Reconstruction of reaction pathways

Reconstruction of Reaction Pathways in a Rock—Fluid System Using MINTEQ... 

Kinetic experiments with synthetic iron oxyhydroxides have shown that the initial microbial reduction rate increases with increasing initial ferric iron concentration up to a given maximum reduction rate (Bonneville et al. 2004). This observation was explained by a saturation of active membrane sites with Fe(III) centers. The respective reaction was best described with a Michaelis-Menten rate expression with the maximum reduction rate per cell positively correlating with the solubility of the iron oxyhydroxides (Bonneville et al. 2004). Kinetic studies involving iron are not only inherently important to describe reaction pathways and to derive rate constants, which can be used in models. Kinetic studies also increasingly focus on iron isotopic fractionation to better understand the iron isotopic composition of ancient sediments, which may assist in the reconstruction of paleo-environments. Importantly, iron isotope fractionation occurs in abiotic and biotic processes the degree of isotopic fractionation depends on individual reaction rates and the environmental conditions, e.g. whether reactions take place within an open or closed system (Johnson et al. 2004). 

Allow the metabolic reconstruction of microbial genomes. EcoCyc provides detailed annotation on 946 metabolic reactions comprising 139 distinct metabolic pathways. EcoCyc also includes information on the signal-transduction pathways, enzymes, and transport proteins of E. coli. MetaCyc describes 3,786 pathways and enzymes of many different organisms with a primary microbial focus. 

The Pd-O bond also varies with the extent of oxidation of Pd. During the methane combustion reaction, the catalyst surface is a non-equilibrium, kineti-cally controlled structure. The oxygen concentration profile in the particle results from a combination of particle reconstruction, oxygen adsorption, bulk diffusion, and oxygen removal. This concentration profile varies as a function of time, and as the oxygen content increases, the Pd-O bond strength decreases. This increase is accompanied by an increase in the specific activity. The most widely accepted reaction pathway is the Mars and van Krevelen redox mechanism, which involves lattice oxygen and uneoordinated Pd centers as active species. Inhibition by products (H2O and CO2) and impurities (SO2) is a major drawback for low temperature combustion. The effect of sulfur is particularly important for catalytic converters for NGV applications because it drastically reduces the methane combustion activity. 

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