Spin-Selective Correlation Experiment for Measurement of Long-Range J Couplings and for Assignment of (R/S) Enantiomers from the Residual Dipolar Couplings and DFT

We report the C-HETSERF experiment for determination of long- and short-range homo- and heteronuclear scalar couplings ((n)J(HH) and (n)J(XH), n >= 1) of organic molecules with a low sensitivity dilute heteronucleus in natural abundance. The method finds significant advantage in measurement of relative signs of long-range heteronuclear total couplings in chiral organic liquid crystal. The advantage of the method is demonstrated for the measurement of residual dipolar couplings (RDCs) in enantiomers oriented in the chiral liquid crystal with a focus to unambiguously assign R/S designation in a 2D spectrum. The alignment tensor calculated from the experimental RDCs and with the computed structures of enantiomers obtained by DFT calculations provides the size of the back-calculated RDCs. Smaller root-mean-square deviations (rmsd) between experimental and calculated RDCs indicate better agreement with the input structure and its correct designation of the stereogenic center.

Selective deprotection of propargyl ethers using tetrathiomolybdate

Benzyltriethylammonium tetrathiomolybdate, [PhCH2NEt3](2)MoS4, 1 deprotects propargyl ethers of alcohols and phenols in a selective manner in high yields. Easily reducible groups like nitro, aldehyde, keto and allyl are not affected.

Protection against UVB inactivation (in vitro) of rat lens enzymes by natural antioxidants

Oxidative damage, through increased production of free radicals, is believed to be involved in UV-induced cataractogenesis (eye lens opacification). The possibility of UVB radiation causing damage to important lenticular enzymes was assessed by irradiating 3 months old rat lenses (in RPMI-1640 medium) at 300 nm (100 mu Wcm(-2)) for 24 h, in the absence and presence of ascorbic acid, alpha-tocopherol acetate and beta-carotene. UVB irradiation resulted in decreased activities of hexokinase, glucose-6-phosphate dehydrogenase, aldose reductase, and Na, K- ATPase by 42, 40, 44 and 57% respectively. While endopeptidase activity (229%) and lipid peroxidation (156%) were increased, isocitrate dehydrogenase activity was not altered on irradiation. In the presence of externally added ascorbic acid, tocopherol and beta-carotene (separately) to the medium, the changes in enzyme activities (except endopeptidase) and increased lipid peroxidation, due to UVB exposure, were prevented. These results suggest that UVB radiation exerts oxidative damage on lens enzymes and antioxidants were protective against this damage.

Highly selective deprotection of tert-butyl esters using ytterbium triflate as a catalyst under mild conditions

Ytterbium triflate catalyses the deprotection of tert-butyl esters selectively in the presence of other esters under mild conditions in almost quantitative yields. The reactions are carried out in nitromethane (45degrees - 50degreesC) using 5 mole percent of the catalyst.

Implementation of conditional phase-shift gate for quantum information processing by NMR, using transition-selective pulses

Experimental realization of quantum information processing in the field of nuclear magnetic resonance (NMR) has been well established. Implementation of conditional phase-shift gate has been a significant step, which has lead to realization of important algorithms such as Grover's search algorithm and quantum Fourier transform. This gate has so far been implemented in NMR by using coupling evolution method. We demonstrate here the implementation of the conditional phase-shift gate using transition selective pulses. As an application of the gate, we demonstrate Grover's search algorithm and quantum Fourier transform by simulations and experiments using transition selective pulses. (C) 2002 Elsevier Science (USA). All rights reserved.

Reactivity switching and selective activation of C-1 or C-3 in 2,3-unsaturated thioglycosides

Reactivity switching and selective activation of C-1 or C-3 in 2,3-unsaturated thioglycosides, namely, 2,3-dideoxy-1-thio-D-hex-2-enopyranosides are reported. The reactivity switching allowed activation of either C-1 or C-3, with the use of either N-iodosuccinimide (NIS)/triflic acid (TfOH) or TfOH alone. C-1 glycosylation with alcohol acceptors occurred in the presence of NIS/TfOH, without the acceptors reacting at C-3. On the other hand, reaction of 2,3-unsaturated thioglycosides with alcohols mediated by triflic acid led to transposition of C-1 ethylthio-moiety to C-3 intramolecularly, to form 3-ethylthio-glycals. Resulting glycals underwent glycosylation with alcohols to afford 3-ethylthio-2-deoxy glycosides. However, when thiol was used as an acceptor, only a stereoselective addition at C-3 resulted, so as to form C-1, C-3 dithio-substituted 2-deoxypyranosides. (C) 2011 Elsevier Ltd. All rights reserved.

Effect of inorganic ions, H(2)O(2) and pH on the photocatalytic inactivation of Escherichia coli with silver impregnated combustion synthesized TiO(2) catalyst

The photocatalytic antibacterial activity of Ag impregnated combustion synthesized TiO(2) (0.25 g/L) was studied against Escherichia coil in presence of UV irradiation. The effect of various parameters, such as anions, canons, hydrogen peroxide and pH, on the photocatalytic inactivation was investigated. The addition of inorganic ions showed a negative effect on inactivation. Among anions, the presence of chloride ions was observed to have a maximum negative effect and reduced the inactivation considerably. Among cations, the bacterial inactivation reduced significantly in the presence of Ca(2+) ions. Hydrogen peroxide addition in combination with Ag/TiO(2) photocatalysis, however, improved the inactivation. Photocatalysis with high concentration of H(2)O(2) yielded complete bacterial inactivation within few minutes. The photocatalytic inactivation of E. coil was not affected by variation in pH. (C) 2011 Elsevier B.V. All rights reserved.

Region Based Structure Layout Optimization by Selective Data Copying

As the gap between processor and memory continues to grow Memory performance becomes a key performance bottleneck for many applications. Compilers therefore increasingly seek to modify an application’s data layout to improve cache locality and cache reuse. Whole program Structure Layout [WPSL] transformations can significantly increase the spatial locality of data and reduce the runtime of programs that use link-based data structures, by increasing the cache line utilization. However, in production compilers WPSL transformations do not realize the entire performance potential possible due to a number of factors. Structure layout decisions made on the basis of whole program aggregated affinity/hotness of structure fields, can be sub optimal for local code regions. WPSL is also restricted in applicability in production compilers for type unsafe languages like C/C++ due to the extensive legality checks and field sensitive pointer analysis required over the entire application. In order to overcome the issues associated with WPSL, we propose Region Based Structure Layout (RBSL) optimization framework, using selective data copying. We describe our RBSL framework, implemented in the production compiler for C/C++ on HP-UX IA-64. We show that acting in complement to the existing and mature WPSL transformation framework in our compiler, RBSL improves application performance in pointer intensive SPEC benchmarks ranging from 3% to 28% over WPSL

Spin State Selective Excitation of Single Quantum Transitions Using Multiple Quantum Spectroscopy- an Aid to Analyse Complex Proton NMR spectra of Oriented Molecules

NMR spectra of molecules oriented in liquid-crystalline matrix provide information on the structure and orientation of the molecules. Thermotropic liquid crystals used as an orienting media result in the spectra of spins that are generally strongly coupled. The number of allowed transitions increases rapidly with the increase in the number of interacting spins. Furthermore, the number of single quantum transitions required for analysis is highly redundant. In the present study, we have demonstrated that it is possible to separate the subspectra of a homonuclear dipolar coupled spin system on the basis of the spin states of the coupled heteronuclei by multiple quantum (MQ)−single quantum (SQ) correlation experiments. This significantly reduces the number of redundant transitions, thereby simplifying the analysis of the complex spectrum. The methodology has been demonstrated on the doubly 13C labeled acetonitrile aligned in the liquid-crystal matrix and has been applied to analyze the complex spectrum of an oriented six spin system.