section_path: Composition/Salts, minerals, and vitamins/Calcium phosphate structure
section_name: Calcium phosphate structure
paragraph_text: Calcium phosphate structure
  
  For many years the most widely accepted theory of the structure of a micelle was that it was composed of spherical casein aggregates, called submicelles, that were held together by calcium phosphate linkages. However, there are two recent models of the casein micelle that refute the distinct micellular structures within the micelle.
  
  The first theory, attributed to de Kruif and Holt, proposes that nanoclusters of calcium phosphate and the phosphopeptide fraction of beta-casein are the centerpiece to micellar structure. Specifically in this view unstructured proteins organize around the calcium phosphate, giving rise to their structure, and thus no specific structure is formed.
  
  Under the second theory, proposed by Horne, the growth of calcium phosphate nanoclusters begins the process of micelle formation, but is limited by binding phosphopeptide loop regions of the caseins. Once bound, protein-protein interactions are formed and polymerization occurs, in which K-casein is used as an end cap to form micelles with trapped calcium phosphate nanoclusters.
  
  Some sources indicate that the trapped calcium phosphate is in the form of Ca (PO);whereas others say it is similar to the structure of the mineral brushite, CaHPO ·2H O.