Search results for "desorption"
showing 10 items of 340 documents
Response of the oxygen sensor NreB to air in vivo: Fe-S-containing NreB and apo-NreB in aerobically and anaerobically growing Staphylococcus carnosus.
2009
ABSTRACT The sensor kinase NreB from Staphylococcus carnosus contains an O 2 -sensitive [4Fe-4S] 2+ cluster which is converted by O 2 to a [2Fe-2S] 2+ cluster, followed by complete degradation and formation of Fe-S-less apo-NreB. NreB·[2Fe-2S] 2+ and apoNreB are devoid of kinase activity. NreB contains four Cys residues which ligate the Fe-S clusters. The accessibility of the Cys residues to alkylating agents was tested and used to differentiate Fe-S-containing and Fe-S-less NreB. In a two-step labeling procedure, accessible Cys residues in the native protein were first labeled by iodoacetate. In the second step, Cys residues not labeled in the first step were alkylated with the fluorescent…
Thermal desorption gas chromatography with mass spectrometry study of outgassing from polymethacrylimide foam (Rohacell®)
2015
Polymethacrylimide foams are used as light structural materials in outer-space devices; however, the foam closed cells contain volatile compounds that are outgassed even at low temperatures. These compounds ignite as plasmas under outer-space radiation and the intense radio-frequency fields used in communications. Since plasmas may cause spacecraft fatal events, the conditions in which they are ignited should be investigated. Therefore, qualitative and quantitative knowledge about polymethacrylimide foam outgassing should be established. Using thermogravimetric analysis, weight losses reached 3% at ca. 200°C. Thermal desorption gas chromatography with mass spectrometry detection was used to…
Development of iron oxide/activated carbon nanoparticle composite for the removal of Cr(VI), Cu(II) and Cd(II) ions from aqueous solution
2018
Iron oxide (Fe3O4) and iron oxide/activated carbon (Fe3O4/AC) were fabricated by co-precipitation method for the removal of Cr(VI), Cu(II) and Cd(II) ions from aqueous solution in batch mode. These nanoparticles were characterized by BET, FTIR, XRD, SEM/TEM and VSM. The optimum conditions for the removal of ions were pH = 2 for Cr(VI) and 6 for Cu(II) and Cd(II), initial metal ion concentration = 50 mg L−1, nanoparticle dose = 50 mg/10 mL, temperature = 25 ± 1 °C, shaking speed = 180 rpm and contact time = 3 h. The equilibrium data of ions sorption were well described by Langmuir, Freundlich, Redlich-Peterson and Intraparticle Diffusion model. The R2 values obtained by Langmuir model were h…
Chitosomes loaded with cranberry proanthocyanidins attenuate the bacterial lipopolysaccharide-induced expression of iNOS and COX-2 in raw 264.7 macro…
2009
Chitosan binds to negatively charged soy lecithin liposomes by an electrostatic interaction driven by its positively charged amino group. This interaction allows stable covered vesicles (chitosomes) to be developed as a suitable targeted carrier and controlled release system. This study investigated the effect of chitosomes on the activation of cranberry proanthocyanidins (PAC) in Raw 264.7 macrophages. Chitosomes were characterized according to size, zeta potential, PAC-loading, and release properties. Results showed an increase in the net positive charge and size of the liposomes as the concentration of chitosan was increased, suggesting an effective covering of the vesicles by means of e…
3α,3′α-Bis(n-acetoxyphenylcarboxy)-5β-cholan-24-oic acid ethane-1,2-diol diesters (n = 2-4):13C NMR chemical shifts, variable-temperature and NOE1H N…
2000
Three novel bile acid-based molecular dimers, 3α,3′α-bis(n-acetoxyphenylcarboxy)-5β-cholan-24-oic acid ethane-1,2-diol diesters (n = 2–4), 1–3, were synthesized from lithocholic acid (3α-hydroxy-5β-cholan-24-oic acid) ethane-1,2-diol diester and isomeric n-acetoxybenzoyl chlorides (n = 2–4). Their cleft type conformational preferences were suggested theoretically by PM3 molecular orbital calculations. Molecular weights determined by the matrix-assisted laser desorption/ionization time-of-flight technique and 13C NMR chemical shifts of the 1–3 are also presented. Copyright © 2000 John Wiley & Sons, Ltd.
13C NMR spectral assignments of 3α,3′α-bis(arylcarboxy)-5β-cholan-24-oic acid ethane-1,2-diol diesters: new lithocholic acid-based molecular clefts
1999
3α,3′α-Bis(arylcarboxy)-5β-cholan-24-oic acid ethane-1,2-diol diesters (1–3) were synthesized by the reaction of an aroyl chloride (aroyl=2,6-dichlorobenzoyl, 2-naphthoyl and 1-pyrenoyl) with lithocholic acid (3α-hydroxy-5β-cholan-24-oic acid) ethane-1,2-diol diester. The 13C NMR chemical shift assignments of the formed molecular clefts 1–3, pyrene-1-carboxylic acid methyl ester (4) (used as model compound) and 1-pyrenoyl chloride (5) are based on literature data and 13C DEPT-135, 1H,13C HMQC and 1H,13C HMBC experiments. The molecular weights of 1–3 were determined by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Copyright © 1999 John Wiley & Sons, Ltd.
Why does vacuum drive to the loading of halloysite nanotubes? The key role of water confinement.
2019
The filling of halloysite nanotubes with active compounds solubilized in aqueous solvent was investigated theoretically and experimentally. Based on Knudsen thermogravimetric data, we demonstrated the water confinement within the cavity of halloysite. This process is crucial to properly describe the driving mechanism of halloysite loading. In addition, Knudsen thermogravimetric experiments were conducted on kaolinite nanoplates as well as on halloysite nanotubes modified with an anionic surfactant (sodium dodecanoate) in order to explore the influence of both the nanoparticle morphology and the hydrophobic/hydrophilic character of the lumen on the confinement phenomenon. The analysis of the…
A laser desorption/resonance enhanced photoionisation TOF-system for the spatially resolved trace analysis of elements
2004
Abstract A novel method for direct and spatially resolved elemental trace analysis with high sensitivity and elemental selectivity is presented. The concept is based on the combination of a commercial MALDI-TOF mass spectrometer with a pulsed laser system for resonant postionisation of neutrals. While the MALDI method is usually applied for investigations of large organic compounds and biomolecules, the technique discussed here concerns the low mass range around 1 ⩽ A ⩽ 300. The analytical performances of the setup with respect to mass analysis, spatial resolution and overall detection efficiency are discussed.
Comparison of two methods skipping cell lysis and protein extraction for identification of bacteria from blood cultures by matrix-assisted laser deso…
2019
ABSTRACT Objective Matrix-assisted laser desorption/ionization time-of-flight mass-spectrometry (MALDI-TOF MS) is widely used for fast identification of bacteria from blood cultures (BC). We compared the performance of two procedures, one including a pre-enrichment step in brain heart infusion and the other a direct method using vacutainer separator gel tubes (DI), for identification of bacteria from blood cultures by MALDI-TOF MS. Material and methods We first prepared a training set of 20 simulated bacteremia specimens, including 10 Gram-negative and 10 Gram-positive species. A total of 145 non-consecutive BCs flagged as positive (68 Gram-negative rods, and 77 Gram-positive cocci) were pr…
MALDI-TOF mass spectrometry identification of filamentous fungi in the clinical laboratory.
2014
Pôle MERS F. Dalle; International audience; This study aimed to validate the effectiveness of a standardised procedure for the MALDI-TOF mass spectrometry (MS)-based identification on a large sample of filamentous fungi routinely identified in university hospitals' laboratories. Non-dermatophyte filamentous fungi prospectively isolated in the routine activity of five teaching hospitals in France were first identified by conventional methods in each laboratory and then by MS in one centre. DNA sequence-based identification resolved discrepancies between both methods. In this study, of the 625 analysed filamentous fungi of 58 species, 501 (80%) and 556 (89%) were correctly identified by conve…