Article| Volume 84, ISSUE 6, P1310-1319, June 2001

Colloidal Calcium Phosphates in Casein Micelles Studied by Slow-Speed-Spinning 31P Magic Angle Spinning Solid-State Nuclear Magnetic Resonance

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      The composition of bovine casein micelles was analyzed by 31P magic angle spinning solid-state nuclear magnetic resonance spectroscopy. By looking at isotropic and anisotropic 31P chemical shift parameters, resonance line shapes, the combination of single-pulse and 1H to 31P cross-polarization spectra, and comparison with spectra for various model compounds combined with multiple-component simulation and iterative fitting procedures, we were able to identify and quantify a variety of inorganic and organic phosphates in the micelles. These include phosphates from mobile and immobile inorganic hydroxyapatite-type phosphates as well as phosphates from κ-casein and the Ca2+-binding phosphoserines from αs1−, αs2−, and β-casein. This information is discussed in relation to previous knowledge and various models for the colloid formation.

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