Manganese complexes as models for manganese-containing pseudocatalase enzymes: Synthesis,structural and catalytic activity studies

Manganese complexes of the type [TpMn(X)] and [TpMn(μ-N₃)(μ-X)MnTp] (X = acetylacetonate, acac; picolinate, pic and Tp = Tp^Ph,Me for acac, Tp = Tp^ipr2 for pic complexes) having Tp^Ph,Me (hydrotris(3-phenyl,5-methyl-pyrazol-1-yl)borate)/Tp^ipr2 (hydrotris(3,5-diisopropyl-pyrazol-1-yl)borate) as a supporting ligand have been synthesized and structurally characterized. IR and X-ray structures suggest that complexes 7 and 9 are binuclear with azido and bidentate ligands (acac/pic) bridging, whereas complexes 6 and 8 are mononuclear with a 5-coordinated metal center. In complex 9 the picolinate is coordinated as tridentate in a η₃-fashion, but in complex 7 acac behaves as bidentate, whereas azide is coordinated in a bridging bidentate μ-1,3-manner in both 7 and 9. Since the coordination geometry of the manganese ions in complex 9 is very similar to the active site structure of manganese-containing pseudocatalase, we have tested the catalytic activity of the same towards the disproportionation of hydrogen peroxide. The catalytic results indicated that complex 9 has reasonably good catalase activity and may be suitable, structurally as well as functionally, as a model for the pseudocatalase enzyme.     

Optimal Control of Batch MMA Polymerization with Specified Time,Monomer Conversion,and Average Polymer Molecular Weights

Summary: In this paper, the optimal control policies are determined for the free-radical polymerization of methyl methacrylate (MMA) in a non-isothermal batch reactor. The temperature of the fluid inside reactor-jacket is used as the control function to realize four different optimal control objectives. Each objective is formulated to optimize a given variable simultaneously specifying another. The first two objectives target the maximization of monomer conversion in a specified operation time, and the minimization of operation time for a specified, final monomer conversion. The last two objectives target the maximization of monomer conversion for specified, final number- and weight-average polymer molecular weights. The realization of these objectives is expected to be very useful for the batch production of polymers. To meet the specification of an optimization variable other than time, the differential model of batch process is expressed and utilized in the range of specified variable. Equations are provided for Jacobian evaluations to help in the accurate solution of process model. A genetic algorithms-based optimal control method is applied to realize the four optimal control objectives. The results of this application show considerable improvements in the performance of batch MMA polymerization.

     

Evaluation of the target-specific therapeutic potential of herbal compounds for the treatment of cancer

Molecular Diversity - Cancer is among one of the most fatal diseases leading to millions of death around the globe. Chemotherapy is the most popular conventional approach for the treatment of...     

Comparative Studies on the Analytical and Antioxidant Activities of the Medicinally Important Stem Bark of Holoptelea integrifolia

JPC – Journal of Planar Chromatography – Modern TLC - Holoptelea integrifolia (Sanskrit: chirivilva, Hindi: chilbil, family: Ulmaceae) is a large deciduous tree, growing up to 18 m...     

Energy transfer from Sm3+ to Er3+ in zinc phosphate glass

A study of energy transfer from samarium to erbium ions in zinc phosphate glass has been performed for a range of donor (1.0 wt% fixed) and acceptor concentrations ranging from 0.2 wt% to 1.2 wt%. The intensity of emission spectra of Sm³⁺ ions in the presence of Er³⁺ ions shows an overall decrease, thereby suggesting a non radiative energy transfer from Sm³⁺ ions to Er³⁺ ions. The interaction mechanism between the donor and acceptor ions is found to be mainly electric dipole-dipole in nature. The parameters required for the quantitative study of energy transfer e.g. energy transfer efficiencies, transfer probabilities, critical transfer distances have been computed.     

Determination of Heavy Metals in Lichens Growing on Different Ecological Habitats in Schirmacher Oasis,East Antarctica

Twelve lichen species growing on different ecological habitats in East Antarctica were analyzed for Cr, Cu, Fe, Pb and Zn. All the species had consistently higher amounts of Fe and Cu, as their substrata were iron and copper mineralized rocks. the foliose and fruticose lichens had a greater concentration of heavy metals than the crustose ones. Significantly, lead was not detected in any sample indicating that the area is still free from pollution.     

Hydrogen-bonded mononuclear nickel(II) benzoate complexes: synthesis and structural studies

[Tp^Ph,MeNi(Cl)Pz^Ph,MeH] (1) has been synthesized by the reaction of hydrotris(3-phenyl-5-methyl-pyrazol-1-yl) borate [Tp^Ph,Me], NiCl₂ · 6H₂O and 3-phenyl-5-methyl-pyrazole [Pz^Ph,MeH]. The reaction of 1 with variously substituted sodium p–X–benzoates resulted in the formation of complexes of the type [Tp^Ph,MeNi(p–X–OBz)Pz^Ph,MeH] (X = H for 2, F for 3, Cl for 4, NO₂ for 5, Me for 6, OMe for 7, OH for 8, CHO for 9 and CN for 10). Single crystal X-ray studies suggest that all these complexes have a five-coordinate metal center and the benzoate groups are monodentate in a square pyramidal geometry. The X-ray studies also reveal that the uncoordinated oxygen atom of the benzoate forms intramolecular hydrogen-bonds with the NH group of the coordinated pyrazole. The substituents present on the benzoate ring are involved in different types of intermolecular interactions and the complexes exhibit different crystal packing. Complexes 2–10 were tested for superoxide dismutase activity. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Synthetic study on the relationship between structure and sweet taste properties of steviol glycosides

The structure activity relationship between the C??-C?? methylene double bond on the aglycone of steviol glycosides and the corresponding impact on their sweet taste has been reported here for the first time. It has been observed that converting stevioside and rebaudioside A to their corresponding ketones by switching the doubly bonded methylene on C-17 for a ketone group actually removes the sweet taste properties of these molecules completely. Regenerating the original molecules tends to restore the sweet taste of both the steviol glycosides. Thus this C??-C?? methylene double bond in rebaudioside A and stevioside can be regarded as a pharmacophore essential for the sweetness property of these molecules.     

Novel bile acid-based cyclic bisimidazolium receptors for anion recognition

[structure: see text] Novel deoxycholic acid-based cyclic receptors, 3 and 4, containing two imidazolium groups and m-xylene and p-xylene as spacers have been synthesized. These receptors bind anions through hydrogen bonds utilizing two imidazolium (C-H)(+) and inwardly directed methylene hydrogens of both acetyl groups. Receptor 3 shows a moderate selectivity for fluoride ion whereas receptor 4 shows high affinity and selectivity for chloride ion in CDCl(3).     

An unusual decarboxylative benzannulation and biaryl formation during copper(I)-promoted halogen atom transfer radical cyclization of 2-allylaryl trichloroacetates

CuCl/bpy-promoted halogen atom transfer radical cyclization of 2-allylaryl trichloroacetates in refluxing benzene gave benzannulated chloroarenes and benzannulated symmetrical biaryls along with reductive dehalogenation products. The unusual decarboxylative benzannulation and biaryl formation might be explained by a further intramolecular radical addition on the benzene ring of the eight-membered lactone intermediate, initially formed through 8-endo-trig halogen atom transfer radical cyclization, followed by decarboxylation, radical dimerization and dehydrochlorination reactions.