Alcian blue staining of proteoglycans in polyacrylamide gels using the "critical electrolyte concentration" approach.

A method is described here for Alcian blue staining of proteoglycans in polyacrylamide gels; this is illustrated using extracts obtained from bovine corneal stroma. Other available methods for visualization of proteoglycans can produce nonspecific staining and frequently a high background in the gel; with a "critical electrolyte concentration" approach, specific staining against a clear background can be obtained.

Bovine corneal stroma contains a structural glycoprotein located in the gap region of the collagen fibrils.

Treatment of bovine corneal stroma using SDS-containing extracting solutions removes a 135,000 MW glycoprotein from the main collagen framework of the tissue. Low-angle synchrotron X-ray diffraction patterns obtained from corneas extracted in this way indicate that the glycoprotein has been removed from the gap regions of the collagen fibrils and is thus an important structural component of the corneal stroma. The glycoprotein (GP 135) shares a number of properties with one of the subunits of type VI collagen, but tests have so far failed to establish their identity.

The organisation of collagen fibrils in the human corneal stroma: a synchrotron X-ray diffraction study.

The low angle equatorial diffraction pattern from the human corneal stroma shows that the collagen fibrils have two preferred orientations: inferior-superior and medial-lateral. We have not observed this effect in any other animal species. This arrangement, which was found to be more pronounced in the posterior than in the anterior stroma, was maintained until the last 1 to 2 millimetres before the limbus at which point uniaxial orientation was observed along the circumference. Our interpretation of this result is that most collagen fibrils wrap around the circumference of the cornea and relatively few continue radially into the limbus where uniformity of collagen fibril diameters is lost.