| 1. |
- Holt, Carl, et al.
(författare)
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Mineralisation of soft and hard tissues and the stability of biofluids.
- 2014
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Ingår i: Journal of Structural Biology. - : Elsevier BV. - 1095-8657 .- 1047-8477. ; 185:3, s. 383-396
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Tidskriftsartikel (refereegranskat)abstract
- Evidence is provided from studies on natural and artificial biofluids that the sequestration of amorphous calcium phosphate by peptides or proteins to form nanocluster complexes is of general importance in the control of physiological calcification. A naturally occurring mixture of osteopontin peptides was shown, by light and neutron scattering, to form calcium phosphate nanoclusters with a core-shell structure. In blood serum and stimulated saliva, an invariant calcium phosphate ion activity product was found which corresponds closely in form and magnitude to the ion activity product observed in solutions of these osteopontin nanoclusters. This suggests that types of nanocluster complexes are present in these biofluids as well as in milk. Precipitation of amorphous calcium phosphate from artificial blood serum, urine and saliva was determined as a function of pH and the concentration of osteopontin or casein phosphopeptides. The position of the boundary between stability and precipitation was found to agree quantitatively with the theory of nanocluster formation. Artificial biofluids were prepared that closely matched their natural counterparts in calcium and phosphate concentrations, pH, saturation, ionic strength and osmolality. Such fluids, stabilised by a low concentration of sequestering phosphopeptides, were found to be highly stable and may have a number of beneficial applications in medicine.
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| 2. |
- Ossowski, Sofie, et al.
(författare)
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Aggregation Behavior of Bovine kappa- and beta-Casein Studied with Small Angle Neutron Scattering, Light Scattering, and Cryogenic Transmission Electron Microscopy
- 2012
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 28:38, s. 13577-13589
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Tidskriftsartikel (refereegranskat)abstract
- In the native bovine casein micelle the calcium sensitive caseins (alpha(S1)-, alpha(S2)- and beta-casein) sequester amorphous calcium phosphate in nanometer-sized clusters, whereas the calcium-insensitive K-casein limits the growth of the micelle. In this paper, we further investigate the self-association of kappa- and beta-casein, which are two of the key proteins that control the substructure of the milk casein micelle, using neutron and light scattering techniques and cryogenic transmission electron microscopy. Results demonstrate that K-casein can, apart from the known self-assembly, form amyloid-like fibrils already at temperatures of 25 degrees C when subject to agitation. This extended aggregation behavior of kappa-casein is inhibited by beta-casein, as reported by others. These findings have implications for the structure and stability of casein micelles. The neutron scattering data was used to gain information on the self-assembly structure of kappa-casein. beta-Casein shows similar self-association behavior as kappa-casein, but unlike kappa-casein, the self-association exhibits temperature dependence within the studied temperatures (6 and 25 degrees C). Here, we will discuss our extended study of the known self-assembly of casein in the context of the fibrillation of kappa-casein.
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