PubMed:4053093 JSONTXT

{"project":"sentences","denotations":[{"id":"TextSentencer_T1","span":{"begin":0,"end":100},"obj":"Sentence"},{"id":"TextSentencer_T2","span":{"begin":101,"end":262},"obj":"Sentence"},{"id":"TextSentencer_T3","span":{"begin":263,"end":410},"obj":"Sentence"},{"id":"TextSentencer_T4","span":{"begin":411,"end":497},"obj":"Sentence"},{"id":"TextSentencer_T5","span":{"begin":498,"end":708},"obj":"Sentence"},{"id":"TextSentencer_T6","span":{"begin":709,"end":956},"obj":"Sentence"},{"id":"TextSentencer_T7","span":{"begin":957,"end":1142},"obj":"Sentence"},{"id":"TextSentencer_T8","span":{"begin":1143,"end":1352},"obj":"Sentence"},{"id":"TextSentencer_T9","span":{"begin":1353,"end":1455},"obj":"Sentence"},{"id":"T1","span":{"begin":0,"end":100},"obj":"Sentence"},{"id":"T2","span":{"begin":101,"end":262},"obj":"Sentence"},{"id":"T3","span":{"begin":263,"end":410},"obj":"Sentence"},{"id":"T4","span":{"begin":411,"end":497},"obj":"Sentence"},{"id":"T5","span":{"begin":498,"end":708},"obj":"Sentence"},{"id":"T6","span":{"begin":709,"end":956},"obj":"Sentence"},{"id":"T7","span":{"begin":957,"end":1142},"obj":"Sentence"},{"id":"T8","span":{"begin":1143,"end":1352},"obj":"Sentence"},{"id":"T9","span":{"begin":1353,"end":1455},"obj":"Sentence"}],"namespaces":[{"prefix":"_base","uri":"http://pubannotation.org/ontology/tao.owl#"}],"text":"Mass spectrometry of oligosaccharides by chloride-attachment reactions: the origin of fragment loss.\nThe direct exposure, negative chemical ionisation, chloride-attachment mass spectrometry of trehalose and sucrose gave abundant chloride-attached molecular ions. The same feature was observed when these sugars were subjected to fast-atom bombardment (f.a.b.) in a glycerol matrix containing ammonium chloride. No characteristic fragment ion was found when trehalose was analysed by either method. In contrast, sucrose gave intense chloride-containing fragments, arising by glycosidic cleavage, when analysed by the first method, whereas such cleavage was not detectable by f.a.b.-ammonium chloride analysis. However, the mass-analysed ion kinetic energy (m.i.k.e.) spectra of the (M + Cl)- ions from either trehalose and sucrose, generated under f.a.b.-ammonium chloride conditions, showed glycosidic cleavage reactions in addition to a large loss of HCl. These cleavage reactions might be attributed to SN2-like reactions on the acetal carbon atom and to base-induced eliminations, and they were enhanced by collision-induced dissociations. However, the relative abundance of such glycosidic cleavages from the ionic state would be too weak to explain the presence of the large chloride-containing fragments in the direct exposure spectra of sucrose. Thus, these ions were mainly produced by a thermal cleavage followed by chloride-attachment reactions."}