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Issue 33, 2016
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Revisiting the interpretation of casein micelle SAXS data

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An in-depth, critical review of model-dependent fitting of small-angle X-ray scattering (SAXS) data of bovine skim milk has led us to develop a new mathematical model for interpreting these data. Calcium-edge resonant soft X-ray scattering data provides unequivocal evidence as to the shape and location of the scattering due to colloidal calcium phosphate, which is manifested as a correlation peak centred at q = 0.035 Å−1. In SAXS data this feature is seldom seen, although most literature studies attribute another feature centred at q = 0.08–0.1 Å−1 to CCP. This work shows that the major SAXS features are due to protein arrangements: the casein micelle itself; internal regions approximately 20 nm in size, separated by water channels; and protein structures which are inhomogeneous on a 1–3 nm length scale. The assignment of these features is consistent with their behaviour under various conditions, including hydration time after reconstitution, addition of EDTA (a Ca-chelating agent), addition of urea, and reduction of pH.

Graphical abstract: Revisiting the interpretation of casein micelle SAXS data

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Publication details

The article was received on 10 May 2016, accepted on 28 Jul 2016 and first published on 28 Jul 2016

Article type: Paper
DOI: 10.1039/C6SM01091A
Citation: Soft Matter, 2016,12, 6937-6953
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    Revisiting the interpretation of casein micelle SAXS data

    B. Ingham, A. Smialowska, G. D. Erlangga, L. Matia-Merino, N. M. Kirby, C. Wang, R. G. Haverkamp and A. J. Carr, Soft Matter, 2016, 12, 6937
    DOI: 10.1039/C6SM01091A

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