A thorough analysis of the single and double proton transfer and the internal rotations of neutral indigo and its dianionic leucoindigo form has been performed for the ground and first singlet excited electronic states using, respectively, DFT and TDDFT state-of-the-art methods. Our theoretical analysis discloses that the diketo isomer is the most stable one in the ground state of indigo but no...

The NOR (nitric oxide reductase) from Paracoccus denitrificans catalyses the two-electron reduction of NO to N(2)O (2NO+2H(+)+2e(-)-->N(2)O+H(2)O). The NOR is a divergent member of the superfamily of haem-copper oxidases, oxygen-reducing enzymes which couple the reduction of oxygen with translocation of protons across the membrane. In contrast, reduction of NO catalysed by NOR is non-electrogen...

PURPOSE This study aimed to quantitatively investigate two main magnetization transfer effects at low B1: the nuclear Overhauser enhancement (NOE) and amide proton transfer in the human brain at 7 T. METHODS The magnetization transfer effects in the human brain were characterized using a four-pool proton model, which consisted of bulk water, macromolecules, an amide group of mobile proteins a...

Gas-phase reactions of singly-charged anions with multiply-protonated peptides, in a RF quadrupole linear ion trap, leads to either peptide deprotonation (proton transfer) or electron deposition (electron transfer). The former process induces peptide backbone cleavage through a reaction scheme analogous to electron capture dissociation (ECD). Here we characterize the preferred reaction pathways...

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...

Hydrogen bonds are important in supramolecular chemistry and responsible for proton transfer processes. This manuscript reports new hydrogen-bonding systems of redox-active acid-base assemblies consisting of dimethylthio-tetrathiafulvalene dicarboxylic acid (H(2)L) coupled with pyridine (py), 2,2'-bipyridine (2,2'-bpy), and 4,4'-bipyridine (4,4'-bpy). The (1)H NMR chemical shifts of the pyridin...

The bacterial reaction center couples light-induced electron transfer to proton pumping across the membrane by reactions of a quinone molecule Q(B) that binds two electrons and two protons at the active site. This article reviews recent experimental work on the mechanism of the proton-coupled electron transfer and the pathways for proton transfer to the Q(B) site. The mechanism of the first ele...

Hydrogen bonding interactions between biological chromophores and their surrounding protein and solvent environment significantly affect the photochemical pathways of the chromophore and its biological function. A common first step in the dynamics of these systems is excited state proton transfer between the noncovalently bound molecules, which stabilizes the system against dissociation and pri...

A comparison of hydride, hydrogen atom, and proton-coupled electron transfer reactions is presented. Herein, hydride and hydrogen atom transfer refer to reactions in which the electrons and protons transfer between the same donor and acceptor, while proton-coupled electron transfer (PCET) refers to reactions in which the electrons and protons transfer between different centers. Within these def...

The diffraction slope parameter is investigated for elastic proton-proton and protonantiproton scattering based on the all available experimental data at intermediate square of momentum transfer in the main. Energy dependence of the elastic diffraction slope is approximated by various analytic functions in a model-independent fashion. The expanded standard logarithmic approximations allow to de...