resumo
Phase diagrams were determined for aqueous two-phase systems (ATPSs) formed by different paired combinations of Dextran (Dex-75), Ficoll-70, polyethylene glycol (PEG-8000), hydroxypropyl starch (PES-100), and Ucon50HB5100 (a random copolymer of ethylene glycol and propylene glycol) all containing 0.15 M NaCl in 0.01 M phosphate buffer, pH 7.4, at 23 degrees C. Partition coefficients of a series of dinitropherylated (DNP) amino acids with aliphatic side-chains were studied in all the ATPSs at particular polymer concentrations. Free energies of transfer of a methylene group between the coexisting phases, Delta G(CH2) were determined as measures of the difference between the hydrophobic character of the phases. Furthermore, partition coefficients of tryptophan (Trp) and its di- and tri-peptides and a set of p-nitrophenyl (NP)-monosaccharides were measured in all the two-phase systems, and the data obtained compared with the Delta G(CH2) values obtained in the systems. It was established that for eight out of 10 of two-phase systems of different polymer compositions the partition coefficients for Trp peptides correlate well with the Delta G(CH2) values. Similar correlations for NP-monosaccharides were valid for seven out of 10 two-phase systems. These observations indicate that the difference between the hydrophobic characters of the coexisting phases represented by the Delta G(CH2) value cannot be used as a single universal measure for comparison of the ATPSs of different polymer compositions. (C) 2008 Elsevier B.V. All rights reserved.
palavras-chave
SOLVATION ENERGY RELATIONSHIP; BIPHASIC SYSTEMS; RELATIVE HYDROPHOBICITY; POLYETHYLENE-GLYCOL; ORGANIC-MOLECULES; METHYLENE GROUP; PARTITION; ACID; PROTEIN; PHASES
categoria
Biochemistry & Molecular Biology; Chemistry
autores
Madeira, PP; Teixeira, JA; Macedo, EA; Mikheeva, LM; Zaslavsky, BY
nossos autores
