Robert L. Ostrander

Specific competitive inhibitor of secreted phospholipase A2 from berries of Schinus terebinthifolius

Two structurally related triterpenoids 1 and 2 from pink peppercorn (berries of Schinus terebinthifolius) are identified and characterized as active site-directed specific competitive inhibitors of the three classes of secreted 14 kDa phospholipase A2. The inhibitors not only protect the active site histidine from alkylation but also inhibit the action of secreted phospholipase A2 from pig pancreas, human synovial fluid, and bee venom. Detailed X-ray crystallographic results on the structures of the inhibitors are provided. By physical methods and X-ray crystallography the triterpenoids were identified as masticadienoic acid and masticadienolic acid (schinol). Several other triterpenoids were ineffective as inhibitors of phospholipase A2; however certain ganoderic acid derivatives showed noticeable inhibition. Results show that the side chain of these acidic tetracyclic terpenoids can access the catalytic-site region of phospholipase A2, whereas the acyclic nucleus is at the interfacial recognition region. The selectivity of the assay protocol used here is demonstrated by the fact that the original screen of ethyl acetate extracts of 60 commercially available spices and herbs was carried out with phospholipase A2 from pig pancreas, and only one extract showed inhibitory action on the hydrolytic activity in the scooting mode. Under such assay conditions the enzyme remains tightly bound to the surface of the substrate vesicles. In this way, nonspecific effects of additives that promote desorption of the enzyme from the substrate vesicle surface, under conditions in which the binding of the enzyme to the vesicle is weak, are avoided. The assay protocol is useful for the kinetic characterization of the inhibitors of phospholipase A2, and it does not give false positive results with amphiphilic and hydrophobic compounds, as is the case with virtually all assay systems in use.

Advances in Precursor Development for CVD of Bariumcontaining Materials

Barium titanate and barium-strontium titanate (BST) are high dielectric materials, likely to replace state-of-the-art capacitor materials for memory applications. Chemical Vapor Deposition (CVD) of these materials has been hampered, particularly by the lack of suitable precursors for barium. Although attempts to make volatile metal-organic barium compounds have met with some progress, a suitably stable, volatile barium source is still in demand. This paper will highlight recent developments at ATM, including syntheses and structures of polyamine and glycol ether adducts which have been designed to limit aggregation of barium diketonates, and stabilize the adducts with respect to ligand dissociation.

Preparation and characterization of the square-based pyramidal cluster anion [H2Ru5(CO)14(μ4-COH)]

Abstract The new compound [PPN][H 2 Ru 5 (CO) 14 (μ 4 -COH)], [PPN][1], (PPN= bis(triphenylphosphine) iminium) is a product in several cluster expansion reactions which use trinuthene oranes as precursors, although the yields are not high. An X-ray diffraction study has shown that in the anion 1 has a square-based pyramidal framework of ruthenium atoms. With the square face capped by a μ 4 -COH group. Studies of the reactivity of 1 have been carried out, but have not shown 1 to be a ready precursor to an Ru 5 C-carbido species as had been expected.

Reactions of {(C5H5)Co[P(O)(OC2H5)2]3}− with MCL3 and M(CH3)Cl2 (M = Ga, In). Crystal and molecular structure of [{(C5H5)Co[P(O)(OC2H5)2]3}2Ga]Ga(CH3)Cl3

Abstract The reaction of GaCl3 or InCl3 with Na{(C5H5)CO[P(O)(OC2H5)2]3} in THF in a 1 1 mole ratio led to the formation of the respective ionic compound [{(C5H5)Co[P(O)(OC2H5)2]3}2M]MCl4 (M = Ga, In). Similar reactions with a metal/ligand molar ratio of 2 1 led to the formation of [{(C5H5)Co[P(O)(OC2H5)2]3}2M]Cl. Analogous reactions starting with M(CH3)Cl2 also led to the formation of the metal(III) cation, with [M(CH3)Cl3]− as the counter ion. The solid state structure of [{(C5H5)Co[P(O)(OC2H5)2]3}2Ga]Ga(CH3)Cl3 · CH2Cl2 has been determined by X-ray crystallography. The geometry about gallium in the cation is nearly a perfect octahedron

Dichromium cage complexes of cyclotetra-, cyclopenta-, and cyclohexa-phosphoxane

Metal-assisted assembly of cis-dimethylpiperidinophosphine oxide (DMP–PO) units around chromium carbonyl at progressively higher temperatures affords dichromium complexes of cyclotetraphosphoxane (two isomers), cyclopentaphosphoxane, and ultimatlely, the novel cyclohexaphosphoxane.