Approach for intestinal mucins is to subject the tissue to several rounds of extraction and then purify the glycoproteins as subunits after reduction of the extraction residue. Other isolation procedures may lead to selective loss of the insoluble species or, where for example vigorous mechanical treatment is used, the isolation of undefined fragments. To isolate mucins from tissue, the mucosa is preferably removed from the underlying connective tissue. The extracts are then dialysed against e.g. 10 vols. The laboratory with little experience in carbohydrate analysis may benefit from using the slot-blot technique developed by Thornton et al.
Mucins chromatograph in the void volume of most commercially available gels.
The chromatographic process is perturbed by the presence of large amounts of DNA, which usually also elutes in the void volume and mucins and DNA are thus not separated. Mucins can usually also be subfractionated into distinct populations using ion-exchange chromatography and agarose gel electrophoresis of the cognate subunits. PAGE is not recommended with oligomeric mucins or even their subunits since the large molecules do not penetrate the gel well. Ion-exchange chromatography has a higher capacity than electrophoresis and is thus the first choice in preparative work. Eperience in ion-exchange chromatography works better with mucin subunits than with whole mucins.