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141.
A non-enzymatic sensor was developed for the determination of glucose in alkaline medium by anodisation of copper in sodium potassium tartrate solution. The morphology of the modified copper electrode was studied by scanning electron microscopy, and its electrochemical behavior by cyclic voltammetry and electrochemical impedance spectroscopy. The electrode enables direct electrocatalytic oxidation of glucose on a CuO/Cu electrode at 0.7 V in 0.1 M sodium hydroxide. At this potential, the sensor is highly selective to glucose even in the presence of ascorbic acid, uric acid, or dopamine which are common interfering species. The sensor displays a sensitivity of 761.9 μA mM?1 cm?2, a linear detection range from 2 μM to 20 mM, a response time of <1 s, and a detection limit of 1 μM (S/N = 3). It was tested for determination of glucose level in blood serum. 相似文献
142.
Babu Rao Chandu Sreekanth Nama Kanchanamala Kanala Balasekhara Reddy Challa Rihana Parveen Shaik Mukkanti Khagga 《Analytical and bioanalytical chemistry》2010,398(3):1367-1374
A novel simple, sensitive, selective, and rapid high-performance liquid chromatography coupled with tandem mass spectrometry
method was developed and validated for quantification of riluzole in human plasma. The chromatography was performed by using
a Zorbax-SB-C18 (4.6 × 75 mm, 3.5 μm) column , isocratic mobile phase 0.1% formic acid/acetonitrile (10:90 v/v), and an isotope-labeled
internal standard (IS), [13C,15N2]riluzole. The extraction of drug and internal standard was performed by liquid–liquid extraction and analyzed by MS in the
multiple reaction monitoring (MRM) mode using the respective [M+H]+ ions, m/z 235.0/165.9 for riluzole and m/z 238.1/169.0 for the IS. The calibration curve was linear over the concentration range 0.5–500.0 ng/ml for riluzole in human
plasma. The limit of quantification (LOQ) was demonstrated at 0.5 ng/ml. The within-batch and between-batch precision were
0.6–2.3% and 1.4–5.7%, and accuracy was 97.1–101.1% and 98.8–101.2% for riluzole respectively. Drug and IS were eluted within
3.0 min. The validated method was successfully applied in a bioequivalence study of riluzole in human plasma. 相似文献
143.
G. Raju V. Ramesh R. Srinivas G. V. M. Sharma B. Shoban Babu 《Journal of mass spectrometry : JMS》2010,45(6):651-663
Two new series of Boc‐N‐α,δ‐/δ,α‐ and β,δ‐/δ,β‐hybrid peptides containing repeats of L ‐Ala‐δ5‐Caa/δ5‐Caa‐L ‐Ala and β3‐Caa‐δ5‐Caa/δ5‐Caa‐β3‐Caa (L ‐Ala = L ‐alanine, Caa = C‐linked carbo amino acid derived from D ‐xylose) have been differentiated by both positive and negative ion electrospray ionization (ESI) ion trap tandem mass spectrometry (MS/MS). MSn spectra of protonated isomeric peptides produce characteristic fragmentation involving the peptide backbone, the Boc‐group, and the side chain. The dipeptide positional isomers are differentiated by the collision‐induced dissociation (CID) of the protonated peptides. The loss of 2‐methylprop‐1‐ene is more pronounced for Boc‐NH‐L ‐Ala‐δ‐Caa‐OCH3 (1), whereas it is totally absent for its positional isomer Boc‐NH‐δ‐Caa‐L ‐Ala‐OCH3 (7), instead it shows significant loss of t‐butanol. On the other hand, second isomeric pair shows significant loss of t‐butanol and loss of acetone for Boc‐NH‐δ‐Caa‐β‐Caa‐OCH3 (18), whereas these are insignificant for its positional isomer Boc‐NH‐β‐Caa‐δ‐Caa‐OCH3 (13). The tetra‐ and hexapeptide positional isomers also show significant differences in MS2 and MS3 CID spectra. It is observed that ‘b’ ions are abundant when oxazolone structures are formed through five‐membered cyclic transition state and cyclization process for larger ‘b’ ions led to its insignificant abundance. However, b1+ ion is formed in case of δ,α‐dipeptide that may have a six‐membered substituted piperidone ion structure. Furthermore, ESI negative ion MS/MS has also been found to be useful for differentiating these isomeric peptide acids. Thus, the results of MS/MS of pairs of di‐, tetra‐, and hexapeptide positional isomers provide peptide sequencing information and distinguish the positional isomers. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
144.
Paulraj Danielraj Babu Varghese S. Sankararaman 《Acta Crystallographica. Section C, Structural Chemistry》2010,66(12):m366-m370
In the tridentate ligand 2,6‐bis(1‐benzyl‐1H‐1,2,3‐triazol‐4‐yl)pyridine, C23H19N7, both sets of triazole N atoms are anti with respect to the pyridine N atom, while in the copper complex aqua[2,6‐bis(1‐benzyl‐1H‐1,2,3‐triazol‐4‐yl)pyridine](pyridine)(tetrafluoroborato)copper(II) tetrafluoroborate, [Cu(BF4)(C5H5N)(C23H19N7)(H2O)]BF4, the triazole N atoms are in the syn–syn conformation. The coordination of the CuII atom is distorted octahedral. The ligand structure is stabilized through intermolecular C—H...N interactions, while the crystal structure of the Cu complex is stabilized through water‐ and BF4‐mediated hydrogen bonds. Photoluminiscence studies of the ligand and complex show that the ligand is fluorescent due to triazole–pyridine conjugation, but that the fluorescence is quenched on complexation. 相似文献
145.
S. Sabiah Babu Varghese Narasimha N. Murthy 《Journal of chemical crystallography》2010,40(12):1195-1198
Abstract
A mononuclear cobalt(II) complex [Co(BP)(Cl2)], 1 with a new N,N-bidentate ligand, BP ([N,N-(1,1′-biphenyl-2,2′-dimethylene)]-2-aminomethyl) pyridine) was synthesized and characterized by elemental analysis, UV–Vis, paramagnetic NMR, magnetic moment and single crystal XRD. The air and moisture stable Co(II) title complex is a 15 electron species which crystallizes in the monoclinic space group P21/n with cell dimensions a = 10.406(3), b = 12.873(4), c = 13.859(7) ?, β = 96.30(3)˚ and Z = 4. The cobalt atom has distorted tetrahedral (td) geometry with coordination provided by an amine and pyridyl nitrogen donors of BP and two terminal chloride ions. The packing is stabilized through C–H···π and van der Waals interactions. 相似文献146.
Fluorophosphate glasses of composition, P2O5 + K2O + KF + MO + Al2O3 + xEu2O3 (M = Mg, Sr and Ba; x = 0.01, 0.05, 0.1, 1.0, 2.0, 4.0 and 6.0 mol%) were prepared and characterized their optical properties. Crystal-field (CF) analysis revealed a relatively weak CF strength around Eu3+ ions in the Ba based fluorophosphate glasses. The Judd-Ofelt parameters have been estimated from the oscillator strengths of 7F0 → 5D2, 7F0 → 5D4 and 7F0 → 5L6 absorption transitions of Eu3+ ions and were used to evaluate the radiative properties of the 5D0 → 7FJ (J = 0-4) transitions. Considerable variation has been observed in the relative intensity ratio of 5D0 → 7F2 to 5D0 → 7F1 transitions of Eu3+ ions due to change in the alkaline earth metal ions. The decay of the 5D0 level shows single exponential and less sensitive to Eu3+ ions concentration as well as MgO/SrO/BaO modifiers. 相似文献
147.
Mithu VS Paul S Kurur ND Madhu PK 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2011,209(2):359-363
We compare in this communication several heteronuclear dipolar decoupling sequences in solid-state nuclear magnetic resonance experiments under a magic-angle spinning frequency of 60 kHz. The decoupling radiofrequency field amplitudes considered are 190 and 10 kHz. No substantial difference was found among the sequences considered here in performance barring the difference in the optimisation protocol of the various schemes, an aspect that favours the use of swept-frequency two pulse phase modulation (SW(f)-TPPM). 相似文献
148.
The dynamics of a semi-flexible sheet or tethered membrane in a solvent is studied using the method of stochastic rotation
dynamics. Hydrodynamic interactions between different parts of the sheet are naturally included in this method. We confirm
the scaling law for the radius of gyration versus sheet size predicted for a self-avoiding tethered membrane. The mean-square displacement shows both sub-diffusive and diffusive
behavior similar to linear polymers. In the intermediate scattering function the sub-diffusive behavior appears as stretched
exponential which we reproduce in our simulations. Thereby, we confirm an early prediction between the roughness and the sub-diffusion
exponent derived from Zimm dynamics (E. Frey, D.R. Nelson, J. Phys. I 1, 1715 (1991)). Finally, we show that the diffusion coefficient of the square sheet is inversely proportional to the edge
length of the sheet again in good agreement with theoretical predictions. 相似文献
149.
The dynamics of a semi-flexible sheet or tethered membrane in a solvent is studied using the method of stochastic rotation dynamics. Hydrodynamic interactions between different parts of the sheet are naturally included in this method. We confirm the scaling law for the radius of gyration versus sheet size predicted for a self-avoiding tethered membrane. The mean-square displacement shows both sub-diffusive and diffusive behavior similar to linear polymers. In the intermediate scattering function the sub-diffusive behavior appears as stretched exponential which we reproduce in our simulations. Thereby, we confirm an early prediction between the roughness and the sub-diffusion exponent derived from Zimm dynamics (E. Frey, D.R. Nelson, J. Phys. I 1, 1715 (1991)). Finally, we show that the diffusion coefficient of the square sheet is inversely proportional to the edge length of the sheet again in good agreement with theoretical predictions. 相似文献
150.
The principal refractive indices of L-lysine monohydrochloride dihydrate (L-LMHCl) single crystal for different wavelengths were measured by minimum deviation method at room temperature. The experimental values of refractive indices fit well with the theoretical Cauchy's equations. The birefringence and the crossing angle between the optical axes were calculated. The parameters of Sellmeier's single term dispersion equation were determined by least square method. A simple interferometric technique was used to observe the interference patterns along the optic plane and to qualitatively analyze the optical homogeneity of the grown crystal. The nonlinear refractive index (n2) and nonlinear absorption coefficient (β) were also determined using Z-scan technique. The piezoelectric resonance in dielectric dispersions was observed at room temperature. 相似文献