title: Stabilities of the fluorescent SH-reagent eosin-5-maleimide and its adducts with sulfhydryl compounds.
abstract: The stabilities of the SH-reagent eosin-5-maleimide (EMA) and its adducts with the SH-compounds L-cysteine, N-acetyl-L-cysteine and glutathione (reduced form) were studied under various conditions in comparison with those of the adducts of N-ethylmaleimide (NEM). Studies by reversed-phase high performance liquid chromatography and mass spectrometry showed that EMA was less stable than NEM at neutral and moderately alkaline pH values. EMA formed a succinimide-type adduct with SH-compounds, and then underwent further modification by nucleophilic attack of OH- or an amino group. The succinimide-type adducts with acetylcysteine and glutathione were converted to open-type adducts, in which the succinimide ring was cleaved, whereas the adduct with cysteine was modified to a thiazine-type adduct. Kinetic analyses showed that these open-type and thiazine-type adducts were readily formed and were stable at moderately alkaline pH values such as pH 8.0 or 9.0.
authors.affiliation: Faculty of Pharmaceutical Sciences, University of Tokushima, Japan.
authors.forename: E
authors.initials: E
authors.lastname: Majima
authors.forename: S
authors.initials: S
authors.lastname: Goto
authors.forename: H
authors.initials: H
authors.lastname: Hori
authors.forename: Y
authors.initials: Y
authors.lastname: Shinohara
authors.forename: Y M
authors.initials: YM
authors.lastname: Hong
authors.forename: H
authors.initials: H
authors.lastname: Terada
mesh_terms: D000111:Acetylcysteine / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid; D003545:Cysteine / Q000737:chemistry; D004355:Drug Stability; D004801:Eosine Yellowish-(YS) / Q000031:analogs & derivatives* / Q000737:chemistry; D005033:Ethylmaleimide / Q000737:chemistry; D005978:Glutathione / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D013058:Mass Spectrometry; D013050:Spectrometry, Fluorescence; D016339:Spectrometry, Mass, Fast Atom Bombardment; D013388:Succinimides / Q000737:chemistry; D013438:Sulfhydryl Compounds / Q000737:chemistry*
chemical_list: D013388:Succinimides; D013438:Sulfhydryl Compounds; C032620:succinimide; C033531:eosin maleimide; D005978:Glutathione; D003545:Cysteine; D005033:Ethylmaleimide; D004801:Eosine Yellowish-(YS); D000111:Acetylcysteine