Electrochemical Reduction of [Ni(Mebpy) 3 ] 2+ : Elucidation of the Redox Mechanism by Cyclic Voltammetry and Steady‐State Voltammetry in Low Ionic Strength Solutions

2020 ◽  
Vol 7 (6) ◽  
pp. 1473-1479
Author(s):  
Koushik Barman ◽  
Martin A. Edwards ◽  
David P. Hickey ◽  
Christopher Sandford ◽  
Yinghua Qiu ◽  
...  
Keyword(s):  
Cyclic Voltammetry ◽  
Steady State ◽  
Ionic Strength ◽  
Electrochemical Reduction ◽  
Redox Mechanism ◽  
Low Ionic Strength

Electrochemical Reduction of [Ni(Mebpy)3]2+. Elucidation of the Redox Mechanism by Cyclic Voltammetry and Steady-State Voltammetry in Low Ionic Strength Solutions.

2020 ◽  
Author(s):  
Koushik Barman ◽  
Martin A. Edwards ◽  
David P. Hickey ◽  
Christopher Sandford ◽  
Yinghua Qiu ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Cyclic Voltammetry ◽  
Steady State ◽  
Ionic Strength ◽  
Outer Sphere ◽  
Oxidation States ◽  
Bulk Solution ◽  
Redox Mechanism ◽  
Predominant Species ◽  
Low Ionic Strength

<p>Bipyridine complexes of Ni are used as catalysts in a variety of reductive transformations. Here, the electroreduction of [Ni(Mebpy)<sub>3</sub>]<sup>2+</sup> (Mebpy = 4,4’-dimethyl-2,2’-bipyridine) in dimethylformamide is reported, with the aim of determining the redox mechanism and oxidation states of products formed under well-controlled electrochemical conditions. Results from cyclic voltammetry, steady-state voltammetry (SSV) and chronoamperometry demonstrate that [Ni(Mebpy)<sub>3</sub>]<sup>2+</sup> undergoes two sequential 1<i>e</i> reductions at closely separated potentials (<i>E</i><sup>0’</sup><sub>1 </sub>= -1.06 ± 0.01 V and <i>E</i><sup>0<i>’</i></sup><sub>2 </sub>=<sub> </sub>-1.15 ± 0.01 V vs Ag/AgCl (3.4 M KCl)). Homogeneous comproportionation to generate [Ni(Mebpy)<sub>3</sub>]<sup>+ </sup>is demonstrated in SSV experiments in low ionic strength solutions. The comproportionation rate constant is determined to be > 10<sup>6</sup> M<sup>-1</sup>s<sup>-1</sup>, consistent with rapid outer-sphere electron transfer. Consequentially, on voltammetric time scales, the 2<i>e</i> reduction of [Ni(Mebpy)<sub>3</sub>]<sup>2+</sup> results in formation of [Ni(Mebpy)<sub>3</sub>]<sup>1+</sup> as the predominant species released into bulk solution. We also demonstrate that [Ni(Mebpy)<sub>3</sub>]<sup>0</sup><sub> </sub>slowly loses a Mebpy ligand (~10 s<sup>-1</sup>).</p>

Electrochemical Reduction of [Ni(Mebpy)3]2+. Elucidation of the Redox Mechanism by Cyclic Voltammetry and Steady-State Voltammetry in Low Ionic Strength Solutions.

2020 ◽  
Author(s):  
Koushik Barman ◽  
Martin A. Edwards ◽  
David P. Hickey ◽  
Christopher Sandford ◽  
Yinghua Qiu ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Cyclic Voltammetry ◽  
Steady State ◽  
Ionic Strength ◽  
Outer Sphere ◽  
Oxidation States ◽  
Bulk Solution ◽  
Redox Mechanism ◽  
Predominant Species ◽  
Low Ionic Strength

<p>Bipyridine complexes of Ni are used as catalysts in a variety of reductive transformations. Here, the electroreduction of [Ni(Mebpy)<sub>3</sub>]<sup>2+</sup> (Mebpy = 4,4’-dimethyl-2,2’-bipyridine) in dimethylformamide is reported, with the aim of determining the redox mechanism and oxidation states of products formed under well-controlled electrochemical conditions. Results from cyclic voltammetry, steady-state voltammetry (SSV) and chronoamperometry demonstrate that [Ni(Mebpy)<sub>3</sub>]<sup>2+</sup> undergoes two sequential 1<i>e</i> reductions at closely separated potentials (<i>E</i><sup>0’</sup><sub>1 </sub>= -1.06 ± 0.01 V and <i>E</i><sup>0<i>’</i></sup><sub>2 </sub>=<sub> </sub>-1.15 ± 0.01 V vs Ag/AgCl (3.4 M KCl)). Homogeneous comproportionation to generate [Ni(Mebpy)<sub>3</sub>]<sup>+ </sup>is demonstrated in SSV experiments in low ionic strength solutions. The comproportionation rate constant is determined to be > 10<sup>6</sup> M<sup>-1</sup>s<sup>-1</sup>, consistent with rapid outer-sphere electron transfer. Consequentially, on voltammetric time scales, the 2<i>e</i> reduction of [Ni(Mebpy)<sub>3</sub>]<sup>2+</sup> results in formation of [Ni(Mebpy)<sub>3</sub>]<sup>1+</sup> as the predominant species released into bulk solution. We also demonstrate that [Ni(Mebpy)<sub>3</sub>]<sup>0</sup><sub> </sub>slowly loses a Mebpy ligand (~10 s<sup>-1</sup>).</p>

scholarly journals Proteolytic removal of three C-terminal residues of actin alters the monomer-monomer interactions

1993 ◽  
Vol 289 (3) ◽  
pp. 897-902 ◽  
Author(s):  
M Mossakowska ◽  
J Moraczewska ◽  
S Khaitlina ◽  
H Strzelecka-Golaszewska
Keyword(s):  
Electron Microscopy ◽  
Steady State ◽  
Ionic Strength ◽  
Rate Constants ◽  
Initial Rate ◽  
Critical Concentration ◽  
Rate Of Polymerization ◽  
Low Ionic Strength ◽  
Hydrolysis Of

Homogeneous preparations of actin devoid of the three C-terminal residues were obtained by digestion of G-actin with trypsin after blocking proteolysis at other sites by substitution of Mg2+ for the tightly bound Ca2+. Removal of the C-terminal residues resulted in the following: an enhancement of the Mg(2+)-induced hydrolysis of ATP in low-ionic-strength solutions of actin; an increase in the critical concentration for polymerization; a decrease in the initial rate of polymerization; and an enhancement of the steady-state exchange of subunits in the polymer. Electron microscopy indicated an increased fragility of the filaments assembled from truncated actin. The results suggest that removal of the C-terminal residues increases the rate constants for monomer dissociation from the polymer ends and from the oligomeric species.

Conformational Transitions in Escherichia coli Ribosomal RNAs as Visualized by Dedicated STEM

1988 ◽  
Vol 46 ◽  
pp. 176-177
Author(s):  
J.S. Wall ◽  
V. Maridiyan ◽  
S. Tumminia ◽  
J. Hairifeld ◽  
M. Boublik
Keyword(s):  
Ionic Strength ◽  
Three Dimensional ◽  
Conformational Transitions ◽  
Dark Field ◽  
Dimensional Structure ◽  
Ribosomal Rnas ◽  
Field Mode ◽  
Freeze Dried ◽  
High Resolution Images ◽  
Low Ionic Strength

The high contrast in the dark-field mode of dedicated STEM, specimen deposition by the wet film technique and low radiation dose (1 e/Å2) at -160°C make it possible to obtain high resolution images of unstained freeze-dried macromolecules with minimal structural distortion. Since the image intensity is directly related to the local projected mass of the specimen it became feasible to determine the molecular mass and mass distribution within individual macromolecules and from these data to calculate the linear density (M/L) and the radii of gyration.2 This parameter (RQ), reflecting the three-dimensional structure of the macromolecular particles in solution, has been applied to monitor the conformational transitions in E. coli 16S and 23S ribosomal RNAs in solutions of various ionic strength.In spite of the differences in mass (550 kD and 1050 kD, respectively), both 16S and 23S RNA appear equally sensitive to changes in buffer conditions. In deionized water or conditions of extremely low ionic strength both appear as filamentous structures (Fig. la and 2a, respectively) possessing a major backbone with protruding branches which are more frequent and more complex in 23S RNA (Fig. 2a).

An Evaluation of a Plasma Fractionation System

1960 ◽  
Vol 4 (01) ◽  
pp. 031-044
Author(s):  
George Y. Shinowara ◽  
E. Mary Ruth
Keyword(s):  
Biological Activity ◽  
Ionic Strength ◽  
Plasma Proteins ◽  
High Concentration ◽  
Significant Evidence ◽  
Native Proteins ◽  
Mobility Data ◽  
Fractionation Procedure ◽  
The Individual ◽  
Low Ionic Strength

SummaryFour primary fractions comprising at least 97 per cent of the plasma proteins have been critically appraised for evidence of denaturation arising from a low temperature—low ionic strength fractionation system. The results in addition to those referable to the recovery of mass and biological activity include the following: The high solubilities of these fractions at pH 7.3 and low ionic strengths; the compatibility of the electrophoretic and ultracentrifugal data of the individual fractions with those of the original plasma; and the recovery of hemoglobin, not hematin, in fraction III obtained from specimens contaminated with this pigment. However, the most significant evidence for minimum alterations of native proteins was that the S20, w and the electrophoretic mobility data on the physically recombined fractions were identical to those found on whole plasma.The fractionation procedure examined here quantitatively isolates fibrinogen, prothrombin and antithrombin in primary fractions. Results have been obtained demonstrating its significance in other biological systems. These include the following: The finding of 5 S20, w classes in the 4 primary fractions; the occurrence of more than 90 per cent of the plasma gamma globulins in fraction III; the 98 per cent pure albumin in fraction IV; and, finally, the high concentration of beta lipoproteins in fraction II.

Photochemical and Electrochemical Reduction of Carbon Dioxide Catalyzed by a Polyoxometalate-Organic Photosensitizer Complex

2018 ◽  
Author(s):  
Chandan Dey ◽  
Ronny Neumann
Keyword(s):  
Carbon Dioxide ◽  
Cyclic Voltammetry ◽  
Formic Acid ◽  
Electrochemical Reduction ◽  
Mass Spectroscopy ◽  
Photochemical Reactions ◽  
Reducing Agent ◽  
Covalent Attachment ◽  
Hybrid Complex ◽  
Open Face

<p>A manganese substituted Anderson type polyoxometalate, [MnMo<sub>6</sub>O<sub>24</sub>]<sup>9-</sup>, tethered with an anthracene photosensitizer was prepared and used as catalyst for CO<sub>2</sub> reduction. The polyoxometalate-photosensitizer hybrid complex, obtained by covalent attachment of the sensitizer to only one face of the planar polyoxometalate, was characterized by NMR, IR and mass spectroscopy. Cyclic voltammetry measurements show a catalytic response for the reduction of carbon dioxide, thereby suggesting catalysis at the manganese site on the open face of the polyoxometalate. Controlled potentiometric electrolysis showed the reduction of CO<sub>2</sub> to CO with a TOF of ~15 sec<sup>-1</sup>. Further photochemical reactions showed that the polyoxometalate-anthracene hybrid complex was active for the reduction of CO<sub>2</sub> to yield formic acid and/or CO in varying amounts dependent on the reducing agent used. Control experiments showed that the attachment of the photosensitizer to [MnMo<sub>6</sub>O<sub>24</sub>]<sup>9-</sup> is necessary for photocatalysis.</p><div><br></div>

scholarly journals A novel procedure for the rapid purification of plastocyanin from pea (Pisum sativum) leaves

1981 ◽  
Vol 193 (1) ◽  
pp. 375-378 ◽  
Author(s):  
A R Ashton ◽  
L E Anderson
Keyword(s):  
Ionic Strength ◽  
Pisum Sativum ◽  
Deae Cellulose ◽  
High Concentrations ◽  
Rapid Purification ◽  
Low Ionic Strength

Plastocyanin is soluble at high concentrations (greater than 3 M) of (NH4)2SO4 but under these conditions will adsorb tightly to unsubstituted Sepharose beads. This observation was utilized to purify plastocyanin from pea (Pisum sativum) in two chromatographic steps. Sepharose-bound plastocyanin was eluted with low-ionic-strength buffer and subsequently purified to homogeneity by DEAE-cellulose chromatography.

scholarly journals Crystallization of tuna ferricytochrome c at low ionic strength.

1990 ◽  
Vol 265 (8) ◽  
pp. 4177-4180
Author(s):  
M H Walter ◽  
E M Westbrook ◽  
S Tykodi ◽  
A M Uhm ◽  
E Margoliash
Keyword(s):  
Ionic Strength ◽  
Ferricytochrome C ◽  
Low Ionic Strength
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