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

摘要

The composition of bovine casein micelles was ana- lyzed by ~31P magic angle spinning solid-state nuclear magnetic resonance spectroscopy. By looking at iso- tropic and anisotropic ~31P chemical shift parameters, resonance line shapes, the combination of single-pulse and ~1H to ~31P cross-polarization spectra, and compari- son with spectra for various model compounds com- bined with multiple-component simulation and itera- tive 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 phos- phates as well as phosphates from K-casein and the Ca~2+-binding phosphoserines from α_s1-, α_s2-, and β-ca- sein. This information is discussed in relation to previ- ous knowledge and various models for the colloid for- mation.