title: Influence of PEGylation on the ability of carboxymethyl-dextran to form complexes with α-lactalbumin.
abstract: Electrostatic interactions between α-lactalbumin (α-lac) and carboxymethyldextran (CMD) in acidic solutions lead to phase-separated complexes. By adding a non-ionic poly(ethylene glycol) (PEG) chain onto the reducing end of CMD, forming carboxymethyl-dextran-block-poly(ethylene glycol) (CMD-b-PEG), the PEG block was hypothesized to reduce interactions with α-lac and promote formation of a micelle-like complex structure. Formation of complexes between α-lac and CMD-b-PEG or α-lac and CMD was determined following acidification by light scattering and electrophoretic mobility. Phase separation, size, and structure of α-lac/CMD-b-PEG complexes were characterized by turbidimetry, dynamic light scattering, and electron microscopy, respectively. Complexes of α-lac/CMD-b-PEG formed at pH values near pH 6, while α-lac/CMD complexes formed at pH 5.5. Both CMD and CMD-b-PEG decreased the charge of α-lac below pH 5.5 and led to phase separation below pH 5. Shift in charge and the critical pH of phase separation were both sensitive to the α-lac to CMD ratio, while the relative amount of CMD-b-PEG did not significantly influence either. Hydrodynamic radii of α-lac/CMD-b-PEG complexes was between 11 and 20 nm, which increased with increasing α-lac to CMD-b-PEG ratio and with decreasing pH. Spheroidal structures of ∼10 nm were also observed in micrographs that were attributed to α-lac/CMD-b-PEG complexes.
authors.affiliation: Purdue University, Department of Food Science, 745 Agriculture Mall Drive, West Lafayette, IN 47907, USA.
authors.forename: Juan
authors.initials: J
authors.lastname: Du
authors.affiliation: Purdue University, Department of Food Science, 745 Agriculture Mall Drive, West Lafayette, IN 47907, USA.
authors.forename: Brad L
authors.initials: BL
authors.lastname: Reuhs
authors.affiliation: Purdue University, Department of Food Science, 745 Agriculture Mall Drive, West Lafayette, IN 47907, USA. Electronic address: joneso@purdue.edu.
authors.forename: Owen G
authors.initials: OG
authors.lastname: Jones
mesh_terms: D003911:Dextrans / Q000737:chemistry*; D007768:Lactalbumin / Q000737:chemistry*; D011092:Polyethylene Glycols / Q000737:chemistry; D011506:Proteins / Q000737:chemistry*
chemical_list: D003911:Dextrans; D011506:Proteins; D011092:Polyethylene Glycols; D007768:Lactalbumin; C014392:carboxymethyl dextran
keywords: Alpha-lactalbumin; Carboxymethyl-dextran; Complex; Complex coacervate core micelle; Copolymer; Poly(ethylene glycol); Polysaccharide; Protein