscopic changes are paralleled by changes in water structure as evidenced by Attenuated Total Reflection\u2014Fourier Transform Infrared (ATR-FTIR) spectroscopic analysis of OH-stretch bands. Through OH-stretch band analysis, we obtain quantitative estimates of the relative fractions of four subpopulations of water structures coexisting in aqueous solutions. These estimates indicate that abrupt changes in hydrogen bond arrangement take place at concentrations below the threshold of macroscopic phase separation. We used these experimental observations to develop a model of phase separation in aqueous media.<\/jats:p>","DOI":"10.3390\/ijms232214366","type":"journal-article","created":{"date-parts":[[2022,11,21]],"date-time":"2022-11-21T02:52:21Z","timestamp":1668999141000},"page":"14366","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":40,"title":["Mechanism of Phase Separation in Aqueous Two-Phase Systems"],"prefix":"10.3390","volume":"23","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-9670-2634","authenticated-orcid":false,"given":"Amber R.","family":"Titus","sequence":"first","affiliation":[{"name":"Cleveland Diagnostics, 3615 Superior Ave., Cleveland, OH 44114, USA"}]},{"given":"Pedro P.","family":"Madeira","sequence":"additional","affiliation":[{"name":"Centro de Investigacao em Materiais Ceramicos e Compositos, Department of Chemistry, 3810-193 Aveiro, Portugal"}]},{"given":"Luisa A.","family":"Ferreira","sequence":"additional","affiliation":[{"name":"Cleveland Diagnostics, 3615 Superior Ave., Cleveland, OH 44114, USA"}]},{"given":"Vladimir Y.","family":"Chernyak","sequence":"additional","affiliation":[{"name":"Department of Chemistry, Wayne State University, 5101 Cass Avenue, Detroit, MI 48202, USA"},{"name":"Department of Mathematics, Wayne State University, 656 W. Kirby, Detroit, MI 48202, USA"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4037-5857","authenticated-orcid":false,"given":"Vladimir N.","family":"Uversky","sequence":"additional","affiliation":[{"name":"Department of Molecular Medicine and Byrd Alzheimer\u2019s Research Institute, Morsani College of Medicine, University of South Florida, Tampa, FL 33613, USA"}]},{"given":"Boris Y.","family":"Zaslavsky","sequence":"additional","affiliation":[{"name":"Cleveland Diagnostics, 3615 Superior Ave., Cleveland, OH 44114, USA"}]}],"member":"1968","published-online":{"date-parts":[[2022,11,19]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1047","DOI":"10.1126\/science.1223728","article-title":"Cell biology. 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