Purification of sarcoplasmic reticulum vesicles through their loading with calcium phosphate

A technique of purification of sarcoplasmic reticulum was devised through selective loading of the vesicular material with calcium phosphate. In presence of amount of disposable calcium lower than the maximum accumulation capacity of the total vesicular population, we have defined conditions of loading which allow the selection by centrifugation. The results described in this work show that about 30% of the starting material can be isolated as a vesicular population homogenous on the stand of the amount of accumulated cation. The purification is achieved by the removal of calcium by dissociation of the precipitate. Freeze-fracture electron microscopy studies show that the more active fraction when freed of calcium phosphate precipitate displays smooth convex (EF_s) and particulated concave (PF_p) fracture planes. It has been verified that the purification described in this work allows the removal of all the inactive material. The rate of calcium uptake of the selected preparation is about twice as large as that displayed by the starting material. The structural homogeneity of this material and the increase in the activity are good evidence for the purity of the selected sarcoplasmic reticulum vesicles.