Three-terminal capacitance cell for stopped-flow measurements of very dilute solutions

2007 ◽  
Vol 78 (2) ◽  
pp. 023902 ◽  
Author(s):  
Martin Tjahjono ◽  
Thomas Davis ◽  
Marc Garland
Keyword(s):  
Stopped Flow ◽  
Dilute Solutions ◽  
Flow Measurements ◽  
Capacitance Cell

Stopped-flow measurements of CO and O2 uptake by hemoglobin in sheep erythrocytes

1963 ◽  
Vol 18 (1) ◽  
pp. 158-165 ◽  
Author(s):  
John A. Sirs ◽  
F. J. W. Roughton
Keyword(s):  
Linear Relation ◽  
Flow System ◽  
Stopped Flow ◽  
Constant Flow ◽  
Dissolved Gas ◽  
O2 Uptake ◽  
Flow Measurements ◽  
Sheep Erythrocytes ◽  
Flow Method ◽  
Comparison Of The Results

A stopped-flow method is described to measure spectrophotometrically the rates of uptake of CO and O2 by the hemoglobin of intact sheep erythrocytes. A comparison of the results obtained with the constant flow system has led to further refinement of the latter procedure. A linear relation is found between the rate of uptake and the concentration of the dissolved gas, and the initial percentage rate of saturation is independent of the concentration of the erythrocytes. Submitted on September 21, 1961

Kinetics and Equilibrium of Binding of Fe3+ by a Fulvic Acid: A Study by Stopped Flow Methods

1975 ◽  
Vol 53 (20) ◽  
pp. 2979-2984 ◽  
Author(s):  
Cooper H. Langford ◽  
Tahir R. Khan
Keyword(s):  
Ionic Strength ◽  
Complex Formation ◽  
Fulvic Acid ◽  
Metal Ion ◽  
Equilibrium Constants ◽  
Acid Dissociation ◽  
Stopped Flow ◽  
Solution Ph ◽  
Sulfosalicylic Acid ◽  
Flow Measurements

The first report of a rate of binding of a metal ion (Fe3+) by a soluble fulvic acid is derived from stopped flow measurements. The rate of complex formation is normal in Wilkins' sense and similar to that for sulfosalicylic acid. Dissociation is slow (t1/2 > 10 s). The binding of Fe3+ by the fulvic acid in acid solution, pH = 1–2.5, was investigated by kinetic analysis in which the reaction of free Fe3+ with sulfosalicylic acid was followed by stopped flow spectrophotometry on a time scale short compared to release of Fe3+ by fulvic acid. Conditional equilibrium constants found were 1.5 ± 0.3 × 104 at pH = 1.5 and 2.5, and 2.8 ± 0.3 × 103 at pH = 1.0 at 25 °C (ionic strength 0.1).

scholarly journals Studies by electron-paramagnetic-resonance spectroscopy and stopped-flow spectrophotometry on the mechanism of action of turkey liver xanthine dehydrogenase

1976 ◽  
Vol 153 (2) ◽  
pp. 297-307 ◽  
Author(s):  
M J Barber ◽  
R C Bray ◽  
D J Lowe ◽  
M P Coughlan
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Redox Potential ◽  
Active Sites ◽  
Electron Paramagnetic Resonance Spectroscopy ◽  
Xanthine Dehydrogenase ◽  
Resonance Spectroscopy ◽  
Stopped Flow ◽  
Paramagnetic Resonance ◽  
Flow Measurements ◽  
Electron Paramagnetic

Studies by e.p.r. (electron-paramagnetic-resonance) spectroscopy and by stopped-flow spectrophotometry on turkey liver xanthine dehydrogenase revealed strong similarities to as well as important differences from the Veillonella alcalescens xanthine dehydrogenase and milk xanthine oxidase. The turkey enzyme is contaminated by up to three non-functional forms, giving molybdenum e.p.r. signals designated Resting I, Resting II and Slow. Slow and to a lesser extent Resting I signals are like those from the Veillonella enzyme, whereas Resting II is very like a resting signal described by K. V. Rajagopolan, P. Handler, G. Palmer & H. Beinert (1968) (J. Biol. Chem. 243, 3784-3796) for aldehyde oxidase. Another non-functional form that gives the Inhibited signal is produced on treatment of the enzyme with formaldehyde. Stopped-flow measurements at 450 nm show that, as for the milk enzyme, reduction by xanthine is rate-limiting in enzyme turnover. The active enzyme gives rise to Very Rapid and Rapid molybdenum(V) e.p.r. signals, as well as to an FADH signal. That these signals are almost indistinguishable from those of the milk enzyme, confirms the similarities between the active sites. There are two types of iron-sulphur centres that give signals like those in the milk enzyme, though with slightly different parameters. Quantitative reduction titration of the functional enzyme with xanthine revealed two important differences between the turkey and the milk enzymes. First, the turkey enzyme FADH/FADH2 system has a redox potential sufficiently low that xanthine is incapable of reducing the flavin completely. This finding presumably explains the very low oxidase activity. Secondly, whereas the Fe/S II chromophore in the milk enzyme has a relatively high redox potential, for the turkey enzyme the value of this potential is lower and similar to that of its Fe/S I chromophore.

Refractive index anomalies in stopped-flow measurements

1976 ◽  
Vol 48 (4) ◽  
pp. 778-779 ◽  
Author(s):  
Mark L. Miller ◽  
Gilbert. Gordon
Keyword(s):  
Refractive Index ◽  
Stopped Flow ◽  
Flow Measurements

scholarly journals Kinetic studies on the oxidation of nitrite by horseradish peroxidase and lactoperoxidase.

1999 ◽  
Vol 46 (4) ◽  
pp. 919-927 ◽  
Author(s):  
L Gebicka
Keyword(s):  
Horseradish Peroxidase ◽  
Nitrogen Dioxide ◽  
Rate Constants ◽  
Kinetic Studies ◽  
The Other ◽  
Stopped Flow ◽  
Nitrite Concentration ◽  
Flow Measurements ◽  
Activity Measurements ◽  
Compound Ii

The reaction of nitrite (NO2-) with horseradish peroxidase and lactoperoxidase was studied. Sequential mixing stopped-flow measurements gave the following values for the rate constants of the reaction of nitrite with compounds II (oxoferryl heme intermediates) of horseradish peroxidase and lactoperoxidase at pH 7.0, 13.3 +/- 0.07 mol(-1) dm3 s(-1) and 3.5 +/- 0.05 x 10(4) mol(-1) dm3 s(-1), respectively. Nitrite, at neutral pH, influenced measurements of activity of lactoperoxidase with typical substrates like 2,2'-azino-bis[ethyl-benzothiazoline-(6)-sulphonic acid] (ABTS), guaiacol or thiocyanate (SCN-). The rate of ABTS and guaiacol oxidation increased linearly with nitrite concentration up to 2.5-5 mmol dm(-3). On the other hand, two-electron SCN- oxidation was inhibited in the presence of nitrite. Thus, nitrite competed with the investigated substrates of lactoperoxidase. The intermediate, most probably nitrogen dioxide (*NO2), reacted more rapidly with ABTS or guaiacol than did lactoperoxidase compound II. It did not, however, effectively oxidize SCN- to OSCN-. NO2- did not influence the activity measurements of horseradish peroxidase by ABTS or guaiacol method.

Sign in / Sign up

Export Citation Format

Share Document