The proton transfer activity of the light-driven proton pump, bacteriorhodopsin (bR) in the photochemical cycle might imply internal water molecules. The free energy of inserting water molecules in specific sites along the bR transmembrane channel has been calculated using molecular dynamics simulations based on a microscopic model. The existence of internal hydration is related to the free ene...

The buffer-mediated proton-transfer reactions of the fluorescent xanthenic derivative 9-[1-(2-Methyl-4-methoxyphenyl)]-6-hydroxy-3H-xanthen-3-one (TG-II) have been studied in different aqueous media. We have employed various buffers to investigate the influence of donor/acceptor systems with different anion and/or cation chemical constituents on the kinetic parameters of proton-transfer. The ki...

Cytochrome c oxidase (CcO), the terminal enzyme of the respiratory chain, reduces oxygen to water and uses the released energy to pump protons across a membrane. Here, we use kinetic master equations to explore the energetic and kinetic control of proton pumping in CcO. We construct models consistent with thermodynamic principles, the structure of CcO, experimentally known proton affinities, an...

Hydrogen (H(+)) and hydroxide (OH(-)) ions in aqueous solution have anomalously large diffusion coefficients, and the mobility of the H(+) ion is nearly twice that of the OH(-) ion. We describe molecular dynamics simulations of a dissociating model for liquid water based on scaling the interatomic potential for water developed by Ojamäe-Shavitt-Singer from ab initio studies at the MP2 level. We...

Cytochrome c oxidase, the terminal enzyme of the respiratory chains of mitochondria and aerobic bacteria, catalyzes electron transfer from cytochrome c to molecular oxygen, reducing the latter to water. Electron transfer is coupled to proton translocation across the membrane, resulting in a proton and charge gradient that is then employed by the F0F1-ATPase to synthesize ATP. Over the last year...

Proton transfer in protonated Nafion fuel cell membranes is studied using several pyrene derivative photoacids. Proton transfer in the center of the Nafion nanoscopic water channels is probed with the highly charged photoacid 8-hydroxypyrene-1,3,6-trisulfonate (HPTS). At high hydration levels, both the time-integrated fluorescence spectrum and the fluorescence kinetics of HPTS permit the determ...

The development of more effective energy conversion processes is critical for global energy sustainability. The design of molecular electrocatalysts for the hydrogen evolution reaction is an important component of these efforts. Proton-coupled electron transfer (PCET) reactions, in which electron transfer is coupled to proton transfer, play an important role in these processes and can be enhanc...

The ion/ion reactions of several dozen reagent anions with triply protonated cations of the model peptide KGAILKGAILR have been examined to evaluate predictions of a Landau-Zener-based model for the likelihood for electron transfer. Evidence for electron transfer was provided by the appearance of fragment ions unique to electron transfer or electron capture dissociation. Proton transfer and ele...

Bis(indolyl)methene displays high selectivity and sensitivity for aspartate and glutamate in water-containing medium based on the proton transfer signaling mode. The presence of acid can easily induce proton transfer to the basic H-bond acceptor moiety, which modulates the internal charge transfer state of the bis(indolyl)methene skeleton and gives rise to dramatic change in color. The detectio...

The abnormal Brfnsted slopes observed for nitroalkanes are interpreted as a variation in the work terms, which is caused by a variation in hydrogen bond strengths with the free energy for proton transfer, rather than as an anomaly in the proton-transfer stage itself.