Abstract:The "C NMR specIra of some polysaccharides and their methyl derivatives have been analysed. The numbers and positions of the assigned '"C NMR signals give some information about the structure of the monomer unit and the positions of the glycosidic linkage but no information about the anomeric configuration. In this case the 'J(C-l,H) coupling constants make it possible to identify the anomeric configuration, because the mean differences of the J values for the a-and 6-anomers are 12Hz (at least 5 Hz) with the … Show more
“…Solvent extraction was usually employed to obtain high yields. NMR spectroscopy confirmed the structure of TMA, , and the 13 C assignments are shown in Figure . 2 …”
Starch ethers having side chains of various lengths,
controlled and uniform degrees of
substitution, and various amylose/amylopectin ratios were obtained by a
one-step chemical
modification of starch. Factors influencing the phase behavior of
these starch ethers were
carefully examined, and the ones having short side chains were found to
exhibit lyotropic
liquid crystallinity over wide ranges in degree of substitution and
amylose/amylopectin ratio.
The starch ethers having longer side chains failed to exhibit
phase separation due to
insufficient degrees of substitution. They generally possessed
enhanced hydrophobicity
relative to starch yet still had controllable numbers of free hydroxyl
groups. The liquid
crystallinity thus produced makes them ideal candidates for a novel
processing technique
designed specifically for permanently orienting main-chain, lyotropic,
liquid-crystalline
polymers.
“…Solvent extraction was usually employed to obtain high yields. NMR spectroscopy confirmed the structure of TMA, , and the 13 C assignments are shown in Figure . 2 …”
Starch ethers having side chains of various lengths,
controlled and uniform degrees of
substitution, and various amylose/amylopectin ratios were obtained by a
one-step chemical
modification of starch. Factors influencing the phase behavior of
these starch ethers were
carefully examined, and the ones having short side chains were found to
exhibit lyotropic
liquid crystallinity over wide ranges in degree of substitution and
amylose/amylopectin ratio.
The starch ethers having longer side chains failed to exhibit
phase separation due to
insufficient degrees of substitution. They generally possessed
enhanced hydrophobicity
relative to starch yet still had controllable numbers of free hydroxyl
groups. The liquid
crystallinity thus produced makes them ideal candidates for a novel
processing technique
designed specifically for permanently orienting main-chain, lyotropic,
liquid-crystalline
polymers.
“…To understand the influence of methylation on the chemical shifts of polysaccharides, the assigned proton and carbon chemical shifts of the permethylated polysaccharide standards were compared to published literature or CASPER-predicted values of the des -methylated variants (Table and Tables S1 and S2). Our initial pool of polysaccharide standards, including cellulose, mixed-linked glucan, starch, dextran, galactan, arabinan, xylan, arabinoxylan, mannan, and glucomannan (see Tables S1 and S2), provided a substantial variety of samples that would allow rigorous analysis of the influence of permethylation on NMR chemical shifts of polysaccharides (permethylated polysaccharide NMR chemical shift data from literature are also available , ). These comparisons led us to observe several general trends for the effect of permethylation on the chemical shifts of ring residue protons and carbons, which are summarized as follows:…”
Plant cell wall polysaccharide
analysis encompasses the utilization
of a variety of analytical tools, including gas and liquid chromatography,
mass spectrometry (MS), and nuclear magnetic resonance (NMR) spectroscopy.
These methods provide complementary data, which enable confident structural
proposals of the many complex polysaccharide structures that exist
in the complex matrices of plant cell walls. However, cell walls contain
fractions of varying solubilities, and a few techniques are available
that can analyze all fractions simultaneously. We have discovered
that permethylation affords the complete dissolution of both soluble
and insoluble polysaccharide fractions of plant cell walls in organic
solvents such as chloroform or acetonitrile, which can then be analyzed
by a number of analytical techniques including MS and NMR. In this
work, NMR structure analysis of 10 permethylated polysaccharide standards
was undertaken to generate chemical shift data providing insights
into spectral changes that result from permethylation of polysaccharide
residues. This information is of especial relevance to the structure
analysis of insoluble polysaccharide materials that otherwise are
not easily investigated by solution-state NMR methodologies. The preassigned
NMR chemical shift data is shown to be vital for NMR structure analysis
of minor polysaccharide components of plant cell walls that are particularly
difficult to assign by NMR correlation data alone. With the assigned
chemical shift data, we analyzed the permethylated samples of destarched,
alcohol-insoluble residues of switchgrass and poplar by two-dimensional
NMR spectral profiling. Thus, we identified, in addition to the major
polysaccharide components, two minor polysaccharides, namely, <5%
3-linked arabinoxylan (switchgrass) and <2% glucomannan (poplar).
In particular, the position of the arabinose residue in the arabinoxylan
of the switchgrass sample was confidently assigned based on chemical
shift values, which are highly sensitive to local chemical environments.
Furthermore, the high resolution afforded by the 1H NMR
spectra of the permethylated switchgrass and poplar samples allowed
facile relative quantitative analysis of their polysaccharide composition,
utilizing only a few milligrams of the cell wall material. The concepts
herein developed will thus facilitate NMR structure analysis of insoluble
plant cell wall polysaccharides, more so of minor cell wall components
that are especially challenging to analyze with current methods.
“…Der Hydrolyseablauf wird anhand der Abnahme der fur Alkylester von Pyrazol-1-thiocarbonsauren typischen w c w*-Bande [lo] verfolgt (fur 4 : eZgZ = 11 700 1mol-' cm-l). [24], der lac-NMR-Spektren loslicher Oligocellulosen [25] sowie von partiell 2,6-methylierter Cellulose [as], Trimethylcellulose [27] und eines Inkrementsystems [28] zur Berechnung der chemischen Verschiebung der Benzyl-…”
Section: Hydrolyse Der Cellulosedibenzylether-derivate 4 In Wasserhalunclassified
Polymergebundene Mikrobiocide werden durch Acylierung von Cellulose und Cellulosedibenzylether mit dem aus 3‐Methyl‐pyrazol und Thiophosgen erhältlichen Thiocarbonsäurechlorid unter Katalyse mit 4‐Dimethylamino‐pyridin hergestellt. Die hydrolytische Wirkstoffreisetzung wird primär über die Hydrophilie der Trägerpolymere sowie den Quellungs‐ bzw. Lösungszustand der Polymer‐Wirkstoff‐Kombination und seine Änderung während der Hydrolyse gesteurt.
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