Comparison of Heat-Induced Aggregation of Globular Proteins
Delahaije, R.J.B.M. ; Wierenga, P.A. ; Giuseppin, M.L.F. ; Gruppen, H. - \ 2015
Journal of Agricultural and Food Chemistry 63 (2015)21. - ISSN 0021-8561 - p. 5257 - 5265.
laser-light scattering - beta-lactoglobulin - ionic-strength - induced denaturation - reaction-kinetics - whey proteins - neutral ph - in-situ - ovalbumin - gels
Typically, heat-induced aggregation of proteins is studied using a single protein under various conditions (e.g., temperature). Because different studies use different conditions and methods, a mechanistic relationship between molecular properties and the aggregation behavior of proteins has not been identified. Therefore, this study investigates the kinetics of heat-induced aggregation and the size/density of formed aggregates for three different proteins (ovalbumin, ß-lactoglobulin, and patatin) under various conditions (pH, ionic strength, concentration, and temperature). The aggregation rate of ß-lactoglobulin was slower (>10 times) than that of ovalbumin and patatin. Moreover, the conditions (pH, ionic strength, and concentration) affected the aggregation kinetics of ß-lactoglobulin more strongly than for ovalbumin and patatin. In contrast to the kinetics, for all proteins the aggregate size/density increased with decreasing electrostatic repulsion. By comparing these proteins under these conditions, it became clear that the aggregation behavior cannot easily be correlated to the molecular properties (e.g., charge and exposed hydrophobicity).
Modification of Ovalbumin with Fructooligosaccharides: Consequences for Network Morphology and Mechanical Deformation Responses
Munialo, C.D. ; Ortega, R.G. ; Linden, E. van der; Jongh, H.H.J. de - \ 2014
Langmuir 30 (2014)46. - ISSN 0743-7463 - p. 14062 - 14072.
protein gels - rheological properties - beta-lactoglobulin - maillard reaction - pea protein - neutral ph - mixed gels - gelation - aggregation - perception
The Maillardation of proteins has been used as a natural alternative to improve its functionality by covalent coupling of proteins with saccharides. However, the impact of Maillard reaction on the structural aspects of protein networks and, as a consequence, the mechanical breakdown properties of the gel networks has not been reported. The objective of this study was to evaluate how the attachment of linear oligo-sugar moieties onto ovalbumin affects its aggregation, network morphology, and consequently the mechanical deformation properties including the ability of the networks to elastically store energy in this material. To potentially alter the morphology of the network structure, ovalbumin was modified by conjugating some of its amino groups with fructooligosaccharide (FOS) moieties via the Maillard reaction. It was demonstrated that the attachment of FOS to ovalbumin does not affect the integrity of the secondary and tertiary structure as characterized using circular dichroism and tryptophan fluorescence. Differences in the network morphology were observed by scanning electron microscopy for FOS-modified ovalbumin variants. Upon increased modification, the microstructure of the gels had more and larger pores and had thinner strands than nonmodified variants. Evaluation of the large deformation properties of the gels demonstrated that FOS-modified gels were less strong and less brittle and showed lower stiffness than nonmodified variants. The recoverable energy (elastically stored energy) of gels reduced with an increase in the degree of modification. The results show that the attachment of FOS to ovalbumin alters the structural and mechanical (large) breakdown properties of the protein gels. The consequences of the alteration of the network structure and large deformation properties of FOS-modified ovalbumin offer opportunities to efficiently design food materials with desirable techno-functional applications
Characteristics and Effects of Specific Peptides on Heat-Induced Aggregation of ß-Lactoglobulin
Kosters, H.A. ; Wierenga, P.A. ; Vries, R.J. de; Gruppen, H. - \ 2011
Biomacromolecules 12 (2011)6. - ISSN 1525-7797 - p. 2159 - 2170.
whey-protein isolate - bacillus-licheniformis protease - induced denaturation - thermal-stability - neutral ph - kinetics - gelation - hydrolysis - identification - fractions
A bovine ß-lactoglobulin hydrolysate, obtained by the hydrolysis by the Glu specific enzyme Bacillus licheniformis protease (BLP), was fractionated at pH 7.0 into a soluble and an insoluble fraction and characterized by LC-MS. From the 26 peptides identified in the soluble fraction, five peptides (A[f97–112] = [f115–128], AB[f1–45], AB[f135–157], AB[f135–158], and AB[f138–162]) bound to ß-lactoglobulin at room temperature. After heating of ß-lactoglobulin in the presence of peptides, eight peptides were identified in the pellet formed, three of them belonging to the previously mentioned peptides. Principle component analysis revealed that the binding at room temperature (to ß-lactoglobulin) was related to the total hydrophobicity and the total charge of the peptides. The binding to the unfolded protein could not be attributed to distinct properties of the peptides. The presence of the peptides caused a 50% decrease in denaturation enthalpy (from 148 ± 3 kJ/mol for the protein alone to 74 ± 2 kJ/mol in the presence of peptides), while no change in secondary structure or denaturation temperature was observed. At temperatures
Net Charge Affects Morphology and Visual Properties of Ovalbumin Aggregates
Weijers, M. ; Broersen, K. ; Barneveld, P.A. ; Cohen Stuart, M.A. ; Hamer, R.J. ; Jongh, H.H.J. de; Visschers, R.W. - \ 2008
Biomacromolecules 9 (2008)11. - ISSN 1525-7797 - p. 3165 - 3172.
heat-induced denaturation - beta-lactoglobulin - light-scattering - protein aggregation - globular protein - amyloid fibrils - ionic-strength - neutral ph - gelation - prediction
The effect of ovalbumin net charge on aggregate morphology and visual properties was investigated using chromatography, electrophoresis, electron microscopy, and turbidity measurements. A range of differently charged ovalbumin variants (net charge ranging from ¿1 to ¿26 at pH 7) was produced using chemical engineering. With increasing net charge, the degree of branching and flexibility of the aggregates decreased. The turbidity of the solutions reflected the aggregate morphology that was observed with transmission electron microscopy. Increasing the stiffness of the aggregates transformed the solutions from turbid to transparent. Artificially shielding the introduced net charge by introducing salt in the solution resulted in an aggregate morphology that was similar to that for low-net-charge variants. The morphology of heat-induced aggregates and the visual appearance of the solutions were significantly affected by net charge. We also found that the morphology of ovalbumin aggregates can be rapidly probed by high-throughput turbidity experiments.