title: Role of sialic acid in selective silver staining of red cell glycophorins.
abstract: A causal relationship between the presence of sialic acid and erythrocyte sialoglycoprotein-specific silver staining (Dzandu et al. 1984) has been examined. Quantitative chemical hydrolysis of sialic acid resulted in total loss of sialoglycoprotein-specific staining suggesting a causal role for sialic acid. It is speculated that under acidic conditions, the highly nucleophilic carboxylates of sialic acid (pKa = 2.6), may determine staining specificity by functioning as primary silver-reactive centers. Because selective staining was abrogated on gel treatment with aldehydes, alkali, thiol reagents or by temperature elevation, it is inferred that the above physico-chemical variables nullified selective staining by creating additional silver nucleation sites which culminate in non-specific staining. Acid treatment of ghosts at 80 degrees C, a standard method for sialic acid hydrolysis caused very specific polypeptide scissions, presumably at aspartyl-proline bonds. Because of the high reproducibility of the membrane protein fragmentation patterns, this method should be ideal for rapid peptide mapping of complex protein mixtures without recourse to isolating and purifying the individual polypeptides.
authors.affiliation: Department of Anatomy and Cell Biology, Texas College of Osteopathic Medicine, Fort Worth 76107.
authors.forename: J K
authors.initials: JK
authors.lastname: Dzandu
mesh_terms: D004591:Electrophoresis, Polyacrylamide Gel; D004910:Erythrocyte Membrane / Q000187:drug effects / Q000648:ultrastructure*; D006868:Hydrolysis; D007700:Kinetics; D019158:N-Acetylneuraminic Acid; D010449:Peptide Mapping; D012794:Sialic Acids / Q000378:metabolism; D012795:Sialoglycoproteins / Q000032:analysis*; D012834:Silver; D013194:Staining and Labeling; D013464:Sulfuric Acids / Q000494:pharmacology
chemical_list: D012794:Sialic Acids; D012795:Sialoglycoproteins; D013464:Sulfuric Acids; D012834:Silver; D019158:N-Acetylneuraminic Acid; C033158:sulfuric acid