Cellulose chains, tertiary

The presence of sulphonic and carboxylic groups enables the iron ions to be in the vicinity of the cellulose backbone chain. In this case, the radicals formed can easily attack the cellulose chain leading to the formation of a cellulose macroradical. Grafting of methyl methacrylate on tertiary aminized cotton using the bi-sulphite-hydrogen peroxide redox system was also investigated [58]. 

The finer details of secondary and tertiary cellulose structure remain somewhat controversial and in any case will not concern us here. It will suffice to say that the chains align themselves side by side to form a substructure of microflbrils 35 A in diameter, and these in turn are linked together in more complex arrangements to form the main cellulose fibres. The microfibrils are believed to contain both amorphous and crystalline regions of aligned cellulose chains and the latter may adopt helical configurations. As a result of the presence of other components, differences exist between wood, cotton and synthetic cellulose fibres. 

The tertiary structure of parallel-running intermolecular hydrogen-bonded cellulose chains further associate by hydrogen bonds and van der Waals forces to produce three-dimensional microfibrils. The microfibrils give an X-ray diffraction pattern that indicates a regular, repeating crystalline stmcture interspersed by less-ordered paracrystalline regions. A model for the microfibrils was proposed by Hess et al. [50] and is presented in Fig. 6.8C. 

Linearity of the polysaccharide primary chains facilitates parallel ordering of the tertiary structures in two (e.g., 0 sheets of cellulose) and three... 

In native state, proteins exist as either fibrous or globular form. Protein should be denatured and unfolded to produce an extended chain structure to form film. Extended protein chains can interact through hydrogen, ionic, and hydrophobic bonds to form a three-dimensional stmcture (24). Protein films are excellent gas barriers but poor moisture barriers because of their hydrophilic nature. Mechanical properties and gas permeability depend on the relative humidity (1). Al-ameri (25) smdied the antioxidant and mechanical properties of soy, whey and wheat protein, and carrageenan and carboxymethyl cellulose films with incorporated tertiary-butylhy-droquinone (TBHQ), butylated hydroxytoluene (BHT), fenugreek, and rosemary extracts. Armitage et al. (26) studied egg albumin film as a carrier of natural antioxidants to reduce lipid oxidation in cooked and uncooked poultry. 

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