Hypothetical mechanism for

Figure 11.8 Hypothetical mechanism for aziridine formation in mitomycin C X = leaving group.

In addition to effects mediated through glucocorticoid secretion (stress-related), a hypothetical mechanism for direct immunotoxicity of organophosphates is the inhibition of esterases and stabilization of the lysosomal membrane of lymphocytes, thus blocking release of lymphokines (Sharma and Reddy 1987). 

Gent, A.N., A hypothetical mechanism for mbber abrasion. Rubber Chem. Technol., 62, 750, 1989. 

Fig. 6.24. Hypothetical mechanism for the hydrolysis of an arginine residue (6.59) to an ornithine (6.60) or a citrulline (6.61) residue...

Fig. 9.6. Postulated mechanisms in the cytochrome P450 catalyzed reductive denitration of organic nitrates. Pathway a shows the hypothetical mechanism for the reduction of organic nitrates to organic nitrites, whereas Pathway b presents the same reaction for organic nitrites.

Figure 3. Hypothetical mechanisms for extracellular feruloylation of matrix polysaccharides. (X = SCoA or Glc H = xylan or H)...

Figure 1. Hypothetical mechanism for shuttling of intermediates of the common aromatic pathway between plastidic and cytosolic compartments. Enzymes denoted with an asterisk (DAHP synthase-Co, chorismate mutase-2, and cytosolic anthranilate synthase) have been demonstrated to be isozymes located in the cytosol. DAHP molecules from the cytosol are shown to be shuttled into the plastid compartment in exchange for EPSP molecules synthesized within the plastid. Abbreviations C3, phosphoenolpyruvate C4, erythrose 4-P DAHP, 3-deoxy-D-arabino-heptulosonate 7-phosphate EPSP, 5-enolpyruvylshikimate 3-phosphate CHA, chorismate ANT, anthranilate TRP, L-tryptophan PPA, prephenate AGN, L-arogenate TYR, L-tyrosine and PHE, L-phenylalanine.

As documented in a review article (9), no experimental data was available to support hypothetical mechanisms for the biosynthesis of hydrolyzable tannins until recently. Enzymatic studies have now changed this unsatisfactory situation, at least as far as the formation of pentagalloylglucose is concerned. Future work will provide insight into those other challenges discussed in this contribution and that still require clarification. 

SCHEME 45. Hypothetical mechanism for epoxidation of aUtenes by H2O2 in phenol... 

The other approach, that is followed here, involves proposing a hypothetical mechanism for the homogeneously catalyzed process using only steps for which there is good precedent in organo-transition metal chemistry and involves choosing a system to optimize those steps that appear to be potentially the most troublesome. A reasonable pathway for reducing CO to methanol is shown in Scheme 1. Steps (a) and (d) show oxidative addition of H2 to a coordinatively unsaturated metal center, a well-known process (5). Step (b) is the insertion of... 

Martin, R.B. and Burr, D.B. (1982) A hypothetical mechanism for the stimulation of osteonal remodeling by fatigue damage. Journal of Biomechanics 15 137-139... 

Figure 1. Hypothetical mechanism for the selective assimilation of bovine testicular fi-galactosidase by generalized gangliosidosis fibroblasts...

Although the enzyme exerts enormous stereochemical and regiochemical control, the reaction that it catalyzes, like others in this chapter, involves only unexceptional chemical steps. A hypothetical mechanism for this process, based on radical chemistry, shows that the steps are, indeed, reasonable (see Figure 28.11). Again, remember that this does not represent the real mechanism, which is certainly more concerted than shown in the figure and probably does not involve any true radical intermediates. 

Figure 7.3 Model of a putative PolyP-PHB-Ca2+ pump, indicating a hypothetical mechanism for co-translocation of Ca2+ and PolyP across the membrane (Reusch, 1992).

To understand why an energy of activation is required for a reaction, we may think about a hypothetical mechanism for the reaction. In our... 

Figure 10. Hypothetical mechanisms for the oxidative chemistry ofl and the reaction of the one-electron oxidation product, l+m. Left from l+% The process corresponding to the slow loss of the EPR signal and two paths for the formation of disulfides upon a second one-electron oxidation. Path A Retaining a dimeric structure, the two-electron reduction of the disulfide regenerates 1. Path B The second one-electron oxidation cleaves the dimer leading to the formation of a mononuclear disulfide complex, in analogy with that shown in Figure 5 and a mononuclear Ni(II) complex that rapidly dimerizes to form 2, in analogy with chemistry known for similar complexes (85). Reduction of the disulfide leads to production of the same mononuclear Ni(II) complex.

In light of these results, hypothetical mechanisms for the oxidation of Ni thiolate complexes by 02 may be discussed. The only well-characterized mechanism for the oxidation of thiolates to sulfinates in transition metal complexes involves 0 as an oxidant and proceeds via the stepwise formation of sulfenates (Scheme 1) (90, 91). 

FIGURE 14. Hypothetical mechanism for proton delivery during MMO catalysis. (From Lee and Lipscomh, 1999). 

Fig. 46. Hypothetical mechanism for the growth of a polymer granule and protuberances 81). By permission of Hiithig Wepf Verlag.

Figure 2. Hypothetical mechanism for the direct wood-to-wood bonding through oxidative phenolic coupling.

Fiaire 4. Hypothetic mechanism for bonding of preoxidized wood with ethylenediamine (left), and bonding of wood with a bifunctional isocyanate... 

Dudek FE, Spitz M. Hypothetical mechanisms for the cellular and neurophysiologic basis of secondary epileptogenesis Proposed role of synaptic reorganization. J Clin Neurophysiol 1997 14 90-101. Enslen M, MilonH, Malnoe A. Effect of low intake of n-3 fatty acids during development on brain phospho-... 

Figure 4. Hypothetic mechanism for the P=S to P=0 conversion showing its analogy with an aromatic epoxi-dation (27).

Figure 3 Hypothetical mechanism for release of formate by GTP cyclohydrolase II.

By analogy to the liquid phase mechanism, and in particular VOLPIN s polysilylvanadates [12b] and works of Y. IWASAWA on tailored metal catalysts and Molybdenum oxides for ethanol oxidation [14] we proposed an hypothetical mechanism for isomerisation vapor phase with a tetrahedral Mo active center (Scheme 3). 

Cohen and Monod (C2) have summarized experimental evidence which shows indeed that special mechanisms of transport of organic nutrients occur in bacteria. They call such transport systems permeases. This term ending in -use implies that the system involves enzymes—an implication not yet proved by available data. At any rate, it is found that permease systems can lead to transport against an apparent rise in concentration, as well as other effects not possible with Fickian diffusion. Various hypothetical mechanisms for operation of permease systems yield rates of permeation which exhibit the Michaelis-Menten type of dependence on substrate (including water) concentration. Perhaps it is in the occurrence of one of these mechanisms that the rate equation [Eq. (38)] assumed by Monod and almost all subsequent workers finds its justification. [For further information on biological transport, see, e.g., Christensen (Cl).]... 

Figure 8. Hypothetical mechanisms for C and HCOj -enhanced radiolytic killing of a bacterium by extracellular pathways. Cl radical formation is suppressed by OH-reactive compounds in solution, but COj radical formation is not. In this case, protection by free radical scavengers must arise by direct competition for the CO3 radical. The reaction scheme also includes an intracellular pathway, although target sites are not specified.

A hypothetical mechanism for the GDH reaction has been proposed (Smith et al., 1975). This involves condensation of the uncharged e-amino... 

FIGURE 3.26 Hypothetical mechanism for sulfur incorporation into coal. 

Fig. 14 Hypothetical mechanisms for O2 formation, a pathway (i) involving one O atom from a solvent water molecule and the other from Ru = O, b pathway (ii) involving both 0 atoms from solvent water molecules (reprinted with permission from American Chemical Society [103])...

Fig. 2. Hypothetical mechanism for ATP hydrolysis based on a model for Mn . ATP bound to activate CF determined from EXAFS analysis.

Theoretical work on a hypothetical mechanism for the Heck reaction based on Pd(II)/Pd(IV) indicates that the oxidative addition of Phi to Pd(II) would be the rate-determining step Sundermann, A., Uzan, 0. and Martin, J.M.L. (2001) Chem. Eur. J., 7, 1703-11. 

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