scholarly journals Cluster exchange reactivity of [2Fe–2S] cluster-bridged complexes of BOLA3 with monothiol glutaredoxins

Metallomics ◽  
2018 ◽  
Vol 10 (9) ◽  
pp. 1282-1290 ◽  
Author(s):  
Sambuddha Sen ◽  
Brian Rao ◽  
Christine Wachnowsky ◽  
J. A. Cowan
Keyword(s):  
Exchange Rate ◽  
Thermodynamic Parameters ◽  
Rate Constants ◽  
Cluster Exchange ◽  
Partner Proteins

Cluster exchange reactivity of a [2Fe–2S]-bridged BOLA3–GLRX5 heterodimer complex with mitochondrial partner proteins is quantitatively evaluated, and exchange rate constants and ITC-determined thermodynamic parameters contrasted with the corresponding BOLA3 heterocomplex with NFU1.

Determination of the Accurate Values of the Rate Constant and Thermodynamic Parameters for the Rotation About the C(sp2)-C(aryl) Bond; Adamantan-1-yl 3-Bromo-2,4,6-trimethylphenyl Ketone

1998 ◽  
Vol 63 (7) ◽  
pp. 955-966
Author(s):  
Eva Přibylová ◽  
Miroslav Holík
Keyword(s):  
Thermodynamic Parameters ◽  
Shape Analysis ◽  
Rate Constants ◽  
Line Shape ◽  
Microsoft Excel ◽  
Hindered Rotation ◽  
H Nmr ◽  
Line Shape Analysis ◽  
Coalescence Temperature

Four programs for the 1H NMR line shape analysis: two commercial - Winkubo (Bruker) and DNMR5 (QCPE 165) and two written in our laboratory - Newton (in Microsoft Excel) and Simtex (in Matlab) have been tested in order to get highly accurate rate constants of the hindered rotation about a single bond. For this purpose four testing criteria were used, two of them were also developed by us. As supplementary determinations the rate constants obtained for the coalescence temperature and for the thermal racemization of chromatographically separated enantiomers were used which fitted well the temperature dependence of the rate constants determined by the line shape analysis. As a test compound adamantan-1-yl 3-bromo-2,4,6-trimethylphenyl ketone was prepared and studied. It was shown that supermodified simplex method used in our algorithm (Simtex), though time consuming, gives the most accurate values of the rate constants and consequently the calculated thermodynamic parameters Ea, ∆H≠, and ∆S≠ lay in relatively narrow confidence intervals.

Synthetic models for active sites of reduced blue copper proteins: minimal geometric change between two oxidation states for fast self-exchange rate constants

2004 ◽  
Vol 7 (11) ◽  
pp. 1188-1190 ◽  
Author(s):  
Kiyoshi Fujisawa ◽  
Koyu Fujita ◽  
Tatsuya Takahashi ◽  
Nobumasa Kitajima ◽  
Yoshihiko Moro-oka ◽  
...  
Keyword(s):  
Exchange Rate ◽  
Rate Constants ◽  
Active Sites ◽  
Oxidation States ◽  
Copper Proteins ◽  
Blue Copper Proteins ◽  
Blue Copper ◽  
Synthetic Models

Protein–protein cross-reactions involving plastocyanin, cytochrome f and azurin: self-exchange rate constants and related studies with inorganic complexes

1992 ◽  
pp. 2145-2151 ◽  
Author(s):  
D. G. A. Harshani de Silva ◽  
Douglas Beoku-Betts ◽  
Panayotis Kyritsis ◽  
K. Govindaraju ◽  
Roy Powls ◽  
...  
Keyword(s):  
Exchange Rate ◽  
Rate Constants ◽  
Cytochrome F ◽  
Cross Reactions ◽  
Inorganic Complexes

scholarly journals Beyond the Active Site: Mechanistic Investigations of the Role of the Secondary Coordination Sphere and Beyond on Multi-Electron Electrocatalytic Reactions and Their Relations Between Kinetics and Thermodynamics

2020 ◽  
Author(s):  
Vincent Wang
Keyword(s):  
Thermodynamic Parameters ◽  
Coordination Sphere ◽  
Active Site ◽  
Rate Constants ◽  
Reduction Reaction ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Secondary Coordination Sphere ◽  
Catalytic Rate ◽  
Rate Limiting

<p>The development of an electrocatalyst with a rapid turnover frequency, low overpotential and long-term stability is highly desired for fuel-forming reactions, such as water splitting and CO<sub>2</sub> reduction. The findings of the scaling relationships between the catalytic rate and thermodynamic parameters over a wide range of electrocatalysts in homogeneous and heterogeneous systems provide useful guidelines and predictions for designing better catalysts for those redox reactions. However, such relationships also suggest that a catalyst with a high catalytic rate is typically associated with a high overpotential for a given reaction. Inspired by enzymes, the introduction of additional interactions through the secondary coordination sphere beyond the active site, such as hydrogen-bonding or electrostatic interactions, have been shown to offer a promising avenue to disrupt these unfavorable relationships. Herein, we further investigate the influence of these cooperative interactions on the faster chemical steps, in addition to the rate-limiting step widely examined before, for molecular electrocatalysts with the structural and electronic modifications designed to facilitate the dioxygen reduction reaction, CO<sub>2</sub> reduction reaction and hydrogen evolving reaction. Based on the electrocatalytic kinetic analysis, the rate constants for faster chemical steps and their correlation with the corresponding thermodynamic parameters are evaluated. The results suggest that the effects of the secondary coordination sphere and beyond on these fuel-forming reactions are not necessarily beneficial for promoting all chemical steps and no apparent relation between rate constants and thermodynamic parameters are found in some cases studied here, which may implicate the design of electrocatalysts in the future. Finally, these analyses demonstrate that the characteristic features for voltammograms and foot-of-the-wave-analysis plots are associated with the specific kinetic phenomenon among these multi-electron electrocatalytic reactions, which provides a useful framework to probe the insights of chemical and electronic modifications on the catalytic steps quantitatively (i.e. kinetic rate constants) and to optimize some of critical steps beyond the rate-limiting step.</p>

Reduction of hexaammineruthenium(III) ions by a series of tris(polypyridyl)chromium(II) ions – Revisiting the Cr(NN)33+/2+ self-exchange rate

2001 ◽  
Vol 79 (7) ◽  
pp. 1124-1127 ◽  
Author(s):  
K Omar Zahir
Keyword(s):  
Exchange Rate ◽  
Excited States ◽  
Rate Constants ◽  
Driving Force ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Outer Sphere ◽  
Laser Flash ◽  
Exchange Rate Constant ◽  
Kinetics Of

The kinetics of the outer-sphere oxidation of Cr(NN)32+ ions (NN = 2,2'-bipyridine, 1,10-phenanthroline, and their substituted analogs) by hexaammineruthenium(III) was studied using laser flash photolysis. The Cr(NN)32+ ions were generated via the reductive quenching of the *Cr(NN)33+ excited states by oxalate ions or by H2edta2–. The second-order rate constants were found to vary with the driving force of the reaction. The rate constants increase from (7.1 ± 0.5) × 106 M–1 s–1 for Cr(5-Clphen)32+ to (2.6 ± 0.2) × 108 M–1 s–1 for Cr(4,7-Me2phen)32+. The self-exchange rate constant for the couple (Cr(NN)33+/2+) was calculated by applying Marcus cross relation to present and other known reactions of Cr(NN)3n+ ions, where n = 3 or 2 with various reactants and is estimated to be (6 ± 4) × 107 M–1 s–1.Key words: tris(polypyridyl)chromium(II)/(III) self-exchange rate, hexaammineruthenium(III), oxidation of Cr(NN)32+.

Base-catalyzed hydrogen isotope exchange of thiocamphor: α-thioenolization rate constants

1978 ◽  
Vol 56 (19) ◽  
pp. 2605-2606 ◽  
Author(s):  
Nick Henry Werstiuk ◽  
Paul Andrews
Keyword(s):  
Exchange Rate ◽  
Rate Constants ◽  
Hydrogen Isotope ◽  
Isotope Exchange ◽  
Deuterium Exchange ◽  
Hydrogen Isotope Exchange

The rates of base-catalyzed protium–deuterium exchange (α-thioenolization) of the exo and endo protons of thiocamphor (1), in 2:1 dioxane-D2O at 25.0 ± 0.5 °C, have been determined by monitoring the uptake of deuterium mass spectrometrically. The exo and endo exchange rate constants, 2.20 × 10−2 and 5.60 × 10−4 M−1 s−1, respectively, are 23.2 and 12.3 times larger than the rate constants for exo and endo exchange in camphor (2). Factors which may determine the rate enhancements are discussed.

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