Protein partitioning in aqueous two-phase systems based on phase-forming polymers is strongly affected by the net charge of the protein, but a thermodynamic description of the charge effects has been hindered by conflicting results. Many of the difficulties could be because of problems in isolating
Aqueous two-phase systems containing urea: Influence of protein structure on protein partitioning
✍ Scribed by Christian Rämsch; Lutz B. Kleinelanghorst; Esther A. Knieps; Jörg Thömmes; Maria-Regina Kula
- Publisher
- John Wiley and Sons
- Year
- 2000
- Tongue
- English
- Weight
- 200 KB
- Volume
- 69
- Category
- Article
- ISSN
- 0006-3592
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✦ Synopsis
During recombinant E. coli fermentation with high-expression levels inclusion bodies are often formed. Aqueous two-phase systems have been successfully used in the presence of urea for the initial recovery step of inclusion bodies from E. coli. Basic studies of the complex interactions are lacking. For a systematic study of protein partitioning in the presence of urea we selected T4-lysozyme mutants with different thermal stability as a model. The stabilization of these variants by phase components was investigated measuring the fluorescence emission of tryptophan residues in the protein. Protein structure was stabilized at pH 7 in the order of S0(4)(2-) >> PEG = Dextran > H(2)O. The conformation of proteins was shown to have a strong influence on the partitioning in aqueous two-phase systems. Tryptophan and its homologuous di- and tripeptdides were partitioned in similar phase systems to normalize for contribution from hydrophobic interactions.
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