Fig. 4. OPN in chicken eggshell.

(A) Immunoblotting for chicken eggshell OPN. Lane 1, total soluble protein extract from decalcified eggshell (1 M HCl); lane 2, acidic eggshell matrix proteins, not retained on CM Sephadex (see Methods). (B) Immunohistochemistry (pink) for OPN protein showing its incorporation and distribution throughout the full thickness of the eggshell (decalcified here). Brackets indicate areas in outermost PL with concentrated OPN amounts. (C) Immunogold labeling for OPN (arrows) and TEM showing the association of OPN with a lacy network of organic matrix dispersed throughout the PL of the eggshell. (B) and (C) are from demineralized shell samples, resulting in the artifactual partial collapse of an organic matrix structure.