Temperature-induced phase partitioning of peptides in water solutions of ethylene oxide and propylene oxide random copolymers

• Published in: Biochimica et biophysica acta Vol. 1335; no. 3; pp. 315 - 325
• Main Authors: Johansson, Hans-Olof, Karlström, Gunnar, Tjerneld, Folke
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 06.06.1997
• Subjects: Aqueous two-phase system; Biologi; Biological Sciences; Chemical Sciences; Epoxy Compounds - chemistry; Ethylene Oxide - chemistry; Glycine - chemistry; Kemi; Models, Chemical; Natural Sciences; Naturvetenskap; Peptide; Peptides - chemistry; Phase separation; Polymer; Polymers; Salts; Solutions; Temperature; Temperature-induced phase separation; Teoretisk kemi; Theoretical Chemistry; Water - chemistry; Polymer; Temperature-induced phase separation; Peptide; Phase separation; Aqueous two-phase system
• ISSN: 0304-4165; 0006-3002; 1872-8006; 1878-2434
• DOI: 10.1016/S0304-4165(96)00150-X

A thermoseparating random copolymer (Ucon 50-HB-5100) composed of (50%) ethylene oxide and (50%) propylene oxide has been used to form an aqueous two-phase system by heating the polymer-water solution above the cloud point of the copolymer. In the formed two-phase system a water rich top phase is in equilibrium with an aqueous polymer rich bottom phase. The partitioning of amino acids and peptides in this aqueous two-phase system has been studied. Hydrophobic peptides (containing aromatic amino acids) were strongly partitioned to the polymer rich phase, while hydrophilic peptides were enriched in the water rich phase. The effect of temperature on the partitioning was investigated and a decreased partitioning to the polymer rich phase was obtained upon temperature increase. The effect of two salts (NaClO 4 and Na 2SO 4) on the partitioning of a positively charged polypeptide, poly(Lys, Trp), was very strong. With NaClO 4 the polypeptide was quantitatively partitioned to the polymer rich phase while with Na 2SO 4 the polypeptide was partitioned to the water rich phase. Model calculations based on a modified Flory-Huggins theory have been performed to better understand the experimental behavior.