title: Selective radioactive labeling of cell surface sialoglycoproteins by periodate-tritiated borohydride.
abstract: Low concentrations of sodium metaperiodate induce specific oxidative cleavage of sialic acids between carbon 7 and carbon 8 or carbon 8 and carbon 9. The aldehydes formed can easily be reduced with NaB3H4 to tritiated 5-acetamido-3,5-dideoxy-L-arabino-2-heptulosonic acid or 5-acetamido-3,5-dideoxy-L-arabino-2-octulosonic acid. At 0 degrees, the periodate anion penetrates the cell plasma membrane very slowly and only externally exposed sialic acids are oxidized. This was shown by (a) limited labeling of the sialoglycoproteins in a preparation of inside-out erythrocyte vesicles; (b) trapping 14C-labeled fetuin within resealed erythrocyte ghosts; fetuin was then poorly labeled, whereas the erythrocyte sialoglycoproteins were highly labeled; (c) comparison of labeled glycoproteins of mouse lymphoid cells before and after treatment with neuraminidase. This simple method of specifically introducing a radioactive label into cell surface sialic acids is useful in the study of cell surface sialic acid-containing glycoproteins.
mesh_terms: D000818:Animals; D001894:Borohydrides; D002250:Carbon Radioisotopes; D004910:Erythrocyte Membrane; D005692:Galactose Oxidase; D006801:Humans; D007553:Isotope Labeling / Q000379:methods; D007700:Kinetics; D008214:Lymphocytes; D008565:Membrane Proteins / Q000097:blood; D051379:Mice; D008970:Molecular Weight; D009439:Neuraminidase; D010504:Periodic Acid; D012795:Sialoglycoproteins / Q000097:blood; D014316:Tritium; D000509:alpha-Fetoproteins
chemical_list: D001894:Borohydrides; D002250:Carbon Radioisotopes; D008565:Membrane Proteins; D012795:Sialoglycoproteins; D000509:alpha-Fetoproteins; D014316:Tritium; D010504:Periodic Acid; D005692:Galactose Oxidase; D009439:Neuraminidase