 termine et al 
 . first demonstrated that sequential dissociative extraction and fractionation procedures with protease inhibitors could provide a convenient approach for the study of mineral compartment constituents . 
 the primary extraction regimen used 4 m guanidine hcl to remove most of the protein from the nonmineralized phase of bone . 
 subsequently , edta - guanidine was used to remove the mineral - phase components . 
 these methods discriminate on the basis of physical - chemical association with a mineral phase rather than on the specific gene products of a particular cell . in the present discussion emphasis 
 is directed at a group of divalent cation binding proteins isolated from the mineral compartment of bone . 
 the localization , synthesis , and chemical characteristics of osteonectin , bone sialoproteins i and ii , and bone acidic glycoprotein-75 are discussed and offered as possible sites for perturbation by the environment with lead exposure.imagesfigure 1.figure 2.figure 2.figure 2.figure 3.figure 3.figure 3.figure 3 . 
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