Search

Abstract A new polymeric copper(II) complex [Cu3L3(μ3-NO3)]n·2nNO3, derived from the Schiff base ligand N'-(pyridin-2-ylmethylene)isonicotinohydrazide (HL) with copper nitrate in methanol, was prepared and characterized by elemental analysis, IR and UV-Vis spectra. The structure of the complex was further confirmed by single crystal X-ray diffraction technique. The Schiff base ligand coordinates to the Cu atoms through the phenolate O, imino O, and two pyridine N atoms. The Cu atom is in a square pyramidal coordination, with the three chelate donor atoms of the Schiff base ligand and the terminal nitrogen donor atom of a symmetry related Schiff base ligand defining the basal plane, and with one oxygen atom of the coordinated nitrate ligand at the apical position. The nitrate ligand bridges three [CuL] units with a crystallographic three fold rotation axis symmetry. The effect of the complex on the antimicrobial activity against Staphylococcus aureus, Escherichia coli, and Candida albicans was studied. [ABSTRACT FROM AUTHOR]

A new dinuclear cobalt(III) complex, 2[Co2L(HL)N3]·5H2O, derived from the reduced Schiff base 6,6'-(2-hydroxypropane-1,3-diyl)bis(azanediyl)bis(methylene)bis(2-bromo-4-chlorophenol) (H3L), was synthesized and characterized by infrared and electronic spectroscopy, and single-crystal X-ray diffraction techniques. The ligand was firstly synthesized and bound to the Co(III) center. The compound contains two dinuclear [Co2L(HL)N3] complex molecules and five water molecules of crystallization. The Co atoms in the complex are in octahedral coordination. The complex shows effective antimicrobial activity. [ABSTRACT FROM AUTHOR]

Two new vanadium complexes, [VO(L1)2] (1) and [V2O2(μ-O)2(L2)2] (2), where L1 is 2-(cyclohexyliminimethyl)-4,6-difluorophenolate, L2 is 2,4-difluoro-6-[(2-isopropylaminoethylimino)methyl]phenolate, have been synthesized and characterized by elemental analysis, FT-IR and UV-Vis spectra, and single crystal X-ray determination. The V atom in complex 1 is in a coordination between trigonal bipyramidal and square pyramidal, and that in complex 2 is in octahedral coordination. The antibacterial activity of the compounds against various bacteria was assayed. The fluoro-substituted groups play an essential role in the biological process. [ABSTRACT FROM AUTHOR]

Methods obtaining gypsum whiskers via calcining dihydrate or hemihydrate gypsum perform high energy consumption. It also performs potential environmental impacts. New methods with energy-saving, high-efficiency, and environmentally friendly perform great challenges, which aim at fabricating gypsum whiskers even nanowhiskers. In this study, we used high-concentration calcium acetate solution and dilute sulfuric acid to fabricate anhydrite calcium sulfate nanowhiskers with microemulsion solution at room temperature. For further research on regulation and modification of its surface, calcium sulfates were modified by silicone quaternary ammonium salt and fatty acid methyl ester sulfonate in order to study their surface structure and crystal evolution during modification. After characterization, it indicated that the phase of calcium sulfate transmitted from anhydrite phase into dihydrite phase with a slight change on the surface layers. Benefiting from stability and activity properties of calcium sulfate nanowhiskers after modified, the compressive strength of cement paste with only 1% calcium sulfates performed increased absolutely 10.1% and 4.3% at conservation age of 3 days and 28 days. [ABSTRACT FROM AUTHOR]

A new cobalt(II) complex, [Co(hfa)2(tmea)], derived from the multifluoro containing ligand hexafluoroacetylacetone (Hhfa) and N,N,N′,N′-tetramethylethane-1,2-diamine (tmea) has been prepared and characterized by elemental analyses, molar conductivity, and single-crystal X-ray crystallographic determination. The crystal of the complex is monoclinic: space groupP21/n, a= 13.903(2),b= 10.406(1),c= 17.913(2) Å, β = 111.342(2)°,V= 2414.0(5) Å3,Z= 4,R1= 0.0757,wR2= 0.1575. The Co atom is coordinated by four O atoms from two hfa ligands, and two N atoms from tmea ligand, and generating octahedral coordination. The effects of the complex on the antimicrobial activity againstStaphylococcus aureus, Escherichia coli, andCandida albicanswere studied. [ABSTRACT FROM PUBLISHER]

Three different tetrazole-carboxylate ligands, Hpymtza, Hpytza, and H2dtzeda were chosen to be reacted with Ca(NO3)2 ·4H2O, resulting in the formation of three coordination compounds, [Ca(pymtza)2(H2O)4] ( 1), [Ca(pytza)2(H2O)2] ( 2), and [Ca(dtzeda)(H2O)2] ( 3) [Hpymtza = 5-(2-pyrimidyl)tetrazole-1-acetic acid, Hpytza = 5-(3-pyridyl)tetrazole-2-acetic acid, and H2dtzeda = 1, 2-bis(tetrazol-5-yl)ethane-N1, N1′-diacetic acid]. X-ray diffraction analysis revealed that compound 1 displays a mononuclear structure, compound 2 is a one dimensional zigzag chain structure, whereas 3 shows a three-dimensional structure. The structures were controlled by not only the different substituents of the tetrazolyl ring, but also the complementary hydrogen bonds. Furthermore, the luminescence properties of compounds 1- 3 were investigated at room temperature in the solid state. These emissions can be tentatively attributed to the ligand centered emission. [ABSTRACT FROM AUTHOR]

Reactions of the isomeric ligands Hpztza [Hpztza = 5-(2-pyrazinyl)tetrazole-2-acetic acid] and Hpmtza [Hpmtza = 5-(2-pyramidyl)tetrazole-2-acetic acid] with TbCl3 ·6H2O or DyCl3 ·6H2O under solvothermal conditions afforded four mononuclear complexes, [ Ln(pztza)2(H2O)6] ·pztza ·3H2O [ Ln = Tb ( 1), Dy ( 2)] and [ Ln(pmtza)2(H2O)6] ·Cl ·3H2O [ Ln = Tb ( 3), Dy ( 4)]. The compounds were characterized by elemental analysis, IR spectroscopy, and single-crystal X-ray diffraction. X-ray diffraction analyses reveal that all structures are mononuclear. The four compounds are self-assembled to form three-dimensional networks by hydrogen bonds. The different positions of the nitrogen atom control the coordination mode of the ligands and further influence the crystal structures. Furthermore, the luminescence properties were also investigated at room temperature in the solid state. [ABSTRACT FROM AUTHOR]

Lithium, magnesium, zinc complexes incorporating substituted symmetrical tridentate pyrrolyl ligands were synthesized conveniently and their application for the cyclotrimerization of isocyanate to corresponding isocyanurate has been investigated. The reaction of 1 equivalent of 2,5-bis(pyrrolidinomethyl)pyrrole {C 4 H 2 NH(2,5-CH 2 NC 4 H 8 ) 2 } with n-BuLi generated [Li{C 4 H 2 N(2,5-CH 2 NC 4 H 8 ) 2 }] 2 ( 1 ) in diethyl ether. Treatment of 2 equivalents of C 4 H 2 NH(2,5-CH 2 NC 4 H 8 ) 2 with MgBu 2 or ZnEt 2 in THF afforded [Mg(THF){C 4 H 2 N(2,5-CH 2 NC 4 H 8 ) 2 } 2 ] ( 2 ) or [Zn{C 4 H 2 N(2,5-CH 2 NC 4 H 8 ) 2 } 2 ] ( 3 ) in high yield, respectively. Compounds 1 , 2 and 3 were characterized by 1 H and 13 C NMR spectra and their molecular structures were determined by single crystal X-ray diffraction. Furthermore, compounds 1 , 2 and 3 were proved to be moderate to good initiators for cyclotrimerization of isocyanate to the corresponding isocyanurate in diethyl ether. [ABSTRACT FROM AUTHOR]

A series of novel N-phenylpyrazolyl aryl methanones derivatives containing the arylthio/sulfinyl/sulfonyl group have been synthesized via multi-step reactions from 3-methyl-1-phenyl-1H-pyrazol-5(4H)-one and characterized by melting point,1H NMR,13C NMR, FT-IR, and HRMS. The crystal structure of (5-(4-chlorophenylsulfonyl)-3-methyl-1-phenyl-1H-pyrazol-4-yl)(2,4-dichlorophenyl)methanone containing the arylsulfonyl moiety is reported. The biological activity results showed that some of the title compounds exhibit favorable herbicidal and insecticidal activities. [ABSTRACT FROM AUTHOR]

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH, EC: 1.2.1.12) is an essential enzyme in the glycolytic pathway. However, recent evidence demonstrates that GAPDH displays a range of new functions unrelated to its glycolytic function. GAPDH has long been known as a 3′ AU-rich element-binding protein; however, its RNA recognition mechanism is still not well understood. Here, we present the first crystal structure of GAPDH3 from Saccharomyces cerevisiae and identify its RNA-binding specificity and propose an RNA recognition model based on structural and biochemical studies. This study sheds light on the RNA-binding mechanism of GAPDH3 and contributes to a better understanding of the molecular mechanisms of its RNA-related functions. © 2014 IUBMB Life, 66(9):631-638, 2014 [ABSTRACT FROM AUTHOR]

Fivedilithium compounds containing bidentate dianionic pyrrolyl ligands,[{2-(CH3NCH2)C4H3N}Li2(TMEDA)3] (1), {[μ-η5-2-[CH3CH2NCH2]C4H3N]Li2(TMEDA)}2(2), {[μ-η5:η1-2-[(CH3)3CNCH2]C4H3N]Li2(TMEDA)}2(3), {[η5-2-[(CH3)2CHNCH2]C4H3N]Li2(TMEDA)}2(4), and{[η5-2-[(CH2)5CHNCH2]C4H3N]Li2(TMEDA)}2(5), were synthesized, and their structural features were provided.Compounds 1–5were proved to be aseries of efficient catalysts for amidation reactions of aldehydeswith amines in good to excellent yields under mild conditions. [ABSTRACT FROM AUTHOR]

Human RNA-binding protein (HuR), a ubiquitously expressed member of the Hu protein family, plays an important role in mRNA degradation and has been implicated as a key post-transcriptional regulator. HuR contains three RNA-recognition motif (RRM) domains. The two N-terminal tandem RRM domains can selectively bind AU-rich elements (AREs), while the third RRM domain (RRM3) contributes to interactions with the poly-A tail of target mRNA and other ligands. Here, the X-ray structure of two methylated tandem RRM domains (RRM1/2) of HuR in their RNA-free form was solved at 2.9 Å resolution. The crystal structure of RRM1/2 complexed with target mRNA was also solved at 2.0 Å resolution; comparisons of the two structures show that HuR RRM1/2 undergoes conformational changes upon RNA binding. Fluorescence polarization assays (FPA) were used to study the protein-RNA interactions. Both the structure and the FPA analysis indicated that RRM1 is the primary ARE-binding domain in HuR and that the conformational changes induce subsequent contacts of the RNA substrate with the inter-domain linker and RRM2 which greatly improve the RNA-binding affinity of HuR. [ABSTRACT FROM AUTHOR]

The limited and unstable interactions between potato starch (PS) and xanthan gum (XG) by simple mixing (SM) lead it difficult to induce substantial changes in starchy products. Structural unwinding and rearrangement of PS and XG by critical melting and freeze-thawing (CMFT) were used to promote PS/XG synergism, and the physicochemical, functionalities, and structural properties were investigated. Compared to "Native" and SM, CMFT promoted the formation of large clusters with a rough granular surface and wrapped by a matrix composed of released soluble starches and XG (SEM), thus making the composite more compact to thermal processes, such as the significantly decreased WSI and SP, and increased the melting temperatures. The enhanced synergism of PS/XG after CMFT effectively decreased the breakdown viscosity from ~3600 (Native) to ~300 mPa·s and increased the final viscosity from ~2800 (Native) to ~4800. CMFT significantly increased the functional properties of PS/XG composite, including water/oil absorptions and resistant starch content. CMFT caused the partial melting and loss of large packaged structures in starch (XRD, FTIR, and NMR), and the melting and the loss of crystalline structure controlled at approximately 20 % and 30 %, respectively, are the most effective for promoting PS/XG interaction. • Critical melting and freeze-thawing (CMFT) enhanced potato starch/xanthan gum (PS/XG) interaction. • Starch melting and crystalline loss controlled at ~20 % and 30 %, respectively, are the most effective. • Soluble starches released by CMFT are beneficial to promote PS/XG interchain entanglement. • CMFT increased the functional properties of starch with decreased digestibility. • CMFT effectively raised the thermal, heating, and shear stability of starch. [ABSTRACT FROM AUTHOR]

The effect of an interchain entanglement on the enhancement of starch and hydrocolloid synergism and their changes in structural and functional properties was investigated. Potato starch (PS) and xanthan gum (XG) were taken as research materials, and critical melting at the onset melting temperature of starch combined with freeze-thawing (CMFT) was used to promote interchain entanglement of PS/XG. The work suggested that CMFT effectively stabilized the aqueous mixture system of PS/XG, showing no phase separation in the water phase system, even after 12 h of storage. The PS/XG composite prepared by CMFT had significantly improved stability against acid, salt, and shear stress during the thermal process DSC demonstrated that CMFT raised the T o of composite to ∼67 from 62.79 °C for native PS. RVA suggested that when pasted in distilled water, acid, and salt solution media, the breakdown viscosity of PS/XG composite declined to ∼380, 660, and 240 from 3615, 1541, and 1114 mPa s for native PS, respectively. CMFT significantly affected the apparent dropping properties of the starch paste, displaying a shorter and more cohesive paste drop against gravity. CMFT effectively improved the gelling properties of starch, with significant improvement in apparent surface adhesion properties and texture of gels, as well as freeze-thawing stability. [Display omitted] •Critical melting and freeze-thawing (CMFT) enhanced potato starch/xanthan gum (PS/XG) synergism. •Release of soluble starches by CMFT effectively promotes interchain entanglement with XG. •Partial melting of the ordered crystalline structure is beneficial to promoting PS/XG interaction. •CMFT significantly improved the pasting and gelling properties of starch. •CMFT effectively raised the thermal, acid, salt, and shear stability of starch paste. [ABSTRACT FROM AUTHOR]

Reactions of two isomeric ligands, 5-(n-pyridyl)tetrazole-2-acetato potassium salt (Kn-pytza, n = 2,4) and PrCl 3 ·6H 2 O under solvothermal conditions, afforded three new complexes, [Pr(2-pytza)(SO 4 )(H 2 O) 3 ]·H 2 O( 1 ), [Pr(4-pytza) 3 (H 2 O) 2 ]·2H 2 O ( 2 ) and [Pr 4 (4-pytza) 5 (OH) 4 (H 2 O) 7 Cl]Cl 2 ·4H 2 O ( 3 ), whose structures are controlled by not only the different positions of the nitrogen atom of the pyridine ring but also the pH value of the solvent system. These compounds have been characterized by elemental analysis, IR and single crystal X-ray diffraction. The X-ray analysis reveals that compound 1 is a two dimensional layer structure made up of a Pr 2 O 6 binuclear unit and the tridentate bridging SO 4 2 − ligand; compound 2 is an unusual one dimensional ladder like chain structure consisting of a Pr 2 O 10 binuclear unit and 4-pytza which acts as a tetradentate ligand via the pyridine-N and the carboxylate group in a μ 1,1,3 -COO bridging mode while compound 3 is an unprecedented two dimensional network composed of a tetranuclear cubane-shaped Pr 4 (OH) 4 8 + cluster (SBU) and tridentate 4-pytza via the pyridine-N and the carboxylate group in a μ 1,3 -COO bridging mode. Various hydrogen bonds exist to assemble the 1D chains or 2D layers into 3D supramolecular network structures. Furthermore, the luminescence properties investigated at room temperature in the solid state show only intraligand emission for 1 and both intraligand and characteristic peaks of Pr 3 + for either compound 2 or 3 . [ABSTRACT FROM AUTHOR]