Mitochondrial and nuclear markers suggest Hanuman langur (Primates: Colobinae) polyphyly: Implications for their species status

Recent molecular studies on langurs of the Indian subcontinent suggest that the widely-distributed and morphologically variable Hanuman langurs (Semnopithecus entellus) are polyphyletic with respect to Nilgiri and urple-faced langurs. To further investigate this scenario, we have analyzed additional sequences of mitochondrial cytochrome b as well as nuclear protamine P1 genes from these species. The results confirm Hanuman langur polyphyly in the mitochondrial tree and the nuclear markers suggest that the Hanuman langurs share protamine P1 alleles with Nilgiri and purple-faced langurs. We recommend provisional splitting of the so-called Hanuman langurs into three species such that the taxonomy is consistent with their evolutionary relationships.

13C nuclear magnetic resonance studies of the binding of alkali and alkaline earth metal salts to amides

3C resonances of carbonyl and methyl groups in amides are shifted down-field on interaction with alkali and alkaline earth metal salts. The magnitude of the shift depends on the ionic potential of the cation. Ions like Li+ bind to the amide carbonyl group both in neat amide solutions as well as in concentrated salt solutions in water.

Structural Insights into the acyl-intermediates of plasmodium falciparum fatty acid synthesis pathway; the mechanism of expansion of acyl carrier protein core

Acyl carrier protein (ACP) plays a central role in fatty acid biosynthesis. However, the molecular machinery that mediates its function is not yet fully understood. Therefore, structural studies were carried out on the acyl-ACP intermediates of Plasmodium falciparum using NMR as a spectroscopic probe. Chemical shift perturbation studies put forth a new picture of the interaction of ACP molecule with the acyl chain, namely, the hydrophobic core can protect up to 12 carbon units, and additional carbons protrude out from the top of the hydrophobic cavity. The latter hypothesis stems from chemical shift changes observed in C-alpha and C-beta of Ser-37 in tetradecanoyl-ACP. C-13, N-15-Double-filtered nuclear Overhauser effect (NOE) spectroscopy experiments further substantiate the concept; in octanoyl (C-8)- and dodecanoyl (C-12)-ACP, a long range NOE is observed within the phosphopantetheine arm, suggesting an arch-like conformation. This NOE is nearly invisible in tetradecanoyl (C-14)-ACP, indicating a change in conformation of the prosthetic group. Furthermore, the present study provides insights into the molecular mechanism of ACP expansion, as revealed from a unique side chain-to-backbone hydrogen bond between two fairly conserved residues, Ile-55 HN and Glu-48 O. The backbone amide of Ile-55 HN reports a pK(a) value for the carboxylate, similar to 1.9 pH units higher than model compound value, suggesting strong electrostatic repulsion between helix II and helix III. Charge-charge repulsion between the helices in combination with thrust from inside due to acyl chain would energetically favor the separation of the two helices. Helix III has fewer structural restraints and, hence, undergoes major conformational change without altering the overall-fold of P. falciparum ACP.

Ru(II)-CO complexes of thioarylazoimidazoles: Syntheses, structures, spectroscopy and DFT calculation

The complexes, cis-(CO)-trans-(Cl)-[Ru(SRaaiNR)(CO)(2)Cl-2] (2) and trans-(Cl)-[Ru(SRaaiNR)(CO)Cl-2] (3) (SRaaiNR = 1-alkyl-2-{(o-thioalkyl)phenylazo}imidazoles; R = Me (1a) and Et (1b)) have been synthesized and characterized. The structural confirmation is achieved by single crystal X-ray structure determinations. The complexes show Ru(III)/Ru(II) couple and ligand reductions. Electronic structure and spectral properties of the complexes have been explained with the DFT and TDDFT calculation. (C) 2009 Elsevier B.V. All rights reserved.

Experimental implementation of a three qubit quantum game with corrupt source using nuclear magnetic resonance quantum information processor

In a three player quantum `Dilemma' game each player takes independent decisions to maximize his/her individual gain. The optimal strategy in the quantum version of this game has a higher payoff compared to its classical counterpart. However, this advantage is lost if the initial qubits provided to the players are from a noisy source. We have experimentally implemented the three player quantum version of the `Dilemma' game as described by Johnson, [N.F. Johnson, Phys. Rev. A 63 (2001) 020302(R)] using nuclear magnetic resonance quantum information processor and have experimentally verified that the payoff of the quantum game for various levels of corruption matches the theoretical payoff. (c) 2007 Elsevier Inc. All rights reserved.

The effects of manganese content and mould size on abrasion and slurry erosion behaviour of chromium-manganese iron systems investigated by positron lifetime spectroscopy

Abrasion and slurry erosion behaviour of chromium-manganese iron samples with chromium (Cr) in the range similar to 16-19% and manganese (Mn) at 5 and 10% levels have been characterized for hardness followed by microstructural examination using optical and scanning electron microscopy. Positron lifetime studies have been conducted to understand the defects/microporosity influence on the microstructure. The samples were heat treated and characterized to understand the structural transformations in the matrix. The data reveals that hardness decreased with increase in Mn content from 5 to 10% in the first instance and then increase in the section size in the other case, irrespective of the sample conditions. The abrasion and slurry erosion losses show increase with increase in the section size as well as with increase in Mn content. The positron results show that as hardness increases from as-cast to heat treated sample, the positron trapping rate and hence defect concentration showed opposite trend as expected. So a good correlation between defects concentration and the hardness has been observed. These findings also corroborate well with the microstructural features obtained from optical and scanning electron microscopy. (C) 2009 Elsevier B. V. All rights reserved.

PVA-PSSA Membrane with Interpenetrating Networks and its Methanol Crossover Mitigating Effect in DMFCs

A membrane with interpenetrating networks between poly(vinyl alcohol) (PVA) and poly(styrene sulfonic acid) (PSSA) coupled with a high proton conductivity is realized and evaluated as a proton exchange membrane electrolyte for a direct methanol fuel cell (DMFC). Its reduced methanol permeability and improved performance in DMFCs suggest the new blend as an alternative membrane to Nafion membranes. The membrane has been characterized by powder X-ray diffraction, scanning electron microscopy, time-modulated differential scanning calorimetry, and thermogravimetric analysis in conjunction with its mechanical strength. The maximum proton conductivity of 3.3×10−2 S/cm for the PVA–PSSA blend membrane is observed at 373 K. From nuclear magnetic resonance imaging and volume localized spectroscopy experiments, the PVA–PSSA membrane has been found to exhibit a promising methanol impermeability, in DMFCs. On evaluating its utility in a DMFC, it has been found that a peak power density of 90 mW/cm2 at a load current density of 320 mA/cm2 is achieved with the PVA–PSSA membrane compared to a peak power density of 75 mW/cm2 at a load current density of 250 mA/cm2 achievable for a DMFC employing Nafion membrane electrolyte while operating under identical conditions; this is attributed primarily to the methanol crossover mitigating property of the PVA–PSSA membrane.

Scanning Tunneling Spectroscopy on Pr0.68Pb0.32MnO3 single crystals

Scanning tunneling microscopy/spectroscopy studies were carried out on single crystals of colossal magnetoresistive manganite Pr0.68Pb0.32MnO3 at different temperatures in order to probe their spatial homogeneity across the metal-insulator transition temperature TM-I(similar to 255 K). A metallic behavior of the local conductance was observed for temperatures T < TM-I. Zero bias conductance (dI/dV)v=(0), which is directly proportional to the local surface density of states at the Fermi level, shows a single distribution at temperatures T < 200 K suggesting a homogeneous electronic phase at low temperatures. In a narrow temperature window of 200 K < T < TM-I, however, an inhomogeneous distribution of (dI/dV)v=(0) has been observed. This result gives evidence for phase separation in the transition region in this compound.

Scanning Tunneling Spectroscopy on Pr0.68Pb0.32MnO3 single crystals

Scanning tunneling microscopy/spectroscopy studies were carried out on single crystals of colossal magnetoresistive manganite Pr0.68Pb0.32MnO3 at different temperatures in order to probe their spatial homogeneity across the metal-insulator transition temperature TM-I(similar to 255 K). A metallic behavior of the local conductance was observed for temperatures T < TM-I. Zero bias conductance (dI/dV)v=(0), which is directly proportional to the local surface density of states at the Fermi level, shows a single distribution at temperatures T < 200 K suggesting a homogeneous electronic phase at low temperatures. In a narrow temperature window of 200 K < T < TM-I, however, an inhomogeneous distribution of (dI/dV)v=(0) has been observed. This result gives evidence for phase separation in the transition region in this compound.

Probing the aging effect in metallic polypyrrole by terahertz time-domain spectroscopy

Terahertz time-domain spectroscopy has been carried out on a metallic film of polypyrrole (PPy doped by PF6). The sample was exposed to air to investigate how the conductivity of the film varies as a function of time. The absorption and dispersion of the film decrease during initial days, and then tend to saturate. The conductivity of unaged sample follows the Drude model, and upon aging the data fit to the localization-modified Drude model. The fitting parameters show that the number of charge carriers decreases during the aging process. The initial rapid decrease in conductivity suggests that some of the delocalized carriers are localized due to aging. (C) 2007 American Institute of Physics.

Impedance studies on high energy Li3+ irradiated PZT thin films

The ferroelectric Pb(Zr0.48Ti0.52)O-3 (PZT) thin films prepared by the pulsed laser deposition technique were studied for their response to high energy lithium ion irradiation through impedance spectroscopy. The Debye peaks, observed in the impedance and modulus plots of irradiatedfilms, shifts towards higher frequencies compared to those of unirradiated films. This is equivalent to the trend observed with increase in temperature in the unirradiated films due to the dielectric relaxation. The irradiated films showed a decrease in the grain resistance compared to the unirradiated films. The activation energy of dielectric relaxation increases from 1.25 eV of unirradiated film to 1.62 eV of irradiated film. The observed modifications in the irradiated film were ascribed to the modifications in the grain structure due to the high value of electronic energy loss.

Negative nuclear Overhauser effects as probes of macromolecular structure

Nuclear Overhauser effects (NOE) and circular dichroism (CD) techniques have been used to probe @-turn conformations in acyclic and cyclic peptides containingPro-Xsequences. The model peptides studied are of the type Piv-Pro-X-NHMe (X = Aib, D-Ala, Gly, Val, and Leu) and Boc-Cys-Pro-X-C s NHMe (X = Aib, L-Ala, D-Ala, Gly, and Leu). In the acyclic series, observation of NOES between Pro C"H and X-NH, together with solvent and temperature dependence of NH chemical shifts, establishes a 4 - 1 hydrogen bond stabilized type I1 @-turn in the Gly, D-Ala, and Aib peptides, in CDC13 and (CD3)2S0. A positive n-r* CD band at -225-230 nm appears to be characteristic of this structure. For the acyclic Pro-Leu peptide the observation of NOE's for both Pro and Leu C"H resonances on saturation of Leu NH is compatible with a type V bend or consecutive y-turn conformation. In the cyclic disulfide series the Pro-Aib and Pro-D-Ala peptides favor type I1 @-turns, whereas all other peptides adopt type I (111) conformations. All the cyclic disulfides exhibit an intense negative CD band at -228-230 nm. The results suggest thatgeneralcorrelations between CD spectral type and specific 0-turn conformations may not be obtained. Evidence for solvent-dependent structural changes in the Pro-Aib sequence in both cyclic and acyclic peptides is presented.

Simultaneous observation of positive and negative nuclear Overhauser effects in oligopeptides due to segmental motio

Nuclear Overhauser effect (NOE) studies of the symmetrical cystine peptides (Formula: see text) (n = 1-3) in dimethylsulfoxide, have resulted in the simultaneous observation of both positive and negative NOEs. Positive NOEs are observed on the Trp C2H and C4H protons of the indole ring upon irradiation of Trp C alpha H and C beta H2 resonances in the peptides where n = 1 and 2. Negative NOEs are observed between backbone NH and C alpha H protons. The magnitudes of the observed NOEs are sensitive to changes in molecular size and solvent viscosity. The results demonstrate that NOEs may be a useful probe of sidechain segmental motion in oligopeptides.