ChemInform Abstract: EFFECTS OF AXIAL LIGATION ON MOLECULAR OXYGEN BINDING BY DONOR ATOMS BUILT IN SATURATED MACROCYCLES. EQUILIBRIUM AND KINETIC STUDY WITH COBALT(II) COMPLEXES OF MACROCYCLIC PENTAAMINES AND OXATETRAAMINE

1980 ◽  
Vol 11 (41) ◽  
Author(s):  
M. KODAMA ◽  
E. KIMURA
1983 ◽  
Vol 87 (23) ◽  
pp. 4681-4686 ◽  
Author(s):  
Frederick R. Hopf ◽  
Milorad M. Rogic ◽  
James F. Wolf

1979 ◽  
Vol 47 (7) ◽  
pp. 409-414 ◽  
Author(s):  
Masao IWAI ◽  
Hiroshi MAJIMA ◽  
Toshio IZAKI

1995 ◽  
Vol 308 (2) ◽  
pp. 641-644 ◽  
Author(s):  
F Spinner ◽  
M R Cheesman ◽  
A J Thomson ◽  
T Kaysser ◽  
R B Gennis ◽  
...  

The cytochrome bd ubiquinol oxidase from Escherichia coli is induced when the bacteria are cultured under microaerophilic or low-aeration conditions. This membrane-bound respiratory oxidase catalyses the two-electron oxidation of ubiquinol and the four-electron reduction of dioxygen to water. The oxidase contains three haem prosthetic groups: haem b558, haem b595 and haem d. Haem d is the oxygen binding site, and it is likely that haem d and b595 form a bimetallic site in the enzyme. Haem b558 has been previously characterized spectroscopically as being low spin and has been shown to be located within subunit I (CydA) of this two-subunit enzyme. It is likely that haem b558 is associated with the quinol oxidation site, which has also been shown to be within subunit I. In a previous effort to locate the specific amino acids axially ligated to haem b558, all six histidines within subunit I were altered by site-directed mutagenesis. Only one, histidine-186, was identified as a likely ligand to haem b558. Hence it was suggested that haem b558 could not have bis(histidine) ligation. In the current work, a combination of low-temperature near-infrared magnetic circular dichroism (NIR-MCD) and EPR spectroscopies have been employed to identify the nature of the haem b558 axial ligands. The NIR-MCD spectrum at cryogenic temperatures is dominated by the low-spin haem b558 component of the complex, and the low-energy band near 1800 nm is strong evidence for histidine-methionine ligation. It is concluded that haem b558 is ligated to histidine-186 plus one of the methionines located within subunit I of the oxidase.


1986 ◽  
Vol 64 (12) ◽  
pp. 1614-1620 ◽  
Author(s):  
A. A. Ali ◽  
E. A. Ogryzlo ◽  
Y. Q. Shen ◽  
P. T. Wassell

The recombination of oxygen atoms has been studied in a discharge flow system at room temperature. The yield of O2(a1Δg) in the recombination on Pyrex has been found to be 0.08 (±0.02). In the gas phase, O2(a) was found to be formed in a process that is second order in [O] and first order in [N2]. The rate constant for this third-order reaction was found to be 3.4 (±0.4) × 10−34 cm6∙molecule−2∙s−1, representing a yield of 0.07 (±0.02). In the presence of molecular oxygen, the rate of production of O2(a) was found to increase. A kinetic study of this effect led to the conclusion that collisions of molecular oxygen with an unidentified precursor can produce O2(a) with high efficiency.


Polymer ◽  
1981 ◽  
Vol 22 (12) ◽  
pp. 1692-1698 ◽  
Author(s):  
G.Gangi Reddy ◽  
T. Nagabhushanam ◽  
K. Venkata Rao ◽  
M. Santappa

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