Electron transport predicting direction

ATP synthesis utilizes the proton concentration gradient created by electron transport, and therefore the magnitude of the gradient is indeed smaller by about 0.5 pH unit during ATP synthesis than in its absence. The number of protons which need to traverse the ATP synthase for the synthesis of one ATP molecule was estimated both from direct measurements and from thermodynamic analysis [22]. Most workers agree that this ratio is very close to 3. When combined with an H /e ratio of 2, this predicts a maximal ATP/eJ ratio of 1.3, in agreement with this ratio as determined by extrapolative techniques [22]. 

How can reduction potentials be used to predict the direction of electron transport ... 

To predict systems most likely to yield meaningful and useful direct electrochemistry, redox enzymes may be divided into two categories. The first comprises those for which one of the redox processes in the catalytic cycle is a discrete outer-sphere (and probably long-range) electron-transfer reaction. Examples include the blue Cu oxidases, ferredoxin-linked reductases, and cytochrome c oxidase and other enzymes of electron-transport chains. In such systems there is exchange of electrons with an extrinsic agent, i.e. one that does not form... 

The kinetics of the electron transfer at the electrode-polymer film interface, which initiates electron transport in the surface layer, is generally considered as a fast process, which is not rate limiting. It was also presumed that the direct electron transfer between the metal substrate and the polymer involves only those redox sites situated in the layer immediately adjacent to the metal surface. As follows from the theory (Eq. 8) the measured charge transport diffusion coefficient should increase linearly with c, whenever the contribution from the electron-exchange reaction is important therefore the concentration dependence of D may be the test of theories based on the electron-exchange reaction mechanism. Despite the fact that considerable efforts have been made to find the predicted linear concentration dependence of D, it has been observed only in a few cases and for a limited concentration range. 

The much simplified picture of the energetics and kinetics for a working DSSC device, which emerged in the early research,is still useful as an introduction of working principles. The chemical complexity of the device must, however, be understood and mastered to improve our ability to identify predictive materials and optimised structure/function relation-ships. The present understanding of these processes is now covered with specific emphasis on the electron transport through the mesoporous TiOi electrode. The reader is also directed to recent review articles on these topics. 

The elucidation of actinide chemistry in solution is important for understanding actinide separation and for predicting actinide transport in the environment, particularly with respect to the safety of nuclear waste disposal.72,73 The uranyl CO + ion, for example, has received considerable interest because of its importance for environmental issues and its role as a computational benchmark system for higher actinides. Direct structural information on the coordination of uranyl in aqueous solution has been obtained mainly by extended X-ray absorption fine structure (EXAFS) measurements,74-76 whereas X-ray scattering studies of uranium and actinide solutions are more rare.77 Various ab initio studies of uranyl and related molecules, with a polarizable continuum model to mimic the solvent environment and/or a number of explicit water molecules, have been performed.78-82 We have performed a structural investigation of the carbonate system of dioxouranyl (VI) and (V), [U02(C03)3]4- and [U02(C03)3]5- in water.83 This study showed that only minor geometrical rearrangements occur upon the one-electron reduction of [U02(C03)3]4- to [U02(C03)3]5-, which supports the reversibility of this reduction. 

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