Low temperature l3c NMR spectra of 80: 20 mixtures of cis and trans-4-CH3-C6HloCHzX, where -CSHlOis 1,4-disubstituted cyclohexyl and X=Br, CN, OH, OCH,, Si(CH,),, Sn(CH3),, Pb(CH,), and HgOCOCH, have been recorded. The signals of the truns (e, e) components were assigned from the ambient temperature
Substitution patterns in methylated starch as studied by enzymic degradation
โ Scribed by Peter A.M. Steeneken; Albert J.J. Woortman
- Publisher
- Elsevier Science
- Year
- 1994
- Tongue
- English
- Weight
- 993 KB
- Volume
- 258
- Category
- Article
- ISSN
- 0008-6215
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โฆ Synopsis
Potato starch was methylated in granular suspension and in solution to degrees of substitution (ds) up to 0.8. The distribution of methyl groups along the starch chains was probed by consecutive enzymic degradation with alpha-amylase and amyloglucosidase, followed by structural characterisation of isolated fragments. A minimum sequence length of two unsubstituted glucose residues is required for amylolysis to occur. At a given ds, larger amounts of glucose and more highly substituted material of high molecular weight were obtained from granular O-methylstarches than from starches methylated in solution.
Although the differences between both classes of methylated starch were not very pronounced, this result is taken as evidence that granular O-methylstarches are substituted in a more blockwise manner.
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