Positive and negative ion electrospray tandem mass spectrometry (ESI MS/MS) of Boc-protected peptides containing repeats of L-Ala-gamma4Caa/gamma4Caa-L-Ala: differentiation of some positional isomeric peptides

High-resolution electrospray ionization (ESI) quadrupole time-of-flight and ion trap tandem mass spectrometry has been used to distinguish the positional isomers of a new class of N-blocked hybrid peptides containing repeats of the amino acids, L-Ala-gamma(4)Caa ((l))/gamma(4)Caa((l))-L-Ala [Caa((l)) = Carbo (lyxose) amino acid, derived from D-mannose]. Both MS/MS and MS(3) of protonated isomeric peptides produce characteristic fragmentation involving the peptide backbone, Boc-group, and the side-chain. It is interesting to observe that the abundant y(n)(+) ions are formed when the corresponding amide -NH does not participate in the helical structures in solution phase and relatively low abundance y(n)(+) ions resulted when the amide -NH involves in the H-bonding. Thus, it was possible to identify the amide -NH hydrogens that participate in the helical structures through H-bonding in solution phase. Further, negative ion ESI MS/MS has also been found to be useful for differentiating these isomeric peptide acids.     

Electrical properties of molybdenite single crystals

Molybdenite crystals used in the present work were grown by direct vapour transport or sublimation method. The electrical resistivities and I-V characteristics were measured at different temperatures in the symmetry plane. The room temperature resistance of a specimen annealed for different periods has also been measured. These results are described and discussed.     

Total synthesis of epoxyquinone meroterpenoid natural product biscognienyne B

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Water-acetic acid mediated an efficient and eco-friendly protocol for the one-pot synthesis of bis-isoxazolyl amino dihydro-1H-indol-4(5H)-ones under mild reaction conditions

A cost-effective and eco-friendly straightforward synthesis of new bis-isoxazolyl amino dihydro-1H-indol-4(5H)-ones is successfully achieved via one-pot three-component reaction of N-isoxazolyl enaminone, aryl glyoxal monohydrates and 4-amino-3-methyl-5-styrylisoxazoles by using water as a reaction medium and acetic acid (AcOH) as cheap and green promoter. The protocol proves to be an efficient and environmentally benign in terms of high yields, low reaction time, operational simplicity, metal-free and wide substrates scope. Most important of all, this reaction process is green.     

Stratified simple random sampling and prior distributions

Summary The problem of stratification with proportional and optimum allocations in the case of simple random sampling has been examined in the light of an appropriate super-population model and a formal proof has been provided here for arranging the auxiliary character in increasing order of magnitude for stratification in the case of proportional allocation and also it is shown here that the same may not be necessary in the case of optimum allocation. However, if the coefficient of variation with respect to the auxiliary variate is same in each stratum the necessity of arraging the auxiliary character in increasing order of magnitude for stratification is established. The results are illustrated with respect to empirical examples. Also, some comparisons among different estimators have been made under the super-population model.     

Pairing in one-dimensional antiferromagnetic superconductors in the presence of a homogeneous magnetic field

Assuming a one-dimensional like electron band and considering the free energy difference δF(= F_s?F_N) near the second order phase transition temperature, it is shown that for an antiferromagnetic superconductor in a homogeneous magnetic field (howsoever weak) the minimum of δF occurs when the state with spatially varying order parameter (having same period as the antiferromagnetic ordering) coexists with the usual BCS state.