The LysR-type transcriptional factor PacR controls heterocyst differentiation and C/N metabolism in the cyanobacterium Anabaena PCC 7120.

PacR (All3953) has previously been identified as a global transcriptional regulator of carbon assimilation in cyanobacteria. In the facultative diazotrophic and filamentous cyanobacterium Anabaena PCC 7120 (Anabaena), inactivation of pacR has been shown to affect cell growth under various conditions. Nitrogen fixation in Anabaena occurs in heterocysts, cells differentiated semiregularly along the filaments following deprivation of combined nitrogen such as nitrate or ammonium.

Nitrate Reductase Activity Assay of Crude Extract.

Nitrate is one of the major inorganic nitrogen sources for microorganisms. Many bacterial and archaeal lineages can express cytoplasmic assimilatory nitrate reductase (NAS), which catalyzes the rate-limiting reduction of nitrate to nitrite in the nitrate assimilation pathway. Here, we present a detailed protocol for measuring nitrate reductase (NaR) activity of NAS enzymes from crude extract using both physiological and non-physiological electron donors.

A recently evolved diflavin-containing monomeric nitrate reductase is responsible for highly efficient bacterial nitrate assimilation.

Nitrate is one of the major inorganic nitrogen sources for microbes. Many bacterial and archaeal lineages have the capacity to express assimilatory nitrate reductase (NAS), which catalyzes the rate-limiting reduction of nitrate to nitrite. Although a nitrate assimilatory pathway in mycobacteria has been proposed and validated physiologically and genetically, the putative NAS enzyme has yet to be identified.

Novel Isochroman Dimers from Stachybotrys sp. PH30583: Fermentation, Isolation, Structural Elucidation and Biological Activities.

The rare anishidiol and five new isochromans, including three novel dimers with unprecedented skeletons, were isolated from sp. PH30583. Their structures were determined by spectral analyses.

GlnR-Mediated Regulation of ectABCD Transcription Expands the Role of the GlnR Regulon to Osmotic Stress Management.

Unlabelled: Ectoine and hydroxyectoine are excellent compatible solutes for bacteria to deal with environmental osmotic stress and temperature damages. The biosynthesis cluster of ectoine and hydroxyectoine is widespread among microorganisms, and its expression is activated by high salinity and temperature changes. So far, little is known about the mechanism of the regulation of the transcription of ect genes and only two MarR family regulators (EctR1 in methylobacteria and the EctR1-related regulator CosR in Vibrio cholerae) have been found to negatively regulate the expression of ect genes.

A preliminary study of the mechanism of nitrate-stimulated remarkable increase of rifamycin production in Amycolatopsis mediterranei U32 by RNA-seq.

Background: Rifamycin is an important antibiotic for the treatment of infectious disease caused by Mycobacteria tuberculosis. It was found that in Amycolatopsis mediterranei U32, an industrial producer for rifamycin SV, supplementation of nitrate into the medium remarkably stimulated the yield of rifamycin SV. However, the molecular mechanism of this nitrate-mediated stimulation remains unknown.

Asymmetric catalytic conjugate addition of acetaldehyde to nitrodienynes/nitroenynes: applications to the syntheses of (+)-α-lycorane and chiral β-alkynyl acids.

The catalytic enantioselective conjugate addition of acetaldehyde to polyconjugated substrates, nitrodienynes and nitroenynes, has been accomplished using organocatalysis. Various functionalized 1,3-enynes and propargylic compounds were obtained in moderate to good yields with high enantioselectivity. The synthetic utilities of the conjugate addition reactions have been highlighted in the concise total synthesis of (+)-α-lycorane and the metal-free synthesis of chiral β-alkynyl acids.

Catalytic enantioselective and divergent total synthesis of (+)-10-oxocylindrocarpidine, (+)-cylindrocarpidine, (-)-N-acetylcylindrocarpinol, and (+)-aspidospermine.

The catalytic enantioselective and divergent total syntheses of Aspidosperma alkaloids (+)-10-oxocylindrocarpidine 7, (+)-cylindrocarpidine 1, (-)-N-acetylcylindrocarpinol 6, and (+)-aspidospermine 8 have been accomplished in 11 steps from a common precursor (15) on the basis of a highly concise route. The route features three metal-catalyzed reactions, including the key Pd-catalyzed decarboxylative asymmetric allylation of carbazolones developed in our laboratory. Our syntheses, using a combination of C-H activation, enantioselective catalysis, and collective synthesis, represent the first total synthesis of 10-oxocylindrocarpidine and the first asymmetric total synthesis of cylindrocarpidine and N-acetylcylindrocarpinol.

Enantioselective total synthesis of (-)-limaspermidine and formal synthesis of (-)-1-acetylaspidoalbidine.

Evolution of the synthetic strategy that culminated in the first asymmetric total synthesis of the Aspidosperma alkaloid limaspermidine is described. The successful enantioselective route to (-)-limaspermidine proceeds in 10 steps and with the isolation of only six intermediates using a Pd-catalyzed enantioselective decarboxylative allylation we have recently developed. This first enantioselective synthesis of (-)-limaspermidine establishes unambiguously its absolute configuration and allows the first asymmetric formal total synthesis of the Aspidoalbine alkaloid (-)-1-acetylaspidoalbidine.

Three of four GlnR binding sites are essential for GlnR-mediated activation of transcription of the Amycolatopsis mediterranei nas operon.

In Amycolatopsis mediterranei U32, genes responsible for nitrate assimilation formed one operon, nasACKBDEF, whose transcription is induced by the addition of nitrate. Here, we characterized GlnR as a direct transcriptional activator for the nas operon. The GlnR-protected DNA sequences in the promoter region of the nas operon were characterized by DNase I footprinting assay, the previously deduced Streptomyces coelicolor double 22-bp GlnR binding consensus sequences comprising a1, b1, a2, and b2 sites were identified, and the sites were then mutated individually to test their roles in both the binding of GlnR in vitro and the GlnR-mediated transcriptional activation in vivo.

Synthesis and evaluation of antitumor activities of novel chiral 1,2,4-triazole Schiff bases bearing γ-butenolide moiety.

Background: 1,2,4-Triazole derivatives have received much attention due to their versatile biological properties including antibacterial, antifungal, anticonvulsant, antiinflammatory, anticancer, and antiproliferative properties. 1,2,4-Triazole nucleus has been incorporated into a wide variety of therapeutically interesting molecules to transform them into better drugs. Schiff bases of 1,2,4-triazoles have also been found to possess extensive biological activities.

Enantioselective conjugate addition of both aromatic ketones and acetone to nitroolefins catalyzed by chiral primary amines bearing multiple hydrogen-bonding donors.

A new class of chiral primary amine catalysts bearing multiple hydrogen-bonding donors have been designed and synthesized. The newly developed bifunctional organocatalysts efficiently catalyzed not only enantioselective conjugate addition of aromatic ketones to nitroolefins in good yields (up to 87%) with excellent enantioselectivities (97→99% ee) but also enantioselective conjugate addition of acetone to nitroolefins in excellent yields (90-96%) with high enantioselectivities (up to 97% ee).

Highly enantioselective one-pot synthesis of spirocyclopentaneoxindoles containing the oxime group by organocatalyzed Michael addition/ISOC/fragmentation sequence.

A highly diastereo- and enantioselective organocatalytic protocol for the synthesis of biologically important spirocyclopentaneoxindoles containing the oxime functional group from easily accessible 3-allyl-substituted oxindoles and nitroolefins has been developed by a one-pot Michael addition/ISOC/fragmentation sequence.

Catalytic asymmetric construction of spirocyclopentaneoxindoles by a combined Ru-catalyzed cross-metathesis/double Michael addition sequence.

Biologically important and synthetically challenging spirocyclopentaneoxindoles with four contiguous stereocenters including one spiroquaternary stereocenter have been constructed in good yields (72-87%) with excellent diastereoselectivity (16:1→30:1 dr) and enantioselectivity (93→99% ee) by a combined Ru-catalyzed cross-metathesis/organocatalyzed asymmetric double-Michael addition sequence.

Enantioselective and regioselective organocatalytic conjugate addition of malonates to nitroenynes.

The first catalytic asymmetric conjugate addition of 1,3-dicarbonyl compounds to nitroenynes catalyzed by cinchona alkaloid-based thiourea organocatalysts has been developed. The 1,4-addition adducts were obtained solely, in moderate to good yields (up to 93%) with good enantioselectivities (up to 99% ee). This protocol affords a conceptually different entry to the precursors of pharmaceutically important chiral β-alkynyl acid derivatives and synthetically useful chiral nitroalkynes.

Ligand-controlled enantioselective [2 + 2] cycloaddition of oxabicyclic alkenes with terminal alkynes using chiral iridium catalysts.

The first catalytic asymmetric [2 + 2] cycloaddition of oxabicyclic alkenes and terminal alkynes has been developed. This iridium-catalyzed enantioselective [2 + 2] cycloaddition allows the formation of four stereocenters in a single step with excellent enantioselectivity (94-->99% ee).

Synthesis of new chiral 2,5-disubstituted 1,3,4-thiadiazoles possessing gamma-butenolide moiety and preliminary evaluation of in vitro anticancer activity.

A new series of chiral 1,3,4-thiadiazoles derivatives possessing gamma-substituted butenolide moiety were synthesized and evaluated for in vitro anticancer properties. All the compounds showed good anticancer activities against Hela cell lines. Of all the studied compounds, compound 9e exhibited the best inhibitory activity with an IC(50) of 0.

Organocatalytic enantioselective Michael addition of 2,4-pentandione to nitroalkenes promoted by bifunctional thioureas with central and axial chiral elements.

Two novel bifunctional amine-thiourea organocatalysts 1 and 2, which both bear central and axial chiral elements, have been developed to promote enantioselective Michael reaction between 1,3-dicarbonyl compounds and nitro olefins. The catalyst 2 afforded the desired products with good levels of enantioselectivity (up to 96% ee), showing clearly that two chiral elements of 2 are matched, and enhance the stereochemical control.