Chemical Fixation of CO2 and Other Heterogeneous Catalytic Studies by Employing a Layered Cu‐Porphyrin Prepared Through Single‐Crystal to Single‐Crystal Exchange of a Zn Analogue

A solvothermal reaction of Zn(NO₃)₂ ? 6 H₂O, tetra‐(4‐pyridyl)porphyrin (H₂TPyP), and 4,4′‐oxybis(benzoic acid) (H₂OBA) resulted in a new two‐dimensional Zn‐ porphyrin metal–organic framework compound, [Zn₂(C₄₀H₂₄N₈)_0.5(C₁₄H₈O₅)(DMA)](DMA)(H₂O)₆ ( 1 ; DMA=N,N‐dimethylacetamide). The Zn^II ions present in 1 could be exchanged by using a solution of Cu(NO₃)₂ ? 3 H₂O in DMA at room temperature to give [Cu₂(C₄₀H₂₄N₈)_0.5(C₁₄H₈O₅)(DMA)](DMA)(H₂O)₃ ( Cu∈1 ). The extra‐framework solvent molecules have been shown to be reversibly removed or exchanged without collapse of the framework. Solvent‐free Cu∈1 was explored as an active heterogeneous catalyst towards three different organic reactions: 1) the chemical fixation of CO₂ into cyclic carbonate at room temperature and 1 atm; 2) the nitroaldol reaction under solvent‐free conditions, and 3) the three‐component coupling of aminopyridine, benzaldehyde, and aryl alkynes followed by 5‐exo‐dig cyclization to produce the important pharmacophore imidazopyridine.     

High-performance liquid chromatography and LC-ESI-MS method for the identification and quantification of two biologically active isomeric coumarinolignoids cleomiscosin A and cleomiscosin B in different extracts of Cleome viscosa

A rapid, sensitive and simple reverse-phase high-performance liquid chromatographic-electrospray ionization-mass spectrometry method for simultaneous determination of cleomiscosin A and cleomiscosin B has been developed and validated. The isomeric coumarinolignoids cleomiscosin A (1) and cleomiscosin B (2) were separated on a Waters symmetry C(18) column with a solvent system composed of acetonitrile-methanol (1:2) and acetic acid-water (0.5:99.5) in a gradient elution mode. The absorption at 326 nm was chosen as the measuring wavelength in which resolution and baseline separation of compounds 1 and 2 could be obtained. The identity of the two isomeric compounds 1 and 2 in the samples were determined on a triple quadrupole mass spectrometer with ESI interface operating in the positive mode. Calibration curves were linear (r(2) > 0.993) over the concentration range 20-200 microg/mL for cleomiscosin A and 10-200 microg/mL for cleomiscosin B with acceptable accuracy and precision, respectively. The intra-day and inter-day precision were 1.13 and 0.82% for cleomiscosin A and 1.78 and 1.28% for cleomiscosin B, respectively. The validated method was successfully applied for the analysis of the above two compounds in different extracts of Cleome viscosa.     

Simple and efficient one‐pot synthesis of 3,4‐dihydro‐2‐pyridones via solid‐supported Bi(III)nitrate catalyzed double michael addition‐azaannulation

4‐Aryl‐5‐carboethoxy‐6‐methyl‐2,3‐dihydro‐2‐pyridones were obtained, in high yield, by heating ternary mixtures of appropriate aldehydes, ethylacetoacetate and compounds possessing NH₂‐C=X functionality, in presence of immobilized Bi(III)nitrate and co‐catalyst Zn(II)chloride, under solventless conditions. The reaction proceeds smoothly at 140±5°C and seems to involve double Michael addition‐azaannulation.     

Spectroscopic studies on the effect of temperature on pH-induced folded states of human serum albumin

Human serum albumin (HSA) is a very important multi-domain transporter protein in the circulatory system responsible for carriage of various kinds of ligands within the physiological system. HSA is also known to undergo conformational transformation at different pH(s) and temperatures. In this report we have studied the binding interactions of a photosensitizing drug, protoporphyrin IX (PPIX) with various conformers of HSA at different temperatures using picosecond time-resolved fluorescence spectroscopy. Also, using dynamic light scattering (DLS) and circular dichroism (CD) spectroscopy we have followed the structural transition of various conformers of HSA at different temperatures. Ensuring the intact binding of PPIX to various conformers of HSA at different temperatures as revealed through time-resolved fluorescence anisotropy decay and significant spectral overlap of emission of Trp214 residue (donor) in domain-IIA and absorption of PPIX (acceptor) bound to domain-IB of HSA, we have applied F?rster's resonance energy transfer (FRET) technique to determine the interdomain separation under various environmental conditions. The alkali-induced conformer of HSA shows almost no change in donor-acceptor distance in contrast to the native and acid-induced conformers of HSA, which show a decrease in distance with increase in temperature. Through this study the non-covalently bound PPIX is shown to be an efficient FRET probe in reporting the different temperature-induced folded states of HSA in buffer solutions of widely differing pH values.     

High-affinity small molecule-phospholipid complex formation: binding of siramesine to phosphatidic acid

Siramesine (SRM) is a sigma-2 receptor agonist which has been recently shown to inhibit growth of cancer cells. Fluorescence spectroscopy experiments revealed two distinct binding sites for this drug in phospholipid membranes. More specifically, acidic phospholipids retain siramesine on the bilayer surface due to a high-affinity interaction, reaching saturation at an apparent 1:1 drug-acidic phospholipid stoichiometry, where after the drug penetrates into the hydrocarbon core of the membrane. This behavior was confirmed using Langmuir films. Of the anionic phospholipids, the highest affinity, comparable to the affinities for the binding of small molecule ligands to proteins, was measured for phosphatidic acid (PA, mole fraction of X(PA) = 0.2 in phosphatidylcholine vesicles), yielding a molecular partition coefficient of 240 +/- 80 x 10(6). An MD simulation on the siramesine:PA interaction was in agreement with the above data. Taking into account the key role of PA as a signaling molecule promoting cell growth our results suggest a new paradigm for the development of anticancer drugs, viz. design of small molecules specifically scavenging phospholipids involved in the signaling cascades controlling cell behavior.     

Comparison of radiometric and non-radiometric methods for uranium determination in groundwater of Punjab,India

Uranium in groundwater samples collected from Punjab state, India was determined using radiometric methods (extractive liquid scintillation and Cerenkov counting). Experimental conditions were optimized by studying the effect of sample pH, quenching and amount of extracting agent added to the scintillation cocktail on recovery of uranium. To ensure the accuracy of results, both radiometric methods were compared with non radiometric method such as adsorptive stripping voltammetry and found to be very good agreement. The distinct advantage of proposed radiometric methods is almost 100 % effective especially extractive liquid scintillation for simultaneous measurement of alpha and beta emitting radionuclides with fast and simple sample preparation.     

Effect of Plant Growth Promoting Bacteria Associated with Halophytic Weed (<Emphasis Type="Italic">Psoralea corylifolia</Emphasis> L) on Germination and Seedling Growth of Wheat Under Saline Conditions

Halotolerant bacteria associated with Psoralea corylifolia L., a luxuriantly growing annual weed in salinity-affected semi-arid regions of western Maharashtra, India were evaluated for their plant growth-promoting activity in wheat. A total of 79 bacteria associated with different parts viz., root, shoot and nodule endophytes, rhizosphere, rhizoplane, and leaf epiphytes, were isolated and grouped based on their habitat. Twelve bacteria isolated for their potential in plant growth promotion were further selected for in vitro studies. Molecular identification showed the presence of the genera Bacillus, Pantoea, Marinobacterium, Acinetobacter, Enterobacter, Pseudomonas, Rhizobium, and Sinorhizobium (LC027447-53; LC027455; LC027457, LC027459, and LC128410). The phylogenetic studies along with carbon source utilization profiles using the Biolog® indicated the presence of novel species and the in planta studies revealed promising results under salinity stress. Whereas the nodule endophytes had minute plant growth-promoting (PGP) activity, the cell free culture filtrates of these strains enhanced seed germination of wheat (Triticum aestivum L). The maximum vigor index was monitored in isolate Y7 (Enterobacter sp strain NIASMVII). Indole acetic acid (IAA) production by the isolates ranged between 0.22 and 25.58 μg mL^?1. This signifies the need of exploration of their individual metabolites for developing next-generation bio-inoculants through co-inoculation with other compatible microbes. This study has potential in utilization of the weed-associated microbiome in terms of alleviation of salinity stress in crop plants.     

High-performance thin-layer chromatographic analysis for the simultaneous quantification of lupeol and ursolic acid in the methanolic fraction of four different species of Bauhinia

JPC – Journal of Planar Chromatography – Modern TLC - A high-performance thin-layer chromatography (HPTLC) method for the simultaneous quantitative determination of lupeol and ursolic...     

The Neumann Problem for the Kohn-Laplacian on the Heisenberg Group ℍn$\mathbb H_{n}$

The existence and uniqueness of the solution of the Neumann problem for the Kohn-Laplacian relative to the Korányi ball on the Heisenberg group \(\mathbb {H}_{n}\) are discussed. Explicit representation for a Green’s type function (Neumann function) for the Korányi ball in \(\mathbb {H}_{n}\) for circular functions has been obtained. This function is then used on the above region in \(\mathbb {H}_{n}\) to solve the inhomogeneous Neumann boundary value problem for certain circular data.