Formation of a metallocycle by dimerization of acrylonitrile. Crystal structure of the hexakis{(1,4-dicyanobutane-1,4-diyl)-nickel(II)} complex

A novel hexanickel(II) complex [Ni₆(NCCHCH₂CH₂CHCN)₆] (2) with 1,4-dicyanobutane-1,4-diyl (L) which was produced by the metal-induced dimerization of acrylonitrile (AN) has been isolated and the structure has been determined crystallographically. Complex 2 is triclinic, space group

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. Each nickel atom is coordinated by two carbon atoms of L and two nitrogen atoms of the cyano group of two other L, providing a square-plenar geometry. The six nickel atoms are bridged by the cyano group and carbon atom to form the slightly distorted octahedral Ni₆ core.     

Mycelial β-N-Acetylglucosaminidase of Streptomyces sp. Having β-N-Acetylgalactosaminidase Activity

Formation of transfer products from soybean arabinogalactan and glycerol by endo-1,4-β-d-galactanase from Penicillium citrinum was described. The amount of transfer products depended on the glycerol concentration. About 50% of the galactose residues which could be liberated from the polysaccharide by the enzyme were transferred to glycerol at an acceptor concentration of 2.5% (w/v). Transfer products with various polymerization degrees were accumulated at the beginning of the reaction and then those with higher polymerization degrees were degraded gradually. At a final stage of the reaction, two transfer products in addition to two hydrolysis products (galactose and galactobiose) were mainly accumulated. The two transfer products were isolated and their structures were examined. They were 2-O-β-d-galactosyl glycerol and O-β-d-galactosyl-(1 → 4)-O-β-d-galactosyl-(1 → 2)glycerol.     

Potent and orally active ET(A) selective antagonists with 5,7-diarylcyclopenteno[1,2-b]pyridine-6-carboxylic acid structures

The synthesis and structure-activity relationships of a series of 5,7-diarylcyclopenteno[1,2-b]pyridine-6-carboxylic acids are described. Our efforts have been focused on modification of the aryl ring at the 5-position and the alkyl substituent at the 2-position of the bottom 4-methoxyphenyl ring in an effort to develop orally available ET(A) selective antagonists with safer profiles in terms of the P-450 enzyme inhibitory activity. Incorporation of a hydroxymethyl group as an alkyl substituent in methylenedioxyphenyl and 6-dihydrobenzofuran derivatives led to the identification of orally bioavailable ET(A) selective antagonists 1f and 7f. These compounds also showed not only excellent binding affinity (IC(50) < 0.10nM, more than 800-fold selectivity for the ET(A) receptor over the ET(B) receptor) but also sufficient oral bioavailability, 48% and 56%, respectively, in rats. Furthermore, these compounds did not exhibit either competitive or mechanism-based inhibition of human cytochrome P450 enzymes.     

Transient gene expression system established in Porphyra yezoensis is widely applicable in Bangiophycean algae

The establishment of transient gene expression systems in the marine red macroalga Porphyra yezoensis has been useful for the molecular analysis of cellular processes in this species. However, there has been no successful report about the expression of foreign genes in other red macroalgae, which has impeded the broader understanding of the molecular biology of these species. We therefore examined whether the P. yezoensis transient gene expression system was applicable to other red macroalgae. The results indicated that a codon-optimized GUS, designated PyGUS, and plant-adapted sGFP(S65T) were successfully expressed under the control of the P. yezoensis PyAct1 promoter in gametophytic cells of six Porphyra species and also in Bangia fuscopurpurea, all of which are classified as Bangiophyceae. In contrast, there were no reporter-expressing cells in the Florideophycean algae examined. These results indicate the availability of PyGUS and sGFP as reporters and the 5' upstream region of the PyAct1 gene as a heterologous promoter for transient gene expression in Bangiophycean algae, which could provide a clue to the efficient expression of foreign genes and transformation in marine red macroalgae.     

3D coordination polymers of [2.2]paracyclophane and in situ silver(I) perfluoro-dicarboxylates: effects of the dicarboxylate spacers and conformations on the formation of complexes

Coordination polymers of [2.2]paracyclophane (pcp) with in situ silver(I) perfluoro-dicarboxylates characterized by single crystal X-ray analysis are described. Structures are found to strongly depend on the dicarboxylate spacer (n). With disilver(I) tetrafluorosuccinate ((CF₂)_n(COOAg)₂, n = 2), 3D network with composition of [Ag₄(pcp)(C₂F₄(CO₂)₂)₂] (1) forms in which silver salts afford infinite double chains and pcp act as linkages between chains. Changing the silver salt to disilver hexafluoroglutarate ((CF₂)_n(COOAg)₂, n = 3) produces 3D pillared-layer structure of composition of [Ag₄(pcp)(C₃F₆(CO₂)₂)₂] · THF (2) (THF = tetrahydrofuran), in which silver salts form 2D sheets and pcp act as pillars between the sheets. With silver octafluoroadipate (HO₂C(CF₂)_nCO₂Ag, n = 4), 2-fold interpenetrated diamond structure, [Ag₂(pcp)₂(HO₂CC₄F₈CO₂)₂]₂ · 2toluene (3), is obtained in which silver-anion chains and silver-pcp chains are connected with each other in the perpendicular manner. The three complexes represent unprecedented metal-organic networks of silver(I) multicarboxylates and polycyclic aromatic compounds. Additionally, the effects of the dicarboxylate conformations as well as the solvents on the resulting structures were discussed.     

Synthesis and crystal structures of silver(I) bridged tetra-phenyl-pyrylium complexes from tetraphenyl-cyclopentadiene

Reactions of silver(I) perchlorate with tetraphenyl-cyclopentadiene (Ph₄H₂C₅) have isolated two novel silver(I) bridged tetraphenyl-pyrylium complexes: [Ag(ClO₄)(Ph₄HC₅O⁺)](ClO₄)⁻ (1) and (2), depending on moisture-content of the reactants. Structure studies using single-crystal X-ray diffraction have showed that complex 1 contains a distorted tetrahedral metal center bridging two neighboring peripheral phenyl rings of one pyrylium cation and two perchlorate anions, whereas 2 involves a three-coordinate metal ion interacting with a pair of phenyl rings and one water molecule, leaving two perchlorate anions free from coordination. For both complexes, the precursor ligand Ph₄H₂C₅ undergoes a ring-enlargement reaction, forming a six-membered pyrylium cation. The fundamentals of the synthesis, structure characterization and some properties are discussed.     

Identification of 5-HT receptor subtypes enhancing inhibitory transmission in the rat spinal dorsal horn in vitro

ABSTRACT: BACKGROUND: 5-hydroxytryptamine (5-HT) is one of the major neurotransmitters widely distributed in the CNS. Several 5-HT receptor subtypes have been identified in the spinal dorsal horn which act on both pre- and postsynaptic sites of excitatory and inhibitory neurons. However, the receptor subtypes and sites of actions as well as underlying mechanism are not clarified rigorously. Several electrophysiological studies have been performed to investigate the effects of 5-HT on excitatory transmission in substantia gelatinosa (SG) of the spinal cord. In the present study, to understand the effects of 5-HT on the inhibitory synaptic transmission and to identify receptor subtypes, the blind whole cell recordings were performed from SG neurons of rat spinal cord slices. RESULTS: Bath applied 5-HT (50 microM) increased the frequency but not amplitudes of spontaneous inhibitory postsynaptic currents (sIPSCs) in 58% of neurons, and both amplitude and frequency in 23 % of neurons. The frequencies of GABAergic and glycinergic mIPSCs were both enhanced. TTX (0.5 microM) had no effect on the increasing frequency, while the enhancement of amplitude of IPSCs was eliminated. Evoked-IPSCs (eIPSCs) induced by focal stimulation near the recording neurons in the presence of CNQX and APV were enhanced in both amplitude by 5-HT. In the presence of Ba2+ (1 mM), a potassium channel blocker, 5-HT had no effect on both frequency and amplitude. A 5-HT2Areceptor agonist, TCB-2 mimicked the 5-HT effect, and ketanserin, an antagonist of 5-HT2A receptor, inhibited the effect of 5-HT partially and TCB-2 almost completely. A 5-HT2C receptor agonist WAY 161503 mimicked the 5-HT effect and this effect was blocked by a 5-HT2C receptor antagonist, N-desmethylclozapine. The amplitude of sIPSCs were unaffected by both agonists. A 5-HT3 receptor agonist mCPBG enhanced both amplitude and frequency of sIPSCs. This effect was blocked by a 5-HT3 receptor antagonist ICS-205,930. The perfusion of 5-HT2B receptor agonist had no effect on sIPSCs. CONCLUSIONS: Our results demonstrated that 5-HT modulated the inhibitory transmission in SG by the activation of 5-HT2A and 5-HT2C receptors subtypes located predominantly at inhibitory interneuron terminals, and 5-HT3 receptors located at inhibitory interneuron terminals and soma-dendrites, consequently enhanced both frequency and amplitude.     

The effect of molecular packing on the occurrence of spin crossover phenomena in one-dimensional Fe(II)-bis-Schiff base complexes

Two new one-dimensional Fe(II)-bis-Schiff base complexes, [Fe(L1)(pyz)] · CH₂Cl₂ (1) and [Fe(L2)(pyz)] · 2CH₂Cl₂ (2) (H₂L1 = bis(O-vanillin)-O-phenylenediimine, H₂L2 = bis(O-vanillin)-2,3-naphthalenediimine, pyz = pyrazine) are reported with their crystal structures and magnetic property. Compound 1 shows a two-step SCO behavior while 2 shows HS at all the temperature range measured. Although the extension of aromatic moiety from benzene (L1) to naphthalene (L2) was introduced for the purpose of strengthening the cooperativity, it leads to the absence of SCO, due to the unanticipated π–π interaction, which leads to the longer Fe–N bond lengths and a weak ligand field around Fe(II) ion.     

Photosynthesis-dependent Ca2+ influx and functional diversity between phospholipases in the formation of cell polarity in migrating cells of red algae

Unicellular spore cells, designated as monospores (also called archeospores), are well known as migrating plant cells, in which establishment of the anterior-posterior axis directs asymmetrical distribution of F-actin. Since the mechanisms of cell polarity formation are not yet fully elucidated in monospores, we investigated the roles of phosphoinositide signaling systems and Ca²⁺ mobilization in migration. Although we have already found the critical involvement of phosphatidylinositol 3-kinase in the establishment of cell polarity, we recently demonstrated the important roles of extracellular Ca²⁺ influx, phospholipase C (PLC) and phospholipase D (PLD). The remarkable characteristics of these factors are that Ca²⁺ influx depends on photosynthetic activity and that PLC and PLD play roles in the establishment and maintenance of cell polarity, respectively. These findings could provide new insight into the regulation of migration in eukaryotic cells.Key words: Ca²⁺ influx, cell polarity, phospholipase C, phospholipase D, photosynthesis, Porphyra yezoensisMonospores are responsible for asexual and clonal propagation of the marine multicellular red algae Porphyra and have an exceptional characteristic as migrating plant cells.^1–5 Monospores possess a round shape just after release from gametophytic blades (Fig. 1A and B), then undergo morphological change during migration. The establishment of cell polarity leads to the determination of anterior-posterior axis and asymmetrical localization of F-actin (Fig. 1C). After migration, monospores adhere to the substratum in which the apical-basal axis has been established for further development (Fig. 1D). Asymmetrical distribution of F-actin is also found in chemotaxic migration of Dictyostelium cells and leukocytes.^6,7 In these cells, reciprocal local accumulation of phosphoinositides, such as phosphatidylinositol-3,4,5-trisphosphate [PtdIns(3,4,5)P₃] at the leading edge and phosphatidylinositol-4,5-bisphosphate [PtdIns(4,5)P₂] at the trailing side, is critical for the establishment of cell polarity. Phosphatidylinositol 3-kinase (PI3K) and PtdIns(3,4,5)P₃-specific D-3-phosphatase PTEN have been identified as key modulators in the establishment of cell polarity, bringing asymmetrical distribution of these two phosphoinositides in plasma membranes.^6,8 Similarly, we found the involvement of PI3K activity in the establishment of cell polarity in migrating monospores,³ suggesting the evolutional conservation of the function of PI3K in migrating eukaryotic cells. On the other hand, the importance of cell wall synthesis has been found in the maintenance of the cell polarity during monospore migration⁴ as reported in Fucus zygotes.^9,10 Therefore, the establishment and maintenance of cell polarity are thought to be regulated separately in monospores of P. yezoensis. In this addendum, further evidence of differential regulation of cell polarity formation by extracellular Ca²⁺ influx and phospholipases in migrating monospores of red algae is documented according to our recent report.⁵Open in a separate windowFigure 1Establishment and maintenance of cell polarity in monospores from the red alga P. yezoensis. (A) Discharge of unicellular monospores from a multicellular gametophytic blade of P. yezoensis strain TU-1. Scale bar = 20 µm. (B–D) Asymmetrical distribution of F-actin during early development of monospores. F-actin was stained with alex Flour 488 phalloidin. (B) Discharged monospore. (C) Migrating monospore. (D) Adhering monospore. Upper and lower photos in each panel show bright-field and fluorescent images, respectively. Arrow in (C) indicates the direction of migration. Scale bars = 5 µm. (e) Schematic representation of our working hypothesis about the formation of cell polarity required for monospore migration. Photosynthesis-dependent [Ca²⁺]_cyt increase regulates PLC and PI3K for the establishment of cell polarity, while PLD is required for the maintenance of the established cell polarity. DG, diacylgycerol; IP3, inositol-1,4,5-trisphosphate; IP3r, IP3 receptor; PC, phosphatidylcholine.     

Ubiquitin promoter�Cterminator cassette promotes genetically stable expression of the taste-modifying protein miraculin in transgenic lettuce

Lettuce is a commercially important leafy vegetable that is cultivated worldwide, and it is also a target crop for plant factories. In this study, lettuce was selected as an alternative platform for recombinant miraculin production because of its fast growth, agronomic value, and wide availability. The taste-modifying protein miraculin is a glycoprotein extracted from the red berries of the West African native shrub Richadella dulcifica. Because of its limited natural availability, many attempts have been made to produce this protein in suitable alternative hosts. We produced transgenic lettuce with miraculin gene driven either by the ubiquitin promoter/terminator cassette from lettuce or a 35S promoter/nos terminator cassette. Miraculin gene expression and miraculin accumulation in both cassettes were compared by quantitative real-time PCR analysis, Western blotting, and enzyme-linked immunosorbent assay. The expression level of the miraculin gene and protein in transgenic lettuce was higher and more genetically stable in the ubiquitin promoter/terminator cassette than in the 35S promoter/nos terminator cassette. These results demonstrated that the ubiquitin promoter/terminator cassette is an efficient platform for the genetically stable expression of the miraculin protein in lettuce and hence this platform is of benefit for recombinant miraculin production on a commercial scale.