Degradation Smith

Fig. 13.—Predicted Sequence of the Smith-Degradation Product of the Glycosphingolipid Shown in Fig. 12. (Predicted Fragment-ions for the permethylated derivative are shown.)...

Smith degradation of PI. A sample of FI (50 mg) was dissolved in 0.5 M NaOH (5 mL) and acetic acid added to pH 7, followed by NaI04 to a final concentration of 50 mM. At the conclusion of the oxidation (7 days) the product was reduced with NaBH4 and dialyzed. An aliquot was removed and the remainder immediately treated with NaI04 and then reduced with NaBH4. Samples of material subjected to one and two cycles of oxidation-reduction were hydrolyzed and reduced, and the products analyzed by GLC as alditol acetates. 

Acid cleavage of reduced oxyheparins occurs at pH 1-3 during155 15 min at 100°, or151 with 5 mMH2S04 during 3 h at 60°. Some desulfation of fragments was reported for Smith-degraded heparan sulfate.151 Also, elimination at pH 12 for 30 min at 20° may cause some loss of sulfate.151... 

Scheme 4. —Smith Degradation of Heparin (Arbitrary Sequence). (R = remnant from a D-glucuronic acid residue.)...

The LPS of E. coli BB was subjected to Smith degradation and then hydrolyzed as listed (compare, Schemes 15 and 16). This hydrolysis was followed by a KDO determination.65... 

Monosaccharide residues containing vicinal hydroxyl groups are oxidized by periodate, and are subsequently removed in the reduction-hydrolysis step. Therefore, the positions to which such monosaccharide residues are linked can be located by methylation analysis performed before, and after, Smith degradation. Alternatively,59 the oxidized and reduced sample is methylated, the ether hydrolyzed, and the product realkylated with CD3I or CH3CH2I. This kind of procedure can have advantages over that first described. For example, methylation before the hydrolysis step hinders the acetal protection of hydroxyl groups that can occur in acid hydrolysis.7... 

An example of the use of Smith degradation for carbohydrate sequencing is a study on the sites of AcNeu-Gal-GlcNAc linkages to... 

Gal-(l — 4>/K31cNAc-(l — 6>a-GalNAc Meconium and Smith degraded ovarian cyst only... 

It should be noted that this reaction is referred to incorrectly by many authors as the Smith degradation. This designation should only be used when advantage is taken of the relative acid-labilities of acetal and glycosidic linkages (see Section XIV, p. 98). As the method here under discussion is an alternative procedure for end-group analysis, it may conveniently be referred to as the Smith end-group analysis. 

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