Acceleration of ortho ester Claisen rearrangement by a commercial microwave oven

Microwave irradiation, using a commercial microwave oven accelerates (in 10–15 min) the three-step ortho ester Claisen rearrangement of allyl and propynyl alcohols in dry DMF in open Erlenmeyer flasks.

The reaction of lambda 3-cyclotriphosphazanes with tetrachloro-ortho-benzoquinone: An unusual ring contraction-rearrangement

Oxidative addition of tetrachloro-ortho-benzoquinone to lambda(3)-cyclotriphosphazanes, [EtNP(OR)](3) results in an unprecedented ring contraction-rearrangement to give diazadiphosphetidines (EtN)(2)[P(OR)(O2C6Cl4)] [P(O2C6Cl4)-[N(Et)P(OR)(2)}] (R = C6H4Br-4 or C(6)H(3)Me(2)-2,6), a process indicated to be thermodynamically favourable on the basis of PM3 calculations.

Affinity-Chromatographic Procedure For The Purification Of The Enzyme From Mung-Bean (Phaseolus, Aureus) Seeds And Conformational-Changes On Its Interaction With Ortho-Phosphate

Flavokinase was purified, for the first time from a plant source [mung bean (Phaseolus aureus)] by affinity chromatography in the presence of orthophosphate and by using C-8 ATP-agarose (ATP linked through the C-8 position to beaded agarose), Cibacron Blue and riboflavin--Sepharoses. An altered substrates-saturation pattern was observed in the presence of K2HPO4. The conformational changes of the enzyme in the presence of K2HPO4 were monitored by fluorescence spectroscopy. These results highlight the regulatory nature of this enzyme.

Microscopic and dielectric studies of ZnO nanoparticles loaded in ortho-chloropolyaniline nanocomposites

We have studied the preparation of zinc oxide nanoparticles loaded in various weight percentages in ortho-chloropolyaniline by in situ polymerization method. The length of the O-chloropolyaniline tube is found to be 200 nm and diameter is about 150 nm wherein the embedded ZnO nanoparticles is of 13 nm as confirmed from scanning electron microscopy as well as transmission electron microscopy characterizations. The presence of the vibration band of the metal oxide and other characteristic bands confirms that the polymer nanocomposites are characterized by their Fourier transmission infrared spectroscopy. The X-ray diffraction pattern of nanocomposites reveals their polycrystalline nature. Electrical property of nanocomposites is a function of the filler as well as the matrix. Cole-Cole plots reveal the presence of well-defined semicircular arcs at high frequencies which are attributed to the bulk resistance of the material. Among all nanocomposites, 30 wt% shows the low relaxation time of 151 s, and hence it has high conductivity.

Ru (II)-Catalyzed C-H Activation: Ketone-Directed Novel 1,4-Addition of Ortho C-H Bond to Maleimides

A 1,4-addition with the nucleophilic center generated at the ortho carbon atom of an aromatic ketone in the presence of the highly reactive alpha-C-H bond, using a directing group strategy, is presented. The reaction yields pharmaceutically useful 3-arylated succinimide derivatives. In order to gain understanding of this redox neutral reaction, despite the presence of copper acetate, and to substantiate the lack of Heck-type products, DFT calculations have been carried out.

Polyketide Quinones Are Alternate Intermediate Electron Carriers during Mycobacterial Respiration in Oxygen-Deficient Niches

Mycobacterium tuberculosis (Mtb) adaptation to hypoxia is considered crucial to its prolonged latent persistence in humans. Mtb lesions are known to contain physiologically heterogeneous microenvironments that bring about differential responses from bacteria. Here we exploit metabolic variability within biofilm cells to identify alternate respiratory polyketide quinones (PkQs) from both Mycobacterium smegmatis (Msmeg) and Mtb. PkQs are specifically expressed in biofilms and other oxygen-deficient niches to maintain cellular bioenergetics. Under such conditions, these metabolites function as mobile electron carriers in the respiratory electron transport chain. In the absence of PkQs, mycobacteria escape from the hypoxic core of biofilms and prefer oxygenrich conditions. Unlike the ubiquitous isoprenoid pathway for the biosynthesis of respiratory quinones, PkQs are produced by type III polyketide synthases using fatty acyl-CoA precursors. The biosynthetic pathway is conserved in several other bacterial genomes, and our study reveals a redox-balancing chemicocellular process in microbial physiology.

Ortho-positronium annihilation: steps toward computing the first order radiative corrections

The 0.2% experimental accuracy of the 1968 Beers and Hughes measurement of the annihilation lifetime of ortho-positronium motivates the attempt to compute the first order quantum electrodynamic corrections to this lifetime. The theoretical problems arising in this computation are here studied in detail up to the point of preparing the necessary computer programs and using them to carry out some of the less demanding steps -- but the computation has not yet been completed. Analytic evaluation of the contributing Feynman diagrams is superior to numerical evaluation, and for this process can be carried out with the aid of the Reduce algebra manipulation computer program.

The relation of the positronium decay rate to the electronpositron annihilation-in-flight amplitude is derived in detail, and it is shown that at threshold annihilation-in-flight, Coulomb divergences appear while infrared divergences vanish. The threshold Coulomb divergences in the amplitude cancel against like divergences in the modulating continuum wave function.

Using the lowest order diagrams of electron-positron annihilation into three photons as a test case, various pitfalls of computer algebraic manipulation are discussed along with ways of avoiding them. The computer manipulation of artificial polynomial expressions is preferable to the direct treatment of rational expressions, even though redundant variables may have to be introduced.

Special properties of the contributing Feynman diagrams are discussed, including the need to restore gauge invariance to the sum of the virtual photon-photon scattering box diagrams by means of a finite subtraction.

A systematic approach to the Feynman-Brown method of Decomposition of single loop diagram integrals with spin-related tensor numerators is developed in detail. This approach allows the Feynman-Brown method to be straightforwardly programmed in the Reduce algebra manipulation language.

The fundamental integrals needed in the wake of the application of the Feynman-Brown decomposition are exhibited and the methods which were used to evaluate them -- primarily dis persion techniques are briefly discussed.

Finally, it is pointed out that while the techniques discussed have permitted the computation of a fair number of the simpler integrals and diagrams contributing to the first order correction of the ortho-positronium annihilation rate, further progress with the more complicated diagrams and with the evaluation of traces is heavily contingent on obtaining access to adequate computer time and core capacity.