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The X-ray crystal structure characterization of recombinant epi-isozizaene synthase (EIZS), a sesquiterpene cyclase from Streptomyces coelicolor A3(2) is described. Comparison of EIZS and D99N EIZS provides insight into the conformational changes required for the substrate binding and catalysis in a bacterial terpenoid cyclase and the binding interactions of benzyltriethylammonium cation (BTAC) which might imitate those of a carbocation intermediate in catalysis.

Presilphiperfolan-8[beta]-ol synthase, encoded by the BcBOT2 gene from the necrotrophic plant pathogen Botrytis cinerea, has catalyzed the multistep cyclization of farnesyl diphosphate to the tricyclic sesquiterpene alcohol presilphiperfolan-8[beta]-ol, the precursor of the phytotoxin botrydial. The results have described the conformation of enzyme-bound farnesyl diphosphate at the active site of presilphiperfolan-8[beta]-ol synthase.

A two-step, cytochrome P450-catalyzed oxidation of epi-isozizaene synthase from Streptomyces coelicolor to yield antibiotic albaflavenone as final product is reported. A site-directed mutagenesis of active site residues in two universally conserved [Mg.sup.2+]-binding domains and the identification of six minor sesquiterpene products produced by the wild-type and mutant proteins provide insight into the mechanism and the role of the enzyme epi-isozizaene synthase.

An efficient one-pot propargylation/cycloisomerization tandem process is developed for preparing substituted oxazole derivatives from propargylic alcohols and amides with use of p-toluenesulfonic acid monohydrate (PTSA) as a bifunctional catalyst. This method has provided an efficient access to substituted oxazoles.

The glycolipid transfer protein (GLTP) catalyzes the intermediate transfer of lipids between membranes. The present study provides a quantitative understanding of GLTP action involving bilayer vesicles that have high and low curvature stress.

The cloning of human glycolipid transfer protein (GLTP) is reported and the environment of the three tryptophans (Trps) of the protein using fluorescence spectroscopy is characterized. Insights into reversible conformational changes accompanying changes in GLTP activity are provided by addition and rapid dilution of urea while monitoring changes in Trp or 1-anilinonaphthalene-8-sulfonic acid fluorescence.

We investigate the distribution of valence and tail states in copper phthalocyanine (CuPc) upon the introduction of minute amounts of the p-dopant molybdenum tris[1,2-bis(trifluoromethyl)ethane-1,2-dithiolene] (Mo(tfd)3), using a combination of electron spectroscopy and carrier transport measurements. Density of gap states, conductivity, and hole-hopping activation energy are measured. We observe the progressive filling (and deactivation) of the deepest tail states by charges introduced by the dopants, as well as significant broadening of the CuPc density of states. Simulations relate this broadening to the electrostatic and structural disorder induced by the dopant in the CuPc matrix. [ABSTRACT FROM AUTHOR]

Constructing nanoparticles into well-defined structures at mesoscale and larger to create novel functional materials remains a challenge. Inspired by atomic epitaxial growth, we propose an "epitaxial assembly" method to form two-dimensional nanoparticle arrays (2D NAs) directly onto desired materials. As an illustration, we employ a series of surfactant-capped nanoparticles as the "artificial atoms" and layered hybrid perovskite (LHP) materials as the substrates and obtain 2D NAs in a large area with few defects. This method is universal for nanoparticles with different shapes, sizes, and compositions and for LHP substrates with different metallic cores. Raman spectroscopic and X-ray diffraction data support our hypothesis of epitaxial assembly. The novel method offers new insights into the controllable assembly of complex functional materials and may push the development of materials science at the mesoscale. [ABSTRACT FROM AUTHOR]

Deduced from thermodynamics and the Thomson-Gibbs equation that the surface energy of crystal face is in proportion to the supersaturation of crystal growth units during the crystal growth, we propose that the exposed crystal faces can be simply tuned by controlling the supersaturation, and higher supersaturation will result in the formation of crystallites with higher surface-energy faces. We have successfully applied it for the growth of ionic (NaCl), molecular (TBPe), and metallic (Au, Pd) micro/nanocrystals with high-surface-energy faces. The above proposed strategy can be rationally designed to synthesize micro/nanocrystals with specific crystal faces and functionality toward specific applications. [ABSTRACT FROM AUTHOR]

The article describes the molecular cloning and biochemical characterization of a second Streptomyces coelicolor terpene synthase, SCO5222, that is shown to catalyze the Mg2+-dependent cyclization of farnesyl disphosphate to a novel sesquiterpene, epiisozizaene. The 361 amino acid SCO5222 protein has 23.8 percent amino acid sequence identity and 51.1 percent similarity over 311 aa with the 336-aa pentalenene synthase of Streptomyces UC5319. The protein encoded SCO5222 includes the two universally conserved Mg2+-binding domains.

Multifunctional materials have always been an attractive research area, but how to combine multiple excellent properties in one compound remains a considerable challenge. Organic-inorganic hybrid compounds are widely used in the design of such materials due to their rich properties and flexible assembly. Herein, two new manganese(II)-based organic-inorganic hybrid compounds, (C 6 NH 16 ) 2 MnBr 4 ( 1 ) and (C 7 NH 18 ) 2 MnBr 4 ( 2 ), are prepared by the solution method. Compounds 1 and 2 both emit extremely strong green light under UV excitation, with high quantum yields of 45.93 and 50.98%, respectively. In addition, reversible solid-state phase transitions and obvious switchable dielectric properties are shown at 378/366 and 361/352 K, respectively. The coexistence of the dual stimulus-response characteristics of temperature and light in compounds 1 and 2 opens a new path for exploring more multifunctional phase transition materials.

Metallic materials with unique surface structure have attracted much attention due to their unique physical and chemical properties. However, it is hard to prepare bulk metallic materials with special crystal faces, especially at the nanoscale. Herein, we report an efficient method to adjust the surface structure of a Cu plate which combines ion implantation technology with the oxidation-etching process. The large number of vacancies generated by ion implantation induced the electrochemical oxidation of several atomic layers in depth; after chemical etching, the Cu(100) planes were exposed on the surface of the Cu plate. As a catalyst for acid hydrogen evolution reaction, the Cu plate with (100) planes merely needs 273 mV to deliver a current density of 10 mA/cm 2 because the high-energy (100) surface has moderate hydrogen adsorption and desorption capability. This work provides an appealing strategy to engineer the surface structure of bulk metallic materials and improve their catalytic properties.

Based on the structures of isoxaflutole (IFT) and N -isobutyl- N -(4-chloro-benzyl)-4-chloro-2-pentenamide, a series of N -benzyl-5-cyclopropyl-isoxazole-4-carboxamides was designed by connecting their pharmacophores ( i.e. , a multitarget drug design strategy). A total of 27 N -benzyl-5-cyclopropyl-isoxazole-4-carboxamides were prepared from 5-cyclopropylisoxazole-4-carboxylic acid and substituted benzylamines, and their structures were confirmed by NMR and MS. Laboratory bioassays indicated that I-26 showed 100% inhibition against Portulaca oleracea and Abutilon theophrasti at a concentration of 10 mg/L, better than the positive control butachlor (50% inhibition for both weeds). A strong growth inhibition was observed, but a typical bleaching phenomenon of IFT could not be observed in the Petri dish assay. I-05 displayed excellent postemergence herbicidal activity against Echinochloa crusgalli and A. theophrasti at a rate of 150 g/ha, and bleaching symptoms were observed in the leaves of treated weeds. The bleaching effect of Chlamydomonas reinhardtii treated by I-05 could be reversed by adding homogentisate. Enzymatic bioassays indicated that I-05 could not inhibit 4-hydroxyphenylpyruvate dioxygenase (HPPD) activity, but II-05 , an isoxazole ring-opening product of I-05 , could inhibit HPPD activity with an EC 50 value of 1.05 μM, similar to that of mesotrione (with an EC 50 value of 1.35 μM). Detailed discussion about observed herbicidal symptoms is provided in the Results and Discussion section. This investigation provided a proof-of-concept foundation that a multitarget drug design strategy could be applied in agrochemical research.

(±)-Melipatulinones A-C ( 1 - 3 ), three unique enantiomeric pairs of lignan-phloroglucinol hybrids along with the biogenetically related compound melipatulignan A ( 4 ), were isolated from the leaves of Melicope patulinervia . Melipatulinones A ( 1 ) and B ( 2 ) share a novel spiro[hydrobenzofuran-2,3'-furan] 5/5/6 tricyclic ring system, while melipatulinone C ( 3 ) features an unprecedented spiro[cyclopenta[ b ]hydrofuran-2,3'-furan] 5/5/5 tricyclic framework. Their structures were determined by spectroscopic methods, electronic circular dichroism (ECD) calculations, and X-ray diffraction. Compounds 1 - 3 exhibited a pancreatic lipase inhibitory effect.