In vitro albumin binding on apatite crystals from developing enamel.

Serum proteins have never been described in enamel as they have been in dentin or bone where they are bound to apatite, may be because of the specific organic/crystal relationship which makes enamel crystals different from the other biological apatites. In the present study, crystals from bovine developing enamel have been isolated to test their ability to bind serum albumin in vitro. Those crystals, although naturally coated with enamelins proved to be able to bind gold-labelled serum albumin. Consequently, free binding sites exist at the surface of these biological crystals. It is suggested that the 'sheath' surrounding crystals in TEM observations is the fixed aspect of a dynamic process in vivo. Finally, the lack of blood proteins in enamel cannot be attributed to a particular property of enamel crystallites.