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Hemicelluloses galactan

Another hemicellulose, Galactan, is a minor component of some coniferous and deciduous woods. Larch wood was shown to contain about 8% of this polymer. ... [Pg.382]

Galactans, mannans (hemicelluloses, cell-wall storage)... [Pg.182]

The hemicelluloses are polymolecular, random-coil, often branched hetero-glycans interspersed with cellulose microfibrils and starch granules in vivo. Glucose, xylose, and arabinose are the prominent sugars, although lesser quantities of galactan, mannan, etc., and minor concentrations of acetic, ferulic and uronic acids, etc., are in evidence. Heterogeneity extends to dimensions and conformation. [Pg.181]

Galactans are found in association with other hemicelluloses in deciduous and coniferous woods, certain seeds and pectins. It is very difficult to obtain the pure polysaccharide. Not much is known of the detailed structure of these molecules,61 and few molecular weight measurements have been carried out. [Pg.309]

Table 15.8 presents the feedstock composition expressed in key components cellulose, hemicellulose (xylan, arabinan, mannan, galactan) and lignin. [Pg.449]

A problem but little discussed in the hterature is the possible association of polysaccharide molecules of various kinds with noncarbohydrate molecules. The association can be random, and a direct fractionation would then be impossible. Thus, it has frequently been observed in the authors laboratory that hemicelluloses containing lignin could not be separated into the pure components, but, after further dehgnification, they could be readily fractionated. It is possible that similar comphcations may also occur with other types of polysaccharide, for example, protein- or lipide-polysac-charide complexes. In this connection, it should be noted that the solution obtained on dehgnification of some materials may contain polysaccharide material of particular interest. For instance, the main part of the galactan present in spruce compression wood can be recovered from such a solution. ... [Pg.57]

Hemicelluloses in reaction woods are quite different from those in the normal woods, namely, galactan and P-(l-3)-gIucan in compression wood and galac-tan in tension wood. It is also well known that a remarkable amount of a water-soluble polysaccharide, arabinogalactan, is contained in the heartwood of larch. Since this polysaccharide occurs mainly in the lumen of tracheids and is not a cell wall component, it may not be included in hemicelluloses. Although structures and distributions of hemicelluloses have been comprehensively studied in the last 20 years, their physiologic meanings in a cell wall are not known yet. This must be the most important point for the future study of hemicelluloses. [Pg.21]

Galactan is the one exception among the hemicelluloses. Its C-O-C interunit link at the C4 is axial (Figure 2.6) and its natural shape is a coil with six monosaccharides per coil (Fukashima et al., 1997). Rather than lying predominantly parallel to the microfibrils, one might speculate that the galactan may be able to coil between... [Pg.41]

The exo-anomeric effect enforces a value of cp around 90° for anomeric axial linkages. This ensures a proclivity towards helical structures (as distinct from the ribbons of 1,4-diequatorially linked polysaccharides), as in starch and glycogen. p-(1 4)-Linked galactans, 1,4 axial-equatorial in the other sense, are known as hemicellulose components of compression and tension wood, the storage polysaccharides of lupins and as arabinogalactans attached to the rhamnogalacturonan I component of pectin, but have not been subject to conformational studies they appear to be biosynthesised from UDP-Gal. " ... [Pg.213]


See other pages where Hemicelluloses galactan is mentioned: [Pg.310]    [Pg.80]    [Pg.310]    [Pg.80]    [Pg.63]    [Pg.164]    [Pg.262]    [Pg.22]    [Pg.20]    [Pg.451]    [Pg.181]    [Pg.182]    [Pg.60]    [Pg.177]    [Pg.139]    [Pg.197]    [Pg.80]    [Pg.392]    [Pg.10]    [Pg.66]    [Pg.198]    [Pg.1473]    [Pg.10]    [Pg.232]    [Pg.261]    [Pg.34]    [Pg.60]    [Pg.286]    [Pg.177]    [Pg.57]    [Pg.291]    [Pg.278]    [Pg.458]    [Pg.18]    [Pg.460]    [Pg.144]    [Pg.193]    [Pg.8]    [Pg.245]    [Pg.150]    [Pg.241]    [Pg.101]   
See also in sourсe #XX -- [ Pg.24 , Pg.37 , Pg.41 , Pg.43 , Pg.191 , Pg.193 ]




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Galactan

Galactane

Galactans

Hemicellulose

Hemicellulose galactan

Hemicellulose galactan

Hemicelluloses

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