scholarly journals Reactivity of photoreduced cytochrome aa3 complexes with molecular oxygen

1981 ◽  
Vol 194 (3) ◽  
pp. 713-720 ◽  
Author(s):  
P Nicholls ◽  
G A Chanady
Keyword(s):  
Cytochrome C ◽  
Absorption Band ◽  
Cytochrome C Oxidase ◽  
Low Temperatures ◽  
Ph Value ◽  
Alkaline Ph ◽  
Cytochrome Aa3 ◽  
Ph Values ◽  
Neutral Ph ◽  
Oxygen Addition

Cytochrome c oxidase (ox heart cytochrome aa3) is reduced on illumination in the presence of a photocatalyst system containing deazaflavin and EDTA. The photo-reduced enzyme reacts with oxygen at neutral pH to give a form of ferric enzyme, whereas a corresponding sample partially reduced by light in the absence of any photocatalyst reacts with oxygen to give an oxyferri species (‘oxygenated’ enzyme). Reduction by the photocatalyst system at an alkaline pH value (9.0) also gives rise to fully reduced oxidase (both haem groups ferrous). At these pH values the immediate product after oxygen addition is a species with a 605-606 nm absorption band, not identical with ferrous cytochrome a, but capable of oxidizing added cytochrome c. This intermediate, which is unstable at neutral pH, may be analogous to the ‘compound B’ obtained by Chance and co-workers [Chance, Saronio & Leigh (1975) J. Biol. Chem. 250, 9226-9237; Chance, Saronio & Leigh (1979) Biochem. J. 177, 931-941] at low temperatures.

scholarly journals In vitro antibacterial activity of propolis extracts on 12 different bacteria in conditions of 3 various pH values

2010 ◽  
Vol 62 (4) ◽  
pp. 915-934 ◽  
Author(s):  
S. Ivancajic ◽  
I. Mileusnic ◽  
Desanka Cenic-Milosevic
Keyword(s):  
Antibacterial Activity ◽  
Ph Value ◽  
Acidic Ph ◽  
Acidic Environment ◽  
Alkaline Ph ◽  
Antibacterial Effects ◽  
Ph Values ◽  
Neutral Ph ◽  
In Vitro Antibacterial Activity

This research investigated the effects of propolis extracted by 5 different solvents and aged for 7 days on twelve species of bacteria classified into four groups according to their pathogenicity in slightly acidic (pH=6), neutral (pH=7) and slightly alkaline (pH=8) environments. Propolis extracted by the examined solvents had antibacterial effects. The strongest effects on the growth of all tested microorganisms, except on the bacteria of the Salmonella genus, regardless of the pH value of the environment, were exerted by propolis extracted by ether, acetone, toluol and chloroform. In some cases the antibacterial action of propolis was best in a slightly acidic environment (pH=6).

scholarly journals Photodegradation of fluoroquinolones in aqueous solution under light conditions relevant to surface waters, toxicity assessment of photoproduct mixtures.

2021 ◽  
Author(s):  
Sarka Klementova ◽  
Martina Poncarová ◽  
Helena Langhansová ◽  
Jaroslava Lieskovská ◽  
David Kahoun ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Antibacterial Activity ◽  
Surface Waters ◽  
Ph Value ◽  
Reaction System ◽  
Photochemical Degradation ◽  
Alkaline Ph ◽  
Light Conditions ◽  
E Coli ◽  
Neutral Ph

Abstract Photochemical degradation of fluoroquinolones ciprofloxacin, enrofloxacin and norfloxacin in aqueous solution under light conditions relevant to surface waters at neutral and alkaline pH was found to proceed readily with half-lives between 0.9 and 2.7 min. The products of photochemical degradation identified by HPLC-MS included defluorinated, hydroxylated, and decarboxylated structures as well as structures with opened cyclic structures. For all of the studied substances, the reaction pathways were influenced significantly by the pH of the reaction system, with more products formed at alkaline pH than at neutral pH: the ratios of products in neutral and alkaline pH were 16/26, 9/19, 15/23 for ciprofloxacin, enrofloxacin, and norfloxacin, respectively. The structures of photoproducts and pathways of photochemical degradation are proposed. The antibacterial activities of photoproduct mixtures tested on E. coli and S. epidermidis were significantly higher in comparison to parental antibiotics in the case of both ciprofloxacin and enrofloxacin with p-values less than 0.0001 in most cases. The effect of the photoproducts was shown to be dependent on the pH value of the original antibiotic solutions before photodegradation: for ciprofloxacin, antibacterial activity against E. coli was more notably pronounced with regard to neutral pH photoproducts, while a less significant, or in one case not significant, effect of pH was observed against S. epidermidis ; for norfloxacin, antibacterial activity against both E. coli and S. epidermidis were especially high with regard to alkaline pH photoproducts

scholarly journals Titration and steady-state behaviour of the 830 nm chromophore in cytochrome c oxidase

1982 ◽  
Vol 203 (3) ◽  
pp. 541-549 ◽  
Author(s):  
P Nicholls ◽  
G A Chanady
Keyword(s):  
Steady State ◽  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Lag Phase ◽  
State Reduction ◽  
Cytochrome Aa3 ◽  
System A ◽  
Reducing Equivalent ◽  
State Behaviour ◽  
Copper Excess

Titration of cyanide-incubated cytochrome c oxidase (ox heart cytochrome aa3) with ferrocytochrome c or with NNN'N'-tetramethyl-p-phenylenediamine initially introduces two reducing equivalents per mol of cytochrome aa3. The first equivalent reduces the cytochrome a haem iron; the second reducing equivalent is not associated with reduction of the 830 nm chromophores (e.p.r.-detectable copper) but is probably required for reduction of the e.p.r.-undetectable copper. Excess reductant introduces a third reducing equivalent into the cyanide complex of cytochrome aa3. During steady-state respiration in the presence of cytochrome c and ascorbate, the 830 nm chromophore is almost completely oxidized. It is reduced more slowly than cytochrome a on anaerobiosis. In the presence of formate or azide, some reduction at 830 nm can be seen in the steady state; in an oxygen-pulsed system, a decrease in steady-state reduction of cytochromes c and a is associated with ab increased reduction of the 830 nm species. In the formate-inhibited system the reduction of a3 on anaerobiosis shows a lag phase, the duration of which corresponds to the time taken for the 830 nm species to be reduced. It is concluded that the e.p.r.-undetectable copper (CuD) is reduced early in the reaction sequence, whereas the detectable copper (CUD) is reduced late. The latter species is probably that responsible for reduction of the cytochrome a3 haem. The magnetic association between undetectable copper and the a3 haem may not imply capability for electron transfer, which occurs more readily between cytochrome a3 and the 830 nm species.

scholarly journals Binding of ligands and spectral shifts in cytochrome c oxidase

1978 ◽  
Vol 173 (1) ◽  
pp. 65-72 ◽  
Author(s):  
Peter Nicholls ◽  
Virginia Hildebrandt
Keyword(s):  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Blue Shift ◽  
Peak Shift ◽  
Cytochrome Aa3 ◽  
Hydrophobic Character ◽  
Mixed Spin ◽  
Spectral Shifts ◽  
Alkyl Isocyanides ◽  
Inhibited Enzyme

1. On addition of reductant (ascorbate plus NNN′N′-tetramethyl-p-phenylenediamine) to isolated cytochrome c oxidase (ox heart cytochrome aa3), in the presence of the inhibitors azide or cyanide, an initial partially reduced species is formed with absorption peaks at 415nm, 445nm and 605nm, which slowly gives rise to the final ‘half-reduced’ species in whose spectrum the 415nm peak has disappeared and a new absorption is seen at 430–435nm. 2. In the absence of reductant, cyanide forms an initial complex with the enzyme with a spectrum similar to that of the uncombined form, which slowly changes into the ‘low-spin’ cyanide form with a peak at 432nm. Azide, in absence of reductant, shifts the Soret peak slightly, but the resulting complex, which is probably thermally ‘mixed-spin’, undergoes no further changes. 3. The Soret-peak shift of oxidized cytochrome a3 which occurs on reduction of the enzyme in the presence of azide is accompanied by a concurrent blue shift of the ferrous cytochrome a peak from 605nm to 603nm. A partial blue shift of the α-peak occurs in the half-reduced sulphide-inhibited enzyme, and a complete blue shift is seen in the analogous complexes with alkyl sulphides [a2+a33+HSR compounds, where R=CH3, C2H5 or (CH3)2CH]. 4. Analogous, albeit less readily decipherable, spectroscopic effects with the ligands imidazole and alkyl isocyanides suggest that on reduction of cytochrome a an interaction occurs between the two haem groups involving (i) a high- to low-spin change in cytochrome a3, and after this, (ii) a change in the molecular environment of the cytochrome a. The latter effect, possibly a decrease in the hydrophobicity of the haem pocket, requires that the ligands on cytochrome a3 have a bulky and partially hydrophobic character.

scholarly journals Detection of a near infra-red absorption band of ferrohaem a3 in cytochrome c oxidase

FEBS Letters ◽  
1992 ◽  
Vol 305 (3) ◽  
pp. 171-173 ◽  
Author(s):  
Peter R. Rich ◽  
A.John Moody ◽  
W.John Ingledew
Keyword(s):  
Cytochrome C ◽  
Absorption Band ◽  
Cytochrome C Oxidase ◽  
Infra Red
Sign in / Sign up

Export Citation Format

Share Document