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Partitioning of low molecular combination peptides in aqueous two‐phase systems of poly(ethylene glycol) and dextran in the presence of small amounts of K 2 HPO 4 /KH 2 PO 4 buffer at 293 K: Experimental results and predictions
Author(s) -
Großmann Christoph,
Tintinger Ralf,
Zhu Jiandung,
Maurer Gerd
Publication year - 1998
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/(sici)1097-0290(19981220)60:6<699::aid-bit7>3.0.co;2-i
Subject(s) - tripeptide , ethylene glycol , chemistry , aqueous solution , partition coefficient , phenylalanine , amino acid , dextran , phase (matter) , chromatography , organic chemistry , biochemistry
Buffered aqueous two‐phase systems are effective extraction systems for separating amphoteric hydrocarbons like, for example, polypeptides from aqueous phases. The design and basic engineering of such processes requires the knowledge of the liquid–liquid equilibrium. The study presented here aims to contribute to the development of methods to predict the partitioning of peptides in aqueous two‐phase systems. Experimental results are reported for the partitioning of small amounts (≈0.001 g solute per gram of solution) of low molecular combination peptides of glycine, L ‐glutamic acid, L ‐phenylalanine, and L ‐lysine (9 dipeptides, gly‐glu, gly‐phe, gly‐lys, glu‐gly, phe‐gly, phe‐glu, lys‐gly, lys‐glu, lys‐phe; 7 tripeptides, gly‐gly‐phe, gly‐phe‐gly, glu‐gly‐phe, phe‐gly‐gly, lys‐gly‐lys, lys‐glu‐gly, lys‐phe‐lys) in aqueous two‐phase systems of high molecular weight dextran (molecular weight about 500,000) and poly(ethylene glycol) (molecular weight about 6,000 and 35,000, respectively) in the presence of small amounts (about 0.05 mol/kg) of K 2 HPO 4 /KH 2 PO 4 buffer at about 293 K. The new data are compared to predictions. Partition coefficients are predicted applying a group contribution excess Gibbs energy model. The model is an osmotic virial equation. It uses surface fractions to encounter for the probability of interactions between solutes. All model parameters were taken from the literature. They were determined exclusively from experimental data for the phase forming systems and for the partitioning of amino acids and their di‐ and tripeptides (containing only a single amino acid), but no experimental data for the partitioning of combinations peptides were used. In most cases predicted partition coefficients agree favourably with the experimental data. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 699–711, 1998.