Poly pathway

In addition, however, several minor but important side reactions concurrently proceed with the main reaction. These side reactions may become significant under certain conditions, particularly when the main reaction is slow because of low monomer reactivities or low concentrations. The principal pathways involved in the formation of poly(amic acid) are as shown in Eigure 1. 

In contrast to vitamin K, there has been considerably more activity on fermentative approaches to vitamin (50). The biosynthetic pathway to vitamin K2 is analogous to that of vitamin except that poly(prenylpyrophosphates) are the reactive alkylating agent (51,52). Menaquinones of varying chain lengths from to have been isolated from bacteria. The most common forms are vitamin K2 35, (40) (45) significant amount of K2 20)... 

Synthetic pathways have been deliberately aimed at producing megamers. For example, poly(amido amine) dendrimers of different generations have been combined to give well-defined core-shell megamers in which a central, large core dendrimer is surrounded by a well-defined number of smaller dendrimers. 

Molecular structural changes in polyphosphazenes are achieved mainly by macromolecular substitution reactions rather than by variations in monomer types or monomer ratios (1-4). The method makes use of a reactive macromolecular intermediate, poly(dichlorophosphazene) structure (3), that allows the facile replacement of chloro side groups by reactions of this macromolecule with a wide range of chemical reagents. The overall pathway is summarized in Scheme I. 

BARTLEY G E, SCOLNIK p A and BEYER p (1999) Two Arabidopsis thaliana carotene desaturases, ph)4oene desaturase and zeta-carotene desaturase, expressed in EicAencA/a coli, catalyze a poly-cis pathway to yield pro-lycopene , Eur JBiochem, 259, 396-403. 

ERNST s and sandmann g (1988) Poly-c carotene pathway in the Scenedesmus mutant C-6D , Arch Microbiol, 150, 590-94. 

Isaacson, T. et al.. Analysis in vitro of the enzyme CRTISO establishes a poly-cis-carotenoid biosynthesis pathway in plants. Plant Physiol. 136, 4246, 2004. 

Matthews, P.D., Luo, R., and Wurtzel, E.T., Maize phytoene desaturase and zetacar-otene desaturase catalyze a poly-Z desaturation pathway implications for genetic engineering of carotenoid content among cereal crops, J. Exp. Botany 54, 2215, 2003. 

Ernst, S. and Sandmann, G., Poly-cis carotene pathway in Scenedesmus mutant C-6D, Arch. Microbiol. 150, 590, 1988. 

Y-L He, S Murby, G Warhurst, L Gifford, D Walker, J Ayrton, R Eastmond, M Rowland. Species differences in size discrimination in the paracellular pathway reflected by oral bioavailability of poly (ethylene glycol) and D-peptides. J Pharm Sci 87 626-633, 1998. 

Figure 16 Molecular structure of a dimer of poly(bis phenol A carbonate) used in a study of degradation pathways [110].

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