Cellulose-like structure

Alginates, found in cell walls of some marine algae and also formed by certain bacteria, consist in part of a linear i-l,4-linked polymer of D-mannuronate with a cellulose-like structure. Alginates also contain... 

The effect of sodium hydroxide on the xanthan flow curves is more than that expected from the charge shielding mechanism observed with sodium chloride. One possible explanation of this effect is base-catalyzed fragmentation reactions [26,32]. Fragmentation reactions break the biopolymer backbone (cellulose-like structure) to smaller saccharide units. Consequently, the hydrodynamic radius of the biopolymer would decrease and the viscosity of the polymer solution would diminish. 

Replicas of the tomato cell walls are very similar to those of onion parench5una cell walls but replicas of the DCB-adapted walls did not show the structure of the walls clearly. The principle components of the adapted walls are shorter thinner fibres which seemed to form a gel-like structure with little evidence of long cellulosic microfibrils characteristic of the unadapted cells. It is possible that such a gel will bind water more strongly and reduce the amount of etching that takes place, resulting in a less well-defined replica (2). 

The linear, but highly branched, molecular structure of the galactomannans is the reason for some specific properties which are quite different from those of the unbranched cellulose-like and water-insoluble mannans and glucomannans. Galactomannans are hydrated in cold water and give stable solutions even in acidic formulas. The interactions of galactomannans with other polysaccharides are the base of a variety of industrial applications. 

At first, a water suspension of pulp has to go through a mechanical treatment that consists of a spring-loaded valve assembly (refiner), where the slurry is pumped at high pressure. The formed MFC is moderately degraded and extremely expanded in surface area. In recent years, cellulose with a nanoscale web-like structure (Fig. 4c) has been made. The fiber diameters are in the range 10-100 nm [19,20]. The degree of fibrillation depends on the number of passes through the refiner (Fig. 4b, c). 

The tamarind fruit (pod) has mainly pulp and seeds. The seeds are covered by a thin parchment, membrane-like structure. The pulp constitutes 30-50% of ripe fruit (Purseglove, 1987 Shankaracharya, 1998). The shell and fibre account for 11-30% and the seed constitutes around 25 10% (Chapman, 1984). The fruit pulp (both ripe and dried) contains mainly tartaric acid, reducing sugars, pectin, tannin, fibre and cellulose. The general composition of tamarind fruits is given in Table 20.1. 

With improvements in elemental analysis, the structure of many simple molecules was elucidated. Elemental analysis, however, didn t help solve the structure of cellulose or natural rubber, materials that we now know are mac-romolecular in nature. In fact, it contributed to a general misconception. For example, natural rubber was found to have a composition equivalent to CSH8, but this only corresponds to the repeating unit of the polymer and says nothing about its long, chain-like structure. 

Monoclinic unit cell of cellulose I according to the model by Meyer and Misch [37], which shows the antiparallel orientation of adjacent chains (left) and the hydrogen-bonding network of two adjacent cellulose chains forming a sheet-like structure according to Gardner and Blackwell [38]... 

Fig. 6. Cellobiohydrolase-cellulose interaction. In the cellulose chain, the (31—4 glycosidic bond alternate sides of the ribbon-like structure. Steric hindrance prevents the cellulose chain from bending or turning within the catalytic domain of cellobiohydrolases. This forces the product into dimer units as the enzyme progresses along the chain...

Like this, the decomposition of cellulose crystal structure initiated and finished at lower temperatures in C, grafted cellulose, and stannic chloride treated cellulose than those in M. 

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