pH Dependence of the Reduction of Dioxygen to Water by CytochromecOxidase. 2. Branched Electron Transfer Pathways Linked by Proton Transfer†

Biochemistry ◽  
2003 ◽  
Vol 42 (17) ◽  
pp. 5074-5090 ◽  
Author(s):  
Istvan Szundi ◽  
Ned Van Eps ◽  
Ólöf Einarsdóttir
Keyword(s):  
Electron Transfer ◽  
Proton Transfer ◽  
Ph Dependence ◽  
Electron Transfer Pathways

scholarly journals Pathway of proton transfer in bacterial reaction centers: replacement of glutamic acid 212 in the L subunit by glutamine inhibits quinone (secondary acceptor) turnover

1989 ◽  
Vol 86 (17) ◽  
pp. 6602-6606 ◽  
Author(s):  
M L Paddock ◽  
S H Rongey ◽  
G Feher ◽  
M Y Okamura
Keyword(s):  
Electron Transfer ◽  
Proton Transfer ◽  
Transfer Rate ◽  
Ph Dependence ◽  
Proton Donor ◽  
Reaction Centers ◽  
Site Directed Mutagenesis ◽  
Back Reaction ◽  
Electron Transfer Rate

The mechanism of proton transfer in the reaction centers (RCs) from Rhodobacter sphaeroides was investigated by site-directed mutagenesis. Replacement of Glu-212 of the L subunit, a protonatable residue located near the secondary acceptor (QB) binding site, by glutamine reduced the in vitro electron turnover from cytochrome c to 2,3-dimethoxy-5-methylbenzoquinone (UQ0) by a factor of 25. The electron transfer rate to QB remained essentially unimpaired. Consequently, it is postulated that the reduced turnover in the mutant is due to a reduced rate of proton transfer to QB2-. The lack of pH dependence of the forward electron transfer rate DQA-QB----DQAQB- and the back reaction rate D+QAQB- ----DQAQB (where D = primary donor and QA = primary acceptor) in the mutant RC indicate that the observed pH dependence in the native RC is due to Glu-212, which has an anomalously high pKa value of 9.5 +/- 0.3. These results support the involvement of Glu-212 as a proton donor to reduced QB.

scholarly journals Enantioselective Protonation of Radical Anion Intermediates in Photoallylation and Photoreduction Reactions of 3,3-Diaryl-1,1-dicyano-2-methylprop-1-ene with Allyltrimethylsilane

Molecules ◽  
2019 ◽  
Vol 24 (14) ◽  
pp. 2677
Author(s):  
Hajime Maeda ◽  
Masayuki Iida ◽  
Daisuke Ogawa ◽  
Kazuhiko Mizuno
Keyword(s):  
Electron Transfer ◽  
Acetic Acid ◽  
Proton Transfer ◽  
Carboxylic Acids ◽  
Photoinduced Electron Transfer ◽  
Radical Anion ◽  
Mandelic Acid ◽  
Proton Source ◽  
Acetonitrile Solutions ◽  
Electron Transfer Pathways

Photoreactions of acetonitrile solutions of 3,3-diaryl-1,1-dicyano-2-methylprop-1-enes (1a–c) with allyltrimethylsilane (2) in the presence of phenanthrene as a photoredox catalyst and acetic acid as a proton source formed photoallylation (3) and photoreduction (4) products via photoinduced electron transfer pathways. When (S)-mandelic acid was used as the proton source, the reactions proceeded with 3.4 and 4.8 %ee for formation of 3 and 4, respectively. The results of studies of the effect of aryl ring substituents and several chiral carboxylic acids suggested that the enantioselectivities of the reactions are governed by steric controlled proton transfer in intermediate complexes formed by π-π and OH-π interactions of anion radicals derived from 1a–c and chiral carboxylic acids.

scholarly journals Redox potentials along the redox-active low-barrier H-bonds in electron transfer pathways

2020 ◽  
Vol 22 (44) ◽  
pp. 25467-25473 ◽  
Author(s):  
Keisuke Saito ◽  
Manoj Mandal ◽  
Hiroshi Ishikita
Keyword(s):  
Electron Transfer ◽  
Proton Transfer ◽  
Redox Potential ◽  
Driving Force ◽  
Electronic Coupling ◽  
Redox Potentials ◽  
Redox Active ◽  
Electron Transfer Pathways

Local proton transfer along redox-active low-barrier H-bonds can alter the driving force or electronic coupling for electron transfer, as the redox potential values depend on the H+ position in low-barrier H-bonds.

scholarly journals Electrochemical Response of Glucose Oxidase Adsorbed on Laser-Induced Graphene

Nanomaterials ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1893
Author(s):  
Sónia O. Pereira ◽  
Nuno F. Santos ◽  
Alexandre F. Carvalho ◽  
António J. S. Fernandes ◽  
Florinda M. Costa
Keyword(s):  
Electron Transfer ◽  
Glucose Oxidase ◽  
Ph Dependence ◽  
High Surface ◽  
High Surface Area ◽  
Cost Effective ◽  
Great Promise ◽  
Glucose Detection ◽  
Half Wave ◽  
Electrochemical Transducers

Carbon-based electrodes have demonstrated great promise as electrochemical transducers in the development of biosensors. More recently, laser-induced graphene (LIG), a graphene derivative, appears as a great candidate due to its superior electron transfer characteristics, high surface area and simplicity in its synthesis. The continuous interest in the development of cost-effective, more stable and reliable biosensors for glucose detection make them the most studied and explored within the academic and industry community. In this work, the electrochemistry of glucose oxidase (GOx) adsorbed on LIG electrodes is studied in detail. In addition to the well-known electroactivity of free flavin adenine dinucleotide (FAD), the cofactor of GOx, at the expected half-wave potential of −0.490 V vs. Ag/AgCl (1 M KCl), a new well-defined redox pair at 0.155 V is observed and shown to be related to LIG/GOx interaction. A systematic study was undertaken in order to understand the origin of this activity, including scan rate and pH dependence, along with glucose detection tests. Two protons and two electrons are involved in this reaction, which is shown to be sensitive to the concentration of glucose, restraining its origin to the electron transfer from FAD in the active site of GOx to the electrode via direct or mediated by quinone derivatives acting as mediators.

scholarly journals Electron transfer pathways in photoexcited lanthanide(III) complexes of picolinate ligands

2021 ◽  
Author(s):  
Daniel Kovacs ◽  
Daniel Kocsi ◽  
Jordann A. L. Wells ◽  
Salauat R. Kiraev ◽  
Eszter Borbas
Keyword(s):  
Electron Transfer ◽  
Metal Binding ◽  
Binding Sites ◽  
Secondary Amide ◽  
Metal Binding Sites ◽  
Electron Transfer Pathways

A series of luminescent lanthanide(III) complexes consisting of 1,4,7-triazacyclononane frameworks and three secondary amide-linked carbostyril antennae were synthesised. The metal binding sites were augmented with two pyridylcarboxylate donors yielding octadentate...

ChemInform Abstract: Energy Transfer, Proton Transfer, and Electron Transfer Reactions Within Zeolites

ChemInform ◽  
2010 ◽  
Vol 30 (8) ◽  
pp. no-no
Author(s):  
V. Ramamurthy ◽  
P. Lakshminarasimhan ◽  
Clare P. Grey ◽  
Linda J. Johnston
Keyword(s):  
Electron Transfer ◽  
Energy Transfer ◽  
Proton Transfer ◽  
Transfer Reactions ◽  
Electron Transfer Reactions

Control of Electron Transfer Pathways in a Dye-Sensitized Solar Cell

2006 ◽  
Vol 97 (20) ◽  
Author(s):  
Ben Brüggemann ◽  
Juan Angel Organero ◽  
Torbjörn Pascher ◽  
Tõnu Pullerits ◽  
Arkady Yartsev
Keyword(s):  
Electron Transfer ◽  
Solar Cell ◽  
Dye Sensitized Solar Cell ◽  
Dye Sensitized ◽  
Electron Transfer Pathways

Reduction of the oxidized bacteriochlorophyll dimer in reaction centers by ferrocene is dependent upon the driving force

2007 ◽  
Vol 11 (03) ◽  
pp. 205-211 ◽  
Author(s):  
László Kálmán ◽  
Arlene L. M. Haffa ◽  
JoAnn C. Williams ◽  
Neal W. Woodbury ◽  
James P. Allen
Keyword(s):  
Electron Transfer ◽  
Rate Constants ◽  
Ph Dependence ◽  
Photosynthetic Bacterium ◽  
Energy Difference ◽  
Reaction Centers ◽  
Free Energy Difference ◽  
Midpoint Potential ◽  
Bacteriochlorophyll Dimer ◽  
Purple Photosynthetic Bacterium

The rates of electron transfer from ferrocene to the oxidized bacteriochlorophyll dimer, P , in reaction centers from the purple photosynthetic bacterium Rhodobacter sphaeroides, were measured for a series of mutants in which the P / P + midpoint potentials range from 410 to 765 mV (Lin et al. Proc. Natl. Acad. Sci. USA 1994; 91: 10265-10269). The observed rate constant for each mutant was found to be linearly dependent upon the ferrocene concentration up to 50 μM. The electron transfer is described as a second order reaction with rate constants increasing from 1.5 to 35 × 106 M -1. s -1 with increasing P / P + midpoint potential. This dependence was tested for three additional mutants, each of which exhibits a pH dependence of the P / P + midpoint potential due to an electrostatic interaction with an introduced carboxylic group (Williams et al. Biochemistry 2001; 40: 15403-15407). For these mutants, the pH dependence of the bimolecular rate constants followed a sigmoidal pattern that could be described with a Henderson-Hasselbalch equation, attributable to the change of the free energy difference for the reaction due to deprotonation of the introduced carboxylic side chains.

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