Helix and hairpin nucleation in short peptides using centrally positioned conformationally constrained dipeptide segments

The effect of incorporation of a centrally positioned Ac(6)c-Xxx segment where Xxx = (L)Val/(D)Val into a host oligopeptide composed of L-amino acid residues has been investigated. Studies of four designed octapeptides Boc-Leu-Phe-Val-Ac(6)c-Xxx-Leu-Phe-Val-OMe (Xxx = (D)Val 1, (L)Val 2) Boc-Leu-Val-Val-Ac(6)c-Xxx-Leu-Val-Val-OMe (Xxx = (D)Val 3, (L)Val 4) are reported. Diagnostic nuclear Overhouse effects characteristic of hairpin conformations are observed for Xxx = (D)Val peptides (1 and 3) while continuous helical conformation characterized by sequential NiH <-> Ni+1H NOEs are favored for Xxx = (L)Val peptides (2 and 4) in methanol solutions. Temperature co-efficient of NH chemical shifts are in agreement with distinctly different conformational preferences upon changing the configuration of the residue at position 5. Crystal structures of peptides 2 and 4 (Xxx = (L)Val) establish helical conformations in the solid state, in agreement with the structures deduced from NMR data. The results support the design principle that centrally positioned type I beta-turns may be used to nucleate helices in short peptides, while type I' beta-turns can facilitate folding into beta-hairpins.

Controls on intense silicate weathering in a tropical river, southwestern India

The Silicate Weathering Rate (SWR) and associated Carbon dioxide Consumption Rate (CCR) in tropical silicate terrain is assessed through a study of the major ion chemistry in a small west flowing river of Peninsular India, the Nethravati River. The specific features of the river basin are high mean annual rainfall and temperature, high runoff and a Precambrian basement composed of granitic-gneiss, charnockite and minor metasediments. The water samples (n = 56) were collected from three locations along the Nethravati River and from two of its tributaries over a period of twelve months. Chemical Weathering Rate (CWR) for the entire watershed is calculated by applying rainwater correction using river chloride as a tracer. Chemical Weathering Rate in the Nethravati watershed is estimated to 44 t.km(-2).y(-1) encompassing a SWR of 42 t.km(-2).y(-1) and a maximum carbonate contribution of 2 t.km(-2).y(-1). This SWR is among the highest reported for granito-gneissic terrains. The assessed CCR is 2.9 . 10(5) mol.km(-2).y(-1). The weathering index (Re). calculated from molecular ratios of dissolved cations and silica in the river, suggests an intense silicate weathering leading to kaolinite-gibbsite precipitation in the weathering covers. The intense SWR and CCR could be due to the combination of high runoff and temperature along with the thickness and nature of the weathering cover. The comparison of silicate weathering fluxes with other watersheds reveals that under similar morpho-climatic settings basalt weathering would be 2.5 times higher than the granite-gneissic rocks. (C) 2012 Elsevier B.V. All rights reserved.

Electrochemical, phosphate hydrolysis, DNA binding and DNA cleavage properties of new polyaza macrobicyclic dinickel(II) complexes

A new class of macrobicyclic dinickel(II) complexes Ni2L1,2 B](ClO4)(4) (1-6), where L-1,L-2 are polyaza macrobicyclic binucleating ligands, and B is a N,N-donor heterocyclic base (viz. 2,2'-bipyridine (bipy) and 1,10-phenanthroline (phen)) are synthesized and characterized. The redox, catalytic, DNA binding and DNA cleavage properties were studied. They exhibit two irreversible waves in the cathodic region around E-pc = -0.95 V and E-pa = -0.85 V vs. Ag/Ag+ in CH3CN-0.1 M TBAP, respectively. The first order rate constants for the hydrolysis of 4-nitrophenylphosphate to 4-nitrophenolate by the dinickel(II) complexes 1-6 are in the range from 3.36 x 10(-5) to 10.83 x 10(-5) Ms-1. The complexes 3 and 6 show good binding propensity to calf thymus DNA giving binding constant values (K-b) in the range from 3.08 x 10(5) to 5.37 x 10(5) M-1. The binding site sizes and viscosity data suggest the DNA intercalative and/or groove binding nature of the complexes. The complexes display significant hydrolytic cleavage of supercoiled pBR322DNA at pH 7.2 and 37 degrees C. The hydrolytic cleavage of DNA by the complexes is supported by the evidence from free radical quenching and T4 ligase ligation. The pseudo Michaelis-Menten kinetic parameters k(cat) = 5.44 x 10(-2) h(-1) and K-M = 6.23 x 10(-3) M for complex 3 were obtained. Complex 3 also shows an enormous enhancement of the cleavage rate, of 1.5 x 10(6), in comparison to the uncatalysed hydrolysis rate (k = 3.6 x 10(-8) h(-1)) of ds-DNA.

Photocytotoxic Oxidovanadium(IV) Complexes of Polypyridyl Ligands Showing DNA-Cleavage Activity in Near-IR Light

Oxidovanadium(IV) complexes VO(pyphen)(L)]Cl2 (1, 2) and VO(pydppz)(L)]Cl2 (3, 4), where L is 1,10-phenanthroline (phen in 1 and 3) and dipyrido3,2-a:2',3'-c]phenazine (dppz in 2 and 4) are prepared and characterized. The crystal structure of VO(pyphen)(phen)](ClO4)2 (1a) shows a six-coordinate VN5O geometry with a VO2+ moiety in which the polypyridyl ligand binds in a meridional fashion and the phen ligand displays a chelating binding mode with an N-donor site trans to the oxidovanadyl group. The complexes show a dd band within 720-750 nm in DMF. The one-electron paramagnetic complexes are 1:2 electrolytes in DMF. The complexes exhibit an irreversible VIV/VIII redox response near -0.85 V vs. SCE in DMF/0.1 M TBAP. The complexes bind to calf thymus (ct) DNA giving Kb values within 7.5 x 104 to 1.1 x 106 M1. The complexes show poor chemical nuclease activity in the dark and exhibit significant DNA-photocleaving activity in near-IR light of 705 and 785 nm forming .OH radicals. Complexes 2-4 show remarkable photocytotoxicity in HeLa cancer cells. FACS analysis of the HeLa cells treated with complex 4 shows cell death as highlighted by the sub G1 peak. Propidium iodide staining data indicate apoptosis as the primary mode of cell death.

Nonstoichiometry, defects and thermodynamic properties of YFeO3, YFe2O4 and Y3Fe5O12

Oxygen nonstoichiometry of three ternary oxides. YFeO3-delta, YFe2O4-alpha and Y3Fe5O12-theta. in the system Y-Fe-O was investigated as a function of oxygen partial pressure by thermogravimetry at high temperature. The defects responsible for nonstoichiometry were identified as oxygen vacancies for YFeO3-delta and YFe2O4-alpha although the manner of variation of nonstoichiometric parameter with oxygen partial pressure for these two oxides is quite different. Cation interstitials are the predominant defects in Y3Fe5O12-theta. Gibbs energies of formation of the three nonstoichiometric oxides were determined using solid-state electrochemical cells in the temperature range from 975 to 1475 K. YFe2O4-alpha was found to be stable only above 1391 K. Gibbs energies of formation of the three stoichiometric compounds from their component binary oxides were obtained by combining information from solid state cells with results of thermogravimetric analysis using the Gibbs-Duhem relation. The results can be summarized as: (1/2)Y2O3 + (1/2)Fe2O3 -> YFeO3;Delta G(f(ox))(O)(+/- 250)(J/mol) = 17, 126-8.263T (1/2)Y2O3 + FeO + (1/2)Fe2O3 -> YFe2O4;Delta G(f(ox))(O)(+/- 260)(J/mol) = -10,352-13.24T (3/2)Y2O3 + (5/2)Fe2O3 -> Y3Fe5O12;Delta G(f(ox))(O)(+/- 780)(J/mol) = -56, 647-31.091T. (C) 2012 Elsevier B.V. All rights reserved.

Design and Synthesis of a Functional Derivative of the Triazinium Cation and Its Rhodium Complex that Shows Photoinduced DNA Cleavage Activity and Photocytotoxicity

The design and synthesis of an intensely blue rhodium(III) complex 3]+ of a new N,N-donor ligand, 8-(quinolin-8-ylamino)pyrido2,1-c]1,2,4]benzotriazin-11-ium, 2]+, which contains a planar pendant triazinium arm, is described. Structural characterization for 3]+ was carried out by using various spectroscopic techniques and single-crystal X-ray crystallography. The organometallic rhodium(III) compound shows a ligand-based reversible reduction at 0.65 V. The electrochemically reduced compound displays a single-line EPR spectrum that signifies the formation of ligand-based free radicals. Compound 3]+ shows a binding propensity to calf thymus DNA to give a Kapp value of 6.05X105 M1. The parent triazinium salt, pyrido2,1-c]1,2,4]benzotriazin-11-ium 1]+ and the ligand salt 2]+ exhibit photoinduced cleavage of DNA in UV-A light, whereas the reference Rh complex 3]+ photocleaves DNA with red light (647.1 nm). The compounds show photonuclease activities under both aerobic and anaerobic conditions. Mechanistic investigations under aerobic conditions with several inhibitors indicate the formation of hydroxyl radicals by means of a photoredox pathway. Under anaerobic conditions, it is believed that a photoinduced oxidation of DNA mechanism is operative. Compound 3]+ exhibits photocytotoxicity in HeLa cervical cancer cells to give IC50 values of (12+/-0.9) mu M in UV-A light at 365 nm and (31.4+/-1.1) mu M in the dark.

Switching of a Sixteen Electrode Array for Wireless EIT System Using a RF-Based 8-Bit Digital Data Transmission Technique

Surface electrode switching of 16-electrode wireless EIT is studied using a Radio Frequency (RF) based digital data transmission technique operating with 8 channel encoder/decoder ICs. An electrode switching module is developed the analog multiplexers and switched with 8-bit parallel digital data transferred by transmitter/receiver module developed with radio frequency technology. 8-bit parallel digital data collected from the receiver module are converted to 16-bit digital data by using binary adder circuits and then used for switching the electrodes in opposite current injection protocol. 8-bit parallel digital data are generated using NI USB 6251 DAQ card in LabVIEW software and sent to the transmission module which transmits the digital data bits to the receiver end. Receiver module supplies the parallel digital bits to the binary adder circuits and adder circuit outputs are fed to the multiplexers of the electrode switching module for surface electrode switching. 1 mA, 50 kHz sinusoidal constant current is injected at the phantom boundary using opposite current injection protocol. The boundary potentials developed at the voltage electrodes are measured and studied to assess the wireless data transmission.

Unique Type II Halogen center dot center dot center dot Halogen Interactions in Pentafluorophenyl-Appended 2,2 `-Bithiazoles

Herein, we report the design and synthesis of 2,2'-bithiazole derivatives with efficient intermolecular halogen interactions. The single crystal X-ray diffraction studies revealed unique type-II halogen interactions in these derivatives. The shortest type-II F center dot center dot center dot F interactions within the distance of 2.67 angstrom, at an angle of 89.1 degrees and 174.2 degrees, was observed for the first time. The Gaussian calculations were performed to further establish predominant F center dot center dot center dot F interactions.

Can Superflares Occur on Our Sun?

Recent observations of Sun-like stars, similar to our Sun in their surface temperature (5600-6000 K) and slow rotation (rotational period > 10 d), using the Kepler satellite by Maehara et al. (2012, Nature, 485, 478) have revealed the existence of superflares (with energy of 10(33)-10(35) erg). From statistical analyses of these superflares, it was found that superflares with energy of 10(34) erg occur once in 800 yr, and superflares with 10(35) erg occur once in 5000 yr. In this paper, we examine whether superflares with energy of 10(33)-10(35) erg could occur on the present Sun through the use of simple order-of-magnitude estimates based on current ideas related to the mechanisms of the solar dynamo. If magnetic flux is generated by differential rotation at the base of the convection zone, as assumed in typical dynamo models, it is possible that the present Sun would generate a large sunspot with a total magnetic flux of similar to 2 x 10(23) Mx (= G cm(2)) within one solar cycle period, and lead to superflares with an energy of 10(34) erg. To store a total magnetic flux of similar to 10(24) Mx, necessary for generating 10(35) erg superflares, it would take similar to 40 yr. Hot Jupiters have often been argued to be a necessary ingredient for the generation of superflares, but we found that they do not play any essential role in the generation of magnetic flux in the star itself, if we consider only the magnetic interaction between the star and the hot Jupiter. This seems to be consistent with Maehara et al.'s finding of 148 superflare-generating solar-type stars that do not have a hot Jupiter-like companion. Altogether, our simple calculations, combined with Maehara et al.'s analysis of superflares on Sun-like stars, show that there is a possibility that superflares of 10(34) erg would occur once in 800 yr on our present Sun.

Continuous beam of laser-cooled Yb atoms

We demonstrate the launching of laser-cooled Yb atoms in a continuous atomic beam. The continuous cold beam has significant advantages over the more-common pulsed fountain, which was also demonstrated by us recently. The cold beam is formed in the following steps: i) atoms from a thermal beam are first Zeeman-slowed to a small final velocity; ii) the slowed atoms are captured in a two-dimensional magneto-optic trap (2D-MOT); and iii) atoms are launched continuously in the vertical direction using two sets of moving-molasses beams, inclined at +/- 15 degrees to the vertical. The cooling transition used is the strongly allowed S-1(0) -> P-1(1) transition at 399 nm. We capture about 7x10(6) atoms in the 2D-MOT, and then launch them with a vertical velocity of 13m/s at a longitudinal temperature of 125(6) mK. Copyright (C) EPLA, 2013

Unified Taxonomy for Reference Ontology of Shape Features in Product Model

This paper presents a unified taxonomy of shape features. Such taxonomy is required to construct ontologies to address heterogeneity in product/shape models. Literature provides separate classifications for volumetric, deformation and free-form surface features. The unified taxonomy proposed allows classification, representation and extraction of shape features in a product model. The novelty of the taxonomy is that the classification is based purely on shape entities and therefore it is possible to automatically extract the features from any shape model. This enables the use of this taxonomy to build reference ontology.

Carbohydrate-appended photocytotoxic (imidazophenanthroline)-oxovanadium(IV) complexes for cellular targeting and imaging

Oxovanadium(IV) complexes VO(aip)(L)](ClO4)(2) (L = phtpy, 1; stpy, 2) and VO(pyip)(L)](ClO4)(2) (L = phtpy, 3; stpy, 4), where aip is 2-(9-anthryl)-1H-imidazo4,5-f]1,10] phenanthroline, pyip is 2-(1-pyrenyl)-1Himidazo4,5-f]1,10] phenanthroline, phtpy is (4'-phenyl)-2,2': 6',2 `'-terpyridine and stpy is (2,2': 6', 2 `'-terpyridin-4'-oxy) ethyl-beta-D-glucopyranoside, were prepared, characterized and their DNA binding and photocleavage activity, cellular uptake and photocytotoxicity in visible light were studied. The complexes are avid binders to calf thymus DNA (K-b similar to 10(5) mol(-1)). They efficiently cleave pUC19 DNA in red light of 705 nm via the formation of HO center dot species. The glucose appended complexes 2 and 4 showed higher photocytotoxicity in HeLa and Hep G2 cells over the normal HEK 293T cells. No such preference was observed for the phtpy complexes 1 and 3. No significant difference in IC50 values was observed for the HEK 293T cells. Cell cycle analysis showed that the glucose appended complexes 2 and 4 are more photocytotoxic in cancer cells than in normal cells. Fluorescence microscopy was done to study the cellular localization of complex 4 having a pendant pyrenyl group.

Electrochemical Determination of Gibbs Energy of Formation of LaCrO3 Using a Composition-Graded Bielectrolyte

Presented are new measurements of the standard Gibbs free energy of formation of rhombohedral LaCrO3 from component oxides La2O3 and Cr2O3 in the temperature range from 875 to 1175K, using a bielectrolyte solid-state cell incorporating single crystal CaF2 and composition-graded solid electrolyte (LaF3)(y)(CaF2)(1-y) (y=0-0.32). The results can be represented analytically as Delta G(f(ox))(o) (+/- 2270)/Jmol(-1)=-72329+4.932 (T/K). The measurements were undertaken to resolve serious discrepancies in the data reported in the literature. A critical analysis of previous electrochemical measurements indicates several deficiencies that have been rectified in this study. The enthalpy of formation obtained in this study is consistent with calorimetric data. The standard enthalpy of formation of orthorhombic LaCrO3 from elements at 298.15K computed from the results of this study is Delta H-f(298.15)(o)/kJmol(-1)=-1536.2 (+/- 7). The standard entropy of orthorhombic LaCrO3 at 298.15K is estimated as 99.0 (+/- 4.5)J(molK)(-1).

Glacial mass balance changes in the Karakoram and Himalaya based on CMIP5 multi-model climate projections

The impact of future climate change on the glaciers in the Karakoram and Himalaya (KH) is investigated using CMIP5 multi-model temperature and precipitation projections, and a relationship between glacial accumulation-area ratio and mass balance developed for the region based on the last 30 to 40 years of observational data. We estimate that the current glacial mass balance (year 2000) for the entire KH region is -6.6 +/- 1 Gta(-1), which decreases about sixfold to -35 +/- 2 Gta(-1) by the 2080s under the high emission scenario of RCP8.5. However, under the low emission scenario of RCP2.6 the glacial mass loss only doubles to -12 +/- 2 Gta(-1) by the 2080s. We also find that 10.6 and 27 % of the glaciers could face `eventual disappearance' by the end of the century under RCP2.6 and RCP8.5 respectively, underscoring the threat to water resources under high emission scenarios.

Influence of exhaust gas heating and L/D ratios on the discharge efficiencies for an activated carbon natural gas storage system

A transient 2D axi-symmetric and lumped parameter (LP) model with constant outflow conditions have been developed to study the discharge capacity of an activated carbon bed. The predicted discharge times and variations in bed pressure and temperature are in good agreement with experimental results obtained from a 1.82 l adsorbed natural gas (ANG) storage system. Under ambient air conditions, a maximum temperature drop of 29.5 K and 45.5 K are predicted at the bed center for discharge rates of 1.0 l min(-1) and 5.0 l min(-1) respectively. The corresponding discharge efficiencies are 77% and 71.5% respectively with discharge efficiencies improving with decreasing outflow rates. Increasing the LID ratio from 1.9 to 7.8 had only a marginal increase in the discharge efficiency. Forced convection (exhaust gas) heating had a significant effect on the discharge efficiency, leading to efficiencies as high as 92.8% at a discharge of 1.0 l min(-1) and 88.7% at 5 l min(-1). Our study shows that the LP model can be reliably used to obtain discharge times due to the uniform pressure distributions in the bed. Temperature predictions with the LP model were more accurate at ambient conditions and higher discharge rates, due to greater uniformity in bed temperatures. For the low thermal conductivity carbon porous beds, our study shows that exhaust gas heating can be used as an effective and convenient strategy to improve the discharge characteristics and performance of an ANG system. (C) 2013 Elsevier Ltd. All rights reserved.