TRANSMISSION ELECTRON-MICROSCOPY STUDIES ON PIG GASTRIC MUCIN AND ITSINTERACTIONS WITH CHITOSAN

Transmission electron microscopy has been employed to visualize the mo lecular structure and organization of a highly purified preparation of pig gastric mucin (molar mass M similar to 9x10(6) g/mol, as determin ed by low speed sedimentation equilibrium), prepared for microscopy by two completely independent methods. Samples were prepared for imaging by air drying on mica (in the presence of 50% glycerol) as well as cr itical point drying in acetone/CO2. The data appear consistent with th e accepted linear model for mucins, and are consistent with regions of variable degrees of glycosylation along the polypeptide backbone chai n, with the overall conformation that of a loose or random coil. The b ehaviour of this mucin in a dilute solution mixture with the potential mucoadhesive polymer chitosan (M similar to 160,000 g/mol) was then e xplored, and a clear interaction was demonstrated, consistent with dil ute solution measurements using sedimentation velocity analysis in the analytical ultracentrifuge.