Aqueous Liquid-Liquid Phase Separation of Natural and Synthetic Polyguanidiniums.

Autor: Prather LJ; Department of Biomedical Engineering, University of Utah, Salt Lake City, UT 84112, USA. l.jack.prather@gmail.com., Weerasekare GM; Department of Biomedical Engineering, University of Utah, Salt Lake City, UT 84112, USA. mahikaw@yahoo.com., Sima M; Department of Biomedical Engineering, University of Utah, Salt Lake City, UT 84112, USA. ms57@utah.edu., Quinn C, Stewart RJ; Department of Biomedical Engineering, University of Utah, Salt Lake City, UT 84112, USA. russell.stewart@utah.edu.
Jazyk: angličtina
Zdroj: Polymers [Polymers (Basel)] 2019 Apr 09; Vol. 11 (4). Date of Electronic Publication: 2019 Apr 09.
DOI: 10.3390/polym11040649
Abstrakt: Protamines are natural polyguanidiniums, arginine(R)-rich proteins involved in the compaction of chromatin during vertebrate spermatogenesis. Salmine, a protamine isolated from salmon sperm, contains 65 mol% R residues, with positively charged guanidino (Gdm⁺) sidechains, and no other amino acids with ionizable or aromatic sidechains. Salmine sulfate solutions undergo liquid-liquid phase separation (LLPS) with a concentration-dependent upper critical solution temperature (UCST). The condensed liquid phase comprises 50 wt % water and >600 mg·ml - ¹ salmine with a constant 1:2 ratio of sulfate (SO₄² - ) to Gdm⁺. Isothermal titration calorimetry, titrating Na₂SO₄ into salmine chloride above and below the UCST, allowed isolation of exothermic sulfate binding to salmine chloride from subsequent endothermic condensation and exothermic phase separation events. Synthetic random polyacrylate analogs of salmine, with 3-guanidinopropyl sidechains, displayed similar counterion dependent phase behavior, demonstrating that the LLPS of polyguanidiniums does not depend upon subunit sequence or polymer backbone chirality, and was due entirely to Gdm⁺ sidechain interactions. The results provide experimental evidence for like-charge pairing of Gdm⁺ sidechains, and an experimental approach for further characterizing these interactions.
Competing Interests: The authors declare no conflict of interest.
Databáze: MEDLINE
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