Zoom-TOFMS: addition of a constant-momentum-acceleration “zoom” mode to time-of-flight mass spectrometry

In this study, we demonstrate the performance of a new mass spectrometry concept called zoom time-of-flight mass spectrometry (zoom-TOFMS). In our zoom-TOFMS instrument, we combine two complementary types of TOFMS: conventional, constant-energy acceleration (CEA) TOFMS and constant-momentum acceleration (CMA) TOFMS to provide complete mass-spectral coverage as well as enhanced resolution and duty factor for a narrow, targeted mass region, respectively. Alternation between CEA- and CMA-TOFMS requires only that electrostatic instrument settings (i.e., reflectron and ion optics) and ion acceleration conditions be changed. The prototype zoom-TOFMS instrument has orthogonal-acceleration geometry, a total field-free distance of 43 cm, and a direct-current glow-discharge ionization source. Experimental results demonstrate that the CMA-TOFMS “zoom” mode offers resolution enhancement of 1.6 times over single-stage acceleration CEA-TOFMS. For the atomic mass range studied here, the maximum resolving power at full-width half-maximum observed for CEA-TOFMS was 1,610 and for CMA-TOFMS the maximum was 2,550. No difference in signal-to-noise (S/N) ratio was observed between the operating modes of zoom-TOFMS when both were operated at equivalent repetition rates. For a 10-kHz repetition rate, S/N values for CEA-TOFMS varied from 45 to 990 and from 67 to 10,000 for CMA-TOFMS. This resolution improvement is the result of a linear TOF-to-mass scale and the energy-focusing capability of CMA-TOFMS. Use of CMA also allows ions outside a given m/z range to be rejected by simple ion-energy barriers to provide a substantial improvement in duty factor. Figure

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Ambient UVA‐Induced Expression of p53 and Apoptosis in Human Skin Melanoma A375 Cell Line by Quinine

This study aimed to analyze the phototoxic mechanism and photostability of quinine in human skin cell line A375 under ambient intensities of UVA (320–400 nm). Photosensitized quinine produced a photoproduct 6‐methoxy‐quinoline‐4‐ylmethyl‐oxonium identified through LC‐MS/MS. Generation of ¹O₂, O₂^??, and ^?OH was measured and further substantiated through their respective quenchers. Photosensitized Quinine (Q) caused degradation of 2‐deoxyguanosine, the most sensitive nucleotide to UV radiation. The intracellular ROS was increased in a concentration‐dependent manner. Significant reduction in metabolic status measured in terms of cell viability (54%) at 25 μg mL^?1 was observed through MTT assay. Results of MTT assay accord NRU assay. Single strand DNA breaks and apoptosis were increased significantly (P < 0.01) as observed through comet assay and EB/AO double staining. Photosensitized quinine caused cells to arrest in G₂ phase of cell cycle and induced apoptosis (5.08%) as revealed through FACS. Real‐Time PCR showed upregulation of p21 (4.56 folds) and p53 (2.811 folds) genes expression. Thus, our study suggests that generation of reactive oxygen species by quinine under ambient intensity of UVA may result into deleterious phototoxic effects among human population.     

N-Aryl Modification in γ-Lactam: Design and Synthesis of Novel Monocyclic γ-Lactam Derivatives as Inhibitor for Bacterial Propagation

In search of novel γ-lactam antibacterial agents as non-β-lactam mimics of some γ-lactam antibiotics, N-aryl modification in the γ-lactam ring has been made to synthesize compounds 4–8 in two to six steps. Compound 4 was synthesized using the intermolecular Michael addition of diethyl N-(6-coumarinyl)-2-aminomalonate and 3-aryl/(2-heteroaryl)acryloyl chloride followed by intramolecular amidification. Hydrolysis and stereoselective decarboxylation of 4 resulted in the formation of trans- γ-lactam carboxylic acids (5), which on side chain homologation followed by saponification of the intermediate γ-lactam monoester (7) afforded γ-lactam carboxylic derivatives 8. Moderate to good bacterial growth inhibition was observed for some of the synthesized compounds against E. coli and S. aureus.     

DBU-CH3I,a Potential Substitute for CH2N2 in the Preparation of Methyl Esters and Methyl Aryl Ethers: Studies with Assorted Acids

DBU-CH₃I has been poised to be a substitute for diazomethane in the preparation of methyl esters from carboxylic acids. The reactions can be carried out in commercial untreated acetone and acetonitrile, which have been exemplified with several methyl esters, otherwise it is difficult to prepare. Bis-esterification using diiodomethane can also be achieved in a similar fashion. Sufficiently acidic phenols are also conveniently O-methylated by the method.     

Pattern formation in reaction-diffusion system in crossed electric and magnetic fields

We consider a reaction-diffusion system in crossed electric and magnetic fields lying on the reaction plane. It is shown that a charge separation along the direction normal to the reaction plane resulting in a diffusional flux may cause a differential flow induced chemical instability and stationary pattern formation on a homogeneous steady state. This pattern is generically different from a Turing pattern modified by the crossed fields. The special role of magnetic field is emphasized. Our theoretical analysis is corroborated by numerical simulation on a reaction-diffusion system in three dimensions.     

Synthesis and characterization of styrene/isoprene/ethylene oxide block copolymers

Poly(ethylene oxide/isoprene/styrene/isoprene/ethylene oxide) block copolymers were synthesized using potassium–napthalene catalyst in tetrahydrofuran. The dynamic and thermal properties and water absorption of these tri-block copolymers were determined and related to their bulk morphology.     

Syntheses,characterization and X-ray crystal structures of Co(III) and Mn(II) complexes of pyrimidine derived Schiff base ligands

Two pyrimidine based NNS tridentate Schiff base ligands S-methyl-3-((2-S-methyl-6-methyl-4-pyrimidyl)methyl)dithiocarbazate [HL₁] and S-benzyl-3-((2-S-methyl-6-methyl-4-pyrimidyl)methyl)dithiocarbazate [HL₂] have been synthesised by 1:1 condensation of 2-S-methylmercapto-6-methylpyrimidine-4-carbaldehyde and S-methyl/S-benzyl dithiocarbazate. One Co(III) and one Mn(II) complex of HL₁ and one Mn(II) complex of HL₂ have been prepared and characterized by elemental analyses, molar conductivities, magnetic susceptibilities and spectroscopic studies. All the bis-chelate complexes have a distorted octahedral arrangement with an N₄S₂ chromophore around the central metal ion. Each ligand molecule binds the metal ion using pyrimidyl nitrogen, azomethine nitrogen and the thiolato sulfur atoms. In the free ligand moieties, the pyrimidine nitrogen atoms, azomethine nitrogen atoms and thione sulfur atoms are in EEE orientation to each other. During chelation, all the donor sites of the ligands are reoriented to ZEZ configuration in order to facilitate the chelation process. In all the complexes, the respective ligand molecule functions as the monoanionic tridentate one. All complexes were analyzed by single crystal X-ray diffraction and significant differences concerning the distortion from octahedral geometry of the coordination environment were observed.