scholarly journals Liquid–liquid phase separation of N-isopropylpropionamide aqueous solutions above the lower critical solution temperature

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Kenji Mochizuki ◽  
Tomonari Sumi ◽  
Kenichiro Koga
Keyword(s):  
Phase Separation ◽  
Liquid Phase ◽  
Aqueous Solutions ◽  
Lower Critical Solution Temperature ◽  
Liquid Phase Separation ◽  
Solution Temperature ◽  
Critical Solution Temperature ◽  
Liquid Liquid Phase Separation

scholarly journals Aqueous Liquid-Liquid Phase Separation of Natural and Synthetic Polyguanidiniums

Polymers ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 649 ◽  
Author(s):  
Prather ◽  
Weerasekare ◽  
Sima ◽  
Quinn ◽  
Stewart
Keyword(s):  
Phase Separation ◽  
Liquid Phase ◽  
Liquid Phase Separation ◽  
Solution Temperature ◽  
Titration Calorimetry ◽  
Polymer Backbone ◽  
Critical Solution Temperature ◽  
Upper Critical Solution Temperature ◽  
Positively Charged ◽  
Liquid Liquid Phase Separation

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.

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