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 ...

Electron-transfer reactions are fundamental to many practical devices, but because of their complexity, it is often very difficult to interpret measurements done on the complete device. Therefore, studies of model systems are crucial. Here the rates of charge separation and recombination in donor-acceptor systems consisting of a series of butadiyne-linked porphyrin oligomers (n = 1-4, 6) append...

A series of monodisperse oligomers consisting of alternating thiophene (T) and perylene bisimide (P), denoted as (TP)(n)T (n = 1, 2, 3, 6), were synthesized and photophysically characterized. The steady-state absorption and fluorescence spectra revealed that the low-energy P-derived band remains almost unchanged upon the increment of the number of the repeat unit n. This can be rationalized as ...

Measurements of voltage changes in response to charge separation within membrane proteins can offer fundamental information on mechanisms of charge transport and displacement processes. A recent example is provided by studies of cytochrome c oxidase. However, the interpretation of the observed voltage changes in terms of the number of charge equivalents and transfer distances is far from being ...

We report upon an analysis of the vibrational modes that couple and drive the state-to-state electronic transfer branching ratios in a model donor-bridge-acceptor system consisting of a phenothiazine-based donor linked to a naphthalene-monoimide acceptor via a platinum-acetylide bridging unit. Our analysis is based upon an iterative Lanczos search algorithm that finds superpositions of vibronic...

Protein and RNA enzymes that catalyze phosphoryl transfer reactions frequently contain active site metal ions that interact with the nucleophile and leaving group. Mechanistic models generally hinge upon the assumption that the metal ions stabilize negative charge buildup along the reaction coordinate. However, experimental data that test this assumption directly remain difficult to acquire. We...

Density functional theory (DFT) was applied to study sulfur-doped graphene clusters as oxygen reduction reaction (ORR) cathode catalysts for fuel cells. Several sulfurdoped graphene clusters with/without Stone−Wales defects were investigated and their electronic structures, reaction free energy, transition states, and energy barriers were calculated to predict their catalytic properties. The re...

Catalytic promiscuity, the ability of an enzyme to catalyze alternative reactions, has been suggested to have played an important role in the evolution of new catalytic activities in protein enzymes. Similarly, promiscuous activities may have been advantageous in an earlier RNA world. The Tetrahymena Group I ribozyme naturally catalyzes the site-specific guanosine attack on an anionic phosphate...