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PubMed1981

[Diarrhea in young calves. 4. Redox potential of the gastrointestinal tract of clinically healthy calves, and calves with spontaneous diarrhea, experimental Escherichia coli infection, and cyclophosphamide treatment].

The redox potential (ROP) dropped strongly in a calf, from two hours after birth to 48 hours of age. The drop in the colon was more strongly pronounced than that in the small intestine. -The Eh values recorded throughout the small intestine of clinically intact calves, aged between four and ten days, were more negative than those in the stomach. The most negative ROP values, which differed with significance from those of all proximal gastro-intestinal sections, were recorded from the caecum. -Intracolonic negativation of ROP in calves, during the first hours of life, must be attributed to progressing germ population. The same relationship is borne out clearly by a pronounced rise in anaerobic germ count accompanied by significant ROP negativation in the colon. -Growing age was accompanied by drastic change in ROP values throughout the gastro-intestinal tract. Calves aged between six and nine weeks were compared to animals aged between four and ten days. ROP values in stomach, proximal and distal jejunum as well as in the ileum of the former group were negative with significance, whereas ROP values in the caecum and colon of the same group were more positive. -Animals with diarrhoea exhibited significant ROP deviations only in the ileum. They were more negative, as compared to clinically intact calves aged between four and ten days. Pathophysiological intestinal disorders which could be measured via ROP were found to play no role at all in the genesis and course of diarrhoea of calf. -No pronounced gastro-intestinal ROP deviations were exhibited by calves with experimentally induced Escherichia coli infection and manifest coli dysentery nor by animals which received cyclophosphamide treatment.

Animals↗
PubMed1986

Electron spin resonance studies on a flavoprotein in neutrophil plasma membranes. Redox potentials of the flavin and its participation in NADPH oxidase.

Plasma membrane fractions of stimulated and resting cells were isolated from pig blood neutrophils. The midpoint redox potential (Em) of the membrane-bound flavin was determined potentiometrically by analysis of the flavin free-radical signal by electron spin resonance (ESR) spectroscopy. In both stimulated and resting cells, a peak position of the titration curve gave an Em value of -280 mV at pH 7.0 (Em7). The flavin free radical showed an ESR spectrum at g = 2.004 with a peak to peak width of 19 G, which indicates that the redox intermediate is a neutral semiquinone. Redox titrations were anaerobically examined at 25 degrees C with NADPH in place of dithionite. Addition of NADPH to plasma membranes of stimulated cells resulted in a rapid change in potential, accompanied by the formation of the ESR signal of flavin free radical. Computer simulation of the titration points gave an ambient midpoint potential of -280 mV (Em7). In contrast, those of resting cells showed a very slow change in potential and no g = 2.00 signal formation. Power saturation behavior of the ESR signal showed a marked difference between those of stimulated and resting cells. ESR characteristics of the flavin are discussed in relation to the membrane-bound NADPH oxidase.

Animals↗
PubMed1985

The amino acid sequence of a high-redox-potential ferredoxin from the purple phototrophic bacterium, Rhodospirillum tenue strain 2761.

The 61-residue amino acid sequence of Rhodospirillum tenue, strain 2761, high-redox-potential ferredoxin (HiPIP) is GTNAAMRKAFNYQDTAKNGKCSGCAQFVPGASPTAAGGCKVIPGDNEIAPGGYCDAFIVKK. It differs from that of R. tenue strain 3761 by 16 amino acid substitutions plus two single-residue deletions. This 26% sequence difference is similar to that observed among separate species of chromatiaceae such as Chromatium vinosum, C. gracile, and Thiocapsa roseopersicina, and is suprising because there are no distinguishing microbiological characteristics separating these two R. tenue strains. The most interesting amino acid substitution in R. tenue 2761 HiPIP is Gly for Asn 45 (C. vinosum numbering). Besides the four cysteines required to bind the four iron-four sulfur cluster, only Tyr 19, Asn 45, and Gly 75 are absolutely conserved in the nine previously determined HiPIP sequences. If HiPIP is used as a measure of divergence of species, then R. tenue and C. vinosum are the most distant purple bacteria examined. Quite the opposite conclusion follows based on the sequences of the cytochromes c'. It is suggested that this anomaly is more likely owing to a change in function for HiPIP with subsequently rapid evolutionary change than to a relatively recent transfer of the cytochrome c' gene between species.

Amino Acid Sequence↗
PubMedDate not supplied

[Intermediate states formed during discharge separation in the reaction centers of Rhodospirillum rubrum in the presence of a low-redox potential].

The intermediate short-lived states arising in reaction centre preparations (RC) of purple bacterium Rhodospirillum rubrum are investigated under the conditions of low redox potential. Excitation by 353 and 530 nm laser pulses produced two states characterized by optical absorption changes in the range of 350--650 nm and lifetimes: 10--30 ns for the first state and 2.5 +/- 0.5 microseconds for the second one. The first state is similar to the state PF, described previously by Parson et al. for RC from Rps. sphaeroides. Carotenoid extraction with isooctane resulted in changing the spectrum with tau = 2.5 microseconds and in the appearance of new absorption changes similar to those for the R state observed before in carotenoidless bacterial strains within microsecond time range. The comparison of the microsecond spectra with difference spectra (continuous light minus dark) of RC from R. rubrum in the range of 350--650 nm made it possible to identify the states with tau = 2.5 microseconds as carotenoid triplet states. The ratio of quantum yields of PR and carotenoid triplet states production was determined as being 1 : 1. The conclusion was made that triplet-triplet energy transfer from state PR to carotenoid is responsible for the production of carotenoid triplet states.

Binding Sites↗
PubMed2004

Critical roles of Asp40 at the haem proximal side of haem-regulated phosphodiesterase from Escherichia coli in redox potential, auto-oxidation and catalytic control.

In haem-regulated phosphodiesterase (PDE) from Escherichia coli (Ec DOS), haem is bound to the PAS domain, and the redox state of the haem iron regulates catalysis by the PDE domain. We generated mutants of Asp40, which forms a hydrogen bond with His77 (a proximal haem axial ligand) via two water molecules, and a salt bridge with Arg85 at the protein surface. The redox potential of haem was markedly increased from 67 mV vs. the standard hydrogen electrode in the wild-type enzyme to 95 mV and 114 mV in the Ala and Asn mutants, respectively. Additionally, the auto-oxidation rate of Ec DOS PAS was significantly increased from 0.0053 to 0.051 and 0.033 min(-1), respectively. Interestingly, the catalytic activities of the Asp40 mutants were abolished completely. Thus, Asp40 appears to play a critical role in the electronic structure of the haem iron and redox-dependent catalytic control of the PDE domain. In this report, we discuss the mechanism of catalytic control of Ec DOS, based on the physico-chemical characteristics of the Asp40 mutants.

Aspartic Acid↗
PubMed2006

[Redox-potential of blood and consistence of energoproviding defence system in cytomegalovirus infection in pregnancy].

We have studied the relationship between the hypoxic change and mitochondrial redox-potential disturbances in the mechanism of pheto-placental insufficiency in pregnancy with cytomegalovirus infection (CMV), detected by the positive anti-CMV-IgG titer and more then 4-fold increase of low avid anti-CMV-IgG. It was shown, that chronic CMV infection induces production of active forms of oxygen, peroxidation of structures and concurrently damage of mitochondria with essential decrease of ATP level. Results of the study have shown the important diagnostic value of estimation of hypoxic-oxidative damage induced by CMV infection. The results also revealed important relationships between the activity of the CMV infection and intensity of mitochondrial damage. On the basis of our investigations we suggest the additional diagnostic test (the determination of citozol NADH dependent isocitratdehydrogenaze activity) to evaluate the depth of CMV induced metabolic disturbances.

Adult↗
PubMed1988

Reduced redox potential during growth of some gram-negative bacteria. Effect on the biochemical and physicochemical surface properties and phagocytosis by polymorphonuclear leukocytes.

When cultivated at reduced redox potential the physico-chemical surface properties were altered in strains of E. coli, Salmonella and Yersinia bacteria. In particular, strains which showed hydrophilic surface properties under normal aerobic cultivation became more hydrophobic when exposed to anaerobic conditions (e.g. E. coli K12, E. coli K12D21, E. coli K12D22, S. minnesota S99, S. typhimurium 395MS, S. braenderup 2828 and Yersinia enterocolitica). Moreover, there were qualitative as well as quantitative differences in the protein profiles of whole bacterial lysates and membrane preparations analysed in SDS-PAGE. There were no qualitative differences in the lipopolysaccharide (LPS) bands. However, when E. coli K12D22 were cultivated aerobically, remarkably more high molecular temperature-sensitive (70 degrees C for 45 min) carbohydrate material was produced (weight about 360 KD and 660 KD). Interaction between polymorphonuclear leukocytes (PMNL) and the E. coli K12D22 strain, measured as chemiluminescence, showed that the anaerobically cultivated bacteria induced a chemiluminescence that was mainly of intracellular origin, while the aerobically cultivated induced an extracellular response. Phagocytosis and killing-studies showed that only anaerobically-grown E. coli were effectively inactivated by the PMNL.

Aerobiosis↗
PubMed2003

Use of redox potential modification by gas improves microbial quality, color retention, and ascorbic acid stability of pasteurized orange juice.

The aim of this paper was to study the effect of both redox potential (Eh) and pasteurization of orange juice on stability of color and ascorbic acid, and growth recovery of microorganisms during storage at 15 degrees C for 7 weeks. Three conditions of Eh, +360 mV (ungassed), +240 mV (gassed with N2), and -180 mV (gassed with N2-H2) were applied to orange juice. Both thermal destruction and recovery of sublethally heat-injured cells of Lactobacillus plantarum and Saccharomyces cerevisiae were investigated. While oxidizing conditions were the most effective for thermal destruction of L. plantarum and S. cerevisiae, reducing conditions decreased recovery of heated cells of S. cerevisiae. In addition, gassing the juice with N2 or N2-H2 increased color retention and ascorbic acid stability. The present study demonstrated that juice must be reduced just after the heat treatment in order, firstly, to maximize microbial destruction during pasteurization, and secondly, to prevent the development of microorganisms and stabilize color and ascorbic acid during storage.

Ascorbic Acid↗
PubMed1999

PAS domains: internal sensors of oxygen, redox potential, and light.

PAS domains are newly recognized signaling domains that are widely distributed in proteins from members of the Archaea and Bacteria and from fungi, plants, insects, and vertebrates. They function as input modules in proteins that sense oxygen, redox potential, light, and some other stimuli. Specificity in sensing arises, in part, from different cofactors that may be associated with the PAS fold. Transduction of redox signals may be a common mechanistic theme in many different PAS domains. PAS proteins are always located intracellularly but may monitor the external as well as the internal environment. One way in which prokaryotic PAS proteins sense the environment is by detecting changes in the electron transport system. This serves as an early warning system for any reduction in cellular energy levels. Human PAS proteins include hypoxia-inducible factors and voltage-sensitive ion channels; other PAS proteins are integral components of circadian clocks. Although PAS domains were only recently identified, the signaling functions with which they are associated have long been recognized as fundamental properties of living cells.

Amino Acid Sequence↗
PubMed1994

Mathematical modelling of the combined effect of water activity, pH and redox potential on the heat destruction.

Heat destruction of seven foodborne microorganisms (Lactobacillus plantarum, Lactobacillus brevis, Saccharomyces cerevisiae, Zygosaccharomyces bailii, Yarrowia lipolytica, Paecilomyces varioti and Neosartoria fischeri) as a function of the temperature, pH, redox potential and water activity was studied in synthetic heating media. Several mathematical models were developed for describing the heat destruction rate, most of them resulted in a good correlation between the fitted and measured values. The determination coefficients of the model-fitting were the best in case of lactobacilli and moulds (0.96-0.99) and the worst in case of the yeasts (0.81-0.88).

Food Microbiology↗
PubMed1991

Influence of redox potential on metabolism of glucose in mixed cultures of rumen microorganisms.

The rumen inocula taken from cows and sheep were incubated in pH controlled anaerobic batch cultures and the effect of the elevated redox potential (Eh) on metabolism of glucose was examined. In Eh regulated cultures (Eh = +100 mV) the VFA production and production of methane were decreased with a concomitant increase of production of lactate. In these cultures counts of lactilytic bacteria tended to be lower and counts of lactic acid bacteria higher than in cultures with a normal Eh. The elevated Eh also exerted an inhibitory effect on the rumen protozoa. The relevance of these changes to the rumen metabolism is discussed.

Animals↗
PubMed1979

The respiratory chain of Paramecium tetraurelia in wild type and the mutant Cl1. I. Spectral properties and redox potentials.

1. Purified mitochondria have been prepared from wild type Paramecium tetraurelia and from the mutant Cl1 which lacks cytochrome aa3. Both mitochondrial preparations are characterized by cyanide insensitivity. Their spectral properties and their redox potentials have been studied. 2. Difference spectra (dithionite reduced minus oxidized) of mitochondria from wild type P. tetraurelia at 77 K revealed the alpha peaks of b-type cytochrome (s) at 553 and 557 nm, of c-type cytochrome at 549 nm and a-type cytochrome at 608 nm. Two alpha peaks at 549 and 545 nm could be distinguished in the isolated cytochrome c at 77 K. After cytochrome c extraction from wild type mitochondria, a new peak at 551 nm was unmasked, probably belonging to cytochdrome c1. The a-type cytochrome was characterized by a split Soret band with maxima at 441 and 450 nm. The mitochondria of the mutant Cl1 in exponential phase of growth differed from the wild type mitochondria in that cytochrome aa3 was absent while twice the quantity of cytochrome b was present. In stationary phase, mitochondria of the mutant were characterized by a new absorption peak at 590 nm. 3. Cytochrome aa3 was present at a concentration of 0.3 nmol/mg protein in wild type mitochondria and ubiquinone at a concentration of 8 nmol/mg protein both in mitochondria of the wild type and the mutant Cl1. Cytochrome aa3 was more susceptible to heat than cytochromes b and c,c1.

Animals↗
PubMed1963

CYTOCHROMES OF A BLUE-GREEN ALGA: EXTRACTION OF A C-TYPE WITH A STRONGLY NEGATIVE REDOX POTENTIAL.

Aqueous extraction of lyophilized Anacystis nidulans cells followed by chromatography on diethylaminoethyl cellulose separates three different c-type cytochromes. Of the two present in highest concentration, cytochrome-554 has a + 0.35-volt redox potential and resembles the cytochrome f of other photosynthetic tissues, while cytochrome-549 has a -0.26-volt potential. The possible participatidn of cytochrome-549 in electron transport in photosynthesis in this alga at a more negative oxidation-reduction potential than previously postulated for any cytochrome is inferred from the similarities in its spectra to the light-induced spectral changes in vivo observed by others.

Chromatography↗
PubMedDate not supplied

[Changes in the redox potential in Escherichia coli growth cessation].

Escherichia coli strains K-12 and M-17 were grown in batch and continuous cultures, with pulse addition of glucose or a nitrogen source as limiting substrates; the redox potential decreased when the growth ceased. The maximal deviation of the Eh was 150 mV when the strain K-12 ceased to grow. The Eh decreased rapidly for 25 min in the strain K-12 and for about 10--12 min in the strain M-17; then the Eh returned slowly to the initial level. The second phase took about 150 min in the strain K-12 and 40 to 60 min in the strain M-17. No changes in the Eh were found when the culture was grown under the anaerobic conditions.

Culture Media↗
PubMed1990

Oxidation-reduction potentials of cytochromes in Ascaris muscle mitochondria: high-redox-potential cytochrome b558 in complex II (succinate-ubiquinone reductase).

Oxidation-reduction midpoint potentials (Ems) were determined at pH 7.0 for cytochromes in the anaerobic respiratory chain of Ascaris mitochondria by redox titration techniques. Cytochrome b558, which is associated with complex II that functions as fumarate reductase in the terminal step of the respiratory chain, was shown to have an Em of -34 mV in the isolated complex II and -54 mV in mitochondria. These values are much higher than the value of Ascaris cytochrome b558. In contrast, Ems of cytochromes C + C1 and cytochrome b559.5 were determined in situ to be 235 mV and 78 mV, respectively, which are comparable to those of their mammalian counterparts.

Animals↗
PubMed2006

A conserved histidine in cytochrome c maturation permease CcmB of Shewanella putrefaciens is required for anaerobic growth below a threshold standard redox potential.

Shewanella putrefaciens strain 200 respires a wide range of compounds as terminal electron acceptor. The respiratory versatility of Shewanella is attributed in part to a set of c-type cytochromes with widely varying midpoint redox potentials (E'(0)). A point mutant of S. putrefaciens, originally designated Urr14 and here renamed CCMB1, was found to grow at wild-type rates on electron acceptors with high E'0 [O2, NO3-, Fe(III) citrate, MnO2, and Mn(III) pyrophosphate] yet was severely impaired for growth on electron acceptors with low E'0 [NO2-, U(VI), dimethyl sulfoxide, TMAO (trimethylamine N-oxide), fumarate, gamma-FeOOH, SO3(2-), and S2O3(2-)]. Genetic complementation and nucleotide sequence analyses indicated that the CCMB1 respiratory mutant phenotype was due to mutation of a conserved histidine residue (H108Y) in a protein that displayed high homology to Escherichia coli CcmB, the permease subunit of an ABC transporter involved in cytochrome c maturation. Although CCMB1 retained the ability to grow on electron acceptors with high E'(0), the cytochrome content of CCMB1 was <10% of that of the wild-type strain. Periplasmic extracts of CCMB1 contained slightly greater concentrations of the thiol functional group (-SH) than did the wild-type strain, an indication that the E(h) of the CCMB1 periplasm was abnormally low. A ccmB deletion mutant was unable to respire anaerobically on any electron acceptor, yet retained aerobic respiratory capability. These results suggest that the mutation of a conserved histidine residue (H108) in CCMB1 alters the redox homeostasis of the periplasm during anaerobic growth on electron acceptors with low (but not high) E'0. This is the first report of the effects of Ccm deficiencies on bacterial respiration of electron acceptors whose E'0 nearly span the entire redox continuum.

ATP-Binding Cassette Transporters↗
PubMed1990

Reduction processes in fast atom bombardment mass spectrometry: interdependence of analyte and matrix redox potentials.

The reduction of selected redox indicator dyes during fast atom bombardment mass spectrometry was investigated in several different matrices. Reduction is indicated by the incorporation of one or more hydrogens into the cation of the dye. The extent of reduction of the analyte can be related to the E 1/2 value of the reduction potential of the dye. Selection of matrix also influences the reduction, the reducing power decreasing in the order glycerol greater than sulfolane greater than thioglycerol greater than hydroxyethyl disulfide greater than nitrobenzyl alcohol. Evidence is given suggesting that reduction is initiated by exposure of the analyte-matrix mixture to atom bombardment. It is shown that reduction can be controlled by the addition of metal ions with a very low reduction potential to the matrix to act as electron scavengers.

Azo Compounds↗
PubMedDate not supplied

[Changes in the redox potential and pO2 in heat shock to Escherichia coli].

When the growing culture of Escherichia coli was subjected to a temperature above 37 degrees C, the pO2 fell abruptly at 42 degrees C; a reversible decrease in the redox potential (ROP) down to the range of negative values was detected if the growth ceased at 46 degrees C. The drop in the ROP took from 6 to 10 min, with the maximal deviation of 42.5 mV. Such changes in the pO2 and ROP were not caused by a heat shock in the stationary cultures. The change in the ROP was not due to a change in the pH and pO2 of the medium. The authors believe that the effect should be attributed to an elimination of the ionic gradients and the electrochemical gradient delta muH+.

Escherichia coli↗