scholarly journals Oxidation-reduction studies of the Mo-(2Fe-2S) protein from Desulfovibrio gigas

1978 ◽  
Vol 173 (2) ◽  
pp. 419-425 ◽  
Author(s):  
J J G Moura ◽  
A V Xavier ◽  
R Cammack ◽  
D O Hall ◽  
M Bruschi ◽  
...  
Keyword(s):  
Reduction Potential ◽  
Type I ◽  
Midpoint Potential ◽  
Desulfovibrio Gigas ◽  
Reduction Potentials ◽  
Point Potential ◽  
Oxidation Reduction ◽  
Reducing Conditions ◽  
Oxidation Reduction Potential ◽  
Type Ia

Potentiometric titration followed by e.p.r. measurements were used to determine the midpoint reduction potentials of the redox centres of a molybdenum-containing iron-sulphur protein previously isolated from Desulfovibrio gigas, a sulphate-reducing bacterium (Moura, Xavier, Bruschi, Le Gall, Hall & Cammack (1976) Biochem. Biophys. Res. Commun. 728 782-789; Moura, Xavier, Bruschi, Le Gall & Cabral (1977) J. Less Common Metals 54, 555-562). The iron-sulphur centres could readily be distinguished into three types by means of g values, temperature effect, oxidation-reduction potential values and reduction rates. The type-I Fe-S centres are observed at 77 K. They show mid-point potential values of −260mV (Fe-S type IA) and −440 mV (Fe-S type IB). Centres of types IA and IB appear to have similar spectra at 77 K and 24 K. The Fe-S type-II centres are only observed below 65 K and have a midpoint potential of −28mV. Long equilibration times (30 min) with dye mediators under reducing conditions were necessary to observe the very slow equilibrating molybdenum signals. The potential values associated with this signal were estimated to be approx. −415 mV for Mo(VI)/Mo(V) and-530mV for Mo(V)/Mo(IV).

scholarly journals OXIDATION-REDUCTION POTENTIALS AND THE POSSIBLE RESPIRATORY SIGNIFICANCE OF THE PIGMENT OF THE NUDIBRANCH CHROMODORIS ZEBRA

1930 ◽  
Vol 13 (3) ◽  
pp. 349-359 ◽  
Author(s):  
Paul W. Preisler
Keyword(s):  
Oxygen Transfer ◽  
Reduction Potential ◽  
Product Form ◽  
Reversible System ◽  
Purple Pigment ◽  
Reduction Potentials ◽  
Oxidation Reduction ◽  
Oxidation Reduction Potential ◽  
Valence Change ◽  
Potential Methods

1. Oxidation-reduction potential methods have been applied to a study of the blue-purple pigment present in solution in the blood and in the tissue cells of the nudibranch Chromodoris zebra. 2. The blue-purple pigment and its yellow reduction product form a reversible system whose Eo' = x0.102 volts at pH 7.0 and whose valence change from oxidant to reductant appears to be one. 3. The system is unlike oxyhemoglobin-hemoglobin in the mode of oxygen transfer. Its rôle as a possible respiratory material is discussed.

Apparatus and techniques for the measurement of oxidation-reduction potentials, pH and oxygen tension in vivo

1957 ◽  
Vol 146 (923) ◽  
pp. 289-297 ◽  
Keyword(s):  
Oxygen Tension ◽  
Reduction Potential ◽  
Model Experiments ◽  
Reduction Potentials ◽  
Oxidation Reduction ◽  
Oxidation Reduction Potential ◽  
Small Voltage

In order to follow the changes which occur in tumours during treatment with radiation, and the effects of radiosensitizing or radioprotecting drugs, apparatus and techniques have been developed to record automatically changes of oxidation-reduction potential on eight different electrodes. Simultaneous records of pH and oxygen tension changes were used as controls in some experiments. The changes of oxygen tension were followed by applying a known small voltage to one electrode and measuring the current which flowed. Calibration of oxygen-tension measurements was attempted by the use of model experiments.

scholarly journals WHAT IS ORP AND WHAT YOU SHOULD KNOW ABOUT IT

2014 ◽  
Vol 11 (1) ◽  
pp. 32-38
Author(s):  
Irena Čerčikienė ◽  
Jolanta Jurkevičiūtė ◽  
Dalė Židonytė
Keyword(s):  
Mineral Water ◽  
Reduction Potential ◽  
The Body ◽  
Acid Base Balance ◽  
Reduction Potentials ◽  
Oxidation Reduction ◽  
Oxidation Reduction Potential ◽  
Bactericidal Properties ◽  
Base Balance ◽  
Two Parameters

Currently in mass media and advertising we often hear about the importance of living water in human daily life. You may ask, “What is living water? Is it really living? Is it alkaline?” The importance of water to the human body can be determined by the oxidation – reduction potential (ORP) – a parameter characterizing the ability of the matter to give and connect electrons, which can be measured not only in water but also in food and in the air. Solutions, which contain negative ORP value (e.g. alkaline ionized water), are characterized by reduction features and have the ability to neutralize free radicals and stop the signs of aging. Solutions containing positive ORP value have oxidative properties, which are typical for the alkaline ionized water, which has bactericidal properties. Thus, the ionized water has two parameters: its pH and oxidation - reduction potential, which make it different from the ordinary water. Ionized water, like the raw unprocessed food, is considered to be the body rejuvenating agent. The basic principle, which should be followed, is to consume food and water, which contain the lowest possible negative ORP. The authors provide the research results, although, it is known that most of water tests are difficult to reproduce due to objective reasons, as water, with the gases dissolved in it, represents a very complicated balanced oxidation – reduction system. Oxidation reduction potentials of drinking and mineral water, as well as other beverages, have been studied, and the dynamics of these parameters in ionized water over time has been determined. Key words: acid-base balance, pH index, oxidation – reduction potential (ORP), ionized water, alkaline water, living water, catholyte, acidic water, inanimate water, anolyte.

Induced changes in oxidation-reduction potentials, pH, and oxygen tension in the intact lactating mammary gland

1957 ◽  
Vol 146 (924) ◽  
pp. 400-415 ◽  
Keyword(s):  
Growth Hormone ◽  
Mammary Gland ◽  
Oxygen Tension ◽  
Reduction Potential ◽  
Reduction Potentials ◽  
Oxidation Reduction ◽  
Oxidation Reduction Potential ◽  
Lactating Mammary Gland ◽  
Other Substances

This work was undertaken to find if a study of oxidation-reduction potentials, pH and oxygen tension would yield information concerning physiological changes induced in lactating mammary glands of rats and rabbits by hormones and other substances. Breathing oxygen at atmospheric pressure caused a rapid rise in oxygen tension in lactating mammary gland, and a small, slower rise of oxidation-reduction potential. Breathing nitrogen had the opposite effect. Oxytocin caused a rapid temporary fall of oxidation-reduction potential, synchronous with milk ejection. With adrenaline the response was more rapid and the oxygen tension fell to zero, to recover within 2 min. Vasopressin produced a slower fall and recovery. Insulin (35 μ g/kg) caused a preliminary rise of oxidation-reduction potential, followed by a fall lasting 1 h. The fall could be largely abolished by glucose. The synthetic oestrogen doisynolic acid caused a triphasic response in the oxidation-reduction potentials and increased oxygen tension in the gland. It reduced, but did not abolish, the changes due to insulin. Desoxycorticosterone glucoside caused a slow rise of oxidation-reduction potential, but did not alter the response to insulin. Intermedin caused a small rise of oxidation-reduction potential. The effects produced by commercial ACTH may have been due to the oxytocin and intermedin present. Growth hormone induced a small diphasic change in the oxidation-reduction potentials. The radiosensitizers tetrasodium 2-methyl-1:4-naphthohydroquinone diphosphate and tetrasodium trimethyl-hydroquinone diphosphate produced marked falls of oxidation-reduction potential even with small doses, without change of oxygen tension. Intravenous potassium ferricyanide appeared to liberate oxygen from haemoglobin in vivo . The pH of mammary gland became slightly more acid after breathing oxygen, and also in the preliminary response to insulin, glucose, doisynolic acid and desoxycorticosterone glucoside; and after oxytocin, vasopressin and growth hormone.

37. Studies in Cheddar Cheese: I. The Oxidation-Reduction Potentials of Ripening Cheddar Cheese

1932 ◽  
Vol 3 (3) ◽  
pp. 241-253 ◽  
Author(s):  
John Gilbert Davis
Keyword(s):  
Reduction Potential ◽  
Cheddar Cheese ◽  
Mean Values ◽  
Reduction Potentials ◽  
Oxidation Reduction ◽  
Oxidation Reduction Potential ◽  
Different Levels

1. A method is described for following the intensity of reduction (or oxidation-reduction potential) at different levels in the interior of ripening Cheddar cheese.2. Variations in this potential throughout the course of ripening are described and mean values assessed.3. Cheese are shown to be not homogeneous throughout their mass; outer zones of more highly oxidised condition exist near the surface of the cheese and round cracks and borings. The depth of these zones increases with the age of the cheese.4. The values obtained can be correlated with the known bacteriological data for Cheddar cheese.5. The significance of the data obtained in relation to cheese faults is discussed.

scholarly journals THE OXIDATION-REDUCTION POTENTIAL OF THE LUCIFERIN-OXYLUCIFERIN SYSTEM

1927 ◽  
Vol 10 (3) ◽  
pp. 385-393 ◽  
Author(s):  
E. Newton Harvey
Keyword(s):  
Dissolved Oxygen ◽  
Reduction Potential ◽  
Water Solution ◽  
Considerable Reduction ◽  
Reduction Potentials ◽  
Oxidation Reduction ◽  
Oxidation Reduction Potential ◽  
Apparent Reduction ◽  
Reduction And Oxidation

The oxidation-reduction potential of the Cypridina luciferin-oxyluciferin system determined by a method of "bracketing" lies somewhere between that of anthraquinone 2-6-di Na sulfonate (Eo' at pH of 7.7 = –.22) which reduces luciferin, and quinhydrone (Eo' at pH of 7.7 = +.24), which oxidizes luciferin. Systems having an Eo' value between –.22 and +.24 volt neither reduce oxyluciferin nor oxidize luciferin. If the luciferin-oxyluciferin system were truly reversible considerable reduction and oxidation should occur between –.22 and +.24. The system appears to be an irreversible one, with both "apparent oxidation" and "apparent reduction potentials" in Conant's sense. Hydrosulfites, sulfides, CrCl2, TiCl3, and nascent hydrogen reduce oxyluciferin readily in absence of oxygen but without luminescence. Luminescence only appears in water solution if luciferin is oxidized by dissolved oxygen in presence of luciferase. Rapid oxidation of luciferin by oxygen without luciferase or oxidation by K3Fe(CN)6 in presence of luciferase but without oxygen never gives luminescence.

scholarly journals In situ measurements of oxidation–reduction potential and hydrogen peroxide concentration as tools for revealing LPMO inactivation during enzymatic saccharification of cellulose

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Adnan Kadić ◽  
Anikó Várnai ◽  
Vincent G. H. Eijsink ◽  
Svein Jarle Horn ◽  
Gunnar Lidén
Keyword(s):  
Reduction Potential ◽  
Enzymatic Saccharification ◽  
The State ◽  
Enzyme Inactivation ◽  
Ex Situ ◽  
Process Economics ◽  
Complete Inactivation ◽  
Oxidation Reduction ◽  
Oxidation Reduction Potential

Abstract Background Biochemical conversion of lignocellulosic biomass to simple sugars at commercial scale is hampered by the high cost of saccharifying enzymes. Lytic polysaccharide monooxygenases (LPMOs) may hold the key to overcome economic barriers. Recent studies have shown that controlled activation of LPMOs by a continuous H2O2 supply can boost saccharification yields, while overdosing H2O2 may lead to enzyme inactivation and reduce overall sugar yields. While following LPMO action by ex situ analysis of LPMO products confirms enzyme inactivation, currently no preventive measures are available to intervene before complete inactivation. Results Here, we carried out enzymatic saccharification of the model cellulose Avicel with an LPMO-containing enzyme preparation (Cellic CTec3) and H2O2 feed at 1 L bioreactor scale and followed the oxidation–reduction potential and H2O2 concentration in situ with corresponding electrode probes. The rate of oxidation of the reductant as well as the estimation of the amount of H2O2 consumed by LPMOs indicate that, in addition to oxidative depolymerization of cellulose, LPMOs consume H2O2 in a futile non-catalytic cycle, and that inactivation of LPMOs happens gradually and starts long before the accumulation of LPMO-generated oxidative products comes to a halt. Conclusion Our results indicate that, in this model system, the collapse of the LPMO-catalyzed reaction may be predicted by the rate of oxidation of the reductant, the accumulation of H2O2 in the reactor or, indirectly, by a clear increase in the oxidation–reduction potential. Being able to monitor the state of the LPMO activity in situ may help maximizing the benefit of LPMO action during saccharification. Overcoming enzyme inactivation could allow improving overall saccharification yields beyond the state of the art while lowering LPMO and, potentially, cellulase loads, both of which would have beneficial consequences on process economics.

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