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  • 1
    Language: English
    In: BioMetals, 2014, Vol.27(2), pp.247-263
    Description: Binding interactions of cadmium (Cd) with rice ascorbate peroxidase (OsAPX) in presence or absence of jasmonate was examined in-silico. OsAPX is a 250 amino acid long protein with 90 % sequence similarity to soybean-APX. The 3D model of OsAPX obtained by homology modeling using soybean APX (PDBID:1OAF) as template was associated with −15975.85 kJ/mol energy, 100 % residues in favoured region, verify score of 0.85, ERRAT score 89.625 and a negative ProSA graph, suggesting OsAPX model to be of good quality, robust and reliable which was submitted with Protein Model Database with PMDBID: PM0078091. The rice ascorbate peroxidase ascorbate [OsAPX–Asc] complex had a substrate binding cavity involving residues at position 30 KSCAPL 35 , 167 RCH 169 and 172 R wherein ascorbate accommodated via three H-bonds involving 30 Lys at the γ-edge of heme. 169 His served as a bridge between heme-porphyrin of OsAPX and ascorbate creating a charge relay system. Cd bound in [OsAPX–Asc–Cd] complex at 29 EKSCAPL 35 , a site similar to ascorbate binding site. The binding of Cd caused breaking of 169 His bridge shifting the protein conformation. Cadmium exhibited four electrostatic interactions via 29 Glu of OsAPX backbone. Docking of [OsAPX–Asc] with jasmonic acid (JA) resulted in [OsAPX–Asc–JA] complex where 4—H-bonds held JA to OsAPX in a cavity at γ-edge on the distal side of heme. The binding of [OsAPX–Asc–JA] to Cd show the metal to bind at a position other than that involved in binding of OsAPX with Cd alone. Results indicate that Cd does not replace iron or ascorbate or JA but binds to OsAPX on the surface at a separate site electrostatically. In presence of JA the interactions involved in formation of [OsAPXAsc] are restored which is otherwise altered by the presence of Cd. The formation and reformation of H-bond take place between the [OsAPX–Asc] and Cd/JA. It is the interaction between heme and ascorbate which is modulated differently in presence of Cd/JA. In absence of JA, Cd-binds to the [OsAPX–Asc] complex at the proximal end of APX near Asc-binding site, whereas in presence of JA, Cd-binds on the opposite site of the Asc-binding site involving 30 Lys and 29 Glu residues. In-silico binding studies well correlate with the wet-lab results where exogenous application of JA increased the activity of OsAPX in rice grown under Cd-stress. Therefore it is concluded that the activity of OsAPX in rice roots and shoots are compromised under Cd-stress alone.
    Keywords: Ascorbate peroxidase ; Cadmium ; Homology modelling ; Jasmonate ; Rice
    ISSN: 0966-0844
    E-ISSN: 1572-8773
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  • 2
    Language: English
    In: Thermochimica Acta, 2011, Vol.513(1), pp.60-67
    Description: Test results for the applicability of existing thermo-gravimetric analysis (TGA) technique to ascertain average number of exohedral chemical attachment in a new class of fullerene dyads consisting of multiple hemi-ortho esters onto fullerenol is presented. Although the method is nicely applicable for higher fullerenol, but homogeneous phase products calculate lower number of addends, whereas, the hetero phase products indicate higher value. Lower value is attributed to either overlapping of thermal events or substituents effects and higher value is the contribution of tetra butyl ammonium hydroxide (TBAH) impurity used as phase transfer catalyst (PTC) in heterogeneous phase reactions. Presence of TBAH impurity is recognized through thermo-gravimetry mass spectrometry (TG-MS) measurement. Appropriate modification of test method to arrive at accurate and precise values of (total mass contribution due to addends only) and (total mass contribution due to fullerene plus char yield) are also reported. Successful use of two more different techniques, viz., electron-spray ionization mass spectrometry (ESI-MS) and X-ray photoelectron spectroscopy (XPS), supplement above results. Influences of fullerene and different substituents on thermal behavior of dyads are assessed.
    Keywords: Fullerene Derivatives ; Tga ; Fullerenol ; Cage Multiple Functionalization ; Chemistry
    ISSN: 0040-6031
    E-ISSN: 1872-762X
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  • 3
    Language: English
    In: Thermochimica Acta, 2012, Vol.530, pp.120-127
    Description: ► First time thermodynamic study of BMGs on the basis of hole theory of liquids. Kauzmann temperature and residual entropy Δ have been studied for BMGs. ► The reduced residual entropy has been proposed to study the GFA of BMGs. The thermodynamic behaviour of bulk metallic glass forming melts have been studied by analyzing the temperature dependence of the Gibbs free energy difference Δ , entropy difference Δ and enthalpy difference Δ between the undercooled melts and corresponding equilibrium solid phases. The study is made by calculating Δ , Δ and Δ in the entire temperature range to for five samples Mg Cu Y , Cu Ti Zr Ni , Zr Cu Al , Zr (Cu Ag ) Al , Zr Cu Ni Al Nb and it is found that the calculated values of these thermodynamic parameters are very close to the experimental values, where and are melting temperature and glass transition temperature, respectively.
    Keywords: Bulk Metallic Glasses ; Thermodynamics ; Gibbs Free Energy ; Glass Forming Ability ; Chemistry
    ISSN: 0040-6031
    E-ISSN: 1872-762X
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  • 4
    Language: English
    In: Thermochimica Acta, 2011, Vol.513(1), pp.38-42
    Description: The Gibbs energy of formation of Ba UO (s) has been determined using manometric technique. The equilibrium CO (g) pressures over the three phase mixture: {Ba UO (s) + Ba UO (s) + BaCO (s)} have been measured using an absolute pressure transducer in the temperature range 1030–1220 K. The corresponding Gibbs energy expression as a function of temperature can be given as: (298.15 K) and (298.15 K) data have been calculated from the above Gibbs energy expression using required values from the literature. The corresponding values are −3143.4 ± 2 kJ mol and 270.8 ± 4 J K mol , respectively. The (298.15 K) value has also been calculated from third law method as −3137.7 ± 4 kJ mol .
    Keywords: Barium Uranates ; Gibbs Energy of Formation ; Enthalpy of Formation ; Entropy ; Manometric Technique ; Chemistry
    ISSN: 0040-6031
    E-ISSN: 1872-762X
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  • 5
    Language: English
    In: Thermochimica Acta, 2012, Vol.528, pp.32-37
    Description: ► Chalcogenide glasses truly emerged as multipurpose materials and have been used to fabricate technologically important solid state devices. We have studied calorimetric parameters of glassy Se Te Sn In ( = 0, 3, 6, 9) alloys using differential scanning calorimetric (DSC) technique under non-isothermal conditions. ► The activation energy of glass transition ( ), fragility index ( ) and stability parameter ( ) have been calculated for glassy Se–Te–Sn–In alloys. ► The activation energy of glass transition decreases with the increase of In content. ► The Se Te Sn In glass is the most thermally stable glass in this system. Glass transition kinetics of glassy Se Te Sn In ( = 0, 3, 6 and 9) alloys have been investigated using differential scanning calorimetric (DSC) technique under non-isothermal conditions at different heating rates 5, 10, 15 and 20 K/min. It is observed that in these glasses, the glass transition temperature ( ) is found to be dependent on composition and heating rates. The activation energy of glass transition ( ), fragility index ( ) and stability parameter ( ) are evaluated for glassy Se–Te–Sn–In alloys. The glass transition activation energy ( ) and fragility index ( ) were found to be minimum at 9 at.% of In, as well as thermal stability parameter ( ) was found to be maximum at same glassy composition due to maximum crosslinking structures. Results indicate that thermal stability increases on the addition of In to ternary Se Te Sn glass. Hence Se Te Sn In glass is the better thermally stable glass in this system.
    Keywords: Differential Scanning Calorimetric ; Glass Transition Temperature ; Glass Activation Energy ; Fragility Index ; Stability Parameter ; Chemistry
    ISSN: 0040-6031
    E-ISSN: 1872-762X
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  • 6
    Language: English
    In: BioMetals, 2014, Vol.27(6), pp.1231-1247
    Description: ZAT12 a C 2 H 2 -zinc-finger protein is an abiotic stress-responsive transcription factor in plants having less information about their structure. Transcription analysis proved that ZAT12 transcripts over-expressed during drought, heat and salt stress conditions which led to an interest in 3-D structural studies of ZAT12 in Brassica carinata . Over-expression of BcZAT12 in transformed tomato plants under abiotic stresses, suggest role of ZAT12 in conferring stress-tolerance in tomato. Sequence analysis of ZAT12 protein (Accession No. ABB55254.1) from B. carinata revealed it as a 161 amino acid long protein with short conserved motif 140 LDLXL 144 in C-terminal, a leucine rich L-Box with— 14 EXXAXCLXXL 23 motif in N-terminal region and presence of two conserved Zinc-Finger motifs “CXXCXXXXXXXQALGGHXXXH” between positions 42–62 and 85–105. The two zinc finger motifs have presence of two conserved glutamic acid (Glu) and phenylalanine (Phe) residues. Two methionine (Met) residues at position 94 and 102 present in ZF-motif-2 were absent in ZF-motif-1. The 94 Met and 97 Ala in ZF-motif-2 were found to be replaced by serine (Ser) in ZF-motif-1. Homology and ab initio structural modeling of ZAT12 encoded BcZAT12 protein of B. carinata resulted in robust 3-D models and were evaluated for structural motifs, associated GO terms and protein-DNA interactions. The BcZAT12 protein model, was of good quality, reliable, stable and is deposited in PMDB database (PMDB ID: PM0078213). BcZAT12 is annotated as an intracellular protein having molecular function in Zn-binding which in turn regulates signal transduction/translation processes in response to abiotic stresses in plants. Results suggest BcZAT12 protein to interact directly with one strand of ds DNA via electrostatic and H-bonds.
    Keywords: Brassica carinata ; Oxidative stress ; Modeling ; ZAT12 ; Zinc finger protein
    ISSN: 0966-0844
    E-ISSN: 1572-8773
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  • 7
    Language: English
    In: Thermochimica Acta, 20 November 2012, Vol.548, pp.27-32
    Description: ► Rate of heat evolution of cement increases with temperature. ► In the presence of CH, hydration of OPC-FA is increased. ► Super plasticizer retards the hydration. Rate of heat evolution during the hydration of OPC, OPC-20 wt% FA, OPC-5 wt% CH and OPC-20 wt%FA-5 wt% CH in the presence of 0.2 and 0.5 wt% super plasticizer has been studied at 35 and 45 °C with the help of TAM Air isothermal calorimeter for 60 h. The results have shown that hydration retarded in the presence of super plasticizer. Higher the concentration of super plasticizer, higher is the retardation. However hydration accelerated with the increase of temperature. Mechanism of hydration is discussed in this manuscript.
    Keywords: Calorimeter ; Portland Cement ; Fly Ash ; Calcium Hydroxide ; Super Plasticizer ; Hydration ; Chemistry
    ISSN: 0040-6031
    E-ISSN: 1872-762X
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  • 8
    Language: English
    In: Thermochimica Acta, 10 December 2014, Vol.597, pp.85-92
    Description: Rod-shaped nanostructures of manganese oxalate (MnC O ) were synthesized via mild thermal precipitation and aging process. Chemical composition of the MnC O nanorods was confirmed using Fourier transform infra-red (FTIR) spectroscopy and energy dispersive X-ray spectroscopy (EDS). X-ray diffraction (XRD) and selected area electron diffraction (SAED) studies revealed the crystal structure. Field emission scanning electron microscopy (FE-SEM) imaging and high resolution transmission electron microscopy (HR-TEM) were employed to study the structural features of the nanorods. The MnC O nanorods were found to be efficient ballistic modifier for the burning rate enhancement of composite solid propellants (CSPs). Thermal analysis using TGA-DSC showed that MnC O nanorods sensitized the thermal decomposition of ammonium perchlorate (AP) and the CSPs. Controlled thermal decomposition of the MnC O nanorods resulted in the formation of managanese oxide nanoparticles with mesoporosity. A plausible mechanism for the burning rate enhancement using MnC O nanorods was proposed.
    Keywords: Manganese Oxalate Nanorods ; Nanocatalysts ; Ammonium Perchlorate ; Manganese Oxide Nanoparticles ; Composite Solid Propellants ; Chemistry
    ISSN: 0040-6031
    E-ISSN: 1872-762X
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  • 9
    Language: English
    In: Thermochimica Acta, 10 August 2014, Vol.589, pp.284-294
    Description: We have studied pentafluoroaniline (C F NH ), pentachlorophenol (C Cl OH) and one solid solution of pentachlorophenol-hexachlorobenzene (C Cl ) using dielectric spectroscopy ( 〈 2 MHz) and differential scanning calorimetry. The dielectric spectra in the disordered phase I of the first two samples did not conform to the Havriliak–Negami shape function; however, another process of smaller magnitude was noticed on the higher frequency side. The resulting relaxation rate of the dominant process along with the literature data suggests that the primary relaxation process in the rotationally disordered phase of hexa-substituted benzenes (HSBs) conforms to Arrhenius equation with apparent activation energy ( ) in the range of 30–80 kJ/mol, dependent on molecular weight/size. The JG-relaxation of a number of HSBs in glassy o-terphenyl matrix was also been studied which allowed us to propose that the observed primary or -relaxation in the neat HSBs is due to the hexad-rotation. Deviation of dielectric spectra from Debye behaviour is discussed.
    Keywords: Glass Transition ; Dielectric Relaxation ; Physicochemical Properties ; Differential Scanning Calorimetry (Dsc) ; Hexa-Substituted Benzenes ; Chemistry
    ISSN: 0040-6031
    E-ISSN: 1872-762X
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  • 10
    Language: English
    In: Thermochimica Acta, 10 February 2013, Vol.553, pp.31-39
    Description: Apparent molar volume, (a), apparent molar isentropic compressibilities, , (b) as a function of molality of L-ascorbic acid in water at different temperatures: ♦, 288.15 K; ■, 298.15 K; Δ, 308.15 K; and ●, 318.15 K. ► , and B-coefficients have been determined in water for the studied vitamins. ► Negative values tend to become positive at higher temperature. ► Results indicate that only nicotinic acid acts as structure maker. Apparent molar volumes , apparent molar isentropic compressibilities , and viscosity -coefficients have been determined for L-ascorbic acid, nicotinic acid, thiamine hydrochloride and pyridoxine hydrochloride in water at temperatures (288.15–318.15) K from density, speed of sound and viscosity measurements, respectively. Partial molar volumes and partial molar isentropic compressibilities at infinite dilution, and viscosity B-coefficients have been calculated from the corresponding data. The partial molar expansibilities , second order derivative and solvation number ( ) have been calculated. Both volumetric and viscometric studies indicate that nicotinic acid acts as structure promoter where as other vitamins act as structure destroyer. The transition state theory has been used to calculate the activation free energy for viscous flow.
    Keywords: Volumetric and Viscometric Properties ; L-Ascorbic Acid ; Nicotinic Acid ; Thiamine Hydrochloride ; Pyridoxine Hydrochloride ; Chemistry
    ISSN: 0040-6031
    E-ISSN: 1872-762X
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