bluuebunny/crossref_metadata_2025_split huggingface dataset:
Zur Rolle der chemischen Synthese in der Entwicklung antibakterieller Wirkstoffe
Authors: Wright Peter M. , Seiple Ian B. , Myers Andrew G. 
Published: July 2014

AbstractDie Entdeckung und Einführung der Antibiotika im frühen zwanzigsten Jahrhundert hatte gewaltige Auswirkungen auf das Gesundheitwesen. Die chemische Synthese ermöglichte die Entwicklung der ersten antibakteriellen Substanzen, Organoarsenverbindungen und Sulfa‐Medikamente, die jedoch bald von wirksameren und weitaus komplexeren natürlichen Antibiotika verdrängt wurden: unter anderem Penicillin, Streptomycin, Tetracyclin und Erythromycin. Diese ersten Abwehrstoffe sind inzwischen – als unvermeidbare Folge der raschen Resistenzentwicklung bei pathogenen Bakterien – deutlich weniger wirksam, was durch die weit verbreitete falsche Anwendung von Antibiotika noch verstärkt wurde. Jahrzehntelang ergänzten Medizinchemiker das Repertoire der Antibiotika durch semisynthetische und in geringerem Maße vollsynthetische Routen, aber ökonomische Faktoren haben einen Rückgang dieser Bemühungen ausgelöst, was die Gesellschaft an den Rand einer Katastrophe führt. Wir sind überzeugt, dass die strategische Anwendung moderner chemischer Synthesemethoden zur Entwicklung antibakterieller Wirkstoffe von entscheidender Bedeutung ist, wenn eine globale Krise abgewendet werden soll.
Enzymatic Synthesis of Lipid II and Analogues
Authors: Huang Lin‐Ya , Huang Shih‐Hsien , Chang Ya‐Chih , Cheng Wei‐Chieh , Cheng Ting‐Jen R. , Wong Chi‐Huey 
Published: July 2014

AbstractThe emergence of antibiotic resistance has prompted active research in the development of antibiotics with new modes of action. Among all essential bacterial proteins, transglycosylase polymerizes lipid II into peptidoglycan and is one of the most favorable targets because of its vital role in peptidoglycan synthesis. Described in this study is a practical enzymatic method for the synthesis of lipid II, coupled with cofactor regeneration, to give the product in a 50–70 % yield. This development depends on two key steps: the overexpression of MraY for the synthesis of lipid I and the use of undecaprenol kinase for the preparation of polyprenol phosphates. This method was further applied to the synthesis of lipid II analogues. It was found that MraY and undecaprenol kinase can accept a wide range of lipids containing various lengths and configurations. The activity of lipid II analogues for bacterial transglycolase was also evaluated.
Motion Capture and Manipulation of a Single Synthetic Molecular Rotor by Optical Microscopy
Authors: Ikeda Tomohiro , Tsukahara Takahiro , Iino Ryota , Takeuchi Masayuki , Noji Hiroyuki 
Published: July 2014

AbstractSingle‐molecule imaging and manipulation with optical microscopy have become essential methods for studying biomolecular machines; however, only few efforts have been directed towards synthetic molecular machines. Single‐molecule optical microscopy was now applied to a synthetic molecular rotor, a double‐decker porphyrin (DD). By attaching a magnetic bead (ca. 200 nm) to the DD, its rotational dynamics were captured with a time resolution of 0.5 ms. DD showed rotational diffusion with 90° steps, which is consistent with its four‐fold structural symmetry. Kinetic analysis revealed the first‐order kinetics of the 90° step with a rate constant of 2.8 s−1. The barrier height of the rotational potential was estimated to be greater than 7.4 kJ mol−1 at 298 K. The DD was also forcibly rotated with magnetic tweezers, and again, four stable pausing angles that are separated by 90° were observed. These results demonstrate the potency of single‐molecule optical microscopy for the elucidation of elementary properties of synthetic molecular machines.
A Localized Tolerance in the Substrate Specificity of the Fluorinase Enzyme enables “Last‐Step” 18F Fluorination of a RGD Peptide under Ambient Aqueous Conditions
Authors: Thompson Stephen , Zhang Qingzhi , Onega Mayca , McMahon Stephen , Fleming Ian , Ashworth Sharon , Naismith James H. , Passchier Jan , O'Hagan David 
Published: July 2014

AbstractA strategy for last‐step 18F fluorination of bioconjugated peptides is reported that exploits an “Achilles heel” in the substrate specificity of the fluorinase enzyme. An acetylene functionality at the C‐2 position of the adenosine substrate projects from the active site into the solvent. The fluorinase catalyzes a transhalogenation of 5′‐chlorodeoxy‐2‐ethynyladenosine (ClDEA) to 5′‐fluorodeoxy‐2‐ethynyladenosine (FDEA). Extending a polyethylene glycol linker from the terminus of the acetylene allows the presentation of bioconjugation cargo to the enzyme for 18F labelling. The method uses an aqueous solution (H218O) of [18F]fluoride generated by the cyclotron and has the capacity to isotopically label peptides of choice for positron emission tomography (PET).
Versatile Synthetic Strategy for Coating Upconverting Nanoparticles with Polymer Shells through Localized Photopolymerization by Using the Particles as Internal Light Sources
Authors: Beyazit Selim , Ambrosini Serena , Marchyk Nataliya , Palo Emilia , Kale Vishal , Soukka Tero , Tse Sum Bui Bernadette , Haupt Karsten 
Published: July 2014

AbstractWe present a straightforward and generic strategy for coating upconverting nanoparticles (UCPs) with polymer shells for their protection, functionalization, conjugation, and for biocompatibility. UCPs are attracting much attention for their potential use as fluorescent labels in biological applications. However, they are hydrophobic and non‐compatible with aqueous media; thus prior surface modification is essential. Our method uses the internal UV or visible light emitted from UCPs upon photoexcitation with near‐infrared radiation, to locally photopolymerize a thin polymer shell around the UCPs. In this way, a large variety of monomers with different chemical functionalities can be incorporated. If required, a second layer can be added on top of the first. Our method can provide a large spectrum of surface functional groups rapidly and in one pot, hence offering a platform for the preparation of libraries of functional polymer‐encapsulated UCPs for applications in bioassays, biosensing, optical imaging, and theranostics.
Search for a Strong, Virtually “No‐Shift” Hydrogen Bond: A Cage Molecule with an Exceptional OH⋅⋅⋅F Interaction
Authors: Struble Mark D. , Kelly Courtney , Siegler Maxime A. , Lectka Thomas 
Published: July 2014

AbstractReported herein is the synthesis of a molecule containing an unusually strong hydrogen bond between an OH donor and a covalent F acceptor, a heretofore somewhat ill‐defined if not controversial interaction. This unique hydrogen bond is to a large extent a product of the tight framework of the rigid caged system. Remarkably, the interaction shows little to no perceptible shift in the OH stretch of the IR spectrum relative to appropriate nonhydrogen‐bound standards in fairly non‐interactive solvents. This fascinating example of what has been termed a virtual “no‐shift” hydrogen bond is investigated through NMR (coupling constants, isotopic chemical shift perturbations, proton exchange rates) and IR studies which all tell a consistent story.
Die C‐H‐Aktivierungs/1,3‐Diin‐Strategie: hochselektive direkte Synthese vielfältiger Bisheterocyclen mithilfe von RhIII‐Katalyse
Authors: Yu Da‐Gang , de Azambuja Francisco , Gensch Tobias , Daniliuc Constantin G. , Glorius Frank 
Published: July 2014

AbstractDie Reaktivität und Selektivität von 1,3‐Diinen in der übergangsmetallkatalysierten C‐H‐Aktivierung wurden genutzt, um zügig vielfältige polysubstituierte Bisheterocyclen aufzubauen, die bedeutend, aber schwer zugänglich sind. Mit der C‐H‐Aktivierungs/1,3‐Diin‐Strategie überwanden wir die Hürden hinsichtlich der Selektivität (Chemo‐ und Regioselektivität sowie Mono‐/Dianellierung) und erhielten sieben Arten von benachbarten Bisheterocyclen durch Knüpfung von vier strategischen Bindungen mit hoher Effizienz und Selektivität.
Spin Selectivity in Electron Transfer in Photosystem I
Authors: Carmeli Itai , Kumar Karuppannan Senthil , Heifler Omri , Carmeli Chanoch , Naaman Ron 
Published: July 2014

AbstractPhotosystem I (PSI) is one of the most studied electron transfer (ET) systems in nature; it is found in plants, algae, and bacteria. The effect of the system structure and its electronic properties on the electron transfer rate and yield was investigated for years in details. In this work we show that not only those system properties affect the ET efficiency, but also the electrons’ spin. Using a newly developed spintronic device and a technique which enables control over the orientation of the PSI monolayer relative to the device (silver) surface, it was possible to evaluate the degree and direction of the spin polarization in ET in PSI. We find high‐spin selectivity throughout the entire ET path and establish that the spins of the electrons being transferred are aligned parallel to their momenta. The spin selectivity peaks at 300 K and vanishes at temperatures below about 150 K. A mechanism is suggested in which the chiral structure of the protein complex plays an important role in determining the high‐spin selectivity and its temperature dependence. Our observation of high light induced spin dependent ET in PSI introduces the possibility that spin may play an important role in ET in biology.
A Protein‐Based Pentavalent Inhibitor of the Cholera Toxin B‐Subunit
Authors: Branson Thomas R. , McAllister Tom E. , Garcia‐Hartjes Jaime , Fascione Martin A. , Ross James F. , Warriner Stuart L. , Wennekes Tom , Zuilhof Han , Turnbull W. Bruce 
Published: July 2014

AbstractProtein toxins produced by bacteria are the cause of many life‐threatening diarrheal diseases. Many of these toxins, including cholera toxin (CT), enter the cell by first binding to glycolipids in the cell membrane. Inhibiting these multivalent protein/carbohydrate interactions would prevent the toxin from entering cells and causing diarrhea. Here we demonstrate that the site‐specific modification of a protein scaffold, which is perfectly matched in both size and valency to the target toxin, provides a convenient route to an effective multivalent inhibitor. The resulting pentavalent neoglycoprotein displays an inhibition potency (IC50) of 104 pM for the CT B‐subunit (CTB), which is the most potent pentavalent inhibitor for this target reported thus far. Complexation of the inhibitor and CTB resulted in a protein heterodimer. This inhibition strategy can potentially be applied to many multivalent receptors and also opens up new possibilities for protein assembly strategies.
Palladium‐Catalyzed Alkoxycarbonylation of Conjugated Dienes under Acid‐Free Conditions: Atom‐Economic Synthesis of β,γ‐Unsaturated Esters
Authors: Fang Xianjie , Li Haoquan , Jackstell Ralf , Beller Matthias 
Published: July 2014

AbstractCarbonylation reactions constitute important methodologies for the synthesis of all kinds of carboxylic acid derivatives. The development of novel and better catalysts for these transformations is of interest for both academic and industrial research. Here, a benign palladium‐based catalyst system for the alkoxycarbonylation of conjugated dienes under acid‐free conditions has been developed. This atom‐efficient transformation provides straightforward access to a variety of β,γ‐unsaturated esters in good to excellent yields and often with high selectivities. As an industrially relevant example the (formal) synthesis of dimethyl adipate and ε‐caprolactam from 1,3‐butadiene is demonstrated.
An Unusual Protein–Protein Interaction through Coupled Unfolding and Binding
Authors: Yu Tae‐Kyung , Shin Seung‐A , Kim Eun‐Hee , Kim Sunghyun , Ryu Kyung‐Seok , Cheong Haekap , Ahn Hee‐Chul , Jon Sangyong , Suh Jeong‐Yong 
Published: July 2014

AbstractAptides, a novel class of high‐affinity peptides, recognize diverse molecular targets with high affinity and specificity. The solution structure of the aptide APT specifically bound to fibronectin extradomain B (EDB), which represents an unusual protein–protein interaction that involves coupled unfolding and binding, is reported. APT binding is accompanied by unfolding of the C‐terminal β strand of EDB, thereby permitting APT to interact with the freshly exposed hydrophobic interior surfaces of EDB. The β‐hairpin scaffold of APT drives the interaction by a β‐strand displacement mechanism, such that an intramolecular β sheet is replaced by an intermolecular β sheet. The unfolding of EDB perturbs the tight domain association between EDB and FN8 of fibronectin, thus highlighting its potential use as a scaffold that switches between stretched and bent conformations.
A High‐Pressure NMR Probe for Aqueous Geochemistry
Authors: Pautler Brent G. , Colla Christopher A. , Johnson Rene L. , Klavins Peter , Harley Stephen J. , Ohlin C. André , Sverjensky Dimitri A. , Walton Jeffrey H. , Casey William H. 
Published: July 2014

AbstractA non‐magnetic piston‐cylinder pressure cell is presented for solution‐state NMR spectroscopy at geochemical pressures. The probe has been calibrated up to 20 kbar using in situ ruby fluorescence and allows for the measurement of pressure dependencies of a wide variety of NMR‐active nuclei with as little as 10 μL of sample in a microcoil. Initial 11B NMR spectroscopy of the H3BO3–catechol equilibria reveals a large pressure‐driven exchange rate and a negative pressure‐dependent activation volume, reflecting increased solvation and electrostriction upon boron‐catecholate formation. The inexpensive probe design doubles the current pressure range available for solution NMR spectroscopy and is particularly important to advance the field of aqueous geochemistry.
A Metal‐Free Three‐Component Reaction for the Regioselective Synthesis of 1,4,5‐Trisubstituted 1,2,3‐Triazoles
Authors: Thomas Joice , John Jubi , Parekh Nikita , Dehaen Wim 
Published: July 2014

AbstractA metal‐free three‐component reaction to synthesize 1,4,5‐trisubstituted 1,2,3‐triazoles from readily available building blocks, such as aldehydes, nitroalkanes, and organic azides, is described. The process is enabled by an organocatalyzed Knoevenagel condensation of the formyl group with the nitro compound, which is followed by the 1,3‐dipolar cycloaddition of the azide to the activated alkene. The reaction features an excellent substrate scope, and the products are obtained with high yield and regioselectivity. This method can be utilized for the synthesis of fused triazole heterocycles and materials with several triazole moieties.
Development of Multinuclear Polymeric Nanoparticles as Robust Protein Nanocarriers
Authors: Wu Jun , Kamaly Nazila , Shi Jinjun , Zhao Lili , Xiao Zeyu , Hollett Geoffrey , John Rohit , Ray Shaunak , Xu Xiaoyang , Zhang Xueqing , Kantoff Philip W. , Farokhzad Omid C. 
Published: July 2014

AbstractOne limitation of current biodegradable polymeric nanoparticles is their inability to effectively encapsulate and sustainably release proteins while maintaining protein bioactivity. Here we report the engineering of PLGA–polycation nanoparticles with a core–shell structure that act as a robust vector for the encapsulation and delivery of proteins and peptides. The optimized nanoparticles can load high amounts of proteins (>20 % of nanoparticles by weight) in aqueous solution without organic solvents through electrostatic interactions by simple mixing, thereby forming nanospheres in seconds with diameters <200 nm. The relationship between nanosphere size, surface charge, PLGA–polycation composition, and protein loading is also investigated. The stable nanosphere complexes contain multiple PLGA–polycation nanoparticles, surrounded by large amounts of protein. This study highlights a novel strategy for the delivery of proteins and other relevant molecules.
Textile‐surface interfacial asymmetric polymerization
Authors: Goto Hiromasa , Jwa Jinmi , Nakajima Kuniharu , Wang Aohan 
Published: July 2014

ABSTRACTThis research demonstrated that polymerization of aniline on cellulose produces chiroptically active composites. Polymerization of aniline in the presence of cotton fibers consisting of chiral cellulose are performed to prepare a polyaniline (PANI)/cotton composite. The polymerization is conducted at the cotton interface. The resultant PANI/cotton composite shows chiroptical activity elucidated with diffuse reflectance circular dichroism. In this reaction, textile‐surface interfacial asymmetric polymerization is performed with imprinting of chiral structure from the cotton as a natural chiroptically active polymer to the PANI. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41118.
Green polycarbonates prepared by the copolymerization of CO2 with epoxides
Authors: Taherimehr Masoumeh , Pescarmona Paolo P. 
Published: July 2014

ABSTRACTPolycarbonates can be prepared by the copolymerization of epoxides with carbon dioxide as an inexpensive, abundant, nontoxic, and renewable feedstock. This review covers the synthesis, the physicochemical properties, and the growing applications of this class of green polymers. The review has been conceived to provide a useful tool for the researchers who are new to this field, as well as to offer an updated overview for those who are already actively working on this topic. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41141.
Preparation of oligochitosan via In situ enzymatic hydrolysis of chitosan by amylase in [Gly]BF4 ionic liquid/water homogeneous system
Authors: Yuan Bing , Li Lu , Xie Congxia , Liu Kun , Yu Shitao 
Published: July 2014

ABSTRACTThe preparation of oligochitosan with excellent performance via in situ enzymatic hydrolysis of chitosan by amylase in ionic liquid system is reported. It has been found that [Gly]BF4 ionic liquid leads to the good solubility and assistant degradation for chitosan, as well as good biocompatibility for amylase. In the homogeneous system that contained 1.0 g chitosan (degree of deacetylation = 88.5%) and 99.0 g 2 wt % [Gly]BF4 aqueous solution, oligochitosan with 2200 viscosity‐average molecular weight has been obtained after 0.12 g amylase being used for 3 h at 50°C and pH 5.0. This result is superior to that conducted in acetic acid system. Moreover, [Gly]BF4 can be easily separated from the product and reused with only slight performance loss (oligochitosan product with 2700 viscosity‐average molecular weight has been obtained after [Gly]BF4 being reused for five times). In addition, the mechanism for enzymatic hydrolysis of chitosan in [Gly]BF4 ionic liquid has been described. The research on the moisture‐absorption, ‐retention, and antibacterial activity of oligochitosan product shows that the smaller molecular weight would bring the better moisture‐absorption and antibacterial properties. The oligochitosan product with 2200 viscosity‐average molecular weight exhibits preferable antibacterial properties to S. aureus and E. coli. At the same time, the moisture‐absorption and ‐retention capacity of the above product can reach 32% (relative humidity (RH) = 43%), 62% (RH = 81%), and 150% (RH = 43%), 35% (dry silica gel) respectively. The enzymatic preparation of oligochitosan through [Gly]BF4 ionic liquid/water homogeneous system can be an efficient and environment‐friendly method for academics and industry. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41152.
Packaging guest proteins into the encapsulin nanocompartment from Rhodococcus erythropolis N771
Authors: Tamura Akio , Fukutani Yosuke , Takami Taku , Fujii Motoko , Nakaguchi Yuki , Murakami Yoshihiko , Noguchi Keiichi , Yohda Masafumi , Odaka Masafumi 
Published: July 2014

ABSTRACTThe encapsulin nanocompartment from Rhodococcus erythropolis N771 (Reencapsulin) was expressed and purified in wild‐type and C‐terminally His‐tagged forms. Negative‐stained transmission electron microscopy, field‐flow fractionation combined with multi‐angle light scattering and dynamic light scattering analyses showed that 60 Reencapsulin monomers were assembled as a spherical particle with a diameter of 28 nm. Heterogeneous guest proteins such as EGFP and firefly luciferase were packaged into the internal cavity of the Reencapsulin nanocompartment by fusing the C‐terminal 37‐amino‐acid sequence of the R. erythropolis N771 DypB peroxidase to the C‐terminus. Reencapsulin has the potential to package target proteins in its internal cavity and/or display them on its external surface, making it a feasible carrier for nanotechnology applications. Biotechnol. Bioeng. 2015;112: 13–20. © 2014 Wiley Periodicals, Inc.
Making Sense in and of the Asexual Community: Navigating Relationships and Identities in a Context of Resistance
Authors: Chasin CJ DeLuzio 
Published: July 2014

AbstractDespite some increased visibility in recent years, the asexual community and asexuality generally remain largely unknown. Aiming to demystify asexuality, this paper discusses the context of anti‐asexual animosity in which the (largely American) asexual community is situated. Specifically, the asexual community constructed itself in response to hostility, including explicit anti‐asexual discrimination, homophobia against asexual people perceived to be lesbian or gay, and the negative impact of (implicit) pathologising low sexual desire. This theoretical paper outlines some of the unique challenges asexual people face negotiating identities and relationships; the collective sense‐making strategies they use (generating language and discourse) to do so; and why these things are central to understanding asexual people's experiences. This is accomplished through a purposeful review of literature and a case study of the Asexual Visibility and Education Network as an asexual community space. Understanding the challenges asexual people face and the resources they invoke to overcome them helps applied psychologists develop the cultural competence they need to work effectively with the asexual people they will encounter. Copyright © 2014 John Wiley & Sons, Ltd.
The Chemistry and Biology of 6‐Hydroxyceramide, the Youngest Member of the Human Sphingolipid Family
Authors: Kováčik Andrej , Roh Jaroslav , Vávrová Kateřina 
Published: July 2014

AbstractSphingolipids are crucial for the life of the cell. In land‐dwelling mammals, they are equally important outside the cell—in the extracellular space of the skin barrier—because they prevent loss of water. Although a large body of research has elucidated many of the functions of sphingolipids, their extensive structural diversity remains intriguing. A new class of sphingolipids based on 6‐hydroxylated sphingosine has recently been identified in human skin. Abnormal levels of these 6‐hydroxylated ceramides have repeatedly been observed in atopic dermatitis; however, neither the biosynthesis nor the roles of these unique ceramide subclasses have been established in the human body. In this Minireview, we summarize the current knowledge of 6‐hydroxyceramides, including their discovery, structure, stereochemistry, occurrence in healthy and diseased human epidermis, and synthetic approaches to 6‐hydroxysphingosine and related ceramides.
Tuning Regioisomer Reactivity in Catalysis using Bifunctional Metal–Organic Frameworks with Mixed Linkers
Authors: Xu Xiaoying , van Bokhoven Jeroen A. , Ranocchiari Marco 
Published: July 2014

AbstractThe activity of two bifunctional metal–organic frameworks (MOFs) with IRMOF‐9 topology that contain amino, phosphine oxide and methyl groups is described. The amino group acts as an active site for the Knoevenagel condensation of ortho, meta or para nitrobenzaldehyde and malononitrile, while the non‐active site diphenylphosphoryl or methyl group moderate the spatial characteristics inside the MOF pores. The functional groups induce a unique catalytic response. The reaction activity was enhanced when catalysed by MOFs comparing with aniline, whereas the phosphine oxide retards formation of the ortho isomer product.