scholarly journals The effect of complex-formation with polyanions on the redox properties of cytochrome c

1980 ◽  
Vol 192 (2) ◽  
pp. 687-693 ◽  
Author(s):  
L C Petersen ◽  
R P Cox
Keyword(s):  
Cytochrome C ◽  
Complex Formation ◽  
Reaction Rates ◽  
Reduced Form ◽  
Stable Complex ◽  
Phase System ◽  
Two Phase ◽  
The Difference ◽  
Low Ionic Strength ◽  
Positively Charged

1. The stable complex formed between mammalian cytochrome c and phosvitin at low ionic strength was studied by partition in an aqueous two-phase system. Oxidized cytochrome c binds to phosvitin with a higher affinity than reduced cytochrome c. The difference was equivalent to a decrease of the redox potential by 22 mV on binding. 2. Complex-formation with phosvitin strongly inhibited the reaction of cytochrome c with reagents that react as negatively charged species, such as ascorbate, dithionite, ferricyanide and tetrachlorobenzoquinol. Reaction with uncharged reagents such as NNN‘N’-tetramethylphenylenediamine and the reduced form of the N-methylphenazonium ion (present as the methylsulphate) was little affected by complex-formation, whereas oxidation of the reduced cytochrome by the positively charged tris-(phenanthroline)cobalt(III) ion was greatly stimulated. 3. A similar pattern of inhibition and stimulation of reaction rates was observed when phosvitin was replaced by other macromolecular polyanions such as dextran sulphate and heparin, indicating that the results were a general property of complex-formation with polyanions. A weaker but qualitatively similar effect was observed on addition of inositol hexaphosphate and ATP. 4. It is suggested that the effects of complex-formation with polyanions on the reactivity of cytochrome c with redox reagents are mainly the result of replacing the positive charge on the free cytochrome by a net negative charge. Any steric effects on polyanion binding are small in comparison with such electrostatic effects.

Transmission Electron Microscopy (TEM) Observations of Phase-Separations of Gamma-Prime Precipitates in Ni-Al-Fe and Ni-Si-Fe Ternary Alloys

2007 ◽  
Vol 26-28 ◽  
pp. 1311-1314 ◽  
Author(s):  
M. Senga ◽  
H. Kumagai ◽  
Tomokazu Moritani ◽  
Minoru Doi
Keyword(s):  
Phase Separation ◽  
Volume Fraction ◽  
Heating Temperature ◽  
Ternary Alloys ◽  
Phase System ◽  
Precipitate Phase ◽  
Two Phase ◽  
Gamma Prime ◽  
Transmission Electron ◽  
The Difference

In Ni-13.0at%Si-3.1at%Fe alloy, when γ/γ’ two-phase microstructure formed at 1123 K is isothermally heated at 923 K which is lower than the temperature where the initial γ/γ’ microstructure forms, the phase-separation of γ/γ’ precipitate phase occurs and γ particles newly appear in each cuboidal γ’ precipitate. While in Ni-10.2at%Al-10.8at%Fe alloy, when γ/γ’ two-phase microstructure formed at 1023 K is isothermally heated at 1123 K which is higher than the temperature where the initial γ/γ’ microstructure forms, the phase-separation of γ’ precipitate phase takes place and γ particles newly appear in each cuboidal γ’ precipitate. Such appearance of new γ particles in γ’ precipitates can be explained by the difference in the volume fraction of γ phase that should exist in the γ/γ’ two-phase system depending on the heating temperature.

The cytochrome system in Mycobacterium lepraemurium

1974 ◽  
Vol 20 (7) ◽  
pp. 943-947 ◽  
Author(s):  
M. Ishaque ◽  
Laszlo Kato
Keyword(s):  
Cytochrome C ◽  
Respiratory Chain ◽  
Cell Suspensions ◽  
Reduced Form ◽  
Difference Spectra ◽  
Whole Cell ◽  
Chain System ◽  
Cytochrome O ◽  
The Difference ◽  
Mycobacterium Lepraemurium

The respiratory chain system of cell suspensions of Mycobacterium lepraemurium was investigated spectrophotometrically. The results obtained indicated that whole cell preparations contained flavins, cytochromes of the a + a3 and b type, as well as two CO-binding pigments; cytochromes a3–CO and a second pigment similar to cytochrome o. The cytochromes were found to be in the reduced form. The presence of cytochrome systems could only be shown after the cell suspensions in the reference cuvette were exposed to oxygen. The positions of the peaks in the difference spectra were similar when the cell suspensions were reduced anaerobically without added substrate or treated with dithionite. The whole cell suspensions of M. lepraemurium were not found to contain detectable quantities of cytochrome c.

Phase-Separation of B2 Precipitates in an Fe-Ni-Al Alloy

2010 ◽  
Vol 638-642 ◽  
pp. 2274-2278 ◽  
Author(s):  
Yasuhiro Kuno ◽  
Yasuo Nakane ◽  
Takao Kozakai ◽  
Minoru Doi ◽  
Junji Yamanaka ◽  
...  
Keyword(s):  
Free Energy ◽  
Phase Separation ◽  
Volume Fraction ◽  
Heating Temperature ◽  
Phase System ◽  
Al Alloy ◽  
Two Phase ◽  
Chemical Free Energy ◽  
The Difference ◽  
The Individual

When Fe-10.3mol%Ni-14.3mol%Al alloy is heated at 1173 K for 8.64104 s, a number of B2 precipitates are dispersed in the A2 matrix. When the two-phase microstructure of A2+B2 is aged at 973 K, the phase-separation of B2 precipitate particles takes place to form a new A2 phase in each B2 particle. In the course of further ageing at 973 K, the new A2 phase grows but decreases in number, and finally only one A2 particle is left in the individual B2 particles. The appearance of new A2 phase in each B2 precipitate is due to the difference in the volume fraction of A2 phase that should exist in A2+B2 two-phase system depending on the heating temperature: i.e., the phase-separation of B2 precipitates starts with the aid of chemical free energy.

Sustainable vanadium(V)-catalyzed oxybromination of styrene: Two-phase system versus ionic liquids

2005 ◽  
Vol 77 (9) ◽  
pp. 1575-1581 ◽  
Author(s):  
Valeria Conte ◽  
Barbara Floris ◽  
Pierluca Galloni ◽  
Adriano Silvagni
Keyword(s):  
Ionic Liquids ◽  
Aqueous Phase ◽  
Chlorinated Solvents ◽  
Reaction Rates ◽  
Point Of View ◽  
Metal Catalyst ◽  
Phase System ◽  
Two Phase ◽  
System Versus ◽  
Bromide Ion

Oxybromination reaction of styrene was performed in a two-phase system of water/ionic liquids (ILs). The aim of the work was to make the mild and efficient two-phase system previously developed for the vanadium(V)-catalyzed oxybromination of alkenes, inspired by the activity of haloperoxidase enzymes, even more interesting from a sustainable point of view. As in that case, a brominating intermediate was formed from the metal catalyst, H2O2, and bromide ion in the acid aqueous phase, but chlorinated solvents were replaced with ILs.[bmim+][PF6-], [bm2im+][PF6-], [bmim+][BF4-], [bmim+][CF3SO3-], and [bmim+][(CF3SO2)2N-] were tested. We report on interesting results in terms of reaction rates and selectivities.

scholarly journals The circular-dichroic properties of the ‘Rieske’ iron-sulphur protein in the mitochondrial ubiquinol: cytochrome c reductase

1987 ◽  
Vol 241 (1) ◽  
pp. 285-290 ◽  
Author(s):  
M Degli Esposti ◽  
F Ballester ◽  
G Solaini ◽  
G Lenaz
Keyword(s):  
Cytochrome C ◽  
Thermus Thermophilus ◽  
Reduced Form ◽  
Bc1 Complex ◽  
Rieske Protein ◽  
Difference Spectra ◽  
Cytochrome C Reductase ◽  
Negative Band ◽  
The Difference ◽  
Circular Dichroic

We have studied the c.d. spectra of the ‘Rieske’ iron-sulphur protein isolated from the ubiquinol: cytochrome c reductase (bc1 complex) of bovine heart mitochondria. Both the oxidized and the reduced form of the ‘Rieske’ protein display a series of well-resolved c.d. features resembling those reported for the ‘Rieske’-type iron-sulphur protein purified from the bacterium Thermus thermophilus [Fee, Findling, Yoshida, Hille, Tarr, Hearshen, Dunham, Day, Kent & Münck (1984) J. Biol, Chem. 259, 124-133]. In particular, the difference spectra, reduced minus oxidized, of both proteins have a distinctive negative band at 497 nm. The c.d. features characteristic of the isolated ‘Rieske’ protein were found in the dichroic spectra of the whole bc1 complex in the region between 450 and 520 nm. The reduction of the enzyme by ascorbate or ubiquinol is accompanied by the formation of a negative band at about 500 nm that corresponds, in all its c.d. properties, to the specific dichroic absorption of the reduced ‘Rieske’ iron-sulphur protein.

scholarly journals Extraction Mechanism of Ferric and Manganese Ions with Aqueous Two-phase System Formed by Ionic Liquid and Polyethylene Glycol

2019 ◽  
Vol 33 (2) ◽  
pp. 229-234
Author(s):  
Pius Dore Ola ◽  
M. Matsumoto
Keyword(s):  
Ionic Liquid ◽  
Polyethylene Glycol ◽  
Hydrochloric Acid ◽  
Metal Salt ◽  
Phase System ◽  
Hydrochloric Acid Concentration ◽  
Two Phase ◽  
Aqueous Two Phase System ◽  
The Difference ◽  
Hcl Concentration

In this work, we employed an aqueous two-phase system formed by an ionic liquid and polyethylene glycol for the separation of Fe(III), which is the most commonly used metal in the world, and Mn(II), which is currently used in many industries. We found that the extraction mechanisms of Fe(III) and Mn(II) were strongly influenced by the concentration of the hydrochloric acid that dissolved the metal salt. The ion pair reaction was the predominant mechanism that generated the Fe(III) and Mn(II) extractions. At a lower concentration of hydrochloric acid, metal ions were extracted because of the reaction between a metal cation and a dodecylsulfonate anion. At a higher concentration of hydrochloric acid, the reaction between a metal chlorocomplex anion and a hexylmethylimidazolium cation also proceeded. The aqueous two-phase system, composed of ionic liquid and polyethylene glycol, is promising for metal separation based on the difference in the affinity of metal with alkyl-sulfonate in a low HCl concentration and in the stability constant of metal chlorocomplex in a high HCl concentration. The maximum extractability of Fe(III) and Mn(III) was 57.8 and 75.3 %, respectively, with 0.3 mol dm–3 hydrochloric acid concentration.

Thermodynamic studies of partitioning behavior of cytochrome c in ionic liquid-based aqueous two-phase system

Talanta ◽  
2011 ◽  
Vol 85 (3) ◽  
pp. 1621-1626 ◽  
Author(s):  
Yanmin Lu ◽  
Wenjuan Lu ◽  
Wei Wang ◽  
Qingwei Guo ◽  
Yanzhao Yang
Keyword(s):  
Ionic Liquid ◽  
Cytochrome C ◽  
Phase System ◽  
Two Phase ◽  
Thermodynamic Studies ◽  
Aqueous Two Phase System ◽  
Partitioning Behavior
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