PubMed:8581890 JSONTXT

{"target":"http://pubannotation.org/docs/sourcedb/PubMed/sourceid/8581890","sourcedb":"PubMed","sourceid":"8581890","source_url":"http://www.ncbi.nlm.nih.gov/pubmed/8581890","text":"Structure of the saponin adjuvant QS-21 and its base-catalyzed isomerization product by 1H and natural abundance 13C NMR spectroscopy.\nThe saponin QS-21, derived from the bark of the Quillaja saponaria Molina tree, has shown great potential as an adjuvant with a number of vaccines. Kinetic studies carried out to establish the stability of vaccine formulations show that commercially supplied QS-21 (primarily QS-21A) is converted slowly at pH 5.5, and rapidly at higher pH, to an equilibrium mixture of two regioisomers, QS-21A and QS-21B, in a ratio of 20:1. NMR studies show that QS-21A and QS-21B differ only in the point of attachment of the fatty acyl moiety to the fucose sugar ring. The major isomer, QS-21A, has the fatty acyl portion attached at the 4-hydroxyl group whereas the minor isomer, QS-21B, has the fatty acyl portion attached at the 3-hydroxyl group. The isomerization most likely involves ionization of the 3-hydroxy group and intramolecular acyl transfer from the 4-hydroxy group. The relative stereochemistry of the triterpene and the sugar anomeric centers is also established by NMR methods.","tracks":[{"project":"GlyCosmos6-Glycan-Motif-Image","denotations":[{"id":"T1","span":{"begin":673,"end":679},"obj":"Glycan_Motif"}],"attributes":[{"id":"A1","pred":"image","subj":"T1","obj":"https://api.glycosmos.org/wurcs2image/0.10.0/png/binary/G82576YO"},{"subj":"T1","pred":"source","obj":"GlyCosmos6-Glycan-Motif-Image"}]},{"project":"GlyCosmos6-Glycan-Motif-Structure","denotations":[{"id":"T1","span":{"begin":673,"end":679},"obj":"https://glytoucan.org/Structures/Glycans/G82576YO"}],"attributes":[{"subj":"T1","pred":"source","obj":"GlyCosmos6-Glycan-Motif-Structure"}]},{"project":"NCBITAXON","denotations":[{"id":"T1","span":{"begin":183,"end":201},"obj":"OrganismTaxon"},{"id":"T2","span":{"begin":202,"end":208},"obj":"OrganismTaxon"}],"attributes":[{"id":"A1","pred":"db_id","subj":"T1","obj":"NCBItxid:32244"},{"id":"A2","pred":"db_id","subj":"T2","obj":"NCBItxid:356573"},{"subj":"T1","pred":"source","obj":"NCBITAXON"},{"subj":"T2","pred":"source","obj":"NCBITAXON"}]},{"project":"sentences","denotations":[{"id":"TextSentencer_T1","span":{"begin":0,"end":134},"obj":"Sentence"},{"id":"TextSentencer_T2","span":{"begin":135,"end":282},"obj":"Sentence"},{"id":"TextSentencer_T3","span":{"begin":283,"end":561},"obj":"Sentence"},{"id":"TextSentencer_T4","span":{"begin":562,"end":691},"obj":"Sentence"},{"id":"TextSentencer_T5","span":{"begin":692,"end":872},"obj":"Sentence"},{"id":"TextSentencer_T6","span":{"begin":873,"end":1004},"obj":"Sentence"},{"id":"TextSentencer_T7","span":{"begin":1005,"end":1118},"obj":"Sentence"},{"id":"T1","span":{"begin":0,"end":134},"obj":"Sentence"},{"id":"T2","span":{"begin":135,"end":282},"obj":"Sentence"},{"id":"T3","span":{"begin":283,"end":561},"obj":"Sentence"},{"id":"T4","span":{"begin":562,"end":691},"obj":"Sentence"},{"id":"T5","span":{"begin":692,"end":872},"obj":"Sentence"},{"id":"T6","span":{"begin":873,"end":1004},"obj":"Sentence"},{"id":"T7","span":{"begin":1005,"end":1118},"obj":"Sentence"}],"namespaces":[{"prefix":"_base","uri":"http://pubannotation.org/ontology/tao.owl#"}],"attributes":[{"subj":"TextSentencer_T1","pred":"source","obj":"sentences"},{"subj":"TextSentencer_T2","pred":"source","obj":"sentences"},{"subj":"TextSentencer_T3","pred":"source","obj":"sentences"},{"subj":"TextSentencer_T4","pred":"source","obj":"sentences"},{"subj":"TextSentencer_T5","pred":"source","obj":"sentences"},{"subj":"TextSentencer_T6","pred":"source","obj":"sentences"},{"subj":"TextSentencer_T7","pred":"source","obj":"sentences"},{"subj":"T1","pred":"source","obj":"sentences"},{"subj":"T2","pred":"source","obj":"sentences"},{"subj":"T3","pred":"source","obj":"sentences"},{"subj":"T4","pred":"source","obj":"sentences"},{"subj":"T5","pred":"source","obj":"sentences"},{"subj":"T6","pred":"source","obj":"sentences"},{"subj":"T7","pred":"source","obj":"sentences"}]}],"config":{"attribute types":[{"pred":"source","value type":"selection","values":[{"id":"GlyCosmos6-Glycan-Motif-Image","color":"#9399ec","default":true},{"id":"GlyCosmos6-Glycan-Motif-Structure","color":"#b3ec93"},{"id":"NCBITAXON","color":"#ec93cd"},{"id":"sentences","color":"#93e7ec"}]}]}}