bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Carbohydrate–Anion Recognition System in Aprotic Solvents
Authors: Ren Bo , Dong Hai , Ramström Olof 
Published: March 2014

AbstractA carbohydrate–anion recognition system in nonpolar solvents is reported, in which complexes form at the B‐faces of β‐D‐pyranosides with H1‐, H3‐, and H5‐cis patterns similar to carbohydrate–π interactions. The complexation effect was evaluated for a range of carbohydrate structures; it resulted in either 1:1 carbohydrate–anion complexes, or 1:2 complex formation depending on the protection pattern of the carbohydrate. The interaction was also evaluated with different anions and solvents. In both cases it resulted in significant binding differences. The results indicate that complexation originates from van der Waals interactions or weak CH⋅⋅⋅A− hydrogen bonds between the binding partners and is related to electron‐withdrawing groups of the carbohydrates as well as increased hydrogen‐bond‐accepting capability of the anions.
Rapid Determination of the Amino Acid Configuration of Xenotetrapeptide
Authors: Kegler Carsten , Nollmann Friederike I. , Ahrendt Tilman , Fleischhacker Florian , Bode Edna , Bode Helge B. 
Published: March 2014

AbstractAn E. coli strain with deletions in five transaminases (ΔaspC ΔilvE ΔtyrB ΔavtA ΔybfQ) was constructed to be unable to degrade several amino acids. This strain was used as an expression host for the analysis of the amino acid configuration of nonribosomally synthesized peptides, including the novel peptide “xenotetrapeptide” from Xenorhabdus nematophila, by using a combination of labeling experiments and mass spectrometry. Additionally, the number of D‐amino acids in the produced peptide was assigned following simple cultivation of the expression strain in D2O.
Biological Evaluation of Multivalent Lewis X–MGL‐1 Interactions
Authors: Eriksson Magdalena , Serna Sonia , Maglinao Maha , Schlegel Mark K. , Seeberger Peter H. , Reichardt Niels‐Christian , Lepenies Bernd 
Published: March 2014

AbstractMyeloid C‐type lectin receptors (CLRs) expressed by antigen‐presenting cells are pattern‐recognition receptors involved in the recognition of pathogens as well as of self‐antigens. The interaction of carbohydrate ligands with a CLR can trigger immune responses. Although several CLR ligands are known, there is limited insight into CLR targeting by carbohydrate ligands. The weak affinity of lectin–carbohydrate interactions often renders multivalent carbohydrate presentation necessary. Here, we have analyzed the impact of multivalent presentation of the trisaccharide Lewis X (LeX) epitope on its interaction with the CLR macrophage galactose‐type lectin‐1 (MGL‐1). Glycan arrays, including N‐glycan structures with terminal LeX, were prepared by enzymatic extension of immobilized synthetic core structures with two recombinant glycosyltransferases. Incubation of arrays with an MGL‐1‐hFc fusion protein showed up to tenfold increased binding to multiantennary N‐glycans displaying LeX structures, compared to monovalent LeX trisaccharide. Multivalent presentation of LeX on the model antigen ovalbumin (OVA) led to increased cytokine production in a dendritic cell /T cell coculture system. Furthermore, immunization of mice with LeX‐OVA conjugates modulated cytokine production and the humoral response, compared to OVA alone. This study provides insights into how multivalent carbohydrate–lectin interactions can be exploited to modulate immune responses.
A Dual Small‐Molecule Rheostat for Precise Control of Protein Concentration in Mammalian Cells
Authors: Lin Yu Hsuan , Pratt Matthew R. 
Published: March 2014

AbstractOne of the most successful strategies for controlling protein concentrations in living cells relies on protein destabilization domains (DD). Under normal conditions, a DD will be rapidly degraded by the proteasome. However, the same DD can be stabilized or “shielded” in a stoichiometric complex with a small molecule, enabling dose‐dependent control of its concentration. This process has been exploited by several labs to post‐translationally control the expression levels of proteins in vitro as well as in vivo, although the previous technologies resulted in permanent fusion of the protein of interest to the DD, which can affect biological activity and complicate results. We previously reported a complementary strategy, termed traceless shielding (TShld), in which the protein of interest is released in its native form. Here, we describe an optimized protein concentration control system, TTShld, which retains the traceless features of TShld but utilizes two tiers of small molecule control to set protein concentrations in living cells. These experiments provide the first protein concentration control system that results in both a wide range of protein concentrations and proteins free from engineered fusion constructs. The TTShld system has a greatly improved dynamic range compared to our previously reported system, and the traceless feature is attractive for elucidation of the consequences of protein concentration in cell biology.
Risk and resiliency factors influencing onset and adolescence‐limited commercial sexual exploitation of disadvantaged girls
Authors: Reid Joan A. 
Published: March 2014

ABSTRACTBackgroundPrevious research into age‐related variables relevant to girls and young women being involved in commercial sexual exploitation (including prostitution) has not distinguished between its onset and limitation to adolescence and its early onset and persistence into adult life.AimsThe aims of this study were to examine variables associated with adolescent versus adult onset of commercial sexual exploitation and identify potential risk and resiliency factors differentiating adolescence‐limited sexual exploitation and early‐onset‐adult persistent exploitation.MethodInterviews with 174 vulnerable mostly African‐American women, 23% of whom reported commercial sexual exploitation in adolescence and/or adulthood, yielded data, which were analysed using multinomial logistic regressions.ResultsAdolescent sexual victimisation, younger age at first alcohol/drug use, being a victim of intimate partner violence and sense of stigmatisation of sexual self/others were all variables associated with adolescent onset of commercial sexual exploitation. Educational attainment differentiated adolescence limited from adolescent‐adult persistent exploitation; exploitation had ceased by adulthood among over two‐thirds of those who completed at least high school education, but only 13% of those exploited into adult life had finished high school.Conclusions and implications for practiceAs level of education was linked to cessation of exploitation by adulthood, support for vulnerable girls to complete education at least to high school level may be protective.The link between early onset of substance misuse and persistent exploitation suggests that education and support specifically targeted within this field could reduce likelihood of persistent abuse.Work directed at improvement of self‐image may also reduce risk of persistent exploitation. Copyright © 2014 John Wiley & Sons, Ltd.
Oxygen‐Terminated Diamond Electrodes in Alkaline Media: Structure and OH Generation
Authors: Quaino Paola M. , Schmickler Wolfgang 
Published: March 2014

AbstractThe structure and energetics of two types of oxygen‐terminated diamond surfaces, the keto and ether configurations, were investigated by density functional theory. To explore OH generation, we studied the approach of a hydroxyl radical to these surfaces. The OH radical strongly interacted with the ether‐type surface, whereas the radical was repelled in the keto configuration. The kinetics of OH generation in alkaline solutions (OH−↔OH+e−) on oxygen‐terminated diamond electrodes was investigated in light of the theory of catalyzed electron transfer. Our results suggested that the electron transfer occurs in the outer‐sphere mode with an activation energy of 0.5 eV.
Utilizing Chromium as the Photoanode Substrate in Dye‐Sensitized Solar Cells
Authors: Behrouznejad Fatemeh , Taghavinia Nima 
Published: March 2014

AbstractFluorine‐doped tin oxide (FTO) is replaced with chromium as the photoanode substrate in a dye‐sensitized solar cell (DSSC), and the effect of chromium(III) oxide on the electron lifetime and the performance of a Cr‐based DSSC is investigated and compared with conventional FTO‐based devices. It is shown that Cr is stable in the chemically aggressive iodide‐based electrolyte, which can be attributed to the compact oxide overlayer. The chromium‐oxide layer also effectively blocks electron recombination from the substrate, while hindering electron transfer from the TiO2 film to the Cr electrode. We show that pretreatment of the electrodeposited Cr film with a colloidal sol of TiO2 is extremely effective in reducing the electron‐transfer resistance at the Cr–TiO2 interface. This effect may be attributed to both increasing interconnections between the mesoporous layer of TiO2 and the rough electrodeposited layer of Cr, as well as inhibition of the thickening Cr2O3 layer during the thermal process. The colloidal sol treatment increases the cell efficiency by 73 % of the initial value (from 2.58 to 4.47 %) and the fill factor from 0.38 to 0.64.
Correlation of Insulin‐Enhancing Properties of Vanadium‐Dipicolinate Complexes in Model Membrane Systems: Phospholipid Langmuir Monolayers and AOT Reverse Micelles
Authors: Sostarecz Audra G. , Gaidamauskas Ernestas , Distin Steve , Bonetti Sandra J. , Levinger Nancy E. , Crans Debbie C. 
Published: March 2014

AbstractWe explore the interactions of VIII‐, VIV‐, and VV‐2,6‐pyridinedicarboxylic acid (dipic) complexes with model membrane systems and whether these interactions correlate with the blood‐glucose‐lowering effects of these compounds on STZ‐induced diabetic rats. Two model systems, dipalmitoylphosphatidylcholine (DPPC) Langmuir monolayers and AOT (sodium bis(2‐ethylhexyl)sulfosuccinate) reverse micelles present controlled environments for the systematic study of these vanadium complexes interacting with self‐assembled lipids. Results from the Langmuir monolayer studies show that vanadium complexes in all three oxidation states interact with the DPPC monolayer; the VIII–phospholipid interactions result in a slight decrease in DPPC molecular area, whereas VIV and VV–phospholipid interactions appear to increase the DPPC molecular area, an observation consistent with penetration into the interface of this complex. Investigations also examined the interactions of VIII‐ and VIV‐dipic complexes with polar interfaces in AOT reverse micelles. Electron paramagnetic resonance spectroscopic studies of VIV complexes in reverse micelles indicate that the neutral and smaller 1:1 VIV‐dipic complex penetrates the interface, whereas the larger 1:2 VIV complex does not. UV/Vis spectroscopy studies of the anionic VIII‐dipic complex show only minor interactions. These results are in contrast to behavior of the VV‐dipic complex, [VO2(dipic)]−, which penetrates the AOT/isooctane reverse micellar interface. These model membrane studies indicate that VIII‐, VIV‐, and VV‐dipic complexes interact with and penetrate the lipid interfaces differently, an effect that agrees with the compounds’ efficacy at lowering elevated blood glucose levels in diabetic rats.
Highly Luminescent and Color‐Tunable Salicylate Ionic Liquids
Authors: Campbell Paul S. , Yang Mei , Pitz Demian , Cybinska Joanna , Mudring Anja‐Verena 
Published: March 2014

AbstractHigh quantum yields of up to 40.5 % can be achieved in salicylate‐bearing ionic liquids. A range of these ionic liquids have been synthesized and their photoluminescent properties studied in detail. The differences noted can be related back to the structure of the ionic liquid cation and possible interionic interactions. It is found that shifts of emission, particularly in the pyridinium‐based ionic liquids, can be related to cation–anion pairing interactions. Facile and controlled emission color mixing is demonstrated through combining different ILs, with emission colors ranging from blue to yellow.
The Protoelectric Potential Map (PPM): An Absolute Two‐Dimensional Chemical Potential Scale for a Global Understanding of Chemistry
Authors: Radtke Valentin , Himmel Daniel , Pütz Katharina , Goll Sascha K. , Krossing Ingo 
Published: March 2014

AbstractWe introduce the protoelectric potential map (PPM) as a novel, two‐dimensional plot of the absolute reduction potential (peabs scale) combined with the absolute protochemical potential (Brønsted acidity: pHabs scale). The validity of this thermodynamically derived PPM is solvent‐independent due to the scale zero points, which were chosen as the ideal electron gas and the ideal proton gas at standard conditions. To tie a chemical environment to these reference states, the standard Gibbs energies for the transfer of the gaseous electrons/protons to the medium are needed as anchor points. Thereby, the thermodynamics of any redox, acid–base or combined system in any medium can be related to any other, resulting in a predictability of reactions even over different media or phase boundaries. Instruction is given on how to construct the PPM from the anchor points derived and tabulated with this work. Since efforts to establish “absolute” reduction potential scales and also “absolute” pH scales already exist, a short review in this field is given and brought into relation to the PPM. Some comments on the electrochemical validation and realization conclude this concept article.
Synthesis of 18F‐Labelled β‐Lactams by Using the Kinugasa Reaction
Authors: Zlatopolskiy Boris D. , Krapf Philipp , Richarz Raphael , Frauendorf Holm , Mottaghy Felix M. , Neumaier Bernd 
Published: March 2014

AbstractOwing to their broad spectrum of biological activities and low toxicity, β‐lactams are attractive lead structures for the design of novel molecular probes. However, the synthesis of positron emission tomography (PET)‐isotope‐labelled β‐lactams has not yet been reported. Herein, we describe the simple preparation of radiofluorinated β‐lactams by using the fast Kinugasa reaction between 18F‐labelled nitrone [18F]‐1 and alkynes of different reactivity. Additionally, 18F‐labelled fused β‐lactams were obtained through the reaction of a cyclic nitrone 7 with radiofluorinated alkynes [18F]‐6 a,b. Radiochemical yields of the Kinugasa reaction products could be significantly increased by the use of different CuI ligands, which additionally allowed a reduction in the amount of precursor and/or reaction time. Model radiofluorinated β‐lactam‐peptide and protein conjugates ([18F]‐10 and 18F‐labelled BSA conjugate) were efficiently obtained in high yield under mild conditions (aq. MeCN, ambient temperature) within a short reaction time, demonstrating the suitability of the developed method for radiolabelling of sensitive molecules such as biopolymers.
Synthesis and Transformations of 5‐Chloro‐2,2′‐Dipyrrins and Their Boron Complexes, 8‐Chloro‐BODIPYs
Authors: Wang Haijun , Vicente M. Graça H. , Fronczek Frank R. , Smith Kevin M. 
Published: March 2014

AbstractSymmetric dipyrrylketones 1 a,b were synthesized in two steps from the corresponding α‐free pyrroles, by reaction with thiophosgene followed by oxidative hydrolysis under basic conditions. The dipyrrylketones produced the corresponding 5‐chloro‐dipyrrinium salts or 5‐ethoxy‐dipyrrins on reaction with phosgene or Meerwein’s salt, respectively. Boron complexation of the dipyrrins afforded the corresponding 8‐functionalized BODIPYs (borondipyrromethenes) in high yields. The 5‐chloro‐dipyrrinium salts reacted with methoxide or ethoxide ions to produce monopyrrole esters, presumably via a 5,5‐dialkoxy‐dipyrromethane intermediate. In contrast, 8‐chloro‐BODIPYs underwent a variety of nucleophilic substitutions of the chloro group in the presence of alkoxide ions, Grignard reagents, and thiols. In the presence of excess alkoxide or Grignard reagent, at room temperature or above, substitution at the boron center also occurred. The 8‐chloro‐BODIPY was a particularly useful reagent for the preparation of 8‐aryl‐, 8‐alkyl‐, and 8‐vinyl‐substituted BODIPYs in very high yields, using Pd0‐catalyzed Stille cross‐coupling reactions. The X‐ray structures of eleven BODIPYs and two pyrroles are presented, and the spectroscopic properties of the synthesized BODIPYs are discussed.
Near‐Infrared‐Light‐Driven Artificial Photosynthesis by Nanobiocatalytic Assemblies
Authors: Lee Joon Seok , Nam Dong Heon , Kuk Su Keun , Park Chan Beum 
Published: March 2014

AbstractArtificial photosynthesis in nanobiocatalytic assemblies aims to reconstruct man‐made photosensitizers, electron mediators, electron donors, and redox enzymes for solar synthesis of valuable chemicals through photochemical cofactor regeneration. Herein, we report, for the first time, on nanobiocatalytic artificial photosynthesis in near‐infrared (NIR) light, which constitutes over 46% of the solar energy. For NIR‐light‐driven photoenzymatic synthesis, we synthesized silica‐coated upconversion nanoparticles, Si‐NaYF4:Yb,Er and Si‐NaYF4:Yb,Tm, for efficient photon‐conversion through Förster resonance energy transfer (FRET) with rose bengal (RB), a photosensitizer. We observed NIR‐induced electron transfer by using linear sweep voltammetric analysis; this indicates that photoexcited electrons of RB/Si‐NaYF4:Yb,Er are transferred to NAD+ through a Rh‐based electron mediator. RB/Si‐NaYF4:Yb,Er nanoparticles, which exhibit higher FRET efficiency due to more spectral overlap than RB/Si‐NaYF4:Yb,Tm, perform much better in the photoenzymatic conversion.
In silico Design, Synthesis, and Screening of Novel Deoxyhypusine Synthase Inhibitors Targeting HIV‐1 Replication
Authors: Schroeder Marcus , Kolodzik Adrian , Pfaff Katharina , Priyadarshini Poornima , Krepstakies Marcel , Hauber Joachim , Rarey Matthias , Meier Chris 
Published: March 2014

AbstractThe human enzyme deoxyhypusine synthase (DHS) is an important host cell factor that participates in the post‐translational hypusine modification of eukaryotic initiation factor 5A (eIF‐5A). Hypusine‐modified eIF‐5A plays a role in a number of diseases, including HIV infection/AIDS. Thus, DHS represents a novel and attractive drug target. So far, four crystal structures are available, and various substances have been tested for inhibition of human DHS. Among these inhibitors, N‐1‐guanyl‐1,7‐diaminoheptane (GC7) has been co‐crystallized in the active site of DHS. However, despite its potency, GC7 is not selective enough to be used in drug applications. Therefore, new compounds that target DHS are needed. Herein we report the in silico design, chemical synthesis, and biological evaluation of new DHS inhibitors. One of these inhibitors showed dose‐dependent inhibition of DHS in vitro, as well as suppression of HIV replication in cell cultures. Furthermore, the compound exhibited no cytotoxic effects at active concentrations. Thus, this designed compound demonstrated proof of principle and represents a promising starting point for the development of new drug candidates to specifically interfere with DHS activity.
The DiPPro Approach: Synthesis, Hydrolysis, and Antiviral Activity of Lipophilic d4T Diphosphate Prodrugs
Authors: Schulz Tilmann , Balzarini Jan , Meier Chris 
Published: March 2014

AbstractBioreversible protection of the β‐phosphate group of nucleoside diphosphates (NDPs) as bis(acyloxybenzyl)phosphate esters is presented. To investigate the structure–activity relationship of these potential NDP prodrugs (DiPPro drugs) a series of DiPPro compounds was synthesized bearing fatty acids of various lengths and d4T as a model nucleoside. For synthesis of the lipophilically modified diphosphate group, preformed phosphoramidites were allowed to react with nucleotides, and the β‐PIII moiety was subsequently oxidized. The chemical and enzymatic stability of these prodrugs was studied in different media such as phosphate buffer (pH 7.3) or CEM cell extracts. In all media, the hydrolysis rate was clearly dependent on the acyl moiety and decreased with increasing alkyl chain length. The compounds showed a markedly lower half‐life in cell extracts than in pH 7.3 phosphate buffer due to the presence of enzyme‐catalyzed cleavage. In all media, the DiPPro compounds released d4T diphosphate (d4TDP) as the main product beside d4TMP. In antiviral assays, the compounds proved to be at least as potent as d4T against HIV‐1 and 2 in wild‐type CEM/0 cells. As a proof of concept, compounds with longer acyl residues showed very good anti‐HIV activities in thymidine‐kinase‐deficient cells (CEM/TK−), indicating their ability to penetrate cell membranes and the delivery of phosphorylated metabolites.
SpiroZin1: A Reversible and pH‐Insensitive, Reaction‐Based, Red‐Fluorescent Probe for Imaging Biological Mobile Zinc
Authors: Rivera‐Fuentes Pablo , Lippard Stephen J. 
Published: March 2014

AbstractA reversible, reaction‐based sensor for biological mobile zinc was designed, prepared, and characterized. The sensing mechanism of this probe is based on the zinc‐induced, ring‐opening reaction of spirobenzopyran to give a cyanine fluorophore that emits in the deep‐red region of the electromagnetic spectrum. This probe is not activated by protons and operates efficiently in aqueous solution at pH 7 and high ionic strength. The mechanism of this reaction was studied by using a combination of kinetics experiments and DFT calculations. The biocompatibility of the probe was demonstrated in live HeLa cells.
The effects of CYP3A4 induction and inhibition on the pharmacokinetics of alisporivir in humans
Authors: Barve Avantika , Kovacs Steven J. , Ke June , Crabbe Rafael , Grosgurin Peter , Menetrey Annick , Nicolas‐Métral Valerie , Dabovic Kristina , Dole Kiran , Zhang Jie , Praestgaard Jens , Sunkara Gangadhar , Stein Daniel 
Published: March 2014

AbstractIn vitro data suggest that alisporivir is a substrate and inhibitor of CYP3A4 and P‐gp. Hence, the potential for drug–drug interactions when alisporivir is co‐administered with CYP3A4 and/or P‐gp inhibitors such as ketoconazole, azithromycin and CYP3A4 inducers such as rifampin were evaluated in three separate clinical studies. Co‐administration with ketoconazole (a strong CYP3A4 inhibitor) increased the Cmax, AUC and terminal elimination half‐life of alisporivir by approximately two‐, eight‐ ,and threefold, respectively. Co‐administration with azithromycin (a putative weak CYP3A4 inhibitor and substrate) had no impact on the Cmax and AUC of alisporivir. Rifampin (a CYP3A4 inducer) caused an approximate 90% reduction in alisporivir Cmax and AUC and a fourfold reduction in alisporivir terminal elimination half‐life. Alisporivir as an inhibitor of CYP3A4 caused a 39% increase in azithromycin exposure. The results from these studies establish alisporivir as a sensitive CYP3A4 substrate in vivo. Consequently, co‐administered potent CYP3A4 inhibitors and inducers are likely to cause clinically significant changes in the exposure to alisporivir.