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

Hans-Olof Johansson, Gunnar Karlström, Folke Tjerneld

Research output: Contribution to journalArticlepeer-review

50 Citations (Scopus)


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 (NaClO4 and Na2SO4) on the partitioning of a positively charged polypeptide, poly(Lys, Trp), was very strong. With NaClO4 the polypeptide was quantitatively partitioned to the polymer rich phase while with Na2SO4 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.
Original languageEnglish
Pages (from-to)315-325
JournalBiochimica et Biophysica Acta. General Subjects
Issue number3
Publication statusPublished - 1997

Bibliographical note

The information about affiliations in this record was updated in December 2015.
The record was previously connected to the following departments: Theoretical Chemistry (S) (011001039), Biochemistry and Structural Biology (S) (000006142)

Subject classification (UKÄ)

  • Theoretical Chemistry
  • Biological Sciences


  • Polymer
  • Phase separation
  • Peptide
  • Aqueous two-phase system
  • Temperature-induced phase separation


Dive into the research topics of 'Temperature-induced phase partitioning of peptides in water solutions of ethylene oxide and propylene oxide random copolymers'. Together they form a unique fingerprint.

Cite this