G E L ELECTROPHORESIS OF MUCINS.
I
Gel Electrophoresis of Mucous Glycoproteins. I. Effect of Gel Porosity" Kenneth G. Holden,-/ Nelson C. F. Yim, Lee J. Griggs, and Jerry A. Weisbach
Great molecular size, the capacity to form viscoelastic gels or very viscous solutions at relatively low concentration, and a high degree of polydispersity are properties of mucous glycoproteins that make their characterization exceedingly difficult. With a view toward developing a suitable micro method of characterization, the electrophoresis of some representative mucins was studied in gels with a range of sieving properties. Canine serum served as a control protein mixture and human fibrinogen was used as a model protein of high molecular weight and extended shape. These substances along with unfractionated canine submaxillary mucin, and purified bovine, ovine, and porcine submaxillary mucins were investigated in gels composed of: 7.5 % acrylamide, 3.0 %
ABSTRACT:
T
he glycoproteins of epithelial mucous secretions represent a class of biological macromolecules whose degree of purity and characterization in general are not readily established by the usual physical methods (Gibbons, 1966). Besides having a high molecular weight (ca. loe), mucous glycoproteins are extended, thread-like molecules, and their effective molecular size is much greater than that of globular proteins of the same molecular weight. A further increase in molecular domain occurs at low ionic strength because of their high charge density (Bettelheim et al., 1962). Even at low concentrations mucous glycoproteins form very viscous solutions; at moderate concentrations (ca. 1 %) viscoelastic gels result. There is also a tendency for these molecules to adhere tenaciously to supporting media used in some fractionation procedures. Furthermore, all mucous glycoprotein preparations that have been carefully examined have been found to be polydisperse. This complicates the interpretation of separation and purification procedures since such materials can theoretically always be subfractionated. As part of projected studies on the chemistry and biosynthesis of mucous glycoproteins, we required a sensitive method for characterizing and assessing the purity of relatively small mucin samples (
