Biochemical pathways, polymer

The special topics discussed are (i) the biological aspects of heterocyclic compounds, i.e. their biosynthesis, toxicity, metabolism, role in biochemical pathways, and their uses as pharmaceuticals, agrochemicals and veterinary products (ii) the use of heterocyclic compounds in polymers, dyestuffs and pigments, photographic chemicals, semiconductors and additives of various kinds and (iii) the use of heterocyclic compounds as intermediates in the synthesis of non-heterocyclic compounds. 

Professor French was intensely interested in the mechanism of hydrolysis of starch, glycogen, and other polymers of D-glucose by various types of enzymes, and by acids. He was also interested in elucidating the biochemical pathways for the synthesis of these polymers, and in methods for characterization of the compounds, A very clever method for studying the mechanism of an enzyme reaction was introduced in... 

Succinic acid, which has the structure HOOC— CH2—CH2—COOH and on a C-mole basis is represented by CH3/2O, is useful as a starting material in the manufacture of solvents and polymers. It is typically made by the catalytic oxidation of butane. However, by that route only about 40 percent of the carbon initially present in the butane is converted to succinic acid. It has been suggested instead to use glucose as a starling material and a biochemical pathway with the following proposed reaction stoichiometry ... 

As natural rubber is a product of nature, its properties are determined by the biochemical pathway by which the polymer is synthesized in the plant. In the case of natural rubber the polymerization process cannot be tailored like that of synthetic rubbers. The only option to modify natural rubber is after it has been harvested from the tree. The important modified forms of natural rubber include hydrogenated natural rubber, chlorinated natural rubber, hydro-halogenated natural rubber, cyclized natural rubber, depolymerised liquid natural rubber, resin modified natural rubber, poly(methyl methacrylate) grafted natural rubber, poly(styrene) grafted natural rubber, and epoxidized natural rubber [33,34]. Thermoplastic natural rubber prepared by blending natural rubber and PP is considered as a physically modified form of natural rubber. 

Many different groups of bacteria, including Bacillus, Pseudomonas, and Thiobacillus, are capable of denitrification. The primary biochemical pathways for organic substrate oxidation by denitri-fiers are similar to that described for aerobic catabolism. Because most of the denitrifiers are facultative anaerobes, they possess a functional TCA cycle that allows them to metabolize substrates completely to carbon dioxide and water. Many denitrifiers do not produce extracellular enzymes required for hydrolysis of polymers thus, they generally rely on hydrolytic enzymes and fermenters to provide readily available substrates (Ljundahl and Erickson, 1985). 

Despite some successes in PHA production by plants, Drs. Yves Poirier and Stevens Brumbley believe production of PHA in crops and plants remains a challenging project. The challenges for the future are to succeed in the synthesis of PHA co-polymer with a narrow range of monomer composition, at levels that do not compromise plant productivity, and to find methods for efficient and economical extraction of polymers from plants. These goals will undonbtedly require a deeper understanding of plant biochemical pathways and advances in biorefinery. 

Biochemical pathways may be described as catabolic, anabolic (biosynthetic), amphibolic or anaplerotic. The principal function of a catabolic sequence is to degrade (usually by an oxidative process) simple organic molecules derived from the breakdown of polymers (e.g. amino acids from proteins) and retain some of the free energy released in a biologically useful form. Anabolic pathways consume energy and synthesize (usually by a reductive process) the simple molecules which are assembled into proteins, nucleic acids, carbohydrate polymers and lipids. Amphibolic pathways, such as the tricarboxylic acid cycle, have both catabolic and anabolic properties. They are central metabolic pathways which furnish, from catabolic sequences, the intermediates which form the substrates of anabolic processes. The... 

Traditional suture materials such as catgut must be removed by a health-care specialist after they have served their purpose. Stitches of these hydroxyester polymers, however, are hydrolyzed slowly over a period of approximately two weeks, and by the time the torn tissues have fully healed, the stitches are fiilly degraded and the sutures need not be removed. Glycolic and lactic acids formed during hydrolysis of the stitches are metabolized and excreted by existing biochemical pathways. 

Microorganisms in nature are capable of synthesising various types of PHA depending on the types of carbon sources available and the biochemical pathways that operate in the cell. It is now possible to synthesise various PHA homopolymers and copolymers that have a certain monomer composition. Synthesis of the PHA polymer chain takes place within the cytoplasm of the bacterial cell, within inclusions known as grannies. 

The knowledge of the chemistry and structure of nucleic acids as well as their metabolic and catabolic pathways has been extensively increased. However, there is very little evidence about the role of transition elements in the biochemistry of nucleic acids. Therefore, this review should emphasize the present status of the literature about studies of transition metal interactions with the monomer and polymer units of nucleic acids. Although this survey is far from being comprehensive it is hoped that the data collected here will be helpful for further investigations on the biochemical behavior of transition metals in nucleic acid metabolism. 

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