Pathways and efficiency

Liu, Y., Majetich, S.A., Tilton, R.D., Sholl, D.S. and Lowry, G.V. (2005) TCE dechlorination rates, pathways, and efficiency of nanoscale iron particles with different properties. Environmental Science and Technology, 39, 1338—1345. 

Photochemists who rely more on experimental data and proofs than on hypotheses know that there are still blank areas in solving the most general problem of photochemistry interrelationships between the nature of the photo-reactive excited state of a molecule and the pathways and efficiency of its chemical deactivations [29]. The categorization of photoreactions of metal-lotetrapyrroles, presented in this article, stems from available published data, and the opinions and deductions of their authors. 

Heterogeneous photocatalysis is a powerful tool for the abatement of organic and inorganic pollutants as well as for the synthesis of useful compounds. For successful application of photocatalysis in purification or production processes, a deep understanding of its mechanistic aspects and knowledge on parameters influencing reaction pathways and efficiency is necessary. 

Two and twelve moles of ATP are produced, respectively, per mole of glucose consumed in the glycolytic pathway and each turn of the Krebs (citrate) cycle. In fat metaboHsm, many high energy bonds are produced per mole of fatty ester oxidized. Eor example, 129 high energy phosphate bonds are produced per mole of palmitate. Oxidative phosphorylation has a remarkable 75% efficiency. Three moles of ATP are utilized per transfer of two electrons, compared to the theoretical four. The process occurs via a series of reactions involving flavoproteins, quinones such as coenzyme Q, and cytochromes. 

Some cellular stimulus-response pathways and second messengers are briefly described. The overall efficiency of receptor coupling to these processes is defined as the stimulus-response capability of the cell. 

Desensitization describes the rapid signal attenuation in response to stimulation of cells by receptor agonists. Changes in the coupling efficiency of receptors to signal transduction pathways and receptor internalization can account for desensitization and the development of pharmacodynamic tolerance. 

The fundamental issue is to describe how much of the residue can be characterized accurately and whether an accounting of the applied mass of pesticide can be maintained throughout the course of the experiment. A series of environmental fate studies is required for pesticide registration in order to characterize the degradation pathways and formation and decline patterns of each major degradate. These studies are typically conducted in the laboratory under controlled conditions, applying radiolabeled pesticides to evaluate the extraction efficiency of various procedures. When standard extraction methods fail to release a significant amount of the applied radioactivity, more efficient and exhaustive extraction procedures are tried in a stepwise fashion... 

Blanpain C, Wittamer V, Vanderwinden JM, et al. Palmitoylation of CCR5 is critical for receptor trafficking and efficient activation of intracellular signaling pathways. J Biol Chem 2001 276(26) 23795-23804. 

Studies of base-base CT in B-form DNA duplexes versus A-form DNA R-NA hybrids also confirmed our fundamental tenet that the pathway of efficient charge transfer will be the well-stacked pathway. In A-form duplexes considerable intra- and interstrand stacking exists. Not surprisingly then, in DNA RNA hybrids we observed a similar distance dependence for the yields of intra- and interstrand CT [105]. So, the distinction between intra- and interstrand CT observed in B-DNA duplexes truly correlates with differences in base stacking. 

However, as a general observation, this study demonstrated the feasibility of the integrated modeling approach to couple an environmental multimedia and a PBPK models, considering multi-exposure pathways, and thus the potential applicability of the 2-FUN tool for health risk assessment. The global sensitivity analysis effectively discovered which input parameters and exposure pathways were the key drivers of Pb concentrations in the arterial blood of adults and children. This information allows us to focus on predominant input parameters and exposure pathways, and then to improve more efficiently the performance of the modeling tool for the risk assessment. 

Other non-traditional preparations of 1,2,3-triazoles have been reported. The rearrangement in dioxane/water of (Z)-arylhydrazones of 5-amino-3-benzoyl-l,2,4-oxadiazole into (2-aryl-5-phenyl-27/-l,2,3-triazol-4-yl)ureas was investigated mechanistically in terms of substituents on different pathways <06JOC5616>. A general and efficient method for the preparation of 2,4-diary 1-1,2,3-triazoles 140 from a-hydroxyacetophenones 139 and arylhydrazines is reported <06SC2461>. 5-Alkylamino-] //-], 2,3-triazoles were obtained by base-mediated cleavage of cycloadducts of azides to cyclic ketene acetals <06S1943>. Oxidation of N-... 

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