Promoters selectivity

In this sense subsurface oxygen is also acting as a promoter. The role of the alkali promoter is then to stabilize Cl and anionically bonded O (or nitrate ions) on the catalyst surface, so they can exert their promotional action. Thus alkalis in this system, which requires electronegative promoters according to the mles of section 2.5, are not really promoters but rather promoter stabilizers. This is proven by their inability to promote selectivity in absence of Cl. 

The above global and local promotional rules suggest, in a straightforward manner, the following three practical rules for promoter selection with respect to rate maximization911 ... 

At this point one might have concluded that, even without any commercial application, electrochemical promotion had offered something useful to promotion and catalysis by establishing the rules of promotion in addition to providing a useful tool for promoter selection. 

Tkatchenko, I., 1991, in Metal Promoted Selectivity in Organic Synthesis , Noels, A.F., Graziani, M. and Hubert, A.J. (Eds.), Kluwer, Dordrecht. 

A.F. Noels, M. Graziani and AJ. Hubert (eds.) Metal Promoted Selectivity in Organic... 

The exact mechanism by which COX-2 inhibition attenuates kindling epileptogenesis is not understood. Notwithstanding, COX-2 inhibition may diminish prostaglandin and/or PAF synthesis, lipid messengers that are both involved in synaptic facilitation [45]. Moreover, kindling epileptogenesis promotes selective neuronal COX-2... 

H. Masuyama, N. Suwaki, Y. Tateishi, H. Nakatsukasa, T. Segawa, and Y. Hiramatsu. The pregnane X receptor regulates gene expression in a ligand- and promoter-selective fashion. Mol Endocrinol. 19 1170-1180 (2005). 

Interchange of these solvents can promote selectivity differences. 

Whereas an AlMe-BlNOL catalyst system had earlier been shown to provide adducts in high exo selectivities [60], 13b promoted selective formation of the endo product. It is reasoned that the much smaller acidic proton obviates steric repul-... 

The catalyst prepared from PPh3 and a simple Ir(I) salt, [IrCl(cod)]2, promotes ( )-selective head-to-head dimerization in good yield, while the combination of [IrCl (cod)]2 with an electron-rich phosphine (PPrj) affords (Z)-enynes with reduced efficiency, but comparable selectivity. The results of [rrCl(cod)]2/PPr3-catalyzed dimerization reactions carried out according to Scheme 9.10 are summarized in Table 9.10. 

Search for effective organic promoters. Selective and active catalysts for Reaction 4 should not only be effective carbonylation catalysts, but also be highly effective in hydrogenation-hydrogenolysis reactions in the presence of CO. The most obvious parameters affecting activity and selectivity include Rh/Ru ratio, partial CO and H2 pressures, temperature, solvent type, and type of iodide promoter. 

Not every eucaryotic promoters possesses a TATA box. For promoters devoid of a TATA box, the initiation sequence is determining for promoter selection and formation of the pre-initiation complex. 

Promoter selection, binding of basal initiation factors... 

Verrijzer, C.P. and Tijan, R. TAFs mediate transcriptional activation and promoter selectivity (1996) Trends Biochem. Sd. 21, 338-342... 

There is an imspecific binding site for double- and single-stranded DNA in the C-terminal region of the p53 protein (Lee et al., 1995, Jayaraman and Prives, 1995). There is evidence that binding of single-stranded DNA regulates promoter selection of p53. It is also plausible that stabilization of the p53 protein is achieved via DNA binding. 

The selective oxidation of a single primary or secondary hydroxyl group within the same molecule has been a challenging problem for synthetic organic chemists. Many oxidizing reagents are known to promote selective oxidation of secondary... 

Farinha, M.A. Kropinski, A. M. (1989). Construction of broad-host-range vectors for general cloning and promoter selection in Pseudomonas and Escherichia coli. Gene, 11, 205-10. 

P. Denis, A. Jean, J. F. Crcizy, A. Mortreux, and F. Petit, J. Am. Chem. Soc., 112, 1292 (1990) A. Mortreux, Ligand Controlled Catalysis Chemo to Stereoselective Syntheses from Olefins and Dienes over Nickel Catalysts, in A. F. Noels, M. Graziani, and A. J. Hubert, eds., Metal Promoted Selectivity in Organic Synthesis, p. 47, Kluwer Academic, Dordrecht, 1991. 

Finally, changes in pH and temperature have been used effectively to promote selective protein precipitation. A change in the pH of the solution alters the ionic state of a protein and may even bring some proteins to a state of charge neutrality. Charged protein molecules tend to repel each other and remain in solution however, neutral protein molecules do not repel each other, so they tend to aggregate and precipitate from solution. A protein is least soluble in aqueous solution when it has no net charge, that is, when it is isoelectric. This characteristic can be used in protein purification, since different proteins usually have different isoelectric pH values. 

Lewis acids inhibit the photochemical deconjugation of a,p- to p,y-unsaturated butenoic acids and promote rearrangement of (E)- to (Z)-isomers. Lewis acids also promote selective (E)- to (Z)-isomerization of the a,p-double bond of methyl 2,4-hexadienoate.6... 

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