Off-the-shelf glycoprotein detection methods

The biological importance of glycoproteins has only partially translated into a wealth of detection reagents and kits. Commercial products are available, says UCSD's Ajit Varki, "But in general, the availability of reagents for the world of glycobiology is not as broad as standard molecular biology." Here are some basic off-the-shelf options:

1. Glycan-specific gel stains

Several companies sell glycoprotein-specific staining reagents based on the oxidation of sugars to aldehydes in the presence of periodate. You can then detect aldehydes via a variety of staining reagents, either in a test tube, on a gel, or following blotting.

Invitrogen's Pro-Q Emerald 300 Glycoprotein Gel Stain Kit ($160) detects glycans via a fluorescent dye, as does Sigma-Aldrich's GlycoProfile III Fluorescent Glycoprotein Detection Kit ($192). The Pierce GelCode Glycoprotein Staining Kit ($204) from Thermo Fisher Scientific is a colorimetric assay, as is Sigma's Glycoprotein Detection Kit ($414). The Amersham ECL Glycoprotein Detection Module ($193) from GE Healthcare pinpoints glycoproteins via a chemiluminescent assay.

2. Gel mobility shift assays

Glycosylated proteins can also be detected on gels via the mobility shift that results from treatment with glycosidases such as PNGase F (which identifies all N-linked glycans) and EndoH (which identifies only select N-glycans). Both are available from New England Biolabs ($110 for 15,000 units of PNGase F; $56 for 10,000 units of EndoH). QA-Bio offers these and several additional enzymes, including O-glycosidase ($380) for O-linked glycans.

3. Lectin-based Western blotting

Some companies (such as Vector Laboratories) offer biotin-labeled plant lectins (which are like sugar-specific antibodies) for the detection of specific sugars in Western blots and immunohistochemical assays. Following treatment with the lectin, detection is achieved using any of a range of streptavidin-based secondary reagents.

4. Lectin arrays

Alternatively, use lectin arrays to capture glycosylated proteins from complex mixtures. Then, probe with antibodies to determine whether your protein of interest has bound the array, and if so, via which of the glycans. Qiagen's Qproteome GlycoArray kit includes six lectin arrays (each containing more than 20 lectins) for $804.