Permethylated samples

IV. Degradation of the Permethylated Sample, and Analysis of the Partially Methylated Sugars... 

The partially methylated monosaccharides obtained on depolymerization of the permethylated sample are preferably analyzed as acetates by g.l.c.-m.s., as shown by Bjomdal and coworkers.41,42 The neutral sugars and the amino sugars obtained in acetolysis-acid hydrolysis are reduced, and acetylated for the analysis, and the amino-hexitol and the neuraminic acid residues are acetylated after methanolysis. Identification with the aid of g.l.c.-m.s. has been described for all of the common components of protein- and lipid-linked glycans and oligosaccharides from animal cells, namely, the neutral sugars,41-43 hexitols,44 hexosamines,29,43,45,46 aminohexitols,31,32 and neuraminic acids.33,34,47... 

Evaluation of Free Phenoeic Units in Lignins by Thioacidolysis oe Permethylated Samples... 

Structural information gained from thioacidolysis of permethylated samples is provided by a routine technique. In contrast, the last development of thioacidolysis, the analysis of lignin-derived dimers after an additional desulfurization step, is not an easy technique to master. 

Subsequent work revealed that chelate formation with Group IA and IIA metal salts could successfully separate N-permethylated TEPA samples. As mentioned, TEPA is the notation given to the commercial polyamine fraction containing mainly the isomeric tetraethylenepenta-mines (6). The N-permethylated pentamine components, characterized by NMR and chemical-ionization mass spectrometry (19), include the two acyclic isomers—Compound 7 and 8—and three derivatives of piperazine—Compounds 9 through 11. Of these, only three of the pentamines—n-HMTP (Compound 7), iso-HMTP (Compound 8), and N,N -c-PMPP (Compound 10)—are present in amounts greater than 10% in a typical N-permethylated sample of TEPA. The amounts of these components found in one such sample are listed in Table V. 

Figure 17. Structural model of LAM and AG. AG is drawn without the mycolic acids attached to the terminal Ara residues. The molecular weight of LAM has been determined by M ALDI-TOF on both native and permethylated samples. The arabinan circle in both LAM and AG represents structural details not yet defined. Detailed characterizations of the various arabinan motifs were based on MS/chemical analysis of fragments obtained through acetolysis, mild acid hydrolysis and endoarabinase digestion as indicated. The branched Ara6 motif is common to both AG and LAM whereas the linear Ara4 terminal motif is found only on LAM. An Ara22 motif as drawn is deduced to be present on AG [15],...

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