Conjugate mechanism

Leonetti JP, Degols G, Lebleu B (1990) Biological activity of oligonucleotide-poly(L-lysine) conjugates mechanism of cell uptake 381. Bioconjug Chem 1 149-153... 

Only recently a selective crossed metathesis between terminal alkenes and terminal alkynes has been described using the same catalyst.6 Allyltrimethylsilane proved to be a suitable alkene component for this reaction. Therefore, the concept of immobilizing terminal olefins onto polymer-supported allylsilane was extended to the binding of terminal alkynes. A series of structurally diverse terminal alkynes was reacted with 1 in the presence of catalytic amounts of Ru.7 The resulting polymer-bound dienes 3 are subject to protodesilylation (1.5% TFA) via a conjugate mechanism resulting in the formation of products of type 6 (Table 13.3). Mixtures of E- and Z-isomers (E/Z = 8 1 -1 1) are formed. The identity of the dominating E-isomer was established by NOE analysis. 

Similar rate accelerations due to the addition of small amounts of DMSO were found in the reactions of 1,2-dinitrobenzene with butylamine in benzene. While the reaction is almost insensitive to other additives, the accelerations observed upon addition of DMSO to benzene exceed expectations based only on considerations of the polarity of the medium9. Catalysis by other HBA additives was recently studied by Hirst and coworkers162 in connection with the homo-/hetero-conjugate mechanism . 

The effect is interpreted as evidence of the operation of the homo-/hetero-conjugate mechanism. The authors presume that for the mechanism given by equation 1, for additives P which are much less basic than the nucleophile N, electrophilic catalysis also occurs both with the hetero-conjugate N+HP formed between the conjugate acid of the nucleophile, N, and P, as well as with the homo-conjugate Nu+HNu. For more basic additives, electrophilic catalysis is possible by the species PH+ and its homo-conjugate PHP+153 162 182. 

The plot of IhAtoh/I vs T for the base hydrolysis of trans-Co (i SSI [14]aneN4)Cl2 is curved slightly (concave down). Bearing in mind the conjugate mechanism for base hydrolysis give a plausible explanation for this behavior. 

Sies H, Ketterer B, eds. Glutathione Conjugation. Mechanisms and Biological Significance. London Academic Press, 1989. 

Caldwell J. Conjugation mechanisms of xenobiotic metabolism Mammalian aspects. In Paulson GD, Caldwell J, Hutton DH, et ah, eds. Xenobiotic Conjugation Chemistry. Washington American Chemical Society, 1986. 

Certain unusual conjugation mechanisms have been uncovered during comparative investigations, but this may be a reflection of inadequate data on other species. Future... 

Specifying the chemical conjugation mechanism, it should be noted that in this case a final product is formed in the overall reaction which acts as a reagent-inducer in the system and with the help of which active particles necessary for speeding up the secondary reaction are generated in the system. 

It is shown that low-temperature liquid-phase oxidation of resinous acids, their salts and dicarboxylic acids, as well as their mixtures with hydrocarbons is accompanied by decarboxylation, the latter not proceeding in the absence of oxidation. The chemical conjugation mechanism in decarboxylation becomes of importance, associated with the production of fatty acids and organics oxidation. 

To demonstrate, the chemical conjugation mechanism may be presented by the following generalized scheme ... 

Sometimes, due to special conditions, chain transformation may hardly be induced. An example of this is the reaction of propylene epoxidation. However, intense generation of active sites (H02) in the primary reaction gives the possibility of suppressing acceptor chain transformation to undesired products and simultaneously stimulating the main direction—epoxidation. This is obtained due to chemical induction, which induces and speeds up selective transformation of propylene (acceptor) to a quite high rate. The authors have implemented such a conjugation mechanism in propylene epoxidation by hydrogen peroxide [10]. 

Scheme (3.28) may be taken for the basic conjugation mechanism of chemical reactions, because it generally reproduces die specificity of chemical induction. Before we determine the determinant for scheme (3.28), a system of differential equations taking into account consumption of the components should be composed ... 

It should be noted that the main amount of redox enzymes in animal and plant cells is accumulated in mitochondria, which are usually called the power plants of the cell, because redox reactions supplying cells with energy proceed in them. Therefore, at present, mitochondria are the main source of information about biological oxidation and energetic conjugation mechanisms. 

Thus, transport of highly active intermediate product through a membrane is the necessary condition for conjugation on membrane catalysts. Moreover, understanding of the conjugation mechanism requires the reaction system to be considered as the entire system divided by a membrane into two parts. In its turn, the membrane must display catalyst properties on both sides. Specific features of catalysis on membrane catalysts allow the promotion of effective chemical conjugation. 

Chemical reaction conjugation on membrane catalysts is considered [30,31] as the simplest model of conjugated processes proceeding in mitochondria. Some functions of this model may be applied to the description of several aspects of respiration and phosphorylation conjugation mechanism. 

To accompany the similarity of chemical and biochemical processes proceeding with membrane catalysts, let us also indicate their specific features, which show the elegancy of Nature s modernization of the chemical conjugation mechanism. 

The above idea may be related to the interpretation of the conjugation mechanism of biooxidation reactions proceeding on the surface of mitochondrial membrane. It is known that Nature always displays great efficiency and rationality in the organization of biochemical processes. It is, therefore, no wonder that the same properties are observed in the structural organization of chemical conjugation, on which cell bioenergetics is based. 

Figure 3.6 The conjugation mechanism of respiration and ADP phosphorylation. Dashed arrow shows H+ ion leakage according to Skulachev.

Note that though the conjugation mechanism scheme for respiration and ADP phosphorylation in Figure 3.6 [33] properly indicates the pathways of H+ ions, their action mechanism as highly active intermediate particles (the conjugation intermediate, owing to which chemical energy of respiration is accumulated in the phosphorylation product) is not disclosed. 

Nature suggests to us an idea to modernize already known and newly discovered catalytic reactions via chemical conjugation mechanism. In general, the task may be formulated as follows ... 

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