The Fluorescent Labeling of Glycoproteins on Sodium Dodecyl Sulfate-Polyacrylamide Gel

A highly sensitive fluorescent staining method for detecting glycosylated proteins on SDS-polyacrylamide gel has been described. The carbohydrate groups in glycoproteins were oxidized with periodate on SDS-polyacrylamide gel to generate aldehyde groups which were subsequently labeled with a fluorescent hydrazide, dansyl glycyl hydrazide (DNS-GLY-NHNH2), under acidic or neutral conditions. Six known glycoproteins, such as ricin, horseradish peroxidase. porcine serum transferrin, human γ-seroglobulin, chorionic gonadotropin (α- and β-subunit), and crude chicken ovalbumin, were labeled with DNS-GLY-NHNH2 on gels. The limit of sensitivity was about 10-20 ng of glycoproteins. The fluorescent staining protocol when used to examine unknown samples is particularly valuable in assessing sample purity and distinguishing glycoproteins from nonglycoproteins. By using this procedure, two glycoproteins have been found in the crude extract of the seeds of the camphor tree. Purified porcine serum transferrin was displayed as two bands on the gel by fluorescent staining. This method is more sensitive than that of fuchsin or dansylhydrazide staining. DNS-GLY-NHNH2 is very stable and easily obtained.