Systematic Optimization of Thin-Layer Chromatography for Wound-Induced Differential Secondary Metabolites in Passiflora foetida

JPC – Journal of Planar Chromatography – Modern TLC -     

A proposed common spatial pharmacophore and the corresponding active conformations of some peptide leukotriene receptor antagonists

Summary Molecular modeling studies were carried out by a combined use of conformational analysis and 3D-QSAR methods to identify molecular features common to a series of hydroxyacetophenone (HAP) and non-hydroxyacetophenone (non-HAP) peptide leukotriene (pLT) receptor antagonists. In attempts to develop a ligand-binding model for the pLT receptor, the Apex-3D program was used to identify biophoric structural patterns that are common to 13 diverse sets of compounds showing different levels of biological activity. A systematic conformational analysis was carried out to obtain sterically accessible conformations for these flexible compounds. Apex-3D was then utilized to propose common biophoric regions based on the selection of one of several conformations (MOPAC-minimized AM1) from each compound's data set that best fits the biophoric pattern and the resulting superimposition with all the other data-set compounds. Apex-3D identified three common biophoric features important for activity: one as the hydroxyl, acetyl, carbonyl and carboxyl groups, which mimic the acid-binding region of an agonist, the other as the hydrogen-bond donating site, and the third part is represented by a plane in which lipophilic aromatic groups align. The structure-activity relationships were then assessed by using the 3D-QSAR model. A common biophore model is proposed from the Apex-3D analysis which may be useful in designing new pLT antagonists. Molecular volumes and electrostatic potential similarities were also calculated in order to obtain the important structural requirements for the activity.     

Effect of iron scrap additives in stearic acid as PCM for thermal energy storage system

Journal of Thermal Analysis and Calorimetry - The thermal energy storage (TES) system is used to store the heat energy for longer periods and retrieve the heat energy as and when required....     

Symmetric 3,5-pyrazole and isoxazole heterocycles comprising a bent core unit: synthesis and mesomorphic characterisation

The synthesis and characterisation of some new liquid crystalline (LC) heteroaromatic compounds containing the five-membered pyrazole/isoxazole rings is reported. Some of the compounds exhibited enantiotropic LC properties. The transition temperatures and LC textures of the mesophases were determined using polarised optical microscopy (POM), differential scanning calorimetry (DSC) and X-ray studies. The five-membered heterocyclic compounds with the pyrazole core exhibit smectic C (SmC) phase, whereas isoxazoles show SmC and nematic (N) phases.     

Synthesis of Dithio-Diphosphine (P2S2COOH)-Based Bifunctional Chelating Agent. Its Coupling Reactions with Peptide Analogs and Steroids

Abstract

Bifunctional chelating agents are important in the development of site-specific radiopharmaceuticals for diagnosis and therapy of cancer. Recently. our Laboratory has developed a new dithio-diphosphine (P₂S₂COOH)-based bifunctional chelating agent [1]. Its coupling to biologically important molecules such as peptide analogs and steroids have been investigated in detail (Scheme I). The intermediate compound P₂S₂ phosphine hydride 3 was synthesized as described in scheme 1 [1]. The coupling of 3 with steroids such as 2/4 amino estrone/estrodiol and the peptide analog GlyGlyOEt was undertaken using peptide the coupling reagent HBTU in the presence of triethylamine. Furthermore. the P₂S₂GlyGlyOEt phosphine hydride was formylated using formaldehyde in ethanol and then complexed with a Re(V) precursor to yield the new Re(V) bioconjugate 5. This offers a potential mute to label biologically active peptides with radionuclides such as Tc-99m and Re-186/188 for use in cancm diagnosis and/or therapy.     

Dripping-jetting transitions in a dripping faucet

Fascinating dynamics is known to result when the flow rate Q at which water drips from a faucet varies. Starting with simple (period-1) dripping, the system transitions as Q increases to complex dripping, where it exhibits period-n (n=2,4, em leader ) and chaotic responses, and then jets once Q exceeds a threshold. New experiments and simulations show that high viscosity (micro) liquids, e.g., syrup, transition directly from simple dripping to jetting as Q increases. Phase diagrams showing transitions between simple and complex dripping and jetting in (Q,micro) space are developed. Values of Q for transition from dripping to jetting are estimated from scaling arguments and shown to accord well with simulations.     

Telomestatin, a potent telomerase inhibitor that interacts quite specifically with the human telomeric intramolecular g-quadruplex

Telomestatin is a natural product isolated from Streptomyces anulatus 3533-SV4 and has been shown to be a very potent telomerase inhibitor. The structural similarity between telomestatin and a G-tetrad suggested to us that the telomerase inhibition might be due to its ability either to facilitate the formation of or trap out preformed G-quadruplex structures, and thereby sequester single-stranded d[T(2)AG(3)](n) primer molecules required for telomerase activity. Significantly, telomestatin appears to be a more potent inhibitor of telomerase (5 nM) than any of the previously described G-quadruplex-interactive molecules. In this communication we provide the first experimental evidence that telomestatin selectively facilitates the formation of or stabilizes intramolecular G-quadruplexes, in particular, that produced from the human telomeric sequence d[T(2)AG(3)](4). A simulated annealing (SA) docking approach was used to study the binding interactions of telomestatin with the intramolecular antiparallel G-quadruplex structure. Each intramolecular G-quadruplex molecule was found to bind two telomestatin molecules (unpublished results). A 2:1 model for the telomestatin bound in the external stacking mode in an energy minimized complex with the human telomeric basket-type G-quadruplex was constructed. Our observation that a G-quadruplex-interactive molecule without significant groove interactions is able to reorient in a G-quadruplex structure proints to the importance of core interaction with an asymmetric G-quadruplex structure in producing selective binding. Furthermore, the G-quadruplex interactions of telomestatin are more selective for the intramolecular structure in contrast to other G-quadruplex-interactive agents, such as TMPyP4.     

Evaluation of Conformal and Non-Conformal Contact Parameters Using Digital Photoelasticity

Experimental studies to exploit photoelastic data of conformal geometries to extract contact parameters are non-existent because closed-form stress field equations were not available until recently. In this paper, the explicit equations recently reported in the literature for a flat punch with rounded edges are generalized so that a single set of equations can be used for a flat punch with rounded edges and Hertzian contacts with arbitrary radii of curvatures. The generality of the governing equations is verified by plotting isochromatics for conformal and non-conformal contact situations. A generic method to evaluate unknown contact parameters from the whole-field isochromatic data for conformal and non-conformal geometries is implemented. The methodology is initially verified using theoretically generated isochromatic data and is then used to experimentally evaluate two contact situations. In view of high-fringe gradient zones, the suitability of various digital photoelastic methods is compared. A novel four-step phase shifting technique is proposed in which isochromatic and isoclinic data can be evaluated using the minimum number of images.     

Optimization of film hole row locations of a nozzle guide vane using network approach

Journal of Thermal Analysis and Calorimetry - Fluid–thermal network simulations have been performed to optimize the each film hole row location of a high-pressure guide vane. In the present...     

New method for C-H arylation/alkylation at α-position of cyclic aliphatic ethers by iron-oxide mediated reaction

We report a new and efficient iron oxide catalyzed cross-coupling reaction between organometallic species such as alkyl/arylmagnesium halides or organolithium species and α-hydrogen bearing cyclic unbranched and branched aliphatic ethers via activation of C(sp(3))-H. In the presence of 1 mol% of iron oxide, five and six membered unbranched cyclic ethers such as tetrahydrofuran and tetrahydropyran gave good to excellent yields of cross-coupled products. Whereas, in case of branched ether such as 2-methyltetrahydrofuran, it was observed that the arylation occurred at both the sides and gave moderate yields of a mixture of regioisomers. Among the organometallic species used, alkyl organometallic reagents gave less yields as compared to aryl organometallics.