scholarly journals Reactions of cytochrome c oxidase with sodium dithionite

1983 ◽  
Vol 209 (1) ◽  
pp. 175-182 ◽  
Author(s):  
G D Jones ◽  
M G Jones ◽  
M T Wilson ◽  
M Brunori ◽  
A Colosimo ◽  
...  
Keyword(s):  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Charge Distribution ◽  
Rate Constants ◽  
Sodium Dithionite ◽  
Second Order ◽  
Stopped Flow ◽  
Entry Site ◽  
Redox Proteins ◽  
Order Rate

The reduction of cytochrome c oxidase (EC 1.9.3.1) by dithionite was investigated by stopped-flow spectrophotometry and flow-flash techniques in the presence of CO. Of the two haem groups present in the enzyme, that associated with cytochrome alpha is the first reduced. The second-order rate constants for reduction of a number of redox proteins (cytochrome c, stellacyanin and azurin) by the S2O4(2-) and SO2.- anions are reported, and the values are compared with those determined for cytochrome c oxidase. These results are discussed in terms of the accessibility and charge distribution of the electron-entry site of cytochrome c oxidase.

scholarly journals The mechanism of reduction of single-site redox proteins by ascorbic acid

1979 ◽  
Vol 177 (2) ◽  
pp. 641-648 ◽  
Author(s):  
A I Al-Ayash ◽  
M T Wilson
Keyword(s):  
Ascorbic Acid ◽  
Rate Constants ◽  
Activation Parameters ◽  
Outer Sphere ◽  
Reducing Agent ◽  
Second Order ◽  
Single Site ◽  
Redox Proteins ◽  
Order Rate ◽  
Temperature Dependences

The reduction of single-site haem and copper redox proteins by ascorbic acid was studied as a function of pH. Evidence is presented that indicates that the double-deprotonated ascorbate anion, ascorbate2-, is the reducing agent, and the pH-independent second-order rate constants for reduction by this species are given. Investigation of the temperature dependences of these rate constants have yielded the values of the activation parameters (delta H++ and delta S++) for reduction. These values, together with ligand-replacement studies, suggest that ascorbate2- acts as an outer-sphere reductant for these proteins. Reasons to account for the apparent inability of ascorbic acid to reduce the alkaline conformer of mammalian ferricytochrome c are suggested.

Kinetic and Mechanistic Study on the Reactions of [Pd(dien)H2O]2+ and [Pt(dien)H2O]2+ with L-Cysteine and S-Methyl-L-cysteine

2005 ◽  
Vol 58 (7) ◽  
pp. 544 ◽  
Author(s):  
Biljana V. Petrović ◽  
Živadin D. Bugarčić
Keyword(s):  
Rate Constants ◽  
Activation Parameters ◽  
Second Order ◽  
Mechanistic Study ◽  
Stopped Flow ◽  
Substitution Reactions ◽  
Order Rate ◽  
Increase With Increase ◽  
Naclo4 Solution ◽  
Entropy Of Activation

The reactions of [Pd(dien)H2O]2+ and [Pt(dien)H2O]2+ (dien = diethylenetriamine or 1,5-diamino-3-azapentane) with l-cysteine and S-methyl-l-cysteine were studied in an aqueous 0.10 M NaClO4 solution using stopped-flow and conventional UV-vis spectrophotometry. The second-order rate constants for the reactions of [Pd(dien)H2O]2+ at pH 1.0 are k1298 = (9.11 ± 0.11) × 102 M−1 s−1 for l-cysteine, and k1298 = (33.79 ± 0.63) × 102 M−1 s−1 for S-methyl-l-cysteine. The second-order rate constants for the reactions of [Pt(dien)H2O]2+ at pH 1.0 with l-cysteine is k1298 = (1.28 ± 0.08) × 10−2 M−1 s−1 and for S-methyl-l-cysteine is k1298 = (3.87 ± 0.02) × 10−2 M−1 s−1. Activation parameters were determined for all reactions, and the negative values of entropy of activation support an associative complex formation mechanism. Substitution reactions were also studied at pH 0.5, 1.0, and 1.5. The rate constants increase with increase in pH. These results are discussed in terms of protolitic equilibrium.

scholarly journals The reduction of Pseudomonas cytochrome c551 oxidase by chromous ions

1977 ◽  
Vol 163 (3) ◽  
pp. 629-632 ◽  
Author(s):  
D Barber ◽  
S R Parr ◽  
C Greenwood
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Rate Constants ◽  
Second Order ◽  
Stopped Flow ◽  
Difference Spectra ◽  
Order Rate ◽  
Flow Apparatus ◽  
Cytochrome C551

The reduction of cytochrome c551 oxidase from Pseudomonas aeruginosa by Cr2+ ions was followed in the stopped-flow apparatus at a number of wavelengths. The c-haem reduction proceeded in a biphasic fashion with second-order rate constants of 2.6 X 10(5)M-1-S-1 and 4.8 X 10(4)M-1-S-1 at 25 degrees C, whereas the biphasic reduction of the d1-haem appeared to be independent of reductant concentration with rate constants of approx. 1.0S-1 and 0.25S-1 respectively. The kinetically determined difference spectra (reduced minus oxidized) for the c- and d1-haems are presented.

Inhibition in Purified Systems and in Human Plasma of Chimaeric Plasminogen Activators Consisting of the NH2-Terminal Region of Tissue-Type Plasminogen Activator and the COOH-Terminal Region of UrokinaseType Plasminogen Activator

1988 ◽  
Vol 60 (02) ◽  
pp. 247-250 ◽  
Author(s):  
H R Lijnen ◽  
L Nelles ◽  
B Van Hoef ◽  
F De Cock ◽  
D Collen
Keyword(s):  
Plasminogen Activator ◽  
Rate Constants ◽  
Plasminogen Activators ◽  
Second Order ◽  
Tissue Type ◽  
Single Chain ◽  
Chain Molecules ◽  
Order Rate ◽  
Type Plasminogen Activator ◽  
Urokinase Type Plasminogen Activator

SummaryRecombinant chimaeric molecules between tissue-type plasminogen activator (t-PA) and single chain urokinase-type plasminogen activator (scu-PA) or two chain urokinase-type plasminogen activator (tcu-PA) have intact enzymatic properties of scu-PA or tcu-PA towards natural and synthetic substrates (Nelles et al., J Biol Chem 1987; 262: 10855-10862). In the present study, we have compared the reactivity with inhibitors of both the single chain and two chain variants of recombinant u-PA and two recombinant chimaeric molecules between t-PA and scu-PA (t-PA/u-PA-s: amino acids 1-263 of t-PA and 144-411 of u-PA; t-PA/u-PA-e: amino acids 1-274 of t-PA and 138-411 of u-PA). Incubation with human plasma in the absence of a fibrin clot for 3 h at 37° C at equipotent concentrations (50% clot lysis in 2 h), resulted in significant fibrinogen breakdown (to about 40% of the normal value) for all two chain molecules, but not for their single chain counterparts. Preincubation of the plasminogen activators with plasma for 3 h at 37° C, resulted in complete inhibition of the fibrinolytic potency of the two chain molecules but did not alter the potency of the single chain molecules. Inhibition of the two chain molecules occurred with a t½ of approximately 45 min. The two chain variants were inhibited by the synthetic urokinase inhibitor Glu-Gly-Arg-CH2CCl with apparent second-order rate constants of 8,000-10,000 M−1s−1, by purified α2-antiplasmin with second-order rate constants of about 300 M−1s−1, and by plasminogen activator inhibitor-1 (PAI-1) with second-order rate constants of approximately 2 × 107 M−1s−1.It is concluded that the reactivity of single chain and two chain forms of t-PA/u-PA chimaers with inhibitors is very similar to that of the single and two chain forms of intact u-PA.

Determination of the Nucleophilicity of Tricarbonyliron Coordinated Cyclohepta-1,3,5-triene

1999 ◽  
Vol 64 (11) ◽  
pp. 1770-1779 ◽  
Author(s):  
Herbert Mayr ◽  
Karl-Heinz Müller
Keyword(s):  
Gibbs Energy ◽  
Ambient Temperature ◽  
Rate Constants ◽  
Second Order ◽  
Order Rate ◽  
Electrophilic Additions ◽  
Kinetics Of

The kinetics of the electrophilic additions of four diarylcarbenium ions (4a-4d) to tricarbonyl(η4-cyclohepta-1,3,5-triene)iron (1) have been studied photometrically. The second-order rate constants match the linear Gibbs energy relationship log k20 °C = s(E + N) and yield the nucleophilicity parameter N(1) = 3.69. It is concluded that electrophiles with E ≥ -9 will react with complex 1 at ambient temperature.

Luminescence Quenching of Rhodamines by Cyclooctatetraene

1987 ◽  
Vol 42 (9) ◽  
pp. 1009-1013 ◽  
Author(s):  
P. Targowski ◽  
B. Ziętek ◽  
A. Bączyński
Keyword(s):  
Rhodamine B ◽  
Rate Constants ◽  
Internal Conversion ◽  
Rhodamine 6G ◽  
Second Order ◽  
Luminescence Quenching ◽  
Intersystem Crossing ◽  
Order Rate ◽  
Quenching Process

Cyclooctatetraene (COT) as a quencher of fluorescence of a series of Rhodamine solutions was studied. The second order rate constants for the quenching process of Rhodamine 110, Rhodamine 19 pchl., Rhodamine 6G pchl., Rhodamine 6G, Tetramethylrhodamine, Rhodamine B and Rhodamine 3B pchl. are given. It was found that COT enhances rather intersystem crossing than internal conversion.

A Study on the β-Elimination Reaction from N-[2-(p-nitrophenyl)ethyl]quinuclidinium and 2-(p-nitrophenyl)ethyl bromide induced by amines in dimethylsulfoxide with formation of p-nitrostyrene

2000 ◽  
Vol 2000 (2) ◽  
pp. 62-63
Author(s):  
Sergio Alunni ◽  
Arianna Rocchi
Keyword(s):  
Rate Constants ◽  
Second Order ◽  
Ethyl Bromide ◽  
Elimination Reaction ◽  
Order Rate

Second order rate constants kE M−1 s−1 for the β-elimination reaction from N-[2-( p-nitrophenyl)ethyl]quinuclidinium and 2-( p-nitrophenyl)ethyl bromide induced by amines of different structure in dimethylsulfoxide at 50 °C have been measured. Application of the Brønsted equation shows a similar behaviour of the two substrates, with values of β = 0.649 and 0.584 respectively.

KINETICS OF THE AQUEOUS ALKALINE HOMOGENOUS HYDROLYSIS OF HIGH EXPLOSIVE 1, 3,5,7-TETRAAZA- 1, 3,5,7-TETRANITROCYCLOOCTANE (HMX)

1994 ◽  
Vol 30 (3) ◽  
pp. 53-61 ◽  
Author(s):  
Harro M. Heilmann ◽  
Michael K. Stenstrom ◽  
Rolf P. X. Hesselmann ◽  
Udo Wiesmann
Keyword(s):  
Temperature Dependence ◽  
Alkaline Hydrolysis ◽  
Rate Constants ◽  
Elevated Temperatures ◽  
Second Order ◽  
Order Rate ◽  
Subsequent Calculation ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Order Rate Equation

In order to get basic data for the design of a novel treatment scheme for high explosives we investigated the kinetics for the aqueous alkaline hydrolysis of 1,3,5,7-tetraaza-1,3,5,7-tetranitrocyclooctane (HMX) and the temperature dependence of the rate constants. We used an HPLC procedure for the analysis of HMX. All experimental data could be fit accurately to a pseudo first-order rate equation and subsequent calculation of second-order rate constants was also precise. Temperature dependence could be modeled with the Arrhenius equation. An increase of 10°C led to an average increase in the second-order rate constants by the 3.16 fold. The activation energy of the second-order reaction was determined to be 111.9 ±0.76 kJ·moJ‒1. We found the alkaline hydrolysis to be rapid (less than 2.5% of the initial HMX-concentration left after 100 minutes) at base concentrations of 23 mmol oH‒/L and elevated temperatures between 60 and 80°C.

scholarly journals The accessibility of protein-bound dinitrophenyl groups to univalent fragments of anti-dinitrophenyl antibody

1976 ◽  
Vol 159 (2) ◽  
pp. 323-333 ◽  
Author(s):  
C G Knight ◽  
N M Green
Keyword(s):  
Dissociation Constant ◽  
Rate Constants ◽  
Alkyl Chain ◽  
Dissociation Constants ◽  
Tryptophan Fluorescence ◽  
Thiol Group ◽  
Second Order ◽  
Thiol Compounds ◽  
Order Rate ◽  
Chain Lengths

A series of N-(N-dinitrophenylaminoalkyl)maleimides were sythesized with alkyl-chain lengths of two, four and six carbon atoms. When these compounds reacted with the thiol group of mercaptalbumin, the tryptophan fluorescence of the protein was quenched. This change in fluorescence was used to determine the rate of reaction of the Dnp (dinitrophenyl)-maleimides with mercaptalbumin. The second-order rate constants were similar to those observed in reactions between low-molecular-weight thiol compounds and maleimides. When N-(N-Dnp-aminoalkyl)succinimidomercaptalbumins were added to univalent fragments of anti-Dnp antibody the antibody fluorescence was quenched. Florescence-quenching titrations showed that the protein-bound Dnp groups were fully available to the antibody even when the alkyl chain was short. The apparent dissociation constants were significantly > that of the interaction between anti-Dnp antibody and the free hapten, 6-(N-Dnp)-aminohexanoate. The antibody fluorescence was quenched efficienty by [dnp-Lys41]ribonuclease A, also with an increased dissociation constant. It could be concluded from the increase in dissociation constant that the Dnp group spent no more than 0.1% of its time in the dissociated state, available to antibody. The second-order rate constants for the association between the Dnp-mercaptablumins and the antibody were determined and were similar in magnitude to those observed in other interactions between protein and anti-protein antibody.

Sign in / Sign up

Export Citation Format

Share Document