Adequate proton supply

An adequate proton supply to an F0 subunit channel in the mitchondrial ATP synthase is less certain. Using the same logic as before, proton supply from the cytosol at pH 7.5 would be only 20 H+ per channel per second. This discrepancy might be overcome by a much wider channel mouth, a slower rate of ATP synthesis per enzyme, or some additional mechanism by which protons are supplied to the mitochondrial ATP synthase. One possibility is that in mitochondria, where ATP synthesis (and therefore proton flux) is driven by a membrane potential, hydrolysis of water at the channel mouth could be a major source for protons. Kasianowicz et al. (46) found it necessary to invoke this possibility to account for the observed rates of protonophore-mediated proton conductance across lipid bilayers. 

We conclude that a chain of hydrogen-bonded water molecules is able to translocate protons at a rate sufficient for measured ATP synthesis if the proton supply from the bulk phase is adequate. In the physiological pH range, the question of proton supply to a putative proton channel becomes... 

The proton exchange membrane fuel cell (PEMFC) has been extensively studied in the last two decades for many applications and especially for low emissions vehicles.Pure hydrogen is the ideal fuel for the PEMFC. However, it cannot be stored practically in sufficient quantities on-board a vehicle and, therefore, there is a need for an adequate supply infrastructure. On-board H2 production from liquid fuel such as methanol is considered as a promising method for fuel cell vehicle application. Hydrogen-rich reformed gas presents 1-2% of CO. Unfortunately, this CO concentration cannot be tolerated by the PEMFC electrodes at low operating temperature. In order to avoid... 

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