The heme-copper oxidase superfamily comprises cytochrome c and ubiquinol oxidases. These enzymes catalyze the transfer of electrons from different electron donors onto molecular oxygen. A B-family hyperthermophilic bacterium Aquifex aeolicus was discovered previously to be able use both naphthoquinol as donors. Its mechanism well evolutionary significance are yet unknown. Here we solved its 3.4...

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...

Diphenyl-, aryl-a-siloxyand %-furany1 carbenes can be protonated by even weak proton donors such as alcohols (by a bimolecular or by a pre-association mechanism involving more than one alcohol molecule) to yield the corresponding carbenium ions, whose spectra and electrophilic patterns of behavior are described. INTRODUCTION Proton transfer reactions to and from heteroatoms (= "normal" Bronsted...

Light is a common source of energy in sustainable technologies for photocurrent generation. To date, such light-harvesting applications, the excited electrons generate photocurrent. Here, we introduce new mechanism generation that based on state proton transfer (ESPT) photoacids and photobases can donate or accept proton, respectively, but only after excitation. We show formed ions following ES...

Among synthetic models of nitrogenases, iron–dinitrogen complexes with an Fe–C bond have attracted increasing attention in recent years. Here we report the synthesis square-planar iron(I)–dinitrogen supported by anionic benzene-based PCP- and POCOP-type pincer ligands as carbon donors. These catalyze formation ammonia hydrazine from reaction dinitrogen (1 atm) a reductant proton source at ?78 °...

Photosystem II-dependent cyclic photophosphorylation activity produced by addition of p-phenylenediamines to KCN-Hg-NH(2)OH-inhibited chloroplasts is the product of two separate reactions when a proton/electron donor is the catalyst. The activity observed with an electron donor as catalyst consists of a single reaction. One of the cyclic reactions, evoked by low (</=40 micromolar) concentration...

Photosynthesis in bacteria involves absorption of light by antenna chromophores and transfer of excitation to reaction centers, which convert the excitation energy to electrochemical potential energy in the form of transmembrane charge separation. A proton pump uses this stored energy to generate proton motive force across the membrane, which in turn is used to synthesize adenosine triphosphate...

The residue phenylalanine 198 (Phe 198) is a prominent cause of the lower activity of human carbonic anhydrase III (HCA III) compared with HCA II and other isozymes which have leucine at this site. We report the crystal structures of HCA III and the site-directed mutant F198L HCA III, both at 2.1 A resolution, and the enhancement of catalytic activity by exogenous proton donors containing imida...

Mechanistic studies show the importance of iodide displacement by additives that accelerate reactions of samarium diiodide. The key feature important for acceleration of reaction rate is the use of proton donors and other additives that have a high enough affinity for Sm(II) to displace iodide yet do not saturate the coordination sphere inhibiting substrate reduction.