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41.
Phase-alternated compositeπ/2 pulses have been constructed for spinI=1 to overcome quadrupole interaction effects in solid state nuclear magnetic resonance (NMR) spectroscopy. Magnus expansion
approach is used to design these sequences in a manner similar to the NMR coherent averaging theory. It is inferred that the
symmetric phase-alternated compositeπ/2 pulses reported here are quite successful in producing quadrupole echo free from phase distortions. This effectiveness
of the present composite pulses is due to the fact that most of them are of shorter durations as compared to the ones reported
in literature. In this theoretical procedure, irreducible spherical tensor operator formalism is employed to simplify the
complexity involved in the evaluation of Magnus expansion terms. It has been argued in this paper that compositeπ/2 pulse sequences for this purpose can also be derived from the broadband inversionπ pulses which are designed to compensate electric field gradient (efg) inhomogeneity in spinI=1 nuclear quadrupole resonance (NQR) spectroscopy. 相似文献
42.
Ramamoorthy A Lee DK Santos JS Henzler-Wildman KA 《Journal of the American Chemical Society》2008,130(33):11023-11029
Characterization of the oligomerization of membrane-associated peptides is important to understand the folding and function of biomolecules like antimicrobial peptides, fusion peptides, amyloid peptides, toxins, and ion channels. However, this has been considered to be very difficult, because the amphipathic properties of the constituents of the cell membrane pose tremendous challenges to most commonly used biophysical techniques. In this study, we present the application of a simple (14)N solid-state NMR spectroscopy of aligned model membranes containing a phosphatidyl choline lipid to investigate the oligomerization of membrane-associated peptides. Since the near-symmetric nature of the choline headgroup of a phosphocholine lipid considerably reduces the (14)N quadrupole coupling, there are significant practical advantages in using (14)N solid-state NMR experiments to probe the interaction of peptide or protein with the surface of model membranes. Experimental results for several membrane-associated peptides are presented in this paper. Our results suggest that the experimentally measured (14)N quadrupole splitting of the lipid depends on the peptide-induced changes in the electrostatic potential of the lipid bilayer surface and therefore on the nature of the peptide, peptide-membrane interaction, and peptide-peptide interaction. It is inferred that the membrane orientation and oligomerization of the membrane-associated peptides can be measured using (14)N solid-state NMR spectroscopy. 相似文献
43.
Dvinskikh SV Yamamoto K Scanu D Deschenaux R Ramamoorthy A 《The journal of physical chemistry. B》2008,112(39):12347-12353
Liquid-crystalline materials containing fullerenes are valuable in the development of supramolecular switches and in solar cell technology. In this study, we characterize the liquid-crystalline and dynamic properties of fullerene-containing thermotropic compounds using solid-state natural abundance (13)C NMR experiments under stationary and magic angle spinning sample conditions. Chemical shifts spectra were measured in isotropic, liquid-crystalline nematic and smectic A and crystalline phases using one-dimensional (13)C experiments, while two-dimensional separated local-field experiments were used to measure the (1)H- (13)C dipolar couplings in mesophases. Chemical shift and dipolar coupling parameters were used to characterize the structure and dynamics of the liquid-crystalline dyads. NMR data of fullerene-containing thermotropic liquid crystals are compared to that of basic mesogenic unit and mesomorphic promoter compounds. Our NMR results suggest that the fullerene-ferrocene dyads form highly dynamic liquid-crystalline phases in which molecules rotate fast around the symmetry axis on the characteristic NMR time scale of approximately 10 (-4) s. 相似文献
44.
N. Ramamoorthy D. V. S. Narasimhan R. S. Mani 《Isotopes in environmental and health studies》2013,49(7):246-249
Presently available 113mSn.113mIn generators use high specific activity 113Sn which cannot be produced in low and medium flux research reactors even with enriched 112Sn. This paper describes a method of preparing 112Sn.113mIn generators using ll3Sn of relatively low specific activity (2—3 Ci/g) obtained by irradiation of enriched 112Sn in CIRUS. In this modified procedure, 113SnCl4 is firmly adsorbed on hydrous zirconia from 3—4 M NaCl solutions of pH 1.3 to 1.5 and the elution of 113mIn is effected by dilute HCl. The generator yields 70% of the theoretically available ll3mIn activity. 113Sn breakthrough has been consistantly less than 0.01% of the 113mIn activity. Stable zirconium contamination in the eluate has been estimated to be less than 1 ppm. The performance characteristics of different varieties of hydrous zirconia have been studied to evaluate the optimum tin loading, indium elution and soluble zirconium contamination. Generators containing upto 700 mCi of tin-113 have been prepared yielding pure indium-113m suitable for medical use. 相似文献
45.
46.
Misfolded proteins in Alzheimer's disease and type II diabetes 总被引:1,自引:0,他引:1
47.
48.
Liu X McCandlish EF McCandlish LE Mikulka-Bolen K Ramesh R Cosandey F Rossetti GA Riman RE 《Langmuir : the ACS journal of surfaces and colloids》2005,21(8):3207-3212
We demonstrated the formation of single-crystal-like materials that contain preferentially oriented arrays of lead zirconate titanate (PZT) cube-shaped particles by self-assembly. Hydrothermally synthesized PZT particles with a bulk composition of Zr/Ti = 70/30 were used in making microcrystal arrays. Spreading a suspension containing PZT cube-shaped particles, 2-propanol, and mineral oil at the air-water interface produced a one-dimensional planar array of PZT particles on the water surface. The array so formed was subsequently transferred onto a flat or curved substrate. X-ray diffraction and electron backscattered diffraction analyses revealed that most of the cube-shaped particles in the array were oriented with their pseudocubic (001) direction aligned parallel to the normal direction of the substrate surface. Filling the arrays with matrixes produced monolayer or multilayer textured composites. The piezoelectric properties of oriented cube-shaped micron-sized particles in the self-assembled arrays were measured using a modified atomic force microscope to reveal the ferroelectric nature of the PZT arrays. 相似文献
49.
K. Kumar K. Ramamoorthy R. Chandramohan K. Sankaranarayanan 《Crystal Research and Technology》2006,41(3):217-220
ZnAl2O4 is a well‐known wide band gap compound semiconductor (Eg=3.8eV), ceramic, opto‐mechanical, anti‐thermal coating in aero‐space vehicles and UV optoelectronic devices. A novel method for the growth of single crystals of a ternary oxide material was developed as a fruit of a long term work. Material to be grown as metal incorporated single crystal was taken as precursor and put into a bath containing acid as reaction speed up reagent (catalyst) as well as solvent with a metal foil as cation scavenger. Using this method, ZnAl2O4 crystals having hexagonal facets are prepared from a single optimized bath. Structural and compositional properties of crystals were studied using Philips, Xpert ‐ MPD: X‐ray diffractometer and Philips, ESEM‐TMP + EDAX. Thus technique was found to be a new low cost and advantageous method for growth of single crystals of ternary oxide a material. We hope that these data be helpful either as a scientific or technical basis in material processing. Dedicated to Prof. P. Ramasamy © 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim 相似文献
50.
Garry D. Annis Steven V. Ley Ramamoorthy Sivaramakrishnan Ana M. Atkinson Donald Rogers David J. Williams 《Journal of organometallic chemistry》1979,182(1):C11-C14
Irradiation of 1,2-epoxy-l-vinylcyclopentane (1) in the presence of Fe(CO)5 leads to the formation of isomeric -and - ferrelactones (2) and (3). The structures of these complexes were determined by X-ray crystallographic methods and on oxidation gave different ratios of β- and δ-lactones. 相似文献