title: Effect of the surface charge on partitioning of chemically modified bovine serum albumin in aqueous two-phase systems.
abstract: In order to assess the influence of the protein charge on its partitioning in poly(ethyleneglycol)/salt aqueous two-phase systems, three bovine serum albumin derivatives with isoelectric points of 5.50, 6.20 and 6.85 were obtained by chemical modification of the protein with a soluble carbodiimide and glycine O-methyl ester and separation of the derivative mixture by liquid isoelectric focusing. The modification reaction was mild enough to preserve the tertiary structure of the proteins, as judged by circular dichroism and fourth derivative UV spectra. The surface hydrophobicity of the bovine serum albumin derivatives was identical, as measured by hydrophobic interaction chromatography. Partitioning of the derivatives in poly(ethyleneglycol)/phosphate and poly(ethyleneglycol)/citrate aqueous two-phase systems between pH 5.2 and 6.5 indicates that partitioning is not dependent on the protein charge in the poly(ethyleneglycol)/salt systems studied.
authors.affiliation: Cátedra de Microbiología Industrial y Biotecnología, Facultad de Farmacia y Bioquímica Junín 956, Buenos Aires, Argentina.
authors.forename: A
authors.initials: A
authors.lastname: Obludziner
authors.forename: S A
authors.initials: SA
authors.lastname: Camperi
authors.forename: O
authors.initials: O
authors.lastname: Cascone
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002021:Buffers; D002234:Carbodiimides / Q000737:chemistry; D002417:Cattle; D005591:Chemical Fractionation; D002942:Circular Dichroism; D019343:Citric Acid / Q000737:chemistry; D004591:Electrophoresis, Polyacrylamide Gel; D007525:Isoelectric Focusing; D007526:Isoelectric Point; D008969:Molecular Sequence Data; D010710:Phosphates / Q000737:chemistry; D011092:Polyethylene Glycols / Q000737:chemistry; D017434:Protein Structure, Tertiary; D012710:Serum Albumin, Bovine / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism; D013056:Spectrophotometry, Ultraviolet; D013431:Sulfates / Q000737:chemistry; D013499:Surface Properties
chemical_list: D002021:Buffers; D002234:Carbodiimides; D010710:Phosphates; D013431:Sulfates; D012710:Serum Albumin, Bovine; D019343:Citric Acid; D011092:Polyethylene Glycols