bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Enantioselective Dakin–West Reaction
Authors: Wende Raffael C. , Seitz Alexander , Niedek Dominik , Schuler Sören M. M. , Hofmann Christine , Becker Jonathan , Schreiner Peter R. 
Published: January 2016

AbstractHere we report the development of the first enantioselective Dakin–West reaction, yielding α‐acetamido methylketones with up to 58 % ee with good yields. Two of the obtained products were recrystallized once to achieve up to 84 % ee. The employed methylimidazole‐containing oligopeptides catalyze both the acetylation of the azlactone intermediate and the terminal enantioselective decarboxylative protonation. We propose a dispersion‐controlled reaction path that determines the asymmetric reprotonation of the intermediate enolate after the decarboxylation.
Cooperative Reductive Elimination: The Missing Piece in the Oxidative‐Coupling Mechanistic Puzzle
Authors: Funes‐Ardoiz Ignacio , Maseras Feliu 
Published: January 2016

AbstractThe reaction between benzoic acid and methylphenylacetylene to form an isocoumarin is catalyzed by Cp*Rh(OAc)2 in the presence of Cu(OAc)2(H2O) as an oxidant and a leading example of oxidative‐coupling reactions. Its mechanism was elucidated by DFT calculations with the B97D functional. The conventional mechanism, with separate reductive‐elimination and reoxidation steps, was found to yield a naphthalene derivative as the major product by CO2 extrusion, contradicting experimental observations. The experimental result was reproduced by an alternative mechanism with a lower barrier: In this case, the copper acetate oxidant plays a key role in the reductive‐elimination step, which takes place through a transition state containing both rhodium and copper centers. This cooperative reductive‐elimination step would not be accessible with a generic oxidant, which, again, is in agreement with available experimental data.
Palladium‐Catalyzed Trifluoromethylation of (Hetero)Arenes with CF3Br
Authors: Natte Kishore , Jagadeesh Rajenahally V. , He Lin , Rabeah Jabor , Chen Jianbin , Taeschler Christoph , Ellinger Stefan , Zaragoza Florencio , Neumann Helfried , Brückner Angelika , Beller Matthias 
Published: January 2016

AbstractThe CF3 group is an omnipresent motif found in many pharmaceuticals, agrochemicals, catalysts, materials, and industrial chemicals. Despite well‐established trifluoromethylation methodologies, the straightforward and selective introduction of such groups into (hetero)arenes using available and less expensive sources is still a major challenge. In this regard, the selective synthesis of various trifluoromethyl‐substituted (hetero)arenes by palladium‐catalyzed C−H functionalization is herein reported. This novel methodology proceeds under comparably mild reaction conditions with good regio‐ and chemoselectivity. As examples, trifluoromethylations of biologically important molecules, such as melatonin, theophylline, caffeine, and pentoxifylline, are showcased.
Nanoplasmonic Photoluminescence Spectroscopy at Single‐Particle Level: Sensing for Ethanol Oxidation
Authors: Zheng Zhaoke , Majima Tetsuro 
Published: January 2016

AbstractSurface plasmon resonances of metal nanoparticles have shown significant promise for the use of solar energy to drive catalytic chemical reactions. More importantly, understanding and monitoring such catalytic reactions at single‐nanoparticle level is crucial for the study of local reaction processes. Herein, using plasmonic photoluminescence (PL) spectroscopy, we describe a novel sensing method for catalytic ethanol oxidation reactions at the single‐nanoparticle level. The Au nanorod monitors the interfacial interaction with ethanol during the catalytic reaction through the PL intensity changes in the single‐particle PL spectra. The analysis of energy relaxation of excited electron–hole pairs indicates the relationship between the PL quenching and ethanol oxidation reaction on the single Au nanorod.
Mechanical Reversibility of Strain‐Promoted Azide–Alkyne Cycloaddition Reactions
Authors: Jacobs Monique J. , Schneider Guenter , Blank Kerstin G. 
Published: January 2016

AbstractMechanophores, that is, molecules that show a defined response to force, are crucial building blocks of mechanoresponsive materials. The possibility of mechanically induced cycloreversion for a series of triazoles formed via strain‐promoted azide–alkyne cycloaddition reactions was investigated by density functional theory calculations, and these triazoles were compared to the 1,4‐ and 1,5‐regioisomers formed in the reaction of an azide with a terminal alkyne. We show that cycloreversion is in principal possible and that the pulling geometry is the most important parameter that determines the probability of cycloreversion. We further compared triazole stability to the mechanical stability of polymers that are frequently used as force transducers in mechanochemical experiments and identified DIBAC (azadibenzylcyclooctyne) as a promising mechanophore for future applications.
Quantifying the Electrocatalytic Turnover of Vitamin B12‐Mediated Dehalogenation on Single Soft Nanoparticles
Authors: Cheng Wei , Compton Richard G. 
Published: January 2016

AbstractWe report the electrocatalytic dehalogenation of trichloroethylene (TCE) by single soft nanoparticles in the form of Vitamin B12‐containing droplets. We quantify the turnover number of the catalytic reaction at the single soft nanoparticle level. The kinetic data shows that the binding of TCE with the electro‐reduced vitamin in the CoI oxidation state is chemically reversible.
Traceless Synthesis of Asymmetrically Modified Bivalent Nucleosomes
Authors: Lechner Carolin C. , Agashe Ninad D. , Fierz Beat 
Published: January 2016

AbstractNucleosomes carry extensive post‐translational modifications (PTMs), which results in complex modification patterns that are involved in epigenetic signaling. Although two copies of each histone coexist in a nucleosome, they may not carry the same PTMs and are often differently modified (asymmetric). In bivalent domains, a chromatin signature prevalent in embryonic stem cells (ESCs), namely H3 methylated at lysine 4 (H3K4me3), coexists with H3K27me3 in asymmetric nucleosomes. We report a general, modular, and traceless method for producing asymmetrically modified nucleosomes. We further show that in bivalent nucleosomes, H3K4me3 inhibits the activity of the H3K27‐specific lysine methyltransferase (KMT) polycomb repressive complex 2 (PRC2) solely on the same histone tail, whereas H3K27me3 stimulates PRC2 activity across tails, thereby partially overriding the H3K4me3‐mediated repressive effect. To maintain bivalent domains in ESCs, PRC2 activity must thus be locally restricted or reversed.
Brief Report: Severe Inflammation Following Vaccination Against Streptococcus pneumoniae in Patients With Cryopyrin‐Associated Periodic Syndromes
Authors: Walker Ulrich A. , Hoffman Hal M. , Williams Rene , Kuemmerle‐Deschner Jasmin , Hawkins Philip N. 
Published: January 2016

ObjectivePneumococcal vaccination is recommended for patients receiving immunosuppressive drugs. We describe unusually severe adverse reactions to pneumococcal vaccination in each of 7 consecutive patients with cryopyrin‐associated periodic syndromes (CAPS).MethodsSeven consecutive patients with CAPS were vaccinated with pneumococcal polysaccharide or conjugate vaccines. Clinical information was collected retrospectively.ResultsWithin a few hours after the vaccination, all 7 patients developed severe local reactions at the injection site. Two patients had to be hospitalized for systemic reactions including fever. All symptoms resolved in a period of 3–17 days.ConclusionOur findings indicate that pneumococcal vaccines can trigger a severe local and systemic inflammatory reaction in patients with CAPS and possibly patients with other autoinflammatory diseases. Careful consideration is warranted when implementing current European League Against Rheumatism immunization guidelines in this patient population.
A 3,7‐Dihydroxyphenoxazine‐based Fluorescent Probe for Selective Detection of Intracellular Hydrogen Peroxide
Authors: Han Zhiqiang , Liang Xiao , Ren Xuejiao , Shang Luqing , Yin Zheng 
Published: January 2016

AbstractA novel N‐borylbenzyloxycarbonyl‐3,7‐dihydroxyphenoxazine fluorescent probe (NBCD) for detecting H2O2 in living cells is described. The probe could achieve high selectivity for detecting H2O2 over other biological reactive oxygen species (ROS). In addition, upon addition of H2O2, NBCD exhibited color change from colorless to pink, which makes it a “naked‐eye” probe for H2O2 detection. NBCD could not only be used to detect enzymatically generated H2O2 but also to detect H2O2 in living systems by using fluorescence spectroscopy, with a detection limit of 2 μm. Importantly, NBCD enabled the visualization of epidermal growth factor (EGF)‐stimulated H2O2 generation inside the cells.
Hybrid Coordination Networks Constructed from ɛ‐Keggin‐Type Polyoxometalates and Rigid Imidazole‐Based Bridging Ligands as New Carriers for Noble‐Metal Catalysts
Authors: Yang Xiao‐Jian , Sun Meng , Zang Hong‐Ying , Ma Yuan‐Yuan , Feng Xiao‐Jia , Tan Hua‐Qiao , Wang Yong‐Hui , Li Yang‐Guang 
Published: January 2016

AbstractThree hybrid coordination networks that were constructed from ɛ‐Keggin polyoxometalate building units and imidazole‐based bridging ligands were prepared under hydrothermal conditions, that is, H[(Hbimb)2(bimb){Zn4PMoV8MoVI4O40}]⋅6 H2O (1), [Zn(Hbimbp)(bimbp)3{Zn4PMoV8MoVI4O40}]⋅DMF⋅3.5 H2O (2), and H[Zn2(timb)2(bimba)2Cl2{Zn4PMoV8MoVI4O40}]⋅7 H2O (3) (bimb=1,4‐bis(1‐imidazolyl)benzene, bimbp=4,4′‐bis(imidazolyl)biphenyl, timb=1,3,5‐tris(1‐imidazolyl)benzene, bimba=3,5‐bis(1‐imidazolyl)benzenamine). All three compounds were characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis, and single‐crystal X‐ray diffraction. The mixed valence of the Mo centers was analyzed by XPS spectroscopy and bond‐valence sum calculations. In all three compounds, the ɛ‐Keggin polyoxometalate (POM) units acted as nodes that were connected by rigid imidazole‐based bridging ligands to form hybrid coordination networks. In compound 1, 1D zigzag chains extended to form a 3D supramolecular architecture through intermolecular hydrogen‐bonding interactions. Compound 2 consisted of 2D curved sheets, whilst compound 3 contained chiral 2D networks. Because of the intrinsic reducing properties of ɛ‐Keggin POM species, noble‐metal nanoparticles were loaded onto these POM‐based coordination networks. Thus, compounds 1–3 were successfully loaded with Ag nanoparticles, and the corresponding composite materials exhibited high catalytic activities for the reduction of 4‐nitrophenol.
Europium‐activated rare earth fluoride (LnF3:Eu3+–Ln = La, Gd) nanocrystals prepared by using ionic liquid/NH4F as a fluorine source via hydrothermal synthesis
Authors: Kasturi S. , Sivakumar V. , Jeon Duk Young 
Published: January 2016

AbstractLanthanide (Ln) fluorides are considered exceptional luminescent rigid host matrices for various optical active Ln3+ ions due to their high refractive index, high chemical stability and low phonon energy, leading to the low probability of non‐radiative decay, which results in higher photoluminescence quantum yield (PLQY) (usually higher than oxide hosts). In this study, Eu3+‐activated Ln fluorides (LnF3:Eu3+–Ln = La, Gd) are synthesized by the hydrothermal method using 1‐butyl‐3‐methylimidazolium tertrafluoroborate [BMIBF4] and NH4F as fluorine precursors. The synthesized nanocrystals (NCs) are structurally and morphologically characterized, and their optical properties investigated using spectrofluorometry. The X‐ray diffraction (XRD) patterns of Eu3+‐substituted and ‐unsubstituted LnF3 (prepared from a different fluorine source) are indexed based on the hexagonal and orthorhombic crystal structure, respectively. Average crystalline sizes are calculated using the Scherrer equation and it is found that the synthesized NCs have an average crystalline size of 12–35 nm. Transmission electron microscopy (TEM) images reveal that the NCs are well dispersed and nearly ellipsoid, with an average size of ~ 5 nm. Eu3+‐activated NCs show characteristic excitation and emission spectra. The emission spectra show both magnetic (5D0–7F1) and electric (5D0–7F2) dipole transition with appropriate CIE color coordinates; however, the intensity of the magnetic dipole transition is high, which is in accordance with local site symmetry. Owing to their unique size and excellent optical properties, the synthesized NCs may have potential application in the fields bio‐imaging and solar concentrators. Copyright © 2016 John Wiley & Sons, Ltd.
Applications of microfluidics in microalgae biotechnology: A review
Authors: Juang Yi‐Je , Chang Jo‐Shu 
Published: January 2016

AbstractMicroalgae have been one of the important sources for biofuel production owing to their competitive advantages such as no need to tap into the global food supply chain, higher energy density, and absorbing carbon dioxide to mitigate global warming. One of the key factors to ensure successful biofuel production is that it requires not only bioprospecting of the microalgae with high lipid content, high growth rate and tolerance to environmental parameters but also on‐site monitoring of the cultivation process and optimization of the culturing conditions. However, as the conventional techniques usually involve in complicated procedures, or are time‐consuming or labor intensive, microfluidics technology offers an attractive alternative to resolve these issues. In this review, applications of microfluidics to bioprospecting in microalgae biotechnology were discussed such as cell identification, cell sorting/screening, cell culturing and cell disruption. In addition, utilization of microalgae in micro‐sized fuel cells and microfluidic platforms for biosensing was addressed. This review reports the recent studies and offers a look into how microfluidics is exploited to tackle the issues encountered in the microalgae biotechnology.
Scale‐up of industrial biodiesel production to 40 m3 using a liquid lipase formulation
Authors: Price Jason , Nordblad Mathias , Martel Hannah H. , Chrabas Brent , Wang Huali , Nielsen Per Munk , Woodley John M. 
Published: January 2016

ABSTRACTIn this work, we demonstrate the scale‐up from an 80 L fed‐batch scale to 40 m3 along with the design of a 4 m3continuous process for enzymatic biodiesel production catalyzed by NS‐40116 (a liquid formulation of a modified Thermomyces lanuginosus lipase). Based on the analysis of actual pilot plant data for the transesterification of used cooking oil and brown grease, we propose a method applying first order integral analysis to fed‐batch data based on either the bound glycerol or free fatty acid content in the oil. This method greatly simplifies the modeling process and gives an indication of the effect of mixing at the various scales (80 L to 40 m3) along with the prediction of the residence time needed to reach a desired conversion in a CSTR. Suitable process metrics reflecting commercial performance such as the reaction time, enzyme efficiency, and reactor productivity were evaluated for both the fed‐batch and CSTR cases. Given similar operating conditions, the CSTR operation on average, has a reaction time which is 1.3 times greater than the fed‐batch operation. We also showed how the process metrics can be used to quickly estimate the selling price of the enzyme. Assuming a biodiesel selling price of 0.6 USD/kg and a one‐time use of the enzyme (0.1% (w/woil) enzyme dosage); the enzyme can then be sold for 30 USD/kg which ensures that that the enzyme cost is not more than 5% of the biodiesel revenue. Biotechnol. Bioeng. 2016;113: 1719–1728. © 2016 Wiley Periodicals, Inc.
A single short session of media perfusion induces osteogenesis in hBMSCs cultured in porous scaffolds, dependent on cell differentiation stage
Authors: Filipowska Joanna , Reilly Gwendolen C. , Osyczka Anna M. 
Published: January 2016

ABSTRACTPerfusing culture media through porous cell‐seeded scaffolds is now a common approach within many tissue engineering strategies. Human bone‐marrow derived mesenchymal stem cells (hBMSC) are a clinically valuable source of osteoprogenitors that respond to mechanical stimuli. However, the optimal mechanical conditions for their osteogenic stimulation in vitro have not been defined. Whereas the effects of short durations of media fluid flow have been studied in monolayers of osteoblastic cells, in 3D culture continuous or repeated perfusion is usually applied. Here, we investigated whether a short, single perfusion session applied to hBMSCs cultured in 3D would enhance their osteogenesis in vitro. We cultured hBMSCs on gelatine‐coated, porous polyurethane scaffolds with osteogenic supplements and stimulated them with a single 2‐h session of unidirectional, steady, 2.5 mL/min media perfusion, at either early or late stages of culture in 3D. Some cells were pre‐treated in monolayer with osteogenic supplements to advance cell differentiation, followed by 3D culture also with the osteogenic supplements. We report that this single, short session of media perfusion can markedly enhance the expression of bone‐related transcription and growth factors, and matrix components, by hBMSCs but that it is more effective when cells reach the pre‐osteoblast or osteoblast differentiation stage. These findings could aid in the optimization of 3D culture protocols for efficient bone tissue engineering. Biotechnol. Bioeng. 2016;113: 1814–1824. © 2016 Wiley Periodicals, Inc.
Efflux transporter engineering markedly improves amorphadiene production in Escherichia coli
Authors: Zhang Congqiang , Chen Xixian , Stephanopoulos Gregory , Too Heng‐Phon 
Published: January 2016

ABSTRACTMetabolic engineering aims at altering cellular metabolism to produce valuable products at high yields and titers. Achieving high titers and productivity can be challenging if final products are largely accumulated intracellularly. A potential solution to this problem is to facilitate the export of these substances from cells by membrane transporters. Amorphadiene, the precursor of antimalarial drug artemisinin, is known to be secreted from Escherichia coli overexpressing the biosynthetic pathway. In order to assess the involvement of various endogenous efflux pumps in amorphadiene transport, the effects of single gene deletion of 16 known multidrug‐resistant membrane efflux transporters were examined. The outer membrane protein TolC was found to be intimately involved in amorphadiene efflux. The overexpression of tolC together with ABC family transporters (macAB) or MFS family transporters (emrAB or emrKY) enhanced amorphadiene titer by more than threefold. In addition, the overexpression of transporters in the lipopolysaccharide transport system (msbA, lptD, lptCABFG) was found to improve amorphadiene production. As efflux transporters often have a wide range of substrate specificity, the multiple families of transporters were co‐expressed and synergistic benefits were observed in amorphadiene production. This strategy of screening and then rationally engineering transporters can be used to improve the production of other valuable compounds in E. coli. Biotechnol. Bioeng. 2016;113: 1755–1763. © 2016 Wiley Periodicals, Inc.
Solubilization and Iterative Saturation Mutagenesis of α1,3‐fucosyltransferase from Helicobacter pylori to enhance its catalytic efficiency
Authors: Choi Yun Hee , Kim Jong Hoon , Park Bum Seok , Kim Byung‐Gee 
Published: January 2016

ABSTRACTα1,3‐Fucosyltransferase (α1,3‐FucT) is essential for the biosynthesis of biologically active α1,3‐fucosyloligosacchairdes (3‐FOs) from human milk oligosaccharides (HMO), particularly 3‐fucosyllactose (3‐FL) trisaccharide. α1,3‐FucT from Helicobacter pylori 26695 (FutA) accepts lactose and LacNAc as glycan acceptors and has a very low level of expression in Escherichia coli, and it shows a low catalytic activity for lactose in the large‐scale synthesis of 3‐FL. To overcome the poor solubility of FutA, codon optimization, and systematic truncation of the protein at the C‐terminus with only one heptad repeat remaining (Δ52 FutA) were conducted to yield 150–200 mg/L of soluble protein of FutA and resulting in more than an 18‐fold increase in the 3‐FL yield. To improve the low level of enzyme catalytic activity for lactose, focused directed evolution was attempted using a semi‐rational approach that combines structure‐guided computational analysis and subsequent iterative saturation mutagenesis (ISM). In order to select the functional residues in active site/substrate binding site, docking simulation was used together with HotSpot Wizard to target evolutionarily variable amino acid positions. A128 site was selected from the key residue located in the active site, and A128N mutant displayed a 3.4‐fold higher catalytic activity than wild‐type Δ52 FutA. Considering that the A128N mutation is located in the deep cleft of the lactose binding site, the residues within the substrate binding sites, especially on the two α‐helices for lactose and one α‐helix for GDP‐fucose, were subjected to structure‐guided ISM. The selected residues from each helix were clustered, and ISM was performed for each cluster in parallel. In particular, the mutant with triple mutations (A128N/H129E/Y132I) located on the α5 helix exhibited a 9.6‐fold improvement in specific activity when compared to wild‐type Δ52 FutA. When such clustered mutations on two α‐helices (α5 and α2/loop) were combined, mutants with triple (A128N/H129E/S46F) and quadruple mutations (A128N/H129E/Y132I/S46F) were generated, which showed the synergistic effects, that is 14.5‐ and 15.5‐fold improvement in specific activity relative to wild‐type Δ52 FutA, respectively. The mutations increased their binding affinity for lactose and kcat values for lactose and GDP‐fucose. The Δ52 FutA quadruple mutant (A128N/H129E/Y132I/S46F) was successfully applied to in vitro synthesis of 3‐FL with an improved yield and productivity (>96% yield based on 5 mM of GDP‐Fuc within 1 h). Biotechnol. Bioeng. 2016;113: 1666–1675. © 2016 Wiley Periodicals, Inc.
Hydrogen‐fed biofilm reactors reducing selenate and sulfate: Community structure and capture of elemental selenium within the biofilm
Authors: Ontiveros‐Valencia Aura , Penton Christopher R. , Krajmalnik‐Brown Rosa , Rittmann Bruce E. 
Published: January 2016

ABSTRACTRemediation of selenate (SeO42−) contamination through microbial reduction is often challenging due to the presence of sulfate (SO42−), which can lead to competition for the electron donor and the co‐production of toxic H2S. Microbial reduction of SeO42− in the presence of SO42− was studied in two hydrogen‐based membrane biofilm reactors (MBfRs). One MBfR was initiated with SO42−‐reducing conditions and gradually shifted to SeO42− reduction. The second MBfR was developed with a SeO42−‐reducing biofilm, followed by SO42− introduction. Biofilms within both MBfRs achieved greater than 90% SeO42− reduction, even though the SeO42− concentration ranged from 1,000–11,000 μg/L, more than 20–200 times the maximum contaminant level for drinking water (50 μg/L). Biofilm microbial community composition, assessed by 16S rRNA gene‐based amplicon pyrosequencing, was distinct between the two MBfRs and was framed by alterations in SeO42− loading. Specifically, high SeO42− loading resulted in communities mainly composed of denitrifying bacteria (e.g., Denitratisoma and Dechloromonas). In contrast, low loading led to mostly sulfate‐reducing bacteria (i.e., Desulfovibrio) and sulfur‐oxidizing bacteria (i.e., Sulfuricurvum and Sulfurovum). SeO42− was reduced to elemental selenium (Se°), which was visualized within the biofilm as crystalloid aggregates, with its fate corresponding to that of biofilm solids. In conclusion, microbial biofilm communities initiated under either SeO42− or SO42−‐reducing conditions attained high SeO42− removal rates even though their microbial community composition was quite distinct. Biotechnol. Bioeng. 2016;113: 1736–1744. © 2016 Wiley Periodicals, Inc.