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).
Rheological properties of patatin gels compared with ß-lactoglobulin, ovalbumin, and glycinin
Creusot, N.P. ; Wierenga, P.A. ; Laus, M.C. ; Giuseppin, M.L.F. ; Gruppen, H. - \ 2011
Journal of the Science of Food and Agriculture 91 (2011)2. - ISSN 0022-5142 - p. 253 - 261.
heat-induced gelation - sunflower helianthus-annuus - potato-tuber protein - ionic-strength - whey proteins - egg-white - soy glycinin - physicochemical properties - interchange reactions - induced denaturation
BACKGROUND: The thermal unfolding and rheological properties of patatin gels were compared with those of commonly used proteins (ß-lactoglobulin, ovalbumin, glycinin). RESULTS: A significant difference between these proteins was observed in both the denaturation temperature (59 °C for patatin; about 20 °C lower than the other proteins) and the onset temperature of gel formation (50–60 °C, compared to 70–85 °C for the other proteins). At low ionic strength the minimal concentration was only 6% (w/v) for patatin, compared to 8–11% for the other proteins. This effect was attributed to the relatively high exposed hydrophobicity of patatin as determined by hydrophobic interaction chromatography. For gels compared at ‘iso-strength’, the frequency dependence was found to be close to identical, while small differences were observed in the strain at fracture. CONCLUSIONS: Patatin was found to form gels with comparable small-deformational rheological properties as typical food proteins. In addition, at concentrations where the elastic modulus was similar for all proteins, the frequency and strain dependence were also comparable. From this it is concluded that patatin is a promising protein to be used in food applications as a gelling agent.
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
Strong impact of ionic strength on the kinetics of fibrilar aggregation of bovine beta-lactoglobulin
Arnaudov, L.N. ; Vries, R.J. de - \ 2006
Biomacromolecules 7 (2006)12. - ISSN 1525-7797 - p. 3490 - 3498.
heat-induced gelation - atomic-force microscopy - globular-proteins - induced denaturation - light-scattering - gels - ph - temperature - growth - model
We investigate the effect of ionic strength on the kinetics of heat-induced fibrilar aggregation of bovine -lactoglobulin at pH 2.0. Using in situ light scattering we find an apparent critical protein concentration below which there is no significant fibril formation for all ionic strengths studied. This is an independent confirmation of our previous observation of an apparent critical concentration for 13 mM ionic strength by proton NMR spectroscopy. It is also the first report of such a critical concentration for the higher ionic strengths. The critical concentration decreases with increasing ionic strength. Below the critical concentration mainly "dead-end" species that cannot aggregate anymore are formed. We prove that for the lowest ionic strength this species consists of irreversibly denatured protein. Atomic force microscopy studies of the morphology of the fibrils formed at different ionic strengths show shorter and curvier fibrils at higher ionic strength. The fibril length distribution changes non-monotonically with increasing ionic strength. At all ionic strengths studied, the fibrils had similar thicknesses of about 3.5 nm and a periodic structure with a period of about 25 nm.
Heat-induced formation of ordered structures of ovalbumin at low ionic strength studied by small angle X-ray scattering
Weijers, M. ; Hoog, E.H.A. de; Cohen Stuart, M.A. ; Visschers, R.W. ; Barneveld, P.A. - \ 2005
Colloids and Surfaces. A: Physicochemical and Engineering Aspects 270-271 (2005)1-3. - ISSN 0927-7757 - p. 301 - 308.
neutron-scattering - induced denaturation - light-scattering - aqueous colloids - globular protein - ph - aggregation - molecules - gels
Small angle X-ray scattering (SAXS) has been performed on native ovalbumin solutions and heated ovalbumin systems at neutral pH and low ionic strength. In native ovalbumin solutions there is a partial ordering, where the interparticle distance (dmax) scales with the protein concentration (C) as d max ~ C-0.28. This exponent indicates that the ovalbumin monomers behave as a uniform distribution of charged spheres in solution. The q-dependent scattering intensity of ovalbumin aggregates can be well described by a form factor of rods. The dependence of dmax for aggregates on the protein concentration was found to be dmax ~ C-0.51, this scaling behavior is in good agreement with that theoretically derived for the distribution of spaces in a random network of straight fibers. The existence of a well-defined interparticle distance between aggregates is confirmed by cryo-TEM. The scattering profiles of native and aggregated ovalbumin were successfully fitted including both form factor and structure factor, using the preferred distance (L), a measure of disorder (¿/L), and the radius (R or a) as fitting parameters.
Multiple steps during the formation of beta-lactoglobulin fibrils
Arnaudov, L.N. ; Vries, R.J. de; Ippel, J.H. ; Mierlo, C.P.M. van - \ 2003
Biomacromolecules 4 (2003)6. - ISSN 1525-7797 - p. 1614 - 1622.
atomic-force microscopy - heat-induced gelation - particle gel formation - globular-proteins - induced denaturation - thermal-denaturation - amyloid fibrils - ovalbumin gels - ionic-strength - ph
In this study, the heat induced fibrilar aggregation of the whey protein beta-lactoglobulin is investigated at low pH and at low ionic strength. Under these circumstances, tapping mode atomic force microscopy results indicate that the fibrils formed have a periodic structure with a period of about 25 nm and a thickness of one or two protein monomers. Fibril formation is followed in situ using light scattering and proton NMR techniques. The dynamic light scattering results show that the fibrils that form after short heating periods (up to a few hours) disintegrate upon slow cooling, whereas fibrils that form during long heating periods do not disintegrate upon subsequent slow cooling. The NMR results show that even after prolonged heating an appreciable fraction of the protein molecules is incorporated into fibrils only when the beta-lactoglobulin concentration is above approximately 2.5 wt %. The data imply multiple steps during the heat induced formation of beta-lactoglobulin fibrils at low pH and at low ionic strength: (partly) denatured protein monomers are either incorporated into fibrils or form instead a low molecular weight complex that is incapable of forming fibrils. Fibril formation itself also involves (at least) two steps: the reversible formation of linear aggregates, followed by a slow process of "consolidation" after which the fibrils no longer disintegrate upon slow cooling.