Design,synthesis and antibacterial activity evaluation of novel 2-(4-((1-aryl-1H-1,2,3-triazol-4-yl)methoxy)phenyl)2-(2-oxoazetidin-1-yl)acetamide derivatives

In this paper, a novel series of 2-(4-((1-aryl-1H-1,2,3-triazol-4-yl)methoxy)phenyl)2-(2-oxoazetidin-1-yl)acetamide derivatives are synthesized in two steps. The first step involved Ugi multicomponent reaction of β-alanine, o-(propargyl)benzaldehyde and isocyanide derivatives. The product of this step, underwent a click 1,3-dipolar cycloaddition reaction with benzyl azide derivatives. The 2-(4-((1-aryl-1H-1,2,3-triazol-4-yl)methoxy)phenyl)2-(2-oxoazetidin-1-yl)acetamide product was characterized and their antibacterial activities were evaluated against various G-positive (Staphylococcus aureus and Bacillus subtilis) and G-negative (Pseudomonas aeruginosa and Escherichia coli) bacteria, using minimal inhibition concentration. The compounds showed very good antimicrobial activity and a number of products have been more active than ciprofloxacin.     

Facile charge-displacement at silicon gives spaced-out reaction

Adsorbates on metals, but not previously on semiconductors, have been observed to display long-range repulsive interactions. On metals, due to efficient dissipation, the repulsions are weak, typically on the order of 5 meV at 10 ?. On the 7×7 reconstruction of the Si(111) surface, charge transport through the surface has been demonstrated by others using charge injection by STM tips. Here we show that for both physisorbed brominated molecules, and for chemisorbed Br-atoms, induced charge-transfer in the Si(111)-7×7 surface can lead to a strong repulsive interaction between adsorbates, calculated as 200 meV at 13.4 ?. This large repulsive interaction must be channeled through the surface since it causes widely spaced "one-per-corner-hole" patterns of physisorption (three cases--directly observed here) and subsequent chemisorption (four cases observed). The patterns were observed by ultrahigh vacuum scanning tunneling microscopy for four different brominated hydrocarbon adsorbates; 1,2-dibromoethane, 1-bromopropane, 1-bromopentane, and bromobenzene, deposited individually on the surface. In every case, adsorbates were overwhelmingly more likely to be found singly than multiply adjacent to a corner-hole, constituting a distinctive pattern having a probability p = 7 × 10(-5) compared to a random distribution.     

Ionic liquid mediated sol-gel sorbents for hollow fiber solid-phase microextraction of pesticide residues in water and hair samples

An ionic liquid mediated sol-gel sorbents for hollow fiber solid-phase microextraction (HF-SPME) was developed for extraction of the pesticides: diazinon, fenitrothion, malathion, fenvalerate, phosalone and tridemorph from human hair and water samples. The analytes were subsequently analyzed with high performance liquid chromatography and diode array detection (HPLC-DAD). Preliminary experiments were carried out in order to study experimental conditions for pesticides' extraction from spiked hair and water samples with HF-SPME using hollow fiber-supported ionic liquid mediated sol-gel sorbent. The sol-gel nanocomposites were reinforced with nanoparticles such as carboxylic functionalized multi-walled carbon nanotubes (COOH-MWCNTs), amino functionalized multi-walled carbon nanotubes (NH(2)-MWCNTs), nano SiO(2), nano TiO(2) and nano MgO comparatively to promote extraction efficiency. In this device, the innovative solid sorbents were developed by the sol-gel method via the reaction of tetraethylorthosilicate (TEOS) with 2-amino-2-hydroxymethyl-propane-1,3-diol (TRIS). In the basic condition (pH 10-11), the gel growth process in the presence of ionic liquid and nanoparticles was initiated. Then, the sol was injected into a polypropylene hollow fiber segment for in situ gelation process. Parameters affecting the efficiency of HF-SPME were thoroughly investigated. Linearity was observed over a range of 0.01-25,000 ng/mL with detection limits between 0.004 and 0.095 ng/mL for the pesticides in the aqueous matrices and 0.003-0.080 ng/mL in the hair matrices. The relative recoveries in the real samples ranged from 82.0% to 94.0% for the pesticides store seller's hair and the work researchers' hair. Results are showing the great possibilities of HF-SPME-HPLC-PDA for analysis of pesticides in biological and environmental samples.     

The impact of protonation and deprotonation of 3-methyl-2'-deoxyadenosine on N-glycosidic bond cleavage

The enzyme-substrate contacts that are believed to be involved in depurination by proton transfer have been modelled by protonation and deprotonation of 3-methyl-2'-deoxyadenosine (3-MDA) using quantum mechanical calculations in the gas-phase and solution media. The change in the charge distribution on the sugar ring and nucleobase that is introduced by the protonation and deprotonation strongly affects the N-glycosidic bond length. The unimolecular cleavage and hydrolysis of the N-glycosidic bond, involving D(N)*A(N) and A(N)D(N) pathways, have been considered at several levels of theory. The trend in the energy barriers is A(N)D(N) > cleavage > D(N)*A(N). All probable proton transfer reactions resulting from enzyme-substrate contacts do not facilitate the N-glycosidic bond cleavage of 3-MDA. The deprotonation of 3-MDA that may result from the interaction between H6 and enzyme do not facilitate bond cleavage. The protonation at N7 induces more positive charge on the sugar ring and further facilitates the depurination relative to the protonation at N1. The changes in the charges calculated on the ribose and nucleobase are in good relationship with the C1'-C2', C1'-O4', and N-glycosidic bond lengths along the cleavage. The change in energy barrier ΔE of glycosidic bond cleavage from the gas-phase to solution media strongly depends on the charge of the species.     

Radio labeling,quality control and biodistribution of <Superscript>99m</Superscript>Tc-cefotaxime as an infection imaging agent

Cefotaxime, a cephalosporin antibiotic, used to treat bacterial infections was investigated to label with ^99mTc. Labeling was performed using sodium dithionite as a reducing agent at 100 °C for 10 min and radiochemical analysis involved ITLC and HPLC methods. The stability of labeled antibiotic was checked in the presence of human serum at 37 °C up to 24 h. The maximum radiolabeling yield was 92 ± 2%. Bacterial binding assay was performed with S. aureus and the in vivo distribution was studied in mice. Images showed minimal accumulation in non-target tissues, with an average target/non-target ratio of 2.89 ± 0.58.     

HPLC and GC Methods for Determination of Lubricants and Their Evaluation in Analysis of Real Samples of Polyethylene

High performance liquid chromatography (HPLC) and gas chromatography (GC) are introduced for analysis of polymer lubricants (stearamide, oleamide and erucamide). In the HPLC method, a reverse phase octadecylsilane (ODS) column along with acetonitrile/methanol (60:40) as a mobile phase were used. Detection of analytes was performed by a UV detector at 202 nm. The analysis time was less than 8 min. In the GC method, polar capillary column and flame ionization detector (FID) were used for separations and detection, respectively. The analysis time by GC was longer than HPLC and was about 30 min. Limits of detection, linear range and repeatability of both methods are similar, but determination of oleamide in real samples by HPLC method is difficult due to complexity of the initial part of HPLC chromatogram in polyethylene samples. That problem is not observed in the GC method. Detection limits in both methods for all analytes are lower than 0.003% which are much lower than the amount of lubricants in commercial polymers (0.05–0.2%).     

Ab initio study of aerogen-bonds between some heterocyclic compounds of benzene with the noble gas elements (Ne,Ar, and Kr)

Structural Chemistry - Ab initio calculations have been performed to study the complexes between the noble gas elements (Ae = Ne, Ar, Kr) with a series of benzene isoelectronic heterocyclic...     

Compatibility of electron ionization and soft ionization methods in gas chromatography/orthogonal time‐of‐flight mass spectrometry

Orthogonal acceleration time‐of‐flight (oa‐TOF) mass spectrometry (MS) was coupled to gas chromatography (GC) to measure ion yields (ratio of ion counts to number of neutrals entering the ion source) and signal‐to‐noise (S/N) in the electron ionization (EI) mode (hard ionization) as well as in the soft ionization modes of chemical ionization (CI), electron capture negative ion chemical ionization (NICI) and field ionization (FI). Mass accuracies of the EI and FI modes were also investigated. Sixteen structurally diverse volatile organic compounds were chosen for this study. The oa‐TOF mass analyzer is highly suited for FI MS and provided an opportunity to compare the sensitivity of this ionization method to the more conventional ionization methods. Compared to the widely used quadrupole mass filter, the oa‐TOF platform offers significantly greater mass accuracy and therefore the possibility of determining the empirical formula of analytes. The findings of this study showed that, for the instrument used, EI generated the most ions with the exception of compounds able to form negative ions readily. Lower ion yields in the FI mode were generally observed but the chromatograms displayed greater S/N and in many cases gave spectra dominated by a molecular ion. Ion counts in CI are limited by the very small apertures required to maintain sufficiently high pressures in the ionization chamber. Mass accuracy for molecular and fragment ions was attainable at close to manufacturer's specifications, thus providing useful information on molecular ions and neutral losses. The data presented also suggests a potentially useful instrumental combination would result if EI and FI spectra could be collected simultaneously or in alternate scans during GC/MS. Copyright © 2009 John Wiley & Sons, Ltd.