Search results for "Escher"
showing 10 items of 728 documents
Transport of C(4)-dicarboxylates in Wolinella succinogenes.
2000
ABSTRACT C 4 -dicarboxylate transport is a prerequisite for anaerobic respiration with fumarate in Wolinella succinogenes , since the substrate site of fumarate reductase is oriented towards the cytoplasmic side of the membrane. W. succinogenes was found to transport C 4 -dicarboxylates (fumarate, succinate, malate, and aspartate) across the cytoplasmic membrane by antiport and uniport mechanisms. The electrogenic uniport resulted in dicarboxylate accumulation driven by anaerobic respiration. The molar ratio of internal to external dicarboxylate concentration was up to 10 3 . The dicarboxylate antiport was either electrogenic or electroneutral. The electroneutral antiport required the prese…
Alternative respiratory pathways of Escherichia coli: energetics and transcriptional regulation in response to electron acceptors
1997
AbstractThe electron-transport chains of Escherichia coli are composed of many different dehydrogenases and terminal reductases (or oxidases) which are linked by quinones (ubiquinone, menaquinone and demethylmenaquinone). Quinol:cytochrome c oxido-reductase (`bc1 complex') is not present. For various electron acceptors (O2, nitrate) and donors (formate, H2, NADH, glycerol-3-P) isoenzymes are present. The enzymes show great variability in membrane topology and energy conservation. Energy is conserved by conformational proton pumps, or by arrangement of substrate sites on opposite sides of the membrane resulting in charge separation. Depending on the enzymes and isoenzymes used, the H+/e− rat…
Anionic Lipids Modulate the Activity of the Aquaglyceroporin GlpF
2015
AbstractThe structure and composition of a biological membrane can severely influence the activity of membrane-embedded proteins. Here, we show that the E. coli aquaglyceroporin GlpF has only little activity in lipid bilayers formed from native E. coli lipids. Thus, at first glance, GlpF appears to not be optimized for its natural membrane environment. In fact, we found that GlpF activity was severely affected by negatively charged lipids regardless of the exact chemical nature of the lipid headgroup, whereas GlpF was not sensitive to changes in the lateral membrane pressure. These observations illustrate a potential mechanism by which the activity of an α-helical membrane protein is modula…
Anthemis wiedemanniana essential oil prevents LPS-induced production of NO in RAW 264.7 macrophages and exerts antiproliferative and antibacterial ac…
2012
Anthemis wiedemanniana is known in folk medicine for the treatment of microbial infections, cancer and also urinary and pulmonary problems. In this study, the chemical composition of the essential oil from A. wiedemanniana was evaluated and its antibacterial activity was tested against 10 bacterial strains. The oil was also tested for its potentiality to inhibit nitric oxide production in RAW 264.7 macrophages and for its cytotoxicity against four human cancer cell lines. A. wiedemanniana oil, rich of oxygenated monoterpenes (25.4%), showed a good antibacterial activity against Gram-positive bacteria and a good activity against the two Gram-negative bacteria, Escherichia coli and Proteus vu…
Anti-Pseudomonas aeruginosa activity of hemlock (Conium maculatum, Apiaceae) essential oil
2018
Conium maculatum is a nitrophilous weed belonging to the Apiaceae family and occurring in hedgerows, pastures, waste ground, along rivers and roadsides. Little is known on the chemistry and bioactivity of other secondary metabolites occurring in the plant. In the present work, we have analysed the chemical composition and antimicrobial activity of the essential oils hydrodistilled from leaves and inflorescenes of C. maculatum growing in Sicily, Italy. The composition of essential oils was achieved by gas chromatography-mass spectrometry (GC-MS) analysis, whereas the inhibitory effects on the growth of two Gram negative strains, namely Escherichia coli and Pseudomonas aeruginosa were assesse…
CrELISA: a fast and robust enzyme-linked immunosorbent assay bypassing the need for purification of recombinant protein
2004
A multitude of antigens has been recently identified by screening of cDNA expression libraries derived from human tumors with autologous sera. Using a phage autoantibody assay and small panels of sera derived from cancer patients or controls it has been shown that some of these antigens display cancer-associated autoantibody responses. The diagnostic and prognostic significance of these potentially cancer-related autoantibodies remains unclear until large-scale assays are developed and serological data are available for hundreds of cancer patients and controls. The major bottleneck for the development of large-scale assays are the cloning, expression and the purification of each of the resp…
Diversity and Evolution of the Phenazine Biosynthesis Pathway
2010
ABSTRACT Phenazines are versatile secondary metabolites of bacterial origin that function in biological control of plant pathogens and contribute to the ecological fitness and pathogenicity of the producing strains. In this study, we employed a collection of 94 strains having various geographic, environmental, and clinical origins to study the distribution and evolution of phenazine genes in members of the genera Pseudomonas , Burkholderia , Pectobacterium , Brevibacterium , and Streptomyces . Our results confirmed the diversity of phenazine producers and revealed that most of them appear to be soil-dwelling and/or plant-associated species. Genome analyses and comparisons of phylogenies inf…
Synthesis, Properties and Antimicrobial Activity of 5-Trifluoromethyl-2-formylphenylboronic Acid
2020
2-Formylphenylboronic acids display many interesting features, not only from synthetic but also from an application as well as structural points of view. 5-Trifluoromethyl-2-formyl phenylboronic acid has been synthesized and characterized in terms of its structure and properties. The presence of an electron-withdrawing substituent results in a considerable rise in the acidity in comparison with its analogues. In some solutions, the title compound isomerizes with formation of the corresponding 3-hydroxybenzoxaborole. Taking into account the probable mechanism of antifungal action of benzoxaboroles, which blocks the cytoplasmic leucyl-tRNA synthetase (LeuRS) of the microorganism, docking stud…
Oxidative stress protection by manganese complexes of tail-tied aza-scorpiand ligands.
2015
The Mn2+ coordination chemistry of double scorpiand ligands in which two polyazacyclophane macrocycles have been connected by pyridine, phenanthroline and bipyridine spacers has been studied by potentiometry, paramagnetic NMR and electrochemistry. All ligands show high stability with Mn2+ and the complexes were formed in a wide pH range. DFT calculations support the structures and coordination geometries derived from the study. A remarkable antioxidant activity was evidenced for these systems by the McCord-Fridovich assay and in Escherichiacoli sodAsodB deficient bacterial cells. The three systems were tested as anti-inflammatory drugs in human macrophages measuring the accumulation of cyto…
Nitic oxide promotes strong cytotoxicity of phenolic compounds against escherichia coli. The influence of antioxidant defenses
2003
[EN] The induction of mutagenic and cytotoxic effects by simple phenolics, including catechol (CAT), 3,4dihydroxyphenylacetic acid (DOPAC), hydroquinone (HQ), and 2,5-dihydroxyphenylacetic (homogentisic) acid (HGA), appears to occur through an oxidative mechanism based on the ability of these compounds to undergo autoxidation, leading to quinone formation with the production of reactive oxygen species. This is supported by the detection of such adverse effects in plate assays using Escherichia coli tester strains deficient in the OxyR function, but not in OxyR(+) strains. The OxyR protein is a redox-sensitive regulator of genes encoding antioxidant enzymes including catalase and alkyl hydro…