bluuebunny/crossref_metadata_2025 huggingface dataset:
Enhanced Water Splitting at Thin Film Tungsten Trioxide Photoanodes Bearing Plasmonic Gold–Polyoxometalate Particles
Authors: Solarska Renata , Bienkowski Krzysztof , Zoladek Sylwia , Majcher Aldona , Stefaniuk Tomasz , Kulesza Pawel J. , Augustynski Jan
Published: October 2014

Tungsten trioxide (WO3) is one of a few stable semiconductor materials liable to produce solar fuel by photoelectrochemical water splitting. To enhance its visible light conversion efficiency, we incorporated plasmonic gold nanoparticles (Au NPs) derivatized with polyoxometalate (H3PMo12O40) species into WO3. The combined plasmonic and catalytic effect of Au NPs anchored to the WO3 surface resulted in a large increase of water photooxidation currents. Shielding the Au NPs with polyoxometalates appears to be an effective means to avoid formation of recombination centers at the photoanode surface.
Synthesis of Triazenes with Nitrous Oxide
Authors: Kiefer Gregor , Riedel Tina , Dyson Paul J. , Scopelliti Rosario , Severin Kay
Published: October 2014

Triazenes are valuable compounds in organic chemistry and numerous applications have been reported. Furthermore, triazenes have been investigated extensively as potential antitumor drugs. Here, we describe a new method for the synthesis of triazenes. The procedure involves a reagent which is rarely used in synthetic organic chemistry: nitrous oxide (N2O, “laughing gas”). Nitrous oxide mediates the coupling of lithium amides and organomagnesium compounds while serving as a nitrogen donor. Despite the very inert character of nitrous oxide, the reactions can be performed in solution under mild conditions. A key advantage of the new procedure is the ability to access triazenes with alkynyl and alkenyl substituents. These compounds are difficult to prepare by conventional methods because the required starting materials are unstable. Some of the new alkynyltriazenes were found to display high cytotoxicity in in vitro tests on ovarian and breast cancer cell lines.
Mild Silver‐Mediated Geminal Difluorination of Styrenes Using an Air‐ and Moisture‐Stable Fluoroiodane Reagent
Authors: Ilchenko Nadia O. , Tasch Boris O. A. , Szabó Kálmán J.
Published: October 2014

An air‐ and moisture‐stable fluoroiodane in the presence of AgBF4 is suitable for selective geminal difluorination of styrenes under mild reaction conditions. One of the CF bonds is formed by transfer of electrophilic fluorine from the hypervalent iodine reagent, while the other one arises from the tetrafluoroborate counterion of silver. Deuterium‐isotope‐labelling experiments and rearrangement of methyl styrene substrates suggest that the reaction proceeds through a phenonium ion intermediate.
Polymer‐anchored Ru(II) complex as an efficient catalyst for the synthesis of primary amides from nitriles and of secondary amides from alcohols and amines
Authors: Islam Sk Manirul , Ghosh Kajari , Singha Roy Anupam , Molla Rostam Ali
Published: October 2014

A polymer‐anchored ruthenium(II) catalyst was synthesized and characterized. Its catalytic activity was evaluated for the preparation of primary amides from aqueous hydration of nitriles in neutral condition. A range of nitriles were successfully converted to their corresponding amides in good to excellent yields. The catalyst was also effective in the preparation of secondary amides from the coupling of alcohols and amines. The catalyst can be facilely recovered and reused six times without a significant decrease in its activity. Copyright © 2014 John Wiley & Sons, Ltd.
Inorganic–organic hybrid materials prepared from zirconium oxo‐clusters and 2‐hydroxyethyl methacrylate
Authors: Girardi Fabrizio , Fambri Luca , Maggini Simona , Di Maggio Rosa
Published: October 2014

This article describes the preparation and characterization of hybrid materials obtained from the polymerization of vinyl‐substituted zirconium oxo‐clusters [Zr6O4(OH)4(OOCCH2CHCH2)12(n‐PrOH)]2·4(CH2CHCH2COOH) (Zr12) and 2‐hydroxyethyl methacrylate (HEMA). The zirconium oxo‐clusters serve as cross‐linking agents, forming a 3D network by means of the copolymerization of their vinylic ligands with HEMA. To optimize the conditions for cross‐linking, the polymerization was monitored with a differential scanning calorimeter. The resulting hybrid materials were also characterized using thermo‐mechanical techniques. There was evidence not only of a greater rigidity above Tg, but also of a better thermal stability for several hybrid formulations than for simple poly‐2‐hydroxyethyl methacrylate. After immersion in water, the hybrids containing 20 or 60% w/w zirconium oxo‐clusters also showed a stable behavior with an equilibrium swelling at about 27 and 18% w/w of water, respectively. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41568.
Listeria monocytogenes repellence by enzymatically modified PES surfaces
Authors: van der Veen Stijn , Nady Norhan , Franssen Maurice C. R. , Zuilhof Han , Boom Remko M. , Abee Tjakko , Schroën Karin
Published: October 2014

The effect of enzyme‐catalyzed modification of poly(ethersulfone) (PES) on the adhesion and biofilm formation of two Listeria monocytogenes strains is evaluated under static and dynamic flow conditions. PES has been modified with gallic acid, ferulic acid and 4‐hydroxybenzoic acid. The surfaces modified with any of these compounds show up to 70% reduced adhesion of L. monocytogenes under static conditions and up to 95% under dynamic flow conditions compared with unmodified surfaces. Also, under static conditions the formation of biofilms is reduced by ∼70%. These results indicate that the brush structures that are formed by the polymers on the PES surface directly influence the ability of microorganisms to interact with the surface, thereby reducing attachment and biofilm formation of L. monocytogenes. Based on these results, it is expected that enzyme‐catalyzed surface modification is a promising tool to reduce microbial adhesion and biofilm formation. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41576.
Are Vibrissae Viable Sensory Structures for Prey Capture in Northern Elephant Seals, Mirounga angustirostris?
Authors: Mcgovern Kristen A. , Marshall christopher D. , Davis Randall W.
Published: October 2014

Little is known about the tactics northern elephant seals (NES) use to capture prey due to the difficulties in observing these animals underwater. NES forage on vertically migrating prey at depths >500 m during day and at night where light levels are negligible. Although NES have increased visual sensitivity in deep water, vision is likely a limited sensory modality. Still images of NES foraging show that the mystacial vibrissae are protracted before prey capture. As a representative phocid, harbor seals can follow hydrodynamic trails using their vibrissae, and are highly sensitive to water velocity changes. In lieu of performance data, vibrissal innervation can be used as a proxy for sensitivity. Although comparative data are few, seals average 1,000 to 1,600 axons per vibrissa (five to eight times more than terrestrial mammals). To test the hypothesis that NES have increased innervation as other pinnipeds, vibrissae from the ventral‐caudal mystacial field from nine individuals were sectioned and stained for microstructure (trichrome) and innervation (Bodian silver stain). Follicles were tripartite and consisted of lower and upper cavernous sinuses separated by a ring sinus containing an asymmetrical ringwulst. The deep vibrissal nerve penetrated the follicular capsule at the base, branched into several bundles, and coursed through the lower cavernous sinus to the ring sinus. Axons in the ring sinus terminated in the ringwulst and along the inner conical body. NES averaged 1,584 axons per vibrissa. The results add to the growing body of evidence that phocids, and perhaps all pinnipeds, possess highly sensitive mystacial vibrissae that detect prey. Anat Rec, 298:750–760, 2015. © 2014 Wiley Periodicals, Inc.
Synthesis of Quaternary‐Carbon‐Containing and Functionalized Enantiopure Pentanecarboxylic Acids from Biocatalytic Desymmetrization of meso‐Cyclopentane‐1,3‐Dicarboxamides
Authors: Ao Yu‐Fei , Wang De‐Xian , Zhao Liang , Wang Mei‐Xiang
Published: October 2014

Catalyzed by Rhodococcus erythropolis AJ270, a nitrile hydratase–amidase containing microbial whole‐cell catalyst under mild conditions, enantioselective desymmetrizations of meso‐cyclopentane‐1,3‐dicarbonitriles and cyclopentane‐1,3‐dicarboxamides were studied. Although the nitrile hydratase was found to exhibit high enzymatic activity, but low 1R enantioselectivity toward dinitriles, a number of 2,2‐unsymmetrically substituted meso‐cyclopentane‐1,3‐dicarboxamide substrates were converted by the 1S enantioselective amidase into quaternary carbon‐bearing enantiopure (1S,2R,3R)‐3‐carbamoylcyclopentanecarboxylic acids in yields up to 94 %. The application of the method was demonstrated by convenient and practical transformations of the resulting (1S,2R,3R)‐2‐allyl‐3‐carbamoylcyclopentanecarboxylic acid derivatives into functionalized cyclopentane‐fused δ‐lactam and δ‐lactone compounds.
Influence of the boreal spring Southern Annular Mode on summer surface air temperature over northeast China
Authors: Zheng Fei , Li Jianping , Clark Robin T. , Ding Ruiqing , Li Fei , Wang Lei
Published: October 2014

Previous evidence has showed that the boreal spring Southern Annular Mode (SAM) regulates summer monsoon precipitation in East Asian subtropics through the Northern Indian Ocean sea surface temperature (NIO SST). This paper further demonstrates how a positive (negative) boreal spring SAM is usually followed by a warmer (cooler) summer over northeast China (NEC), suggesting impacts of the SAM even extend to the northern mid‐latitudes. A positive spring SAM usually leads to anomalous anticyclonic sinking motion over NEC during summer through the NIO SST, which results in cloud reduction and changes in radiation, and thus surface warming.
Synthesis, phase evolution and optical properties of Tb3+‐doped KF–YbF3 system materials
Authors: Cao Chunyan , Cao Renping , Guo Siling , Xie An. , Noh Hyeon Mi. , Jeong Jung Hyun
Published: October 2014

KF–YbF3 system materials have been synthesized by a hydrothermal method without any surfactant or template. By controlling the reactant ratios of KF:Yb3+, the hydrothermal temperature and the pH of the prepared solutions, the final products can evolve among the orthorhombic phase of YbF3, the cubic phase of KYb3F10 and the cubic phase of KYbF4. The X‐ray diffraction (XRD) patterns of the samples prove the phase evolution of the final products. The morphologies of the samples were characterized using field emission scanning electron microscopy (FE‐SEM) images and the evolution of the morphology is consistent with that of the crystalline phases. The optical properties of Tb3+ in the samples were characterized by PL excitation and emission spectra, as well as luminescent decay curves. Copyright © 2014 John Wiley & Sons, Ltd.
D‐Amino acids inhibit initial bacterial Adhesion: Thermodynamic evidence
Authors: Xing Su‐Fang , Sun Xue‐Fei , Taylor Alicia A. , Walker Sharon L. , Wang Yi‐Fu , Wang Shu‐Guang
Published: October 2014

Bacterial biofilms are structured communities of cells enclosed in a self‐produced hydrated polymeric matrix that can adhere to inert or living surfaces. D‐Amino acids were previously identified as self‐produced compounds that mediate biofilm disassembly by causing the release of the protein component of the polymeric matrix. However, whether exogenous D‐amino acids could inhibit initial bacterial adhesion is still unknown. Here, the effect of the exogenous amino acid D‐tyrosine on initial bacterial adhesion was determined by combined use of chemical analysis, force spectroscopic measurement, and theoretical predictions. The surface thermodynamic theory demonstrated that the total interaction energy increased with more D‐tyrosine, and the contribution of Lewis acid–base interactions relative to the change in the total interaction energy was much greater than the overall nonspecific interactions. Finally, atomic force microscopy analysis implied that the hydrogen bond numbers and adhesion forces decreased with the increase in D‐tyrosine concentrations. D‐Tyrosine contributed to the repulsive nature of the cell and ultimately led to the inhibition of bacterial adhesion. This study provides a new way to regulate biofilm formation by manipulating the contents of D‐amino acids in natural or engineered systems. Biotechnol. Bioeng. 2015;112: 696–704. © 2014 Wiley Periodicals, Inc.
Engineering a horseradish peroxidase C stable to radical attacks by mutating multiple radical coupling sites
Authors: Kim Su Jin , Joo Jeong Chan , Song Bong Keun , Yoo Young Je , Kim Yong Hwan
Published: October 2014

Peroxidases have great potential as industrial biocatalysts. In particular, the oxidative polymerization of phenolic compounds catalyzed by peroxidases has been extensively examined because of the advantage of this method over other conventional chemical methods. However, the industrial application of peroxidases is often limited because of their rapid inactivation by phenoxyl radicals during oxidative polymerization. In this work, we report a novel protein engineering approach to improve the radical stability of horseradish peroxidase isozyme C (HRPC). Phenylalanine residues that are vulnerable to modification by the phenoxyl radicals were identified using mass spectrometry analysis. UV‐Vis and CD spectra showed that radical coupling did not change the secondary structure or the active site of HRPC. Four phenylalanine (Phe) residues (F68, F142, F143, and F179) were each mutated to alanine residues to generate single mutants to examine the role of these sites in radical coupling. Despite marginal improvement of radical stability, each single mutant still exhibited rapid radical inactivation. To further reduce inactivation by radical coupling, the four substitution mutations were combined in F68A/F142A/F143A/F179A. This mutant demonstrated dramatic enhancement of radical stability by retaining 41% of its initial activity compared to the wild‐type, which was completely inactivated. Structure and sequence alignment revealed that radical‐vulnerable Phe residues of HPRC are conserved in homologous peroxidases, which showed the same rapid inactivation tendency as HRPC. Based on our site‐directed mutagenesis and biochemical characterization, we have shown that engineering radical‐vulnerable residues to eliminate multiple radical coupling can be a good strategy to improve the stability of peroxidases against radical attack. Biotechnol. Bioeng. 2015;112: 668–676. © 2014 Wiley Periodicals, Inc.
Clearance of the rodent retrovirus, XMuLV, by protein A chromatography
Authors: Bach Julia , Connell‐Crowley Lisa
Published: October 2014

Protein A chromatography is the most common unit operation used in the manufacture of therapeutic monoclonal antibodies (mAbs) due to its high affinity and specificity for the IgG Fc domain. However, protein A chromatography is often not effective for viral clearance. Typical log reduction values (LRV) for the model retrovirus XMuLV range between 1 and 4 logs, while effective steps such as viral filtration can achieve 5–7 logs of clearance. XMuLV LRVs obtained on protein A are reproducible for a given mAb, but can vary widely for different mAbs, even with the same operating conditions. In order to understand the mechanism of XMuLV clearance on protein A, we have investigated its partitioning on Mabselect SuRe protein A resin and explored how the virus interacts with resin, product, and impurities. The results show that XMuLV has some interaction with the resin backbone and ligand, but also appears to bind to and coelute with the mAb. The interaction with product was further examined by evaluating the effect of feed conditions, loading, and different washes on XMuLV partitioning on the column. Understanding the mechanism of XMuLV removal on a protein A, resin provides insight into the variability and low viral clearance of this step and suggests ways in which the removal of virus by this step can be improved. Biotechnol. Bioeng. 2015;112: 743–750. © 2014 Wiley Periodicals, Inc.
Long‐term three‐dimensional perfusion culture of human adult bone marrow mononuclear cells in bioreactors
Authors: Schmelzer Eva , Finoli Anthony , Nettleship Ian , Gerlach Jörg C.
Published: October 2014

The construction and long‐term maintenance of three‐dimensional in vitro bone marrow models is of great interest but still quite challenging. Here we describe the use of a multi‐compartment hollow‐fiber membrane based three‐dimensional perfusion bioreactor for long‐term culture of whole human bone marrow mononuclear cells. We also investigated bioreactors with incorporated open‐porous foamed hydroxyapatite scaffolds, mimicking the in vivo bone matrix. Cells in bioreactors with and without scaffolds were cultured to 6 weeks and compared to Petri dish controls. Cells were analyzed for gene expression, surface markers by flow cytometry, metabolic activity, hematopoietic potential, viability, and attachment by immunocytochemistry. Cells in bioreactors were metabolic active during long‐term culture. The percentages of hematopoietic stem cell and mature endothelial cell fractions were maintained in bioreactors. The expression of most of the analyzed genes stabilized and increased after long‐term culture of 6 weeks. Compared to Petri dish culture controls, bioreactor perfusion culture improved in both the short and long‐term, the colony formation unit capacity of hematopoietic progenitors. Cells attached to the ample surface area provided by hydroxyapatite scaffolds. The implementation of a hydroxyapatite scaffold did not influence colony formation capacity, percentages of cell type specific fractions, gene expression, cell viability or metabolic turnover when compared to control cells cultured in bioreactors without scaffolds. In conclusion, three‐dimensional perfusion bioreactor culture enables long‐term maintenance of primary human bone marrow cells, with hydroxyapatite scaffolds providing an in vivo‐like scaffold for three‐dimensional culture. Biotechnol. Bioeng. 2015;112: 801–810. © 2014 Wiley Periodicals, Inc.
Shear stress upregulates IL‐1β secretion by Chlamydia pneumoniae‐ infected monocytes
Authors: Cheeniyil Aswathi , Evani Shankar J. , Dallo Shatha F. , Ramasubramanian Anand K.
Published: October 2014

Infectious agents are increasingly implicated in the development and progression of chronic inflammatory diseases. Several lines of evidence suggest that the common intracellular respiratory pathogen, Chlamydia pneumoniae contributes to the well‐established risk factors of atherosclerosis but the exact mechanism is not well understood. It is believed that C. pneumoniae‐infected monocytes travel from the lung to the atherosclerotic foci, during which the cells experience mechanical stimuli due to blood flow. In this work, we characterized the effect of physiological levels of shear stress on C. pneumoniae‐infected human monocytes in an in vitro flow model. We found that a shear stress of 5 dyn/cm2 enhanced the expression of pro‐inflammatory cytokine IL‐1β only in infected, but not in uninfected, monocytes. We also found that this enhancement is due to the upregulation of IL‐1β gene expression due to shear stress. Our results demonstrate that mechanotransduction is an important, heretofore unaddressed, determinant of inflammatory response to an infection. Biotechnol. Bioeng. 2015;112: 838–842. © 2014 Wiley Periodicals, Inc.
Prognosis according to histochemical analysis of liver metastases removed at liver resection
Authors: Brunner S M , Kesselring R , Rubner C , Martin M , Jeiter T , Boerner T , Ruemmele P , Schlitt H J , Fichtner-Feigl S
Published: October 2014

Background

Liver metastases occur in 40–50 per cent of patients with colorectal cancer and determine long-term survival. The aim of this study was to examine the immunological architecture of colorectal liver metastases and its impact on patient survival.

Methods

Specimens from patients with colorectal liver metastases were stained with haematoxylin and eosin and Masson trichrome, immunostained for α-smooth muscle actin, CD4, CD45RO and CD8, and analysed by flow cytometry. In addition to histomorphological evaluation, immunohistochemically stained sections were analysed for cell numbers in the tumour area, infiltrative margin and distant liver stroma separately. These findings were correlated with clinical data and patient outcome.

Results

Tumour containment by a fibrotic capsule around liver metastases was observed in 37·8 per cent of 201 patients and was prognostic for improved survival (median (s.e.) survival 64 (6) and 31 (4) months for patients with capsule and no capsule respectively; P < 0·001) and independently led to higher R0 resection rates (P = 0·040). In multivariable analysis, CD45RO+ cell infiltration at the peritumoral margin with low CD45RO+ cell infiltration in the distant liver stroma (P = 0·001) and fibrotic capsule formation (P = 0·008) both independently prolonged patient survival. Using these two factors, a cellular immune score was designed and shown to stratify patient survival in test and validation samples (both P < 0·001).

Conclusion

Fibrotic capsule formation and localized cell infiltration of colorectal liver metastases by CD45RO+ cells were related to prolonged patient survival. Based on these immunological criteria a cellular immune score was developed to stratify patients according to prognosis.
Outcomes after implementing a tailored endoscopic step-up approach to walled-off necrosis in acute pancreatitis
Authors: Bang J Y , Holt B A , Hawes R H , Hasan M K , Arnoletti J P , Christein J D , Wilcox C M , Varadarajulu S
Published: October 2014

Background

The aim of the study was to compare the outcomes of patients with pancreatic or peripancreatic walled-off necrosis by endoscopy using the conventional approach versus an algorithmic approach based on the collection size, location and stepwise response to intervention.

Methods

This was an observational before–after study of consecutive patients managed over two time intervals. In the initial period (2004–2009) symptomatic patients with walled-off necrosis underwent conventional single transmural drainage with placement of two stents and a nasocystic catheter, followed by direct endoscopic necrosectomy, if required. In the later period (2010–2013) an algorithmic approach was adopted based on size and extent of the walled-off necrosis and stepwise response to intervention. The main outcome was treatment success, defined as a reduction in walled-off necrosis size to 2 cm or less on CT after 8 weeks.

Results

Forty-seven patients were treated in the first interval and 53 in the second. There was no difference in patient demographics, clinical or walled-off necrosis characteristics and laboratory parameters between the groups, apart from a higher proportion of women and Caucasians in the later period. The treatment success rate was higher for the algorithmic approach compared with conventional treatment (91 versus 60 per cent respectively; P < 0·001). On multivariable logistic regression, management based on the algorithm was the only predictor of treatment success (odds ratio 6·51, 95 per cent c.i. 2·19 to 19·37; P = 0·001).

Conclusion

An algorithmic approach to pancreatic and peripancreatic walled-off necrosis, based on the collection size, location and stepwise response to intervention, resulted in an improved rate of treatment success compared with conventional endoscopic management.
Trace quantification of 1‐triacontanol in beagle plasma by GC‐MS/MS and its application to a pharmacokinetic study
Authors: Wang Chunfeng , Fan Ali , Zhu Xiaojie , Lu Yang , Deng Shuhua , Gao Wenchao , Zhang Wei , Liu Qi , Chen Xijing
Published: October 2014

1‐Triacontanol (TA), a member of long chain fatty alcohol, has recently been received great attention owing to its antitumor activity. In this study, an accurate, sensitive and selective gas chromatography–tandem mass spectrometry method was developed and validated for the quantification of TA in beagle plasma using 1‐octacosanal as the internal standard (IS) for the first time. With temperature programming, chromatographic separation was carried out on an HP‐5MS column, using helium as carrier gas and argon as collision gas, both at a flow rate of 1 mL/min. TA was analyzed using positive ion electrospray ionization in multiple‐reaction monitoring mode, with the precursor to product ion transitions of m/z 495.6 → 97.0 and m/z 467.5 → 97.0 for TA and the IS, respectively. The lower limit of quantitation, linearity, intra‐ and interday precision, accuracy, stability, extraction recovery and matrix effect of TA were within the acceptable limits. The validated method was successfully applied to a pharmacokinetic study of TA in beagles. Copyright © 2014 John Wiley & Sons, Ltd.
Quantification of heteroclitin D in rat plasma: validation of an LC/MS/MS method and its application in a preclinical pharmacokinetic study
Authors: Zhang Fan , Zhang Nan , Pang Li , Tan Yan , Xu Hong
Published: October 2014

A rapid, sensitive and specific liquid chromatography tandem mass spectrometry (LC/MS/MS) method was developed and validated for the quantification of heteroclitin D in rat plasma after using gambogic acid as internal standard (IS). Chromatographic separation was done on a Thermo Hypersil GOLD column (30 × 2.1 mm, 3 µm) using a mobile phase consisting of methanol–water–formic acid (80:20:0.1, v/v/v). The mass spectrometer worked with positive electrospray ionization in multiple reaction monitoring mode, using target ions at [M + H]+ m/z 483.3 for heteroclitin D and [M + H]+ m/z 629.3 for the IS. The standard curve was linear (R2 ≥0.995) over the concentration range 9.98–2080 ng/mL and had good back‐calculated accuracy and precision. The intra‐ and interday precision and accuracy determined on three quality control samples (29.94, 166.4 and 1872 ng/mL) were ≤12.8 and –8.9–3.6%, respectively. The extraction recovery was ≥88.2% and the lower limit of quantification was 9.98 ng/mL. The method was successfully applied to evaluate pharmacokinetics of heteroclitin D in Sprague–Dawley rats following a single intravenous bolus injection of 2.0 mg/kg heteroclitin. Copyright © 2014 John Wiley & Sons, Ltd.
Synthesis of Amines by Reductive Amination of Aldehydes and Ketones using Co3O4/NGr@C Catalyst
Authors: Pisiewicz Sabine , Stemmler Tobias , Surkus Annette‐Enrica , Junge Kathrin , Beller Matthias
Published: October 2014

Heterogenized non‐noble metal‐based catalysts allow for cost‐efficient and environmentally benign hydrogenations. Here, we have developed a straightforward reductive amination methodology using molecular hydrogen in the presence of a Co3O4/NGr@C catalyst system. Various carbonyl compounds were transformed with secondary amines to the corresponding tertiary amines with good to excellent yields and selectivity. The Co3O4/NGr@C catalyst is recycled up to five times without significant loss of activity.
Lipase‐Catalyzed Doubly Enantioselective Ring‐Opening Resolution between Alcohols and Lactones: Synthesis of Chiral Hydroxyl Esters with Two Stereogenic Centers
Authors: Xia Bo , Li Yanyan , Cheng Guilin , Lin Xianfu , Wu Qi
Published: October 2014

A novel lipase B from Candida antarctica‐catalyzed doubly enantioselective ring‐opening resolution between racemic alcohols and lactones was developed. By using this strategy, three optically pure compounds including hydroxyl esters with two stereogenic centers and recovered alcohols and lactones were obtained simultaneously in high yields and ee. This process was used for the resolution of various racemic alcohols with different substituent groups and lactones with different ring sizes (four‐ and seven‐ membered lactones). The scale‐up experiments were also successful. Moreover, molecular docking was performed to explain the molecular basis of this doubly enantioselective ring‐opening resolution. As an attractive and efficient strategy, lipase‐catalyzed doubly enantioselective ring‐opening resolution will be widely used in the synthesis of optically pure hydroxyl esters with two stereogenic centers.
Synthesis of Quinoxalines by a Carbon Nanotube–Gold Nanohybrid‐Catalyzed Cascade Reaction of Vicinal Diols and Keto Alcohols with Diamines
Authors: Shah Nimesh , Gravel Edmond , Jawale Dhanaji V. , Doris Eric , Namboothiri Irishi N. N.
Published: October 2014

A one‐pot oxidation–condensation method for the synthesis of quinoxalines from readily available benzoins or benzhydrols and 1,2‐phenylenediamines or 2,3‐diaminopyridine by use of a gold–carbon nanotube nanohybrid as a heterogeneous catalyst is reported. Quinoxalines are formed under mild conditions in air and in excellent yields. The simple and efficient methodology offers a safe and sustainable alternative to conventional acid and/or base‐catalyzed thermal processes.
Enhanced Electron Transfer in Enzymatic Bioelectrodes by a Poly(vinyl alcohol) N‐Methyl‐4(4′‐formylstyryl) Pyridinium Methosulfate Acetal Cationic Polymer
Authors: Umasankar Yogeswaran , Ramasamy Ramaraja P.
Published: October 2014

A novel method for enzyme immobilization has been developed for use in enzymatic biofuel cell cathodes and anodes. Enzyme immobilization was achieved on a glassy carbon electrode (GCE) modified with multi‐walled carbon nanotubes (MWNTs) using the freestanding cationic polymer poly(vinyl alcohol) N‐methyl‐4(4′‐formylstyryl) pyridiniummethosulfateacetal (PVA‐SbQ). The enzymes entrapped within the polymer chains possess the ability to exchange electrons with the electrode through their respective substrates. The enzyme catalysts studied for biofuel cell cathodes were tyrosinase and laccase, and for biofuel cell anodes alcohol dehydrogenase (ADH) and glucose oxidase (GOx). The advantage of using PVA‐SbQ for enzyme immobilization was demonstrated by using cyclic voltammetry. The experimental results showed that the freestanding PVA‐SbQ polymer chains retained a higher enzyme activity on the MWNT‐modified electrodes compared to cross‐linked PVA‐SbQ chains. Electrochemical impedance spectroscopy was applied to understand the electron‐transfer resistance of cross‐linked PVA‐SbQ. The experimental results also show that enzyme/PVA‐SbQ/MWNT electrodes generate a higher current compared to control electrodes without MWNTs or the polymer. We conclude that the PVA‐SbQ polymer enhances both enzyme immobilization and electrochemical charge transfer in enzyme bioelectrodes, showing promise for the development of high‐performance biofuel cells.
Highly Efficient Membraneless Glucose Bioanode Based on Corynascus thermophilus Cellobiose Dehydrogenase on Aryl Diazonium‐Activated Single‐Walled Carbon Nanotubes
Authors: Ortiz Roberto , Ludwig Roland , Gorton Lo
Published: October 2014

We present an approach for electrode modification by using the oxidoreductase cellobiose dehydrogenase from the ascomycete Corynascus thermophilus (CtCDH). CtCDH is a two‐domain enzyme, in which the catalytic dehydrogenase domain (DHCDH) hosts flavin adenine dinucleotide (FAD) as cofactor and is connected through a flexible linker to a small cytochrome domain with a heme b cofactor (CYTCDH). This domain is responsible for the electron transfer from DHCDH to macromolecular electron acceptors, and is capable of direct electron transfer (DET) with electrode surfaces. CtCDH is optimal at pH values between 7 and 9 and exhibits one of the lowest apparent KM values for glucose (2.4×104 μM) in contrast to the majority of other CDHs, which have acidic optimal pH values and have very low or no activity for glucose. Glassy carbon (GC) electrodes were modified by drop‐casting single‐walled carbon nanotubes (SWCTs) and further modifying with aryl diazonium salts (DS). When adsorbed on such GC‐SWCT‐DS electrodes, CYTCDH showed efficient DET in the presence of a substrate. Six different functional groups for the aryl amines were studied and compared to non‐DS modified GC‐SWCT electrodes. The charge of the grafted aryl amines was investigated and it was found that surfaces modified with aniline, 4‐aminophenol, and 4‐aminobenzoic acid (ABA) contain negative charges at pH 7.4. On the other hand, surfaces modified with p‐phenylenediamine (PD), N,N‐dimethyl‐p‐phenylenediamine, and N,N‐diethyl‐p‐phenylenediamine remain uncharged. To date, the highest DET current density (JMAX=32.5 μA cm−2 for lactose and JMAX=16.2 μA cm−2 for glucose) for a CDH‐modified electrode at human physiological pH can be obtained by using a GC‐SWCT‐ABA CtCDH modified electrode. The use of glutaraldehyde (GA) in GC‐SWCT‐PD‐modified electrodes increases the JMAX twofold. The modified electrodes with DS showed a more negative onset potential for the catalytic current. For GC‐SWCT‐ABA modified electrodes and GC‐SWCT‐PD with GA, a change in the onset potential of −62 and −66 mV, respectively, was found compared with non‐DS modified electrodes. The prepared bioanodes show a loss in response current of 15 % after 9 days of continuous measurements from the original signal in 5 mM glucose, using 50 mM phosphate buffer solution at pH 7.40 at 37 °C.
Effect of Synthesis Parameters on the Electrochemical Properties of High‐Surface‐Area Mesoporous Titanium Oxide with Polypyrrole Nanowires in the Pores
Authors: Smith Luke A. C. , Romer Frederick , Trudeau Michel L. , Smith Mark E. , Hanna John V. , Antonelli David M.
Published: October 2014

This paper describes the synthesis and characterisation of high‐surface‐area mesoporous titanium oxides with polypyrrole nanowires within the pores, and the subsequent variation of synthesis parameters such as polymer‐loading level and pore size to improve performance. These modifications are employed to improve the electron conductivity of the amorphous host and exploit the high internal surface areas of over 800 m2g−1 for potential use as a lithium battery cathode material, once fully optimised, with fast charge‐transfer kinetics expected from the proximity of the vast majority of the redox sites at, or near, the surface of the inner pore walls. A full structural characterisation, in addition to electrochemical assessments, of the composite materials is presented and compared to the pristine mesoporous titanium oxide hosts. The best synthesis conditions were achieved with 5 % polymer loading and the largest pore sized host materials. Excessive polymer loading and smaller pore sizes lead to decreased performance, possibly due to inhibition of Li+ transport. The C18 templated TiO2 composite produced the best capacity retention at 58 % retention, and the C12 composite produced the highest initial capacity of 170 mAh g−1 by using a current density of 1 mAcm−2.
Hierarchical Tubular Structures Grown from the Gel/Liquid Interface
Authors: Steenbjerg Ibsen Casper Jon , Mikladal Bjørn Fridur , Bjørnholt Jensen Uffe , Birkedal Henrik
Published: October 2014

Three dimensional hierarchical materials are widespread in nature but are difficult to synthesize by using self‐assembly/organization. Here, we employ a gel–liquid interface to obtain centimeter‐long ∼100 μm diameter tubes with complex mineral wall structures that grow from the interface into solution. The gel, made from gelatin, is loaded with metal chloride salt, whereas the solution is a high pH anion source. Tubes were obtained with a range of cations (Ca2+, Sr2+, Ba2+, Cu2+, and Zn2+) and anions (CO32−and PO43−). The crystalline phases found in the tube walls corresponded to expectations from solution chemistries and phase solubilities. The growth mechanism is found to be akin to that of chemical gardens. The divalent cations modify the strength of the gelatin gel in a manner that involves not only simple electrostatic screening, but also ion‐specific effects. Thus, tubes were not obtained for those ions and/or concentrations that significantly changed the gel’s mechanical structure. At high Cu2+loading, for example, vertical convection bands, not Liesegang bands, were observed in the gels.
Amide‐Functionalized Naphthyridines on a RhII–RhII Platform: Effect of Steric Crowding, Hemilability, and Hydrogen‐Bonding Interactions on the Structural Diversity and Catalytic Activity of Dirhodium(II) Complexes
Authors: Sarkar Mithun , Daw Prosenjit , Ghatak Tapas , Bera Jitendra K.
Published: October 2014

Ferrocene‐amide‐functionalized 1,8‐naphthyridine (NP) based ligands {[(5,7‐dimethyl‐1,8‐naphthyridin‐2‐yl)amino]carbonyl}ferrocene (L1H) and {[(3‐phenyl‐1,8‐naphthyridin‐2‐yl)amino]carbonyl}ferrocene (L2H) have been synthesized. Room‐temperature treatment of both the ligands with Rh2(CH3COO)4 produced [Rh2(CH3COO)3(L1)] (1) and [Rh2(CH3COO)3(L2)] (2) as neutral complexes in which the ligands were deprotonated and bound in a tridentate fashion. The steric effect of the ortho‐methyl group in L1H and the inertness of the bridging carboxylate groups prevented the incorporation of the second ligand on the {RhII–RhII} unit. The use of the more labile Rh2(CF3COO)4 salt with L1H produced a cis bis‐adduct [Rh2(CF3COO)4(L1H)2] (3), whereas L2H resulted in a trans bis‐adduct [Rh2(CF3COO)3(L2)(L2H)] (4). Ligand L1H exhibits chelate binding in 3 and L2H forms a bridge‐chelate mode in 4. Hydrogen‐bonding interactions between the amide hydrogen and carboxylate oxygen atoms play an important role in the formation of these complexes. In the absence of this hydrogen‐bonding interaction, both ligands bind axially as evident from the X‐ray structure of [Rh2(CH3COO)2(CH3CN)4(L2H)2](BF4)2 (6). However, the axial ligands reorganize at reflux into a bridge‐chelate coordination mode and produce [Rh2(CH3COO)2(CH3CN)2(L1H)](BF4)2 (5) and [Rh2(CH3COO)2(L2H)2](BF4)2 (7). Judicious selection of the dirhodium(II) precursors, choice of ligand, and adaptation of the correct reaction conditions affords 7, which features hemilabile amide side arms that occupy sites trans to the Rh–Rh bond. Consequently, this compound exhibits higher catalytic activity for carbene insertion to the CH bond of substituted indoles by using appropriate diazo compounds, whereas other compounds are far less reactive. Thus, this work demonstrates the utility of steric crowding, hemilability, and hydrogen‐bonding functionalities to govern the structure and catalytic efficacyof dirhodium(II,II) compounds.
Modular Thiol–Ene Chemistry Approach towards Mesoporous Silica Monoliths with Organically Modified Pore Walls
Authors: Göbel Ronald , Hesemann Peter , Friedrich Alwin , Rothe Regina , Schlaad Helmut , Taubert Andreas
Published: October 2014

The surface modification of mesoporous silica monoliths through thiol–ene chemistry is reported. First, mesoporous silica monoliths with vinyl, allyl, and thiol groups were synthesized through a sol–gel hydrolysis–polycondensation reaction from tetramethyl orthosilicate (TMOS) and vinyltriethoxysilane, allyltriethoxysilane, and (3‐mercaptopropyl)trimethoxysilane, respectively. By variation of the molar ratio of the comonomers TMOS and functional silane, mesoporous silica objects containing different amounts of vinyl, allyl, and thiol groups were obtained. These intermediates can subsequently be derivatized through radical photoaddition reactions either with a thiol or an olefin, depending on the initial pore wall functionality, to yield silica monoliths with different pore‐wall chemistries. Nitrogen sorption, small‐angle X‐ray scattering, solid‐state NMR spectroscopy, elemental analysis, thermogravimetric analysis, and redox titration demonstrate that the synthetic pathway influences the morphology and pore characteristics of the resulting monoliths and also plays a significant role in the efficiency of functionalization. Moreover, the different reactivity of the vinyl and allyl groups on the pore wall affects the addition reaction, and hence, the degree of the pore‐wall functionalization. This report demonstrates that thiol–ene photoaddition reactions are a versatile platform for the generation of a large variety of organically modified silica monoliths with different pore surfaces.
Recent Advances in Trifluoromethylation Reactions with Electrophilic Trifluoromethylating Reagents
Authors: Barata‐Vallejo Sebastián , Lantaño Beatriz , Postigo Al
Published: October 2014

Electrophilic trifluoromethylation reactions have been the latest approach to achieve the fluoroalkylation of compounds with newly‐discovered reagents, such as the Togni’s (1‐trifluoromethyl‐1,2‐benziodoxol‐3‐(1 H)‐one), Umemoto’s (S‐(trifluoromethyl)dibenzothiophenium tetrafluoroborate), Yagupolskii’s (S‐(trifluoromethyldiarylsulfonium salts), Shreeve’s (S‐(trifluoromethyl)dibenzothiophenium triflate), and Shibata’s (trifluoromethylsulfoximine salts) reagents. All these reagents produce an electrophilic trifluoromethylating (CF3+) species that undergoes reaction with nucleophiles. In addition, these latter reactive species (i.e. CF3+) can undergo electron‐transfer (ET) processes affording CF3⋅ radicals that expand the scope to substrates other than conventional nucleophiles that can undergo reaction. In this Review, we shall discuss the trifluoromethylation reactions of diverse families of organic substrates of biological interest as a means to comparing the reagents scope and best reaction conditions. Some, though not all, of these reactions require the assistance of metal or organometallic catalysts. Some require additives and catalysts to promote the fluoroalkylation reaction, but invariably all are initiated and carried out by electrophilic trifluoromethylating species.
Rapid Characterization of Molecular Diffusion by NMR Spectroscopy
Authors: Pudakalakatti Shivanand M. , Chandra Kousik , Thirupathi Ravula , Atreya Hanudatta S.
Published: October 2014

An NMR‐based approach for rapid characterization of translational diffusion of molecules has been developed. Unlike the conventional method of acquiring a series of 2D 13C and 1H spectra, the proposed approach involves a single 2D NMR spectrum, which can be acquired in minutes. Using this method, it was possible to detect the presence of intermediate oligomeric species of diphenylalanine in solution during the process of its self‐assembly to form nanotubular structures.
Tunable Trimers: Using Temperature and Pressure to Control Luminescent Emission in Gold(I) Pyrazolate‐Based Trimers
Authors: Woodall Christopher H. , Fuertes Sara , Beavers Christine M. , Hatcher Lauren E. , Parlett Andrew , Shepherd Helena J. , Christensen Jeppe , Teat Simon J. , Intissar Mourad , Rodrigue‐Witchel Alexandre , Suffren Yan , Reber Christian , Hendon Christopher H. , Tiana Davide , Walsh Aron , Raithby Paul R.
Published: October 2014

A systematic investigation into the relationship between the solid‐state luminescence and the intermolecular Au⋅⋅⋅Au interactions in a series of pyrazolate‐based gold(I) trimers; tris(μ2‐pyrazolato‐N,N′)‐tri‐gold(I) (1), tris(μ2‐3,4,5‐ trimethylpyrazolato‐N,N′)‐tri‐gold(I) (2), tris(μ2‐3‐methyl‐5‐phenylpyrazolato‐N,N′)‐tri‐gold(I) (3) and tris(μ2‐3,5‐diphenylpyrazolato‐N,N′)‐tri‐gold(I) (4) has been carried out using variable temperature and high pressure X‐ray crystallography, solid‐state emission spectroscopy, Raman spectroscopy and computational techniques. Single‐crystal X‐ray studies show that there is a significant reduction in the intertrimer Au⋅⋅⋅Au distances both with decreasing temperature and increasing pressure. In the four complexes, the reduction in temperature from 293 to 100 K is accompanied by a reduction in the shortest intermolecular Au⋅⋅⋅Au contacts of between 0.04 and 0.08 Å. The solid‐state luminescent emission spectra of 1 and 2 display a red shift with decreasing temperature or increasing pressure. Compound 3 does not emit under ambient conditions but displays increasingly red‐shifted luminescence upon cooling or compression. Compound 4 remains emissionless, consistent with the absence of intermolecular Au⋅⋅⋅Au interactions. The largest pressure induced shift in emission is observed in 2 with a red shift of approximately 630 cm−1 per GPa between ambient and 3.80 GPa. The shifts in all the complexes can be correlated with changes in Au⋅⋅⋅Au distance observed by diffraction.
BODIPY‐Based Oligo(ethylene glycol) Dendrons as Fluorescence Thermometers: When Thermoresponsiveness Meets Intramolecular Electron/Charge Transfer
Authors: Wang Hua , Wu Yongquan , Tao Pan , Fan Xing , Kuang Gui‐Chao
Published: October 2014

The temperature‐dependent photophysical properties of a series of 4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene (BODIPY) derivatives with different oligo(ethylene glycol) (OEG) dendrons were investigated. Weak fluorescence emission was observed for these BODIPY derivatives in dilute solution with low viscosity. BDP‐G0 and BDP‐G1‐TEG exhibit a high quantum yield in viscous glycerol solutions, contrary to the moderate and little fluorescence enhancement for BDP‐G1 and BDP‐G2 under the same conditions. The photoinduced electron transfer (PET) may have quenched the fluorescence, as supported by calculation. Interestingly, the thermoresponsive BODIPY derivatives show heat‐induced luminescence enhancement with a high signal‐to‐noise ratio and their emission maxima are dependent on the structures of branched tri(ethylene glycol) moieties. Finally, preliminary studies on the BODIPY derivatives as intracellular fluorescence indicators in living HeLa cells were carried out.
Photochemically Engineering the Metal–Semiconductor Interface for Room‐Temperature Transfer Hydrogenation of Nitroarenes with Formic Acid
Authors: Li Xin‐Hao , Cai Yi‐Yu , Gong Ling‐Hong , Fu Wei , Wang Kai‐Xue , Bao Hong‐Liang , Wei Xiao , Chen Jie‐Sheng
Published: October 2014

A mild photochemical approach was applied to construct highly coupled metal–semiconductor dyads, which were found to efficiently facilitate the hydrogenation of nitrobenzene. Aniline was produced in excellent yield (>99 %, TOF: 1183) using formic acid as hydrogen source and water as solvent at room temperature. This general and green catalytic process is applicable to a wide range of nitroarenes without the involvement of high‐pressure gases or sacrificial additives.
Surface Architectures Built around Perylenediimide Stacks
Authors: Charbonnaz Pierre , Zhao Yingjie , Turdean Raluca , Lascano Santiago , Sakai Naomi , Matile Stefan
Published: October 2014

Simple stacks of perylenediimides (PDIs) grown directly on solid surfaces are an intriguing starting point for the construction of multicomponent architectures because their intrinsic activity is already very high. The ability of PDI stacks to efficiently generate photocurrent originates from the strong absorption of visible light and the efficient transport of both electrons and holes after generation with light. The objective of this study was to explore whether or not the excellent performance of these remarkably simple single‐channel photosystems could be further improved in more sophisticated multicomponent architectures. We report that the directional construction of strings of anions or cations along the PDI stacks does not significantly improve their activity; that is, the intrinsic activity of PDI stacks is too high to yield ion‐gated photosystems. The directional construction of electron‐ and hole‐transporting stacks of naphthalenediimides (NDIs) and oligothiophenes along the central PDI stack did not improve photocurrent generation under standard conditions either. However, the activity of double‐channel photosystems increased with increasing thickness, whereas increasing charge recombination with single‐channel PDI stacks resulted in decreasing activity with increasing length. Most efficient long‐distance charge transport was found with double‐channel photosystems composed of PDIs and NDIs. This finding suggests that over long distances, PDI stacks transport holes better than electrons, at least under the present conditions. Triple‐channel photosystems built around PDI stacks with oligothiophenes and triphenylamines were less active, presumably because hole mobility in the added channels was inferior to that in the original PDI stacks, thus promoting charge recombination.