Oxygen uptake and evolution by iron porphyrin enzymes

1959 ◽  
Vol 12 (1) ◽  
pp. 47
Author(s):  
NK King ◽  
ME Winfield
Keyword(s):  
Ascorbic Acid ◽  
Carbon Atom ◽  
Oxygen Uptake ◽  
Cytochrome Oxidase ◽  
Metal Atom ◽  
Iron Porphyrin ◽  
Reduction Step ◽  
The Third ◽  
Catalase Peroxidase ◽  
Electron Deficiency

Three detailed mechanisms are considered for the catalatic decomposition of H2O2. It is shown that the first of these, akin to the earlier hypotheses for catalase action, cannot satisfy the magnetic, titrimetric, and kinetic evidence. The second mechanism involves oxidation of the FeIII porphyrin to the equivalent of FeV. The electron deficiency is distributed over the ligands so that even in the most oxidized complex the iron is in the FeIV or possibly even the FeIII state. In the third scheme it is suggested that the reduction step (in which O2 is liberated) takes place at a carbon atom, while the site of the oxidation is the metal atom as commonly supposed. The liberation of O2 from H2O2 can be catalysed by 6-coordinate ruthenium II complexes. In the catalytic cycle, the metal appears to be oxidized to Rdv, then reduced to RuII. Ethanol or ascorbic acid can substitute for H2O2 in the reduction. Evidence for H2O2 attack on the ligands is suggestive but not conclusive. A brief comment is made on the bonding of oxygen to haemoglobin and myoglobin. The accumulated evidence for the structures of catalase, peroxidase, and myoglobin complexes is utilized in a scheme for the uptake of oxygen by cytochrome oxidase.

Electrochemical Studies of an Iron Porphyrin Immobilized on Nb2O5/SiO2 and Its Application for Simultaneous Determination of Dopamine and Ascorbic Acid Using Multivariate Calibration Methodology

2007 ◽  
Vol 19 (24) ◽  
pp. 2543-2550 ◽  
Author(s):  
Tatiane Skeika ◽  
Crislaine Marcovicz ◽  
Shirley Nakagaki ◽  
Sérgio Toshio Fujiwara ◽  
Karen Wohnrath ◽  
...  
Keyword(s):  
Ascorbic Acid ◽  
Simultaneous Determination ◽  
Multivariate Calibration ◽  
Iron Porphyrin ◽  
Electrochemical Studies

Cytochrome oxidase and ascorbic acid in the normal and regenerating tail of the Scincid lizard, Mabuya carinata

1975 ◽  
Vol 93 (3) ◽  
pp. 411-420 ◽  
Author(s):  
A.V. Ramachandran ◽  
N. Radhakrishnan ◽  
R.V. Shah
Keyword(s):  
Ascorbic Acid ◽  
Cytochrome Oxidase

scholarly journals Ascorbic acid levels in maternal milk: differences with respect to ascorbic acid status during the third trimester of pregnancy

1998 ◽  
Vol 79 (5) ◽  
pp. 431-437 ◽  
Author(s):  
Rosa M. Ortega ◽  
M. Elena Quintas ◽  
Pedro Andrés ◽  
Rosa M. Martínez ◽  
Ana M. López-Sobaler
Keyword(s):  
Ascorbic Acid ◽  
Fruits And Vegetables ◽  
Maternal Serum ◽  
Third Trimester ◽  
Mature Milk ◽  
The Third ◽  
Acid Intake ◽  
Vitamin Intake ◽  
Acid Status ◽  
Transition Milk

The aim of the present investigation was to study the relationship between ascorbic acid status during the third trimester of pregnancy and levels of this vitamin in transition milk (days 13–14 of lactation) and mature milk (day 40 of lactation). To this end, the pregnancies and lactation periods of fifty-seven healthy women between 18 and 35 years of age (27 (sd 3.7) years) were monitored. Vitamin intake during the third trimester was determined by recording the consumption of foods over 5 d, and by registering the quantities provided by dietary supplements. Ascorbic acid levels in maternal serum during this stage of pregnancy, and in transition and mature milk samples, were determined by spectrophotometry. Those subjects with ascorbic acid intakes below that recommended (80 mg/d) (group L) showed lower consumption of fruit and vegetables than did those with greater intakes (group H). The consumption of ascorbic acid supplements was very low, and was only seen in three group H subjects. The difference in ascorbic acid intake was reflected at serum level. Group L subjects showed significantly lower serum values than did group H subjects (30.1 (sd 36.3) μmol/l compared with 101.1 (sd 168.1) μmol/l). Vitamin intake also influenced the composition of transition milk. Group L subjects showed significantly lower levels of ascorbic acid in milk than did group H subjects (255.5 (sd 220.3) μmol/l compared with 437.8 (sd 288.4) μmol/l). The results of the present study reveal the need to increase the consumption of fruits and vegetables during pregnancy and to monitor maternal ascorbic acid intake and vitamin C status.

scholarly journals Stickstoffverbindungen von Elementen der dritten Hauptgruppe mit intra- und intermolekularen Donor-Akzeptor-Bindungen, V [1]. Spezielle Gallium- und Indiumamide mit Alkoxogruppen / Nitrogen Compounds of Elements of the Third Main Group with Intra- and Intermolecular Donor Acceptor Bonds, V [1]. Special Gallium and Indium Amides with Alkoxo Groups

1988 ◽  
Vol 43 (5) ◽  
pp. 505-512 ◽  
Author(s):  
M. Veith ◽  
J. Pöhlmann
Keyword(s):  
Metal Atom ◽  
Nmr Spectra ◽  
Main Group ◽  
Nitrogen Compounds ◽  
Temperature Dependent ◽  
H Nmr ◽  
The Third ◽  
Donor Acceptor ◽  
Molecular Compounds ◽  
Chelating Effect

AbstractThe lithium alkoxoamidosilane (Me2Si(OtBu)(NtBu)Li)2 (4) and its trimethyltin derivative Me2Si(OtBu)(NtBu)SnMe3 (7) have been used, to introduce the ligand Me2Si(OtBu)(NtBu) = L into molecular compounds of gallium and indium. The following molecules were synthesized: L-M(Me)Cl (M = Ga (5), In (6)), L-InMe2 (8), L-InX2 (X = Cl (9), Br (10)), L2InX (X = Cl (11), Br (12)) and L2Ga2Cl2 (22). The ligand L is assumed to chelate the metal atom on the basis of temperature dependent 1H NMR spectra. The chelating effect is more pronounced in the gallium derivatives than in the indium analogues. Equilibria between L2InX/InX3 and LInX2 have been observed in diethylether solutions. No metal(I) derivatives LGa or LIn could be isolated. L2Ga2Cl2 (22), formally containing gallium(ll), can be sublimed without decomposition at 110 °C in vacuo.

Selective determination of dopamine in the presence of ascorbic acid at the carbon atom wire modified electrode

2005 ◽  
Vol 578 (2) ◽  
pp. 323-329 ◽  
Author(s):  
Kuan-Hong Xue ◽  
Fei-Fei Tao ◽  
Wen Xu ◽  
Shou-Yin Yin ◽  
Jia-Mei Liu
Keyword(s):  
Ascorbic Acid ◽  
Carbon Atom ◽  
Modified Electrode ◽  
Selective Determination

Mechanically changed band gap of single walled carbon nanotube: a third neighbor tight-binding approach

Open Physics ◽  
2010 ◽  
Vol 8 (3) ◽  
Author(s):  
Mehdi Pakkhesal ◽  
Rahim Ghayour
Keyword(s):  
Carbon Nanotube ◽  
Carbon Atom ◽  
Band Gap ◽  
Tight Binding ◽  
Electronic Band ◽  
Single Walled Carbon Nanotube ◽  
Single Walled Carbon ◽  
The Third ◽  
Analytical Derivation ◽  
Electronic Band Gap

AbstractAnalytical derivation of electronic band gap of Single Walled Carbon Nanotube (SWCNT) under a small percent of uniaxial and torsional strains is in this paper. Our approach is based on a kind of π-Tight Binding (π-TB) approximation which includes interactions of the second and the third neighbors of each carbon atom in addition to the nearest ones. Implementing the approach of this paper, yields more precise results than those of other researches.

Supraicosahedral (metalla) carboranes

2003 ◽  
Vol 75 (9) ◽  
pp. 1325-1333 ◽  
Author(s):  
Alan S. F. Boyd ◽  
Anthony Burke ◽  
David Ellis ◽  
Daniel Ferrer ◽  
Barry T. Giles ◽  
...  
Keyword(s):  
Binding Energy ◽  
Metal Atom ◽  
General Concept ◽  
Reduction Step ◽  
Kinetic Instability ◽  
Partial Degradation

Although supraicosahedral (hetero) boranes have long been of interest to theoreticians, the area is under-developed from a synthetic viewpoint. The synthesis of supraicosahedral carboranes by reduction then capitation (RedCap) of C2B10 species is attractive, but unsuccessful as long as the cage carbon atoms are free to separate in the reduction step. Studies on 4,1,6-MC2B10 13-vertex metallacarboranes have shown that the partial degradation of such species can be a facile process, in spite of the fact that the binding energy of the metal atom to the carborane framework can be at least as high as that of a {BH}fragment. These findings support the general concept of the kinetic instability of 1,6-C2B11 species, explaining why a supraicosahedral carborane could not be made from 1,2-C2B10H12. However, tethering together the two cage C atoms with a C6H4(CH2)2 strap ultimately allowed the synthesis of the first supraicosahedral carborane. This species has a henicosahedral geometry, and there is evidence that a facile rearrangement from kinetic to thermodynamic isomer has occurred. The RedCap synthesis of this unprecedented cluster has the potential to be applied successively, yielding 14-,15-,16-, etc. vertex carboranes, the larger of which may be sufficiently kinetically stable to exist without a C,C tether.

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