13C NMR longitudinal relaxation time studies of a molecular tweezers derived from a calixarene-porphyrin conjugate

Zn(II)porphyrin-substituted calix[4]arene 1 serves as molecular tweezers for 1,4-diazabicyclo[2.2.2] octane (DABCO) selectively, which led to the formation of Ensemble I. The molecular segments composing the calixarene cavity change upon inclusion of DABCO as Ensemble I were evaluated through (13)C NMR longitudinal relaxation times (T(1)) for the first time. As for Ensemble I, the 1:1 complex should be formed. The T(1) values for Ensemble I are generally smaller than those for 1: in CDCl(2)CDCl(2), DT1 = 5.03 s for C-1, 5.31 s for C-2, 0.13 s for C-3, 0.7 s for C-4, and 0.16 s for C-5. This substantiates that the rings of Ensemble I are firmly freezed because of the two-point coordination by DABCO. In 1, the T1 values for C-3 are always greater than those for C-4, and the difference between C-3 and C-4 is slight. As for Ensemble I, on the other hand, the difference between C-3 and C-4 is large. We can suggest two different motions for phenol units in 1 and Ensemble I: a rotational motion around a C-1 to C-4 axis (A) and a seesaw motion around a C-2 to C-2' axis (B). The data indicate that in Ensemble I motion (A) is predominant over motion (B). This indicates that motion (B) is specifically suppressed because of the two-point coordination interactions in Ensemble I.     

Au/Ni/Ni(OH)2/C Nanocatalyst with High Catalytic Activity and Selectivity for m-dinitrobenzene Hydrogenation

Catalysis Letters - The Au/Ni/Ni(OH)2/C bimetallic nanocatalysts with different Au loadings (Au/Ni/Ni(OH)2/C-1: 0.05 wt%Au; Au/Ni/Ni(OH)2/C-2: 0.46 wt%Au; Au/Ni/Ni(OH)2/C-3: 2.60 wt%Au) were...     

Enhanced hydrogen evolution reaction catalyzed by carbon-rich Mo4.8Si3C0.6/C/SiC nanocomposites via a PDC approach

In this study, mesoporous carbon-rich Mo_4.8Si₃C_0.6/C/SiC ceramic nanocomposites were successfully prepared via a single-source precursor route, starting from allylhydridopolycarbosilane (AHPCS, SMP-10), bis(acetylacetonato) dioxomolybdenum (VI) [MoO₂(acac)₂], and divinylbenzene (DVB). Besides, polystyrene (PS) was used as a pore former. The obtained carbon-rich single-source precursor/PS mixtures were pyrolyzed at 1100°C, and then annealed at 1350°C-1600°C to fabricate a series of carbon-rich Mo_4.8Si₃C_0.6/C/SiC ceramics comprised of high carbon content above 50 wt%. In comparison to the carbon-poor materials, the carbon-rich samples retain the higher specific surface area up to 214.6-304 m²/g at higher annealing temperatures (1350°C-1600°C) due to the enhancement of carbothermal reaction. The carbon-rich samples synthesized at 1500°C, denoted as SM/Mo/PS/DVB 2-1-4-2 1500 exhibit enhanced electrocatalytic performance with ultra-low overpotentials of 119 mV vs reversible hydrogen electrode at a current density of 10 mA cm⁻² in acidic media, which is superior to that of the Mo_4.8Si₃C_0.6/C/SiC ceramic (138 mV) with lower carbon content reported in our previous study. Therefore, our porous materials comprised of high carbon content and Nowotny phase (Mo_4.8Si₃C_0.6, NP) are considered as promising catalysts for the hydrogen evolution reaction (HER).     

Backbone and side-chain 13C and 15N signal assignments of the alpha-spectrin SH3 domain by magic angle spinning solid-state NMR at 17.6 Tesla

The backbone and side-chain 13C and 15N signals of a solid 62-residue (u-13C,15N)-labelled protein containing the alpha-spectrin SH3 domain were assigned by two-dimensional (2D) magic angle spinning (MAS) 15N-13C and 13C-13C dipolar correlation spectroscopy at 17.6 T. The side-chain signal sets of the individual amino acids were identified by 2D 13C-13C proton-driven spin diffusion and dipolar recoupling experiments. Correlations to the respective backbone nitrogen signals were established by 2D NCACX (CX=any carbon atom) experiments, which contain a proton-nitrogen and a nitrogen-carbon cross-polarisation step followed by a carbon-carbon homonuclear transfer unit. Interresidue correlations leading to sequence-specific assignments were obtained from 2D NCOCX experiments. The assignment is nearly complete for the SH3 domain residues 7-61, while the signals of the N- and C-terminal residues 1-6 and 62, respectively, outside the domain boundaries are not detected in our MAS spectra. The resolution observed in these spectra raises expectations that receptor-bound protein ligands and slightly larger proteins (up to 20 kDa) can be readily assigned in the near future by using three-dimensional versions of the applied or analogous techniques.     

Studies on the Biosynthesis of the Antibiotic Moenomycin A

Feeding experiments ( ¹³C and ¹⁵N‐labeled precursors) shed light on the biosynthetic origin of the chromophore (unit A of 1 ), the N‐acetyl groups, the 4‐C‐methyl group of the moenuronamide unit (part F of 1 ), the sugar units, and the lipid part (unit I of 1 ) of the antibiotic moenomycin A( 1 ). The lipid part is completely isoprenoid and is constructed via the non‐mevalonate pathway. The central C ₁₀ part originates from a precursor like geranyl or linalyl diphosphate and is formed by a route involving ring formation between C‐2 and C‐6 of the monoterpene unit, two successive rearrangements to give a 7‐membered ring intermediate and cleavage of the ring between C‐5 and C‐11 (moenocinol numbering).     

Reverse prenyltransferase in the biosynthesis of fumigaclavine C in Aspergillus fumigatus: gene expression, purification, and characterization of fumigaclavine C synthase FGAPT1

A putative prenyltransferase gene-fgaPT1-has been identified in the biosynthetic gene cluster of fumigaclavines in Aspergillus fumigatus AF293. The gene was cloned and overexpressed in Escherichia coli, and the His6-fusion FgaPT1 was purified to near homogeneity and characterized biochemically. The enzyme was found to convert fumigaclavine A into fumigaclavine C by attaching a dimethylallyl moiety to C-2 of the indole nucleus in a "reverse" manner, that is, by connection of C-3 of the dimethylallyl moiety to an aromatic nucleus. FgaPT1 is a soluble, dimeric protein with a subunit size of 50 kDa. K m(app) values for fumigaclavine A and dimethylallyl diphosphate were determined to be 6 and 13 microM, respectively, while the turnover number was 0.8 s(-1). Metal ions such as Mg2+ and Ca2+ are not essential for the enzymatic activity. FgaPT1 showed relatively strict substrate specificity towards fumigaclavine A, with only dimethylallyl diphosphate being accepted as a donor under our conditions. FgaPT1 is the first reverse prenyltransferase from fungi to have been purified and characterized in homogenous form after heterologous overproduction. Surprisingly, it shows very low sequence similarity to the recently identified prenyltransferase LtxC from cyanobacteria, which also catalyzes the reverse prenylation of an indole nucleus.     

The effects of pH on the molecular distribution of water soluble ruthenium(II) hydrides and its consequences on the selectivity of the catalytic hydrogenation of unsaturated aldehydes

The effect of pH on the formation and equilibrium distribution of the water soluble ruthenium hydrides [HRuCl(TPPMS)₂]₂, [HRuCl(TPPMS)₃] and [H₂Ru(TPPMS)₄] (TPPMS=(3-sulfonatophenyl)diphenylphosphine sodium salt) was studied in aqueous solution by pH-potentiometric and

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and

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NMR methods. Depending on the pH, [RuCl₂(TPPMS)₂]₂ and its hydrido-derivatives hydrolyse extensively, giving rise to formation of hydroxo-ruthenium complexes. It was established that at pH≤3.3 the dominant ruthenium(II) species was [HRuCl(TPPMS)₃], while at pH≥7 it was [H₂Ru(TPPMS)₄]. While [HRuCl(TPPMS)₃] catalyzed the slow, selective hydrogenation of the C=C bond in trans-cinnamaldehyde, [H₂Ru(TPPMS)₄] was found an active and selective catalyst for C=O reduction. Consequently, the selectivity of the hydrogenation of trans-cinnamaldehyde could be completely inverted by minor changes in the solution pH, shifting the equilibrium between [HRuCl(TPPMS)₃] and [H₂Ru(TPPMS)₄].     

A Novel Mouse Monoclonal Antibody C42 against C-Terminal Peptide of Alpha-1-Antitrypsin

The C-terminal-fragments of alpha1-antitrypsin (AAT) have been identified and their diverse biological roles have been reported in vitro and in vivo. These findings prompted us to develop a monoclonal antibody that specifically recognizes C-36 peptide (corresponding to residues 359–394) resulting from the protease-associated cleavage of AAT. The C-36-targeting mouse monoclonal Immunoglobulin M (IgM) antibody (containing κ light chains, clone C42) was generated and enzyme-linked immunosorbent assay (ELISA)-tested by Davids Biotechnologie GmbH, Germany. Here, we addressed the effectiveness of the novel C42 antibody in different immunoassay formats, such as dot- and Western blotting, confocal laser microscopy, and flow cytometry. According to the dot-blot results, our novel C42 antibody detects the C-36 peptide at a range of 0.1–0.05 µg and shows no cross-reactivity with native, polymerized, or oxidized forms of full-length AAT, the AAT-elastase complex mixture, as well as with shorter C-terminal fragments of AAT. However, the C42 antibody does not detect denatured peptide in SDS-PAGE/Western blotting assays. On the other hand, our C42 antibody, unconjugated as well as conjugated to DyLight488 fluorophore, when applied for immunofluorescence microscopy and flow cytometry assays, specifically detected the C-36 peptide in human blood cells. Altogether, we demonstrate that our novel C42 antibody successfully recognizes the C-36 peptide of AAT in a number of immunoassays and has potential to become an important tool in AAT-related studies.     

But-3-ene-1,2-diol: a mechanism-based active site inhibitor for coenzyme B12-dependent glycerol dehydratase

Coenzyme B(12)-dependent glycerol dehydratase is a radical enzyme that catalyses the conversion of glycerol into 3-hydroxypropanal and propane-1,2-diol into propanal via enzyme-bound intermediate radicals. The substrate analogue but-3-ene-1,2-diol was studied in the expectation that it would lead to the 4,4-dihydroxylbut-2-en-1-yl radical, which is stabilised (allylic) and not reactive enough to retrieve a hydrogen atom from 5'-deoxyadenosine, thereby interrupting the catalytic cycle. Racemic and enantiomerically pure but-3-ene-1,2-diols and their [1,1-(2)H(2)], [2-(2)H] and [4,4-(2)H(2)] isotopomers were synthesised and characterised by NMR spectroscopy. (S)-[4-(14)C]but-3-ene-1,2-diol was also prepared. Kinetic measurements showed but-3-ene-1,2-diol to be a competitive inhibitor of glycerol dehydratase (K(i)=0.21 mM, k(i)=5.0x10(-2) s(-1)). With [4-(14)C]but-3-ene-1,2-diol it was demonstrated that species derived from the diol become tightly bound to the enzyme's active site, but not covalently bound, because the radioactivity could be removed upon denaturation of the enzyme. EPR measurements with propane-1,2-diol as substrate generated sharp signals after 10 s that disappeared after about 1 min. In contrast, EPR resonances appeared and disappeared more slowly when but-3-ene-1,2-diol was incubated with the enzyme. Among the deuterated isotopomers, only [1,1-(2)H(2)]but-3-ene-1,2-diol showed a significantly different EPR spectrum from that of the unlabelled diol; this indicated that coupling between the unpaired electron and a deuterium at C-1 was stronger than with deuterium at C-2 or C-4. The experiments suggest the formation of the 1,2-dihydroxybut-3-en-1-yl radical, which decomposes to unidentified product(s).     

Ultrasound-assisted synthesis of santalbic acid and a study of triacylglycerol species inSantalum album (Linn.) seed oil

Methyl ricinoleate (1) was treated with bromine and the dibromo derivative (2) was reacted with ethanolic KOH under ultrasonic irradiation to give 12-hydroxy-octadec-9-ynoic acid upon acidification with dil. HCl. The latter compound was methylated with BF₃/methanol to give methyl 12-hydroxy-octadec-9-ynoate (3). Compound3 was treated with methanesulfonyl chloride in the presence of triethylamine in CH₂Cl₂ to give methyl 12-mesyloxy-octadec-9-ynoate (4). Reaction of methyl 12-mesyloxy-octadec-9-ynoate with aqueous KOH under ultrasonic irradiation (20 kHz) gave (11E)-octadecen-9-ynoic acid (5, santalbic acid, 40%) and (11Z)-octadecen-9-ynoic acid (6, 60%) on acidification with dil. HCl. These isomers were separated by urea fractionation. The¹³C nuclear magnetic resonance (NMR) spectroscopic properties of the methyl ester and the triacylglycerol (TAG) esters of these enynoic fatty acid isomers were studied. The carbon shifts of the unsaturated carbon nuclei of the methyl ester of theE-isomer were unambiguously assigned as 88.547 (C-9), 79.287 (C-10), 109.760 (C-11), and 143.450 (C-12) ppm while the unsaturated carbon shifts of the (Z)-enynoate isomer appeared at 94.277 (C-9), 77.561 (C-10), 109.297 (C-11), and 142.668 (C-12) ppm. In the¹³C NMR spectral analysis of the TAG molecules of type AAA containing either the (Z)-or (E)-enyne fatty acid, the C-1 to C-6 carbon atoms on the α- and β-acyl positions were differentiated. The unsaturated carbon atoms in the α- and β-acyl chains were also resolved into two signals except that of the C-11 olefinic carbon. Sandal (Santalum album) wood seed oil (a source of santalbic acid) was separated by silica chromatography into three fractions. The least polar fraction (7.2 wt%) contained TAG which had a random distribution of saturated and unsaturated fatty acids, of which oleic acid (69%) was the predominant component. The second fraction (3.8 wt%) contained santalbic acid (58%) and oleic acid (28%) together with some other normal fatty acids. Santalbic acid in this fraction was found in both the α- and β-acyl positions of the glycerol “backbone”. The most polar fraction (89 wt%) consisted of TAG containing santalbic acid only. The distribution of the various fatty acids on the glycerol “backbone” was supported by the results from the¹³C NMR spectroscopic analysis.     

Effect of Dispersion Condition of Calcium Carbonate on the Crystallization and Melting Behavior of Polypropylene/CaCO3 Nanocomposites

Polypropylene/calcium carbonate (PP/CaCO₃) nanocomposites were prepared by melt compounding (C-1) and novel compounding process (C-2), respectively. Scanning electronic microscope (SEM) results illustrated that CaCO₃ nanoparticles were well dispersed at nanoscale in C-2, whereas the nanoparticles were mostly aggregate in C-1. Differential scanning calorimetry (DSC) measurements indicated the onset crystallization temperature was increased by 11.4°C and the supercooling wasdecreased by 13.68°C in C-2. A faster crystallization rate, a higher melting point, and a higher degree of crystallization in C-2 were also detected. Polarization light microscope (PLM) photographs showed the spherulites sizes of C-2 were 60 mm, whereas common spherulites with an average size of about 200 mm were observed in both pure PP and C-1. These phenomena demonstrated that the well-dispersed CaCO₃ nanoparticles could result in heterogeneous nucleation effect on PP even at quite low loading Q2 (1.5% wt.).     

醇醚羧酸盐的工业应用性能研究

醇醚羧酸及其盐（简称AEC）对15%的强酸、4%的烧碱和H2O2氧化剂稳定，200mg/L-500mg/L的水硬度不影响其溶液稳定性，EO加合数为9的AE9C综合性能更佳，能耐受12%的烧碱，在饱和的MgCl2、CaCl2、NaCl水溶液中能形成稳定透明溶液，而电解质和耐硬水性能优异，AE9C的水溶液（2%）在240℃依然稳定，具有很高的工业应用价值，酸型产品AE9C-H对石蜡的乳化能力和对苯的增溶量分别为3.62min和3.3mL，高盐型产品AE9C-Na的对应值2.28min和1.1,而低EO加合数的AE3C-Na具有更好的润湿性能。     

Design,synthesis, structure,and stability of novel multi-principal element (Ti,Zr,Hf,W)C ceramic with a miscibility gap

Here we design a novel multi-principal element carbide system (Ti,Zr,Hf,W)C with a miscibility gap using computational tools and report on the formation of a single-phase (Ti,Zr,Hf,W)C after spark plasma sintering. The (Ti,Zr,Hf,W)C shows high nanohardness (32.7 GPa) and fracture toughness (5 MPa·m^1/2). Aging studies at 1350 °C for 100 h show that the single-phase carbide solid solution is quite stable even though this temperature is within the predicted miscibility gap of the system. Detailed electron microscopy characterization shows that phase separation has initiated with minor decomposition after aging by forming rock-salt (Ti,W)C- and (Zr,Hf)C-rich phases as well as hexagonal WC precipitates. We show that the (Ti,W)C- and (Zr,Hf)C-rich phases form a lamellar structure upon aging and the interlamellar spacing is considerably coarser than what has been previously found for the binary (Ti,Zr)C system. The decomposition kinetics, on the other hand, is sluggish due to the reduced driving force for phase decomposition.     

Evaluation of Benzo[c]Chrysene Dihydrodiols in the Morphological Cell Transformation of Mouse Embryo Fibroblast C3H10T1/2CL8 Cells

The morphological cell transforming activities of three dihydrodiols of benzo[c]chrysene (B[c]C), trans?B[c]C-7,8-diol, trans?B[c]C-9,10-diol, and trans?B[c]C-1,2-diol were compared to those of B[c]C in order to study the possible routes of metabolic activation in transformable C3H10T1/2 mouse embryo fibroblasts. B[c]C-treated C3H10T1/2 cells exhibited a concentration-related increase in morphologically transformed foci over a concentration range of 0–3 μg/ml. At 3 μg/ml, B[c]C induced 1.23 Type II & III foci/dish, with 73% of the dishes exhibiting Type II or Type III foci, and a survival of 87%. trans?B[c]C-7,8-diol produced concentration-related responses over a range of 0–5 μg/ml. At 3 μg/ml, trans?B[c]C-7,8-diol produced 1.13 Type II & III foci/dish with 72% of the dishes exhibiting foci, and a survival of 76%. trans?B[c]C-9,10-diol was inactive as a morphological cell transforming agent over a concentration range of 0–3 μg/ml. trans?B[c]C-1,2-diol was also inactive as a morphological cell transforming agent over a concentration range of 0–3 μg/ml. These results suggest that a K-region dihydrodiol of B[c]C, trans?B[cC-7,8-diol, may play a role in the ability of B[c]C to morphologically transform C3H10T1/2 cells.     

Interaction of ceria and ytterbia in air within temperature range 1500 – 600 °C

Phase equilibria and structure transformations in the CeO₂–Yb₂O₃ system have been studied in air within the temperature range 1500 - 600 °C in the full concentration range using X-ray diffraction analysis (XRD) and petrography methods. It was established that the system is characterized by the formation of solid solutions on the basis of cubic modification of Yb₂O₃ (C- type) and fluorite CeO₂ (F- type) separated by two-phase (F + C) region. The systematic study that covered whole composition range excluded formation of new phases. Solubility limits and concentration dependences of lattice parameters were determined for the phases forming in the system.     

不同体系Pd/C催化剂的制备及对甲酸的电催化氧化

采用不同体系制备了碳载Pd催化剂(Pd/C),发现在乙二醇体系中制备的Pd/C催化剂对甲酸氧化具有最负的峰电位和最低的起始氧化电位,Tafel斜率最小为155mV,并且在1h的计时电流曲线测试表明,用乙二醇体系制备的Pd/C-3催化剂具有较高的稳定电流。TEM结果可以看出,用乙二醇体系制备的Pd/C催化剂Pd粒子在活性碳表面分散得最好,Pd粒径的大小约为4～5nm。     

Oxazoline-Containing Phosphazene Derivatives Part II Polymer Preparation and Modification Through the Reactivity of Oxazoline Moieties on Cyclophosphazenes

   In this paper we report the synthesis, the characterization and the practical utilization of two cyclophosphazenes (CPs) substituted with two (C-2-OXA) and six (C-6-OXA) 2-(4-hydroxyphenyl)-2-oxazoline groups, respectively. The first chemical observation on these substrates is that the reactivity of the oxazoline groups is preserved even when these products are attached to the phosphorus atoms of a cyclophosphazene ring. By reaction of C-2-OXA with organic molecules, e.g. adipic acid, and macromolecules, e.g. poly(ethylene terephthalate) (PET), the oxazoline substituents open their heterocycles to form cyclolinear polymers or to act as chain extenders. Similarly, the ring-opening polymerization reaction of C-6-OXA in the presence of cationic initiators allows the production of a new class of cyclomatrix polymers. The characterization of the new materials is reported. Dedicated to Prof. C.W.Allen     

Characterization of the biosynthesis gene cluster for alkyl-O-dihydrogeranyl-methoxyhydroquinones in Actinoplanes missouriensis

A polyketide biosynthesis gene cluster (agq) was found on the genome of a rare actinomycete, Actinoplanes missouriensis. Streptomyces lividans expressing agqA encoding a type III polyketide synthase produced alkylresorcinols mainly from C(16-17) fatty acids. Heterologous expression of the agq genes in S. lividans indicated the function of cognate polyketide modification enzymes; a monooxygenase AgqB hydroxylates the alkylresorcinols to yield 6-alkyl-2-hydroxyhydroquinones, a methyltransferase AgqC catalyzes O-methylation of the alkyl-hydroxyhydroquinones to yield 6-alkyl-2-methoxyhydroquinones, and a UbiA-like prenyltransferase AgqD attaches a prenyl group to the C-4 hydroxy group of the alkyl-methoxyhydroquinones to yield 6-alkyl-4-O-geranyl-2-methoxyhydroquinones and 6-alkyl-4-O-dihydrofarnesyl-2-methoxyhydroquinones derived from C(16-17) fatty acids. In contrast, A. missouriensis was found to produce 6-alkyl-4-O-dihydrogeranyl-2-methoxyhydroquinones derived from C(16-18) fatty acids by the function of the agq gene cluster. All of these prenylated phenolic lipids were novel compounds.     

Palladium(0) allylic alkylation in a two-phase system or with a supported aqueous phase catalyst

The reaction of allylic carbonates with various acyclic and cyclic carbonucleophiles is catalyzed by the system Pd(OAc)₂ and P(C₆H₄-m-SO₃Na)₃ (or tppts) in a two-phase liquid medium H₂O-nitrile, the activity of the catalyst depending mainly on the nature of the nitrile, the temperature of the reaction and the ratio palladium/tppts. The same system Pd(OAc)₂ and P(C₆H₄-m-SO₃Na)₃ supported on silica catalyzes also this reaction. The formation of the active palladium species in the two cases is followed by

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NMR spectroscopy and discussed.     

C-9石油树脂化学结构的波谱分析

利用傅里叶红外光谱(FT-IR)、热解气相色谱-质谱(Py/GC-MS)等测试手段对C-9石油树脂进行表征,以期获得有关石油树脂大分子链骨架、侧链、特征基团等结构信息。结果表明:C-9石油树脂大分子链是以苯乙烯、(邻,间,对)-甲基苯乙烯、双环戊二烯、茚、甲基茚等结构单元为主体的弱极性物质,分子链上存在烯烃双键。这样的结构特征也使C-9石油树脂的主体碳链连结着丰富的苯系支链而具良好的粘结性能,另外石油树脂大分子链上的烯烃双键为活性基团的引入提供了可能。