In this research we employed single-molecule electric recording techniques to investigate effects of the transmembrane and dipole potential on the reversible protonation of acidic residues from the constriction zone of the OmpF porin. Our results support the paradigm according to which the protonation state of aspartate 113 and glutamate 117 residues from the constriction region of OmpF is infl...

Carbanionic intermediates play a central role in the catalytic transformations of amino acids performed by pyridoxal-5'-phosphate (PLP)-dependent enzymes. Here, we make use of NMR crystallography-the synergistic combination of solid-state nuclear magnetic resonance, X-ray crystallography, and computational chemistry-to interrogate a carbanionic/quinonoid intermediate analogue in the β-subunit a...

We present a computational scheme to compute the pH-dependence of binding free energy with explicit solvent. Despite the importance of pH, the effect of pH has been generally neglected in binding free energy calculations because of a lack of accurate methods to model it. To address this limitation, we use a constant-pH methodology to obtain a true ensemble of multiple protonation states of a ti...

The proton permeation process of the stator complex MotA/B in the flagellar motor of Escherichia coli was investigated. The atomic model structure of the transmembrane part of MotA/B was constructed based on the previously published disulfide cross-linking and tryptophan scanning mutations. The dynamic permeation of hydronium/sodium ions and water molecule through the channel formed in MotA/B w...

The u.v. difference spectra generated when methotrexate, trimethoprim or folate bind to Lactobacillus casei dihydrofolate reductase were analysed. The difference spectrum produced by methotrexate binding is shown to consist of three components: (a) one closely resembling that observed on protonation of methotrexate, reflecting an increased degree of protonation on binding; (b) a pH-independent ...

Tryptophan hydroxylase, the initial and rate-limiting enzyme in serotonin biosynthesis, is inactivated by peroxynitrite in a concentration-dependent manner. This effect is prevented by molecules that react directly with peroxynitrite such as dithiothreitol, cysteine, glutathione, methionine, tryptophan, and uric acid but not by scavengers of superoxide (superoxide dismutase), hydroxyl radical (...

protonation of the reactive intermediates generated in the raction between dalkyl acetylenedicarboxylates and triphenylphosphine by isonitrosoacetophenone leads to vinyltriphenylphosphonium salts, which undergo intramolecular wittig reaction to produce dalkyl 4-phenyl-n-hydroxypyrrole-2,3-dicarboxylates in moderate yields.

The protonation of different species of glycylisoleucine were studied in the pH range of 1.5 - 10 at25 °C using potentiometric technique. Investigations were performed in sodium perchlorate andtetraethylammonium iodide as background electrolytes at I (0.1, 0.2, 0.3, 0.4, 0.5, and 0.6) moldm-3. The parameters based on the protonation constants were calculated, and their dependenceson ionic stren...