Directive role

With regards to the overall balance of combustion, the chemical structure of the motor or heating fuel, e.g., the number of carbon atoms in tbe chain and the nature of the bonding, does not play a direct role the only important item is the overall composition, that is, the contents of carbon, hydrogen, and — eventually— oxygen in the case of alcohols or ethers added to the fuel. 

The only above reaction in which bacteria plays a direct role is Reaction 6.4, the cathodic depolarization process. 

Uroporphyrinogen I (16c), a constitutional isomer of uroporphyrinogen III, also plays no direct role in porphyrin and corrin biosynthesis, but this unnatural substrate is methylated to give 17c10c f in the presence of SAM by the methyl transferase of some bacteria. A constitutional type I dihydroisobacteriochlorin can be obtained by methylation of uroporphyrinogen I with methylase Ml. Methyltransferase M1 is able to methylate the unnatural precorrin once more to give the trimethylpyrrocorphin type I.IOc 1... 

This chapter also considers concentration variables that do not themselves necessarily play a role in the mechanism. For example, pH variations may affect the rate of a reaction because an acidic species (HA) is ionized (to A ). The size and direction of the pH effect depend in this instance on how either or both of these species enter the mechanism. Of course, in aqueous solution H+ and OH- may play direct roles as well. 

Because the Na+ and N03 ions appear as both reactants and products, they play no direct role in the reaction. They are spectator ions, ions that are present while the reaction takes place but remain unchanged, like spectators at a sports event. Because spectator ions remain unchanged, we can simplify the chemical equation by canceling them on each side of the arrow in the ionic equation ... 

The a-amino group of the new aminoacyl-tRNA in the A site carries out a nucleophilic attack on the esterified carboxyl group of the peptidyl-tRNA occupying the P site (peptidyl or polypeptide site). At initiation, this site is occupied by aminoacyl-tRNA mef. This reaction is catalyzed by a peptidyltransferase, a component of the 285 RNA of the 605 ribosomal subunit. This is another example of ribozyme activity and indicates an important—and previously unsuspected—direct role for RNA in protein synthesis (Table 38-3). Because the amino acid on the aminoacyl-tRNA is already activated, no further energy source is required for this reaction. The reaction results in attachment of the growing peptide chain to the tRNA in the A site. 

In addition to their direct role in the bioremediation of contaminants, plants can play an important role in their dissemination through consumption by ruminants. The detoxification and metabolism of higher plants has been reviewed by Sandermann (1994), and some illustrative examples include the following ... 

This reaction is characteristic of aromatic and ethylene compounds. The amine group does not play a direct role in it. 

The industrial catalyst for n-butane oxidation to maleic anhydride (MA) is a vanadium/phosphoras mixed oxide, in which bulk vanadyl pyrophosphate (VPP) (VO)2P207 is the main component. The nature of the active surface in VPP has been studied by several authors, often with the use of in situ techniques (1-3). While in all cases bulk VPP is assumed to constitute the core of the active phase, the different hypotheses concern the nature of the first atomic layers that are in direct contact with the gas phase. Either the development of surface amorphous layers, which play a direct role in the reaction, is invoked (4), or the participation of specific planes contributing to the reaction pattern is assumed (2,5), the redox process occurring reversibly between VPP and VOPO4. 

The suggested catalytic cycle for the diamine catalysts indicates that the NH group of the diamine plays a direct role in the hydride transfer through a six-membered TS.53 A feature of this mechanism is the absence of direct contact between the ketone and the metal. Rather, the reaction is pictured as a nucleophilic delivery of hydride from ruthenium, concerted with a proton transfer from nitrogen. 

One of the recent crystallographic structures of the full length HHR identifies five well-defined divalent ion binding sites, one of them (the C-site) being located in the catalytic pocket and being suggested to have a direct role in catalysis [127],... 

Mast cells do not appear to play a direct role in host protection against primary T. muris infection, as no correlation was found between intestinal... 

The mercuration of ferrocenylimines with Hg(OAc)2 has been studied. - 6 Mercuration occurs selectively at the a-position relative to the imine group to afford compounds 86a-i (Scheme gy107,108 The regioselectivity of these reactions points to the directing role of the Lewis-basic imine functionality. Similar factors probably play a role in the formation of the ferrocenylketone and ferrocenylaldehyde derivatives 87a-f and 87g-j, respectively. These derivatives readily react with amines to afford the corresponding imines (Scheme 9). Presumably, the Lewis-acidic mercury center of the monomercurated ferrocenylketones and ferrocenylaldehydes activates the carbonyl functionality toward nucleophilic attack by the amine. 

Like all other cytokines, administration of IL-2 can induce side effects that can be dose limiting. Serious side effects, including cardiovascular, hepatic or pulmonary complications, usually necessitate immediate termination of treatment. Such side effects may be induced not only directly by IL-2, but also by a range of additional cytokines whose synthesis is augmented by IL-2 administration. These cytokines, which can include IL-3, -4, -5 and -6, as well as TNF and IFN-y, also likely play a direct role in the overall therapeutic benefits accrued from IL-2 administration. 

Rao, C. and Sanfilippo, J. 1997. New understanding in the biochemistry of implantation - potential direct roles of luteinizing hormone and human chorionic gonadotropin. Endocrinologist 7(2), 107-111. 

A direct role of pectic enzymes produced by the pathogen in the process of infection is indicated by (a) the ability of all known pathogens to produce pectic enzymes, (b) the correlation between the production of these enzymes and the virulence observed in most pathogenic isolates,79,274 278 (c) the presence of pectic enzymes pro-... 

The crystal structure determinations of tetrametaphosphimates showed that N-H 0 hydrogen bonds between the ring anions play an important structure directing role. The iPCfNH) rings adopt approximately a chair, boat, or saddle conformation. Examples for conformations in (P02NH)t ions as well as some structural aspects of tetrametaphosphimates are given in Fig. 3. 

However, in other respects spin plays no direct role in construction of the non-relativistic H. If higher accuracy is desired, perturbative expressions such as (1.5) can be used to evaluate spin-dependent corrections to the non-relativistic model. 

Branching in polymers plays a direct role in their crystallizability, as packing configurations are directly influenced by the nature and frequency of branches along a given polymer backbone. Much has been done in the past to understand the effect of randomly placed branches on the chain, yet no study has been performed on perfectly controlled branching in polyethylene. 

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