Hydrogen Bond Arrangement Is Shown to Differ in Coexisting Phases of Aqueous Two-Phase Systems.

Pedro P Madeira,Vladimir N Uversky,Elizabeth K Mann,Jay Adin Mann,Alexander I Belgovskiy,William V Meyer,Luisa A Ferreira,Anthony E Smart,Boris Y Zaslavsky,Amber R Titus

doi:10.3390/biom11121787

Abstract

Analysis by attenuated total reflection–Fourier transform infrared spectroscopy shows that each coexisting phase in aqueous two-phase systems has a different arrangement of hydrogen bonds. Specific arrangements vary for systems formed by different solutes. The hydrogen bond arrangement is shown to correlate with differences in hydrophobic and electrostatic properties of the different phases of five specific systems, four formed by two polymers and one by a single polymer and salt. The results presented here suggest that the arrangement of hydrogen bonds may be an important factor in phase separation.

Highlights

Accepted: 26 November 2021Aqueous two-phase systems (ATPSs) are formed in mixtures of two different polymers, such as polyethylene glycol (PEG) and Ficoll, Dextran or polyvinylpyrrolidone (PVP), or a single polymer (e.g., PEG or PVP) and an inorganic salt, such as sodium sulfate or phosphate, in water when their concentrations exceed a certain threshold
The purpose of the present study is to explore whether the arrangements of hydrogen bonds in water differs in the coexisting phases of Accepted: November 2021Aqueous two-phase systems (ATPSs) formed by two polymers and by a single polymer and inorganic salt
We explored whether these differences are correlated with the solvent properties of the phases established previously [33,35] and investigated in this work for two additional ATPSs

Summary

Introduction

Aqueous two-phase systems (ATPSs) are formed in mixtures of two different polymers, such as polyethylene glycol (PEG) and Ficoll, Dextran or polyvinylpyrrolidone (PVP), or a single polymer (e.g., PEG or PVP) and an inorganic salt, such as sodium sulfate or phosphate, in water when their concentrations exceed a certain threshold. The separation of an aqueous mixture of two polymers into two coexisting phases was suggested [1–3] to serve as a model of a liquid–liquid phase separation (LLPS). Synthetic polymers differ from biological macromolecules, such as proteins and nucleic acids, the underlying physical principles of phase separation may well be the same. The associative LLPS in aqueous media involves the formation of coacervates, i.e., complexes of oppositely charged polyelectrolytes forming a concentrated phase, which separates from the diluted phase.

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