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Lecture IX Polysaccharides I
Structural Determination Lecture #9 - Polysaccharides I - Determination of structure Will cover Structural Determination of PSs (general principles only)
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CHO Classification I Monosaccharides Oligosaccharides Polysaccharides
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CHO Classification V Polysaccharides > 20 monosaccharide units
Homo- and heteroglycans Linear Branched Note: DP = Degree of Polymerization
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Carbohydrate Structure I
Monosaccharides Glycosides Oligosaccharides Polysaccharides Generalizations I
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Carbohydrate Structure I
Monosaccharides Glycosides Oligosaccharides Polysaccharides Generalizations II polydisperse = range of MW polymolecular=linkages vary…. A polydisperse collection
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Polysaccharide Structure
Preparation/Purification Remove foreign material Extraction/Isolation Filtration, dialysis, etc. Precipitation
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Lignin Wood = cellulose + lignin(20-30%)
Lignin = non-CHO polymer, contain-ing aromatic rings bearing -OCH3 (methoxyl) groups. Methanol derived from wood comes from the lignin component (hence, MeOH = “wood alcohol”)
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Polysaccharide Structure
Structural Analysis(generalities) Sugar residues Ring size(s) Anomeric configurations Linkage types Sequence of sugar residues Substituent groups DP/MW/Higher Orders of Structure
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Polysaccharide Structure
Structural Analysis(generalities) Sugar residues Hydrolysis HPLC and/or GLC Structure of Heparin
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Polysaccharide Structure
Structural Analysis(generalities) Sugar residues HPLC ( Separation of sugar anomers
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Polysaccharide Structure
Structural Analysis(generalities) Sugar residues Linkage types/ring sizes Methylation analysis
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Reactions of Carbohydrates III Hydroxyl Groups- Ether Formation
Methylation analysis Methylate polysaccharide Hydrolyze (acid) Analyze hydrolizate Deduce where PS linkages were
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Methylation Analysis I
CH2OH OH HO A CH2 B C ROH RO- 30% NaOH For example …….. 1. Strong base in DMSO 2. Methyl Iodide (Me I) O CH2OMe OMe MeO A CH2 B C 90% formic acid 100o, 1 hr Note, “Me” = CH3-
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Methylation Analysis II
MeO O CH2OMe OMe A OH m.p. = 72oC 2,3,4,6-Tetra-O-methyl-D-galactose + O CH2OH OMe MeO HO B OH Cool, concentrate Dil H2SO4 14 hrs, 100o, neutralize A syrup + 2,3-Di-O-methyl-D-mannose O CH2OMe OMe HO C MeO OH A syrup 2,3,6-Tri-O-methyl-D-mannose
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Methylation Analysis III
MeO O CH2OMe OMe A OH O CH2OH OMe MeO HO B OH O CH2OMe OMe HO C MeO OH + + 2,3-Di-O-methyl-D-mannose 2,3,6-Tri-O-methyl- D-mannose 2,3,4,6-Tetra-O-methyl- D-galactose 1. NaBH4 reduction 2. Acetylation CH2OAc CH2OMe C OAc OMe MeO A < CH2OAc C OAc MeO B < CH2OAc CH2OMe C OAc MeO < + + Note, “Ac” = CH3C- =O Note, “Me” = CH3 Partially methylated alditol acetates
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Methylation Analysis IV Possible Structures (shorthand)
4)Man(1 Gal 1 6 A 6)Man(1 4)Man(1 Gal 1 4 A 1 2 B C B C Gal 1 4 Man 6 4)Man(1 3 A Gal 1 4 Man 6)Man(1 A C C B B
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Polysaccharide Structure
Structural Analysis(generalities) Sugar residues Linkage types/ring sizes Monosaccharide sequence
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Polysaccharide Structure
Structural Analysis(generalities) Sugar residues Linkage type Monosaccharide sequence Linkage configuration
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Polysaccharide Structure
Structural Analysis(generalities) Sugar residues Linkage type Monosaccharide sequence Linkage configuration DP/MW/Higher Orders of Structure
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H2O H+ bond w/in chain H+ bond between chains H2O K+ ion ligands (6 each)
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