نتایج جستجو برای: proton transfer
تعداد نتایج: 349521 فیلتر نتایج به سال:
The passage of proton trough proteins is common to all membranal energy conserving enzymes. While the routes differ among the various proteins, the mechanism of proton propagation is based on the same chemical-physical principles. The proton progresses through a sequence of dissociation association steps where the protein and water molecules function as a solvent that lowers the energy penalty ...
Significant discrepancies have been observed between proton form factors as measured by Rosenbluth separation and polarization transfer techniques. There are indications that this difference may be caused by corrections to the one photon exchange approximation that are not taken into account in standard radiative correction procedures. In this paper, we constrain the two-photon amplitudes by co...
Proton-transfer reaction mass spectrometry (PTR-MS) is a technique developed almost exclusively for the detection of gaseous organic compounds in air. Volatile organic compounds (VOCs) in air have both natural and anthropogenic sources. Natural sources include the emission of organic gases by living objects, both plants and animals. A well-known example, which is discussed later in this review,...
Proton transfer across single-layer graphene proceeds with large computed energy barriers and is therefore thought to be unfavourable at room temperature unless nanoscale holes or dopants are introduced, or a potential bias is applied. Here we subject single-layer graphene supported on fused silica to cycles of high and low pH, and show that protons transfer reversibly from the aqueous phase th...
We studied the effect of proton-coupled electron transfer on lifetimes of the charge-separated radicals produced upon light irradiation of the thiomethyl-naphthalimide donor SMe-NI-H in the presence of nitro-cyano-pyridine acceptor (NO(2)-CN-PYR). The dynamics of electron and proton transfer were studied using femtosecond pump-probe spectroscopy in the UV/vis range. We find that the photoinduce...
In the catalysis of the hydration of carbon dioxide and dehydration of bicarbonate by human carbonic anhydrase II (HCA II), a histidine residue (His64) shuttles protons between the zinc-bound solvent molecule and the bulk solution. To evaluate the effect of the position of the shuttle histidine and pH on proton shuttling, we have examined the catalysis and crystal structures of wild-type HCA II...
The role of water molecules in assisting proton transfer (PT) is investigated for the proton-pumping protein ferredoxin I (FdI) from Azotobacter vinelandii. It was shown previously that individual water molecules can stabilize between Asp(15) and the buried [3Fe-4S](0) cluster and thus can potentially act as a proton relay in transferring H(+) from the protein to the μ(2) sulfur atom. Here, we ...
The proton transfer channel for the reaction of HBr + with HBr is investigated in a state-specific manner by preparing the reagent ion in a selected internal state by resonance-enhanced ionization (REMPI) and monitoring the disappearance of this ion by laser-induced fluorescence (LIF). A rate constant for proton transfer of (6.7 + 1.6) × 10-10 cm3/s is found. The reaction of HBr + with HBr and ...
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