scholarly journals Changes in intermediate haemoglobins during methaemoglobin reduction by NADPH-flavin reductase

1979 ◽  
Vol 179 (1) ◽  
pp. 227-231 ◽  
Author(s):  
A Tomoda ◽  
T Yubisui ◽  
A Tsuji ◽  
Y Yoneyama
Keyword(s):  
Isoelectric Focusing ◽  
Rate Constants ◽  
Reaction Rate ◽  
Flavin Reductase ◽  
Inositol Hexaphosphate ◽  
Reaction Rate Constants ◽  
Beta 2

The changes in intermediate haemoglobins produced during methaemoglobin reduction by NADPH-flavin reductase were analysed by an isoelectric-focusing method. The alpha 3+ beta 2+ and alpha 2+ beta 3+ valency hybrids were observed as intermediate haemoglobins and changed consecutively with time during the reaction. On the basis of the analyses, the course of methaemoglobin reduction was found to involve two different pathways: (1) methaemoglobin kappa+1 leads to alpha 3+ beta 2+ kappa+2 leads to oxyhaemoglobin; (2) methaemoglobin kappa+3 leads to alpha 2+ beta 3+ kappa+4 leads to oxyhaemoglobin. The reaction rate constants of each phase (kappa+1–kappa+4) were also estimated. The addition of inositol hexaphosphate to the reaction mixture did not affect the overall reaction. The mechanism of methaemoglobin reduction by NADPH-flavin reductase is discussed on the basis of these results.

scholarly journals Mechanism of methaemoglobin reduction by human erythrocytes

1980 ◽  
Vol 188 (2) ◽  
pp. 535-540 ◽  
Author(s):  
A Tomoda ◽  
M Ida ◽  
A Tsuji ◽  
Y Yoneyama
Keyword(s):  
Methylene Blue ◽  
Isoelectric Focusing ◽  
Rate Constants ◽  
Time Course ◽  
Reaction Rate ◽  
Polyacrylamide Gel ◽  
Human Erythrocytes ◽  
Redox Potentials ◽  
Reaction Rate Constants ◽  
Beta 2

The time course of methaemoglobin reduction in human erythrocytes treated with nitrite was studied at pH 7.4, 37 degrees C, in the presence or absence of Methylene Blue, and the changes in methaemoglobin, intermediate haemoglobins and oxyhaemoglobin during the reaction were analysed by isoelectric-focusing on Ampholine/polyacrylamide-gel plates. In both cases, with or without the dye, the intermediate haemoglobins were found to be present at (alpha 3+beta 2+)2 and (alpha 2+beta 3+)2 valency hybrids from their characteristic position on electrophoresis, but amounts changed consecutively with time. The amount of (alpha 3+beta 2+)2 was always greater than that of the (alpha 2+beta 3+)2 valency hybrid. This result is explained by the differences in redox potentials between alpha- and beta-chains in methaemoglobin tetramer. It was concluded that methaemoglobin was reduced in human erythrocytes through these two different pats: methaemoglobin leads to k+3 (alpha 2+beta 3+)2 leads to k+3 oxyhaemoglobin. The reaction rate constants k'+1 (= k+1+k+3) and k'+2(=k+2+k+4) were estimated from the changes in each component methaemoglobin, intermediate haemoglobins [(alpha 3+beta 2+)2+(alpha 2+beta 3+)2] and oxyhaemoglobin.

scholarly journals Changes in intermediate haemoglobins during autoxidation of haemoglobin

1981 ◽  
Vol 195 (2) ◽  
pp. 485-492 ◽  
Author(s):  
A Tomoda ◽  
Y Yoneyama ◽  
A Tsuji
Keyword(s):  
Isoelectric Focusing ◽  
Phosphate Buffer ◽  
Time Course ◽  
Inositol Hexaphosphate ◽  
Reaction Rate Constants ◽  
The Media ◽  
Beta 2 ◽  
Quantitative Changes ◽  
Ph Range ◽  
Experimental Values

The time course of haemoglobin autoxidation was studied under various conditions at 37 degrees C, and the changes in oxyhaemoglobin, intermediate haemoglobins and methaemoglobin during the reaction were analysed by isoelectric focusing on Ampholine/polyacrylamide-gel plates. Under various conditions (10 mM-phosphate buffer, 10 mM-phosphate buffer with 0.1 M-phosphate buffer, 10 mM-phosphate buffer with 0.1 M-NaCl, and 10 mM-phosphate buffer with 0.5 mM-inositol hexaphosphate; pH range 6.6-7.8 each case), the intermediate haemoglobins were found to be present as (alpha 2+ beta 3+)2 and (alpha 3+ beta 2+)2 valency hybrids from their characteristic positions on electrophoresis. Oxyhaemoglobin changed consecutively to (alpha 2+ beta 3+)2 and (alpha 3+ beta 2+)2, which were further oxidized to methaemoglobin, and the amounts of (alpha 3+beta 2+)2 were greater than those of (alpha 2+ beta 3+)2 during the reaction. The modes of the quantitative changes in oxyhaemoglobin, intermediate haemoglobins, and methaemoglobin were very similar in all the media used except for the inositol hexaphosphate addition. In the presence of inositol hexaphosphate, the autoxidation rates were considerably accelerated, and the modes of the changes in the haemoglobin derivatives were also considerably altered; the effects of this organic phosphate were maximal at acidic pH and minimal at alkaline pH. It was concluded that haemoglobin autoxidation proceeds by first-order kinetics through two paths: and (formula: see text). The reaction rate constants (k+1-k+4) best fitting all experimental values obtained by the isoelectric-focusing analysis were evaluated. By using these values, the mechanism of haemoglobin autoxidation is discussed.

Measurement of the OH Reaction Rate Constants for CF3CH2OH, CF3CF2CH2OH, and CF3CH(OH)CF3

1999 ◽  
Vol 103 (15) ◽  
pp. 2664-2672 ◽  
Author(s):  
Kazuaki Tokuhashi ◽  
Hidekazu Nagai ◽  
Akifumi Takahashi ◽  
Masahiro Kaise ◽  
Shigeo Kondo ◽  
...  
Keyword(s):  
Rate Constants ◽  
Reaction Rate ◽  
Reaction Rate Constants

scholarly journals PREDICTION OF REACTION RATE CONSTANTS OF HYDROXYL RADICAL WITH ORGANIC COMPOUNDS

2014 ◽  
Vol 59 (1) ◽  
pp. 2252-2259 ◽  
Author(s):  
ZHEN CHEN ◽  
XINLIANG YU ◽  
XIANWEI HUANG ◽  
SHIHUA ZHANG
Keyword(s):  
Hydroxyl Radical ◽  
Organic Compounds ◽  
Rate Constants ◽  
Reaction Rate ◽  
Reaction Rate Constants

scholarly journals Constraining condensed-phase formation kinetics of secondary organic aerosol components from isoprene epoxydiols

2016 ◽  
Vol 16 (3) ◽  
pp. 1245-1254 ◽  
Author(s):  
T. P. Riedel ◽  
Y.-H. Lin ◽  
Z. Zhang ◽  
K. Chu ◽  
J. A. Thornton ◽  
...  
Keyword(s):  
Aqueous Phase ◽  
Atmospheric Aerosols ◽  
Rate Constants ◽  
Reaction Rate ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Heterogeneous Reactions ◽  
Model Calculations ◽  
Reaction Rate Constants ◽  
Aerosol Mass

Abstract. Isomeric epoxydiols from isoprene photooxidation (IEPOX) have been shown to produce substantial amounts of secondary organic aerosol (SOA) mass and are therefore considered a major isoprene-derived SOA precursor. Heterogeneous reactions of IEPOX on atmospheric aerosols form various aerosol-phase components or "tracers" that contribute to the SOA mass burden. A limited number of the reaction rate constants for these acid-catalyzed aqueous-phase tracer formation reactions have been constrained through bulk laboratory measurements. We have designed a chemical box model with multiple experimental constraints to explicitly simulate gas- and aqueous-phase reactions during chamber experiments of SOA growth from IEPOX uptake onto acidic sulfate aerosol. The model is constrained by measurements of the IEPOX reactive uptake coefficient, IEPOX and aerosol chamber wall losses, chamber-measured aerosol mass and surface area concentrations, aerosol thermodynamic model calculations, and offline filter-based measurements of SOA tracers. By requiring the model output to match the SOA growth and offline filter measurements collected during the chamber experiments, we derive estimates of the tracer formation reaction rate constants that have not yet been measured or estimated for bulk solutions.

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