Ethyl 3'-(2,4-dichloro-phen-yl)-5'-hydr-oxy-5'-methyl-4',5'-dihydro-spiro-[fluorene-9,2'(3'H)-furan]-4'-carboxyl-ate.

The furan ring and the five-membered fluorene unit in the title compound, C(26)H(22)Cl(2)O(4), adopt envelope conformations. Inter-molecular C-H⋯O inter-actions between symmetry-related mol-ecules involving two C-H groups and an O atom as a bifurcated acceptor generate centrosymmetric hydrogen-bonded dimers with cyclic R(2) (2)(16) and R(2) (2)(8) ring motifs. A short C-H⋯Cl intramolecular contact occurs in the molecule.

Efficacy of Melia azedarach L. extract on the malarial vector Anopheles stephensi Liston (Diptera: Culicidae).

Methanolic extracts of leaves and seeds from the chinaberry tree, Melia azedarach L. (Meliaceae) was tested against mature and immature mosquito vector Anopheles stephensi Liston (Diptera) under laboratory condition. The extract showed strong larvicidal, pupicidal, adulticidal, antiovipositional activity, repellency and biting deterency. The M. azedarach seed and leaf extracts were used to determine their effect on A. stephensi adults and their corresponding oviposition and consequent adult emergence in comparison with the control. The seed extracts showed high bioactivity at all doses, while the leaf extracts proved to be active, only in the higher dose. Results obtained from the laboratory experiment showed that the seed extracts suppressed the pupal and adult activity of A. stephensi even at low dose. In general, first and second instar larvae were more susceptible to both leaves and seed extracts. Clear dose-response relationships were established with the highest dose of 2% plant extract evoking 96% mortality. Entire development of A. stephensi was inhibited by M. azedarach treatment. Less expensive (less than 0.50 US dollars per 1 kg seed), naturally accruing bio-pesticide could be an alternative for chemical pesticides.

Reactivity of pyridine-2,4,6-tricarboxylic acid toward Zn(II) salts under different reaction conditions.

Pyridine-2,4,6-tricarboxylic acid (ptcH(3)) readily reacts with a Zn(II) salt at room temperature to form different products depending upon the presence or absence of pyridine in the reaction mixture. In the presence of pyridine, the ligand breaks to form infinitely zigzag coordination polymers with the empirical formula [Zn(Ox)(py)(2)]n(Ox = oxalate, py = pyridine). The backbone is formed from Zn(II)-oxalate where two pyridine molecules are coordinated to each Zn(II) ion giving it hexacoordination. The orientation of the bound pyridines is slightly different when Zn(II)-nitrate is used compared to that when Zn(II)-sulfate (or acetate) salt is used. In absence of pyridine, the ligand remains intact and forms a mixture of a carboxylate-bridged coordination polymer and a discrete carboxylate-bridged 12-membered metallomacrocycle.

A rapid and stereoselective route to the trans-hydrindane ring system.

A short and stereoselective route to the trans-hydrindane derivative, a potential building block for the synthesis of steroidal and related molecules, was achieved by the operation of indium, tin, and ruthenium based reagents, starting from a tetrabromo norbornyl derivative.

Structure of discrete (H2O)12 clusters present in the cavity of polymeric interlinked metallocycles of Nd(III) or Gd(III) and a podand ligand.

A new podand ligand has been designed and synthesized which reacts hydrothermally with either Nd(III) or Gd(III) nitrate forming an array of linked metallocycles with void spaces. Discrete dodecameric water clusters occupy the voids in the structures. The structure of the cluster can be described as an open-cube octamer buttressed on two sides by dimers to form the overall dodecamer. These clusters join different arrays of linked metallocycles.

Crystallization and preliminary investigations on a telomeric repeat sequence C4A2C4A2.

Repeat units based on the telomeric sequence of the ciliated protozoan Tetrahymena, d(C(4)A(2))(2), have been crystallized. Cytosine-rich DNA stretches are known to reside in telomeres and centromeres of eukaryotic chromosomes, playing crucial roles in the structural stability of the chromosome in addition to their connection with cancer and aging. Preliminary investigations on the telomeric repeat sequence C(4)A(2)C(4)A(2) from CD studies and X-ray crystal data suggest it to be a right-handed interdigitated tetraplex structure with hemiprotonated C.C(+) base pairs. The molecules appear to be packed one on top of another forming a discontinuous helix along c simulating a poly-C fibre, an arrangement which maximizes the number of cytosines stacked.

An A-DNA structure with two independent duplexes in the asymmetric unit.

The crystal and molecular structure of the self-complementary A-DNA decamer sequence d(G4CGC4) was solved at 1.9 A resolution. The decamer crystallizes in space group P21 with two independent duplexes in the asymmetric unit. Duplex 1 has interactions which are distributed symmetrically about its length compared with duplex 2. The two end base pairs of duplex 1 have a similar NH.O hydrogen-bond pattern involving GGC segments of duplex 2 and a symmetry-related neighbour, while the end base pairs of duplex 2 interact with the GCC and GGG segments of its symmetry-related neighbours through NH.O and NH.N hydrogen bonds and a water-mediated hydrogen bond between the carboxyl groups of C40 and C8. In addition to the C4'-C5' torsion angle gamma assuming the trans conformation in certain steps, this angle also adopts the gauche- conformation at C37 as opposed to the preferred gauche+ conformation, with a concomitant change in phosphodiester P-O5' (alpha) in the opposite sense. This facilitates stacking between adjacent bases. The study suggests that the structural alterations in the two molecules in the asymmetric unit originate from an inherent propensity of the d(G4CGC4) base sequence for varied intermolecular interactions and malleability.

Cross-talk between protein kinase C and protein kinase A down-regulates the respiratory burst in polymorphonuclear leukocytes.

In this paper it has been shown that increase in intracellular cAMP by epinephrine or its analogue dibutyryl cAMP (Bt2cAMP) abolishes in a dose-dependent manner the protein kinase C (PKC)-mediated respiratory burst in polymorphonuclear leukocytes. The mechanism of inhibition has been shown to involve induction of cytosolic phosphoprotein phosphatase activity specific to cells receiving dual signals (PKC, PKA), as minimum respiratory burst was associated with cells with maximum phosphatase activity. Inclusion of specific PKA inhibitor completely restricted the development of dual signal-induced phosphatase activity in vitro, demonstrating the requirement of multisite phosphorylation of the phosphatase for the development of its activity. Purified phosphatase had a molecular weight of 78,000 and could exert its inhibitory effect on PKC-triggered respiratory burst in permeabilized cells, clearly showing that down-regulation of oxidase activity involved dephosphorylation by the phosphatase. Interaction of the purified phosphatase with eight-fold purified NADPH oxidase as revealed by fluorescence studies further confirmed the role of the phosphatase in the respiratory burst event. Taken together, we have been able to establish that cross-talk between protein kinase C and protein kinase A is essential to 'turn off' generation of reactive oxygen species.

Mechanism of inhibition by cyclic AMP of protein kinase C-triggered respiratory burst in Ehrlich ascites tumour cells.

The superoxide anion generation in Ehrlich ascites tumour (EAT) cells increased more than two-fold in the presence of the tumour promoter, tetradecanoyl phorbol myristate acetate (TPA). Epinephrine and dibutryl cAMP (Bt2 cAMP) inhibited in a dose-dependent manner, both basal and TPA-triggered superoxide generation in EAT cells. The kinetics of inhibition of superoxide generation showed a maximum inhibition between 30 and 40 min of preincubation with epinephrine or Bt2 cAMP of EAT cells and coincided with an increase in activity of a phosphoprotein phosphatase. In TPA-treated EAT cells, epinephrine or Bt2 cAMP increased the phosphatase activity in a dose-dependent manner. In vitro EGTA, EDTA and sodium fluoride inhibited phosphatase activity. Superoxide generation in response to TPA in Triton-permeabilized EAT cells was inhibited by inclusion of the phosphatase in the assay. Taken together, these results clearly suggest that the phosphatase activity in EAT cells develops as a result of protein kinase A (PKA) and protein kinase C (PKC)-mediated phosphorylation of the phosphatase which then mediates dephosphorylation of the PKC-triggered phosphorylation of proteins to inhibit respiratory burst. A cross-talk between PKA and PKC pathways negatively modulates superoxide generation in EAT cells.

Capsaicin inhibits calmodulin-mediated oxidative burst in rat macrophages.

In this study we seek to elucidate the interaction of capsaicin with the calmodulin mediated signal pathways in macrophages, by comparing its action on macrophage functions with a known calmodulin antagonist, fluphenazine. Kinetics of capsaicin uptake by macrophages (10(3) cells) revealed that a maximum of 200 microM capsaicin was taken up within 10 min. Ca2+ ionophore triggered generation of superoxide anion and hydrogen peroxide by macrophages was inhibited in a dose-dependent manner by fluphenazine (IC50, 20 microM and 12 microM, respectively) and also by capsaicin (IC50, 30 microM and 9 microM, respectively), suggesting an involvement of calmodulin in the regulation of NADPH oxidase. In vitro both fluphenazine and capsaicin inhibited Ca2(+)-Mg2+ ATPase and cAMP-phosphodiesterase from macrophages and this inhibition was reversed by exogenous addition of calmodulin. Fluorescence studies revealed a direct Ca2+ dependent interaction of capsaicin with calmodulin. From these results we suggest that capsaicin acts via calmodulin to inhibit stimulus-induced macrophage oxidative burst and also that calmodulin regulates the oxidative burst in macrophages.