Photoinitiated proton-coupled electron transfer (PCET) kinetics has been investigated in a series of four modified tyrosines linked to a ruthenium photosensitizer in acetonitrile, with each tyrosine bearing an internal hydrogen bond to a covalently linked pyridine or benzimidazole base. After correcting for differences in driving force, it is found that the intrinsic PCET rate constant still va...

In bacteriorhodopsin Asp85 has been proposed to function both as a negative counterion to the Schiff base and as proton acceptor in the early stages of the photocycle. To test this proposal further, we have replaced Asp85 by His. The rationale for this replacement is that although His can function as a proton acceptor, it cannot provide a negative charge at residue 85 to serve as a counterion t...

Crystals of human carbonic anhydrase II with a specific point mutation, His 64 to Ala, have been grown in a solution of ammonium sulfate in the presence of mercury chloride. The crystals appear in approximately two weeks and belong to the monoclinic space group P21, with unit cell parameters of a = 42.2 Å, b = 41.4 Å, c = 71.9 Å, β = 104.2 and one carbonic anhydrase molecule in the asymmetric u...

Proton transfers are fundamental to chemical processes in solution and biological systems. Often, the well-known Grotthuss mechanism is assumed where a series of sequential "proton hops" initiates from the donor and combines to produce the net transfer of a positive charge over a long distance. Although direct experimental evidence for the sequential proton hopping has been obtained recently, a...

The absorption spectra of chloramphenicol aqueous solution were obtained experimentally. isomers and the effect on formation H-bonded complexes calculated interpreted using quantum chemistry methods. Calculation results showed that spectrum by position bands their nature is largely determined nitrobenzene fragment with little participation propanol dichloroacetamide fragments chloramphenicol. p...

Channelrhodopsins serve as photoreceptors that control the motility behavior of green flagellate algae and act as light-gated ion channels when heterologously expressed in animal cells. Here, we report direct measurements of proton transfer from the retinylidene Schiff base in several channelrhodopsin variants expressed in HEK293 cells. A fast outward-directed current precedes the passive chann...

The catalytic cycle of numerous enzymes involves the coupling between proton transfer and electron transfer. Yet, the understanding of this coordinated transfer in biological systems remains limited, likely because its characterization relies on the controlled but experimentally challenging modifications of the free energy changes associated with either the electron or proton transfer. We have ...

We review studies of subunit III-depleted cytochrome c oxidase (CcO III (-)) that elucidate the structural basis of steady-state proton uptake from solvent into an internal proton transfer pathway. The removal of subunit III from R. sphaeroides CcO makes proton uptake into the D pathway a rate-determining step, such that measurements of the pH dependence of steady-state O(2) consumption can be ...

Proton transfer in polymer electrolyte membrane is an essential mechanism fuel cell (PEMFC). The development of PEM mostly relies on modification with proton conductive species followed by casting. This brings the random existence to result a limit conductivity. present work proposes alignment species, i.e., donor and acceptor chains, through surface-initiated polymerization so that proceeds ef...

In this work we give an overview of the methodologies required to compute the rate of proton transfer in hydrogen bonded systems in solution Using ab initio or density functional methods we determine proton potentials of a truncated sys tem as a function of proton donor proton acceptor distance as well as nonbonding parameters By classical molecular dynamics we evaluate a swarm of proton po ten...