[Isolation of a phosphoprotein from preeruptive dentin from molars of domestic pigs (Sus scrofa domesticus)]. / Isolierung von Phosphoprotein aus Dentin präeruptiver Molaren des Hausschweins (Sus scrofa domesticus).

Isolation of a phosphoprotein from dentin of pre-eruptive molars of Sus scrofa domesticus. A protein with a relative molecular mass of 60,000 kD was isolated from dentin of unerupted pig molars. The electrophoretically homogeneous protein was identified as phosphoprotein with a specific staining procedure. The phosphorylation degree is 75%. The amino-acid composition and the molecular mass were compared with values of other species.

Effect of phosphoprotein on precipitation and crystallization of calcium phosphate salts. An in vitro study using an agar gel matrix model.

The effect of dentin phosphoprotein (DPP) over a wide concentration range on precipitation and crystallization of calcium phosphate was studied in supersaturated solutions at pH 7.8 and 25 degrees C with a gel matrix model. The protein was isolated and purified from dentin of unerupted pig teeth. Depending on the incubation conditions the protein showed opposite effects on the life-time as well as on the relative particle size of amorphous calcium phosphate (ACP). This may be due to different conformation states of the protein. In the presence of Mg2+ the inhibitory effect of the protein on the lifetime is pronounced. An inhibition of the amount of ACP precipitate and the crystal growth rate by the phosphoprotein seems to be independent of its conformation state.

Studies of calcium phosphate formation in artificial matrices.

An in vitro system is described allowing turbidimetric measurements of calcium phosphates (or other sparingly soluble salts) formed by one-dimensional double diffusion in an agar gel matrix. The basic conditions were investigated over a wide concentration range of calcium and phosphate, and characterized by IR spectra, transmission electron microscopy and selected parameters of the turbidity curve, i.e. the maximal turbidity, the life time of the amorphous calcium phosphate, the optical dispersion and the crystallization rate. The system was also applied to well known effectors, like F-, Mg2+, pyrophosphate and citrate ions as well as two compounds of biological matrices, hyaluronidate and chondroitin-4-sulphate. The results agree well with those observed in aqueous solutions, showing that the overall process in the gel matrix is identical. The economical and efficient method is suitable for large-scale kinetic determinations of compounds affecting nucleation, precipitation and transformation processes of calcium phosphates and other precipitating systems.