title: A specific fluorogenic reaction for tryptophan residues using isatin in organic solvents.
abstract: The development of new fluorogenic reactions for specific chemical groups is of increasing interest in cytochemistry. We describe the application of the nonfluorescent compound isatin on methanol-fixed blood smears. When treated with 0.1% isatin in absolute ethanol or acetone for 30 min and observed under violet-blue exciting light, eosinophil leucocyte granules show a bright green fluorescence. This fluorogenic reaction is abolished after blocking of tryptophan residues by performic acid oxidation. Spectrofluorometric studies with amino acids in vitro reveal that isatin forms a unique and specific fluorescent product with tryptophan.
authors.affiliation: Department of Biology, Faculty of Sciences, Autonomous University of Madrid, Spain.
authors.forename: C I
authors.initials: CI
authors.lastname: Trigoso
authors.forename: N
authors.initials: N
authors.lastname: Ibañez
authors.forename: J C
authors.initials: JC
authors.lastname: Stockert
mesh_terms: D000096:Acetone; D000596:Amino Acids / Q000737:chemistry; D000818:Animals; D002645:Chickens; D002843:Chromatin / Q000737:chemistry; D003594:Cytoplasmic Granules / Q000737:chemistry; D004285:Dogs; D004804:Eosinophils / Q000648:ultrastructure; D004912:Erythrocytes / Q000648:ultrastructure; D000431:Ethanol; D006736:Horses; D006801:Humans; D007510:Isatin; D007962:Leukocytes / Q000648:ultrastructure; D000432:Methanol; D051381:Rats; D012997:Solvents; D013050:Spectrometry, Fluorescence; D014364:Tryptophan / Q000032:analysis*
chemical_list: D000596:Amino Acids; D002843:Chromatin; D012997:Solvents; D000096:Acetone; D000431:Ethanol; D007510:Isatin; D014364:Tryptophan; D000432:Methanol