ABSTRACT
Bovine ß-lactoglobulin (ß-LG) was conjugated with fructo-oligosaccharides (FOS) by Maillard reaction to investigate the relationship among antigenicity, functional properties, and conformational changes of ß-LG. When comparing the antigenicity of ß-LG conjugated with FOS at different ratios, the lowest antigenicity of ß-LG was observed at a ratio of 1:4, which was about 7 times lower than that of the control ß-LG. Thus, the ratio of 1:4 was chosen to conjugate ß-LG with FOS, and the functional properties and conformational changes of ß-LG-FOS conjugates were investigated. The functional properties (solubility, emulsifying ability, and emulsion stability) of ß-LG were enhanced after conjugation with FOS. Furthermore, the molecular weight of ß-LG increased from 18.4 to 19.9 kDa after conjugation with FOS, as evaluated by sodium dodecyl sulfate-PAGE and mass spectrometry. Partial unfolding of ß-LG occurred after conjugation with FOS, as reflected by the quenching of fluorescence, the red-shift of fluorescence spectra, and the increase of ß-strands, which may contribute to the decrease in antigenicity and the improvement of functional properties.
Subject(s)
Oligopeptides/chemistry , Animals , Antigens/immunology , Cattle , Electrophoresis, Polyacrylamide Gel , Emulsions , Enzyme-Linked Immunosorbent Assay , Fructose/chemistry , Fructose/immunology , Fructose/metabolism , Mass Spectrometry , Oligopeptides/immunology , Oligopeptides/metabolism , Oligosaccharides/chemistry , Oligosaccharides/immunology , Oligosaccharides/metabolism , Protein Conformation , Protein Stability , SolubilityABSTRACT
Our previous research indicated that dynamic high-pressure microfluidization (DHPM) had a significant effect on the antigenicity of ß-lactoglobulin (ß-LG). In this study, aggregation and conformational changes subjected to DHPM (0.1-160 MPa) were investigated in relation to antigenicity. When DHPM pressure increased from 0.1 to 80 MPa, disaggregation of ß-LG samples and partial unfolding of the molecule were accompanied by an increase in ß-LG antigenicity, which was reflected in the decrease of particle size, increase of free sulfhydryl (SH) contents and ß-strands contents, and slight exposure of aromatic amino acid residues. At pressures above 80 MPa, the reaggregation of ß-LG may contribute to the decrease in antigenicity, which was reflected by an increase in particle size, the formation of aggregates, a decrease of in SH and ß-strands contents, and slight changes in aromatic amino acid residues. Aggregation and conformational changes of ß-LG under DHPM was related to its antigenicity.
