bluuebunny/crossref_metadata_2025 huggingface dataset:
A parallel stranded G‐quadruplex composed of threose nucleic acid (TNA)
Authors: Liao Jen‐yu , Anosova Irina , Bala Saikat , Van Horn Wade D. , Chaput John C.
Published: October 2016

G‐rich sequences can adopt four‐stranded helical structures, called G‐quadruplexes, that self‐assemble around monovalent cations like sodium (Na+) and potassium (K+). Whether similar structures can be formed from xeno‐nucleic acid (XNA) polymers with a shorter backbone repeat unit is an unanswered question with significant implications on the fold space of functional XNA polymers. Here, we examine the potential for TNA (α‐l‐threofuranosyl nucleic acid) to adopt a four‐stranded helical structure based on a planar G‐quartet motif. Using native polyacrylamide gel electrophoresis (PAGE), circular dichroism (CD) and solution‐state nuclear magnetic resonance (NMR) spectroscopy, we show that despite a backbone repeat unit that is one atom shorter than the backbone repeat unit found in DNA and RNA, TNA can self‐assemble into stable G‐quadruplex structures that are similar in thermal stability to equivalent DNA structures. However, unlike DNA, TNA does not appear to discriminate between Na+ and K+ ions, as G‐quadruplex structures form equally well in the presence of either ion. Together, these findings demonstrate that despite a shorter backbone repeat unit, TNA is capable of self‐assembling into stable G‐quadruplex structures.
LC–MS/MS method development for quantification of doxorubicin and its metabolite 13‐hydroxy doxorubicin in mice biological matrices: Application to a pharmaco‐delivery study
Authors: Mazzucchelli Serena , Ravelli Alessandro , Gigli Fausto , Minoli Mauro , Corsi Fabio , Ciuffreda Pierangela , Ottria Roberta
Published: October 2016

This study describes the development of simple, rapid and sensitive liquid chromatography tandem mass spectrometry method for the simultaneous analysis of doxorubicin and its major metabolite, doxorubicinol, in mouse plasma, urine and tissues. The calibration curves were linear over the range 5–250 ng/mL for doxorubicin and 1.25–25 ng/mL for doxorubicinol in plasma and tumor, over the range 25–500 ng/mL for doxorubicin and 1.25–25 ng/mL for doxorubicinol in liver and kidney, and over the range 25–1000 ng/mL for doxorubicin and doxorubicinol in urine. The study was validated, using quality control samples prepared in all different matrices, for accuracy, precision, linearity, selectivity, lower limit of quantification and recovery in accordance with the US Food & Drug Administration guidelines. The method was successfully applied in determining the pharmaco‐distribution of doxorubicin and doxorubicinol after intravenously administration in tumor‐bearing mice of drug, free or nano‐formulated in ferritin nanoparticles or in liposomes. Obtained results demonstrate an effective different distribution and doxorubicin protection against metabolism linked to nano‐formulation. This method, thanks to its validation in plasma and urine, could be a powerful tool for pharmaceutical research and therapeutic drug monitoring, which is a clinical approach currently used in the optimization of oncologic treatments.
Support vector machine classification of arterial volume‐weighted arterial spin tagging images
Authors: Shah Yash S. , Hernandez‐Garcia Luis , Jahanian Hesamoddin , Peltier Scott J.
Published: October 2016

Introduction

In recent years, machine‐learning techniques have gained growing popularity in medical image analysis. Temporal brain‐state classification is one of the major applications of machine‐learning techniques in functional magnetic resonance imaging (fMRI) brain data. This article explores the use of support vector machine (SVM) classification technique with motor‐visual activation paradigm to perform brain‐state classification into activation and rest with an emphasis on different acquisition techniques.

Methods

Images were acquired using a recently developed variant of traditional pseudocontinuous arterial spin labeling technique called arterial volume‐weighted arterial spin tagging (AVAST). The classification scheme is also performed on images acquired using blood oxygenation–level dependent (BOLD) and traditional perfusion‐weighted arterial spin labeling (ASL) techniques for comparison.

Results

The AVAST technique outperforms traditional pseudocontinuous ASL, achieving classification accuracy comparable to that of BOLD contrast images.

Conclusion

This study demonstrates that AVAST has superior signal‐to‐noise ratio and improved temporal resolution as compared with traditional perfusion‐weighted ASL and reduced sensitivity to scanner drift as compared with BOLD. Owing to these characteristics, AVAST lends itself as an ideal choice for dynamic fMRI and real‐time neurofeedback experiments with sustained activation periods.
Erlotinib induces the human non–small‐cell lung cancer cells apoptosis via activating ROS‐dependent JNK pathways
Authors: Shan Fenglian , Shao Zewei , Jiang Shenghua , Cheng Zhaozhong
Published: October 2016

Although erlotinib (ERL) has drawn more and more attention toward its anticancer properties effect, the underlying mechanisms of ERL's anticancer properties effect remain unclear yet. So, the aim of this research was to explore the underlying anticancer mechanisms of ERL and to explore whether the reactive oxygen species (ROS)‐dependent c‐Jun N‐terminal kinase (JNK) pathway contributed to the anticancer properties provided by ERL. In our study, we used MTT assay to detect the anticell growth ability of ERL on human non–small‐cell lung cancer cell lines (A549). The extent of cell apoptosis was determined by Hoechst 33342 staining and fluorescence‐activated cell sorter (FACS) assay. Then, DCFH‐DA and JC‐1 staining were used to monitor intracellular reactive oxygen species (ROS) and mitochondrial membrane potential (MMP), respectively. Finally, the effect of ERL on phosphorylation state of JNK protein and downstream apoptosis concerned proteins were detected by western blotting assay. Results showed that ERL significantly suppressed the growth and reproduction of A549 cells with the concentration rising up in vitro. Hoechst 33342 staining and FACS assay also confirmed the proapoptosis effect of ERL on A549 cells with the concentration rising up. Furthermore, exposure of A549 cells to ERL increased the intracellular ROS production. As expected, intracellular ROS activated the proapoptotic JNK signaling pathway and inhibited the activation of EFGR signaling pathway. Our results also revealed that ERL could induce cell‐cycle arrest at G0/G1 period. Activation of JNK protein decreased MMP and downregulated content of antiapoptotic protein Bcl‐2 concomitant with the upregulated content of proapoptotic protein Bax in A549 cells. In addition, c‐Jun and cleaved caspase‐3 were also activated by the phosphorylated JNK induced by ERL. All of these proapoptosis effect of ERL was reversed by administration of N‐acetylcysteine (NAC), which performed as a ROS scavenger. Our results suggest that ERL induces A549 cells apoptosis via activating ROS‐dependent JNK pathways in human non–small lung cancer cells that provide a new experimental foundation for cancer therapy.
Role of comorbidity on outcome of head and neck cancer: a population‐based study in Thuringia, Germany
Authors: Göllnitz Irene , Inhestern Johanna , Wendt Thomas G. , Buentzel Jens , Esser Dirk , Böger Daniel , Mueller Andreas H. , Piesold Jörn‐Uwe , Schultze‐Mosgau Stefan , Eigendorff Ekkehard , Schlattmann Peter , Guntinas‐Lichius Orlando
Published: October 2016

To examine the impact of comorbidity on overall survival (OS) in a population‐based study of patients with head and neck cancer who were treated between 2009 and 2011. Data of 1094 patients with primary head and neck carcinomas without distant metastasis from the Thuringian cancer registries were evaluated concerning the influence of patient's characteristics and comorbidity on OS. Data on comorbidity prior to head and neck cancer diagnosis was adapted to the Charlson Comorbidity (CCI), age‐adjusted CCI (ACCI), head and neck CCI (HNCCI), simplified comorbidity score (SCS), and to the Adult Comorbidity Evaluation–27 (ACE‐27). Most patients were male (80%; median age: 60 years; 50% stage IV tumors). Smoking, alcohol abuse, and anemia were registered for 38%, 33%, and 23% of the patients, respectively. Predominant therapy was surgery + radiochemotherapy (30%), surgery (29%), and surgery + radiotherapy (21%). Mean CCI, ACCI, HNCCI, SCS and ACE‐27 were 1.0 ± 1.5, 2.6 ± 2.1, 0.6 ± 0.8, 4.4 ± 4.2, and 0.9 ± 0.9, respectively. Median follow‐up was 25.7 months. Multivariable analyses showed that higher age, higher UICC stage, no therapy, including surgery or radiotherapy, alcohol abuse, and anemia, higher comorbidity were independent risk factors for worse OS (all P < 0.05). According to the discriminatory power analysis none of the five comorbidity scores was superior to the other scores to prognosticate OS. This population‐based study showed that comorbidity is frequent in German patients with head and neck cancer and is an important risk factor for poor OS. Comorbidity should be routinely assessed and taken into account in prospective clinical trials.
Salmonella entericaserovar Typhi and gallbladder cancer: a case–control study and meta‐analysis
Authors: Koshiol Jill , Wozniak Aniela , Cook Paz , Adaniel Christina , Acevedo Johanna , Azócar Lorena , Hsing Ann W. , Roa Juan C. , Pasetti Marcela F. , Miquel Juan F. , Levine Myron M. , Ferreccio Catterina ,   the Gallbladder Cancer Chile Working Group
Published: October 2016

In Chile, where gallbladder cancer (GBC) rates are high and typhoid fever was endemic until the 1990s, we evaluated the association betweenSalmonella entericaserovar Typhi (S. Typhi) antibodies andGBC. We tested 39GBCcases, 40 gallstone controls, and 39 population‐based controls forS. Typhi Vi antibodies and performed culture and quantitative polymerase chain reaction for the subset with bile, gallstone, tissue, and stool samples available. We calculated gender and education‐adjusted odds ratios (ORs) and 95% confidence intervals (CIs) for the association withGBC. We also conducted a meta‐analysis of >1000GBCcases by combining our results with previous studies.GBCcases were more likely to have high Vi antibody titer levels than combined controls (OR: 4.0, 95%CI: 0.9–18.3), althoughS. Typhi was not recovered from bile, gallstone, tissue, or stool samples. In our meta‐analysis, the summary relative risk was 4.6 (95%CI: 3.1–6.8,Pheterogeneity=0.6) for anti‐Vi and 5.0 (95%CI: 2.7–9.3,Pheterogeneity = 0.2) for bile or stool culture. Our results are consistent with the meta‐analysis. Despite differences in study methods (e.g.,S. Typhi detection assay), most studies found a positive association betweenS. Typhi andGBC. However, the mechanism underlying this association requires further investigation
Additive interactions between PRKAA1 polymorphisms and Helicobacter pylori CagA infection associated with gastric cancer risk in Koreans
Authors: Eom Sang‐Yong , Hong Seon‐Mi , Yim Dong–Hyuk , Kwon Hyo‐Jin , Kim Dae‐Hoon , Yun Hyo‐Yung , Song Young‐Jin , Youn Sei‐Jin , Hyun Taisun , Park Joo‐Seung , Kim Byung Sik , Kim Yong‐Dae , Kim Heon
Published: October 2016

Although several studies reported genetic polymorphisms in protein kinase AMP‐activated alpha 1 catalytic subunit (PRKAA1) and their associations with gastric cancer risk, few have evaluated associations between Helicobacter pylori infection and PRKAA1 gene‐environment interactions. Here, we evaluated the effects of interactions between H. pylori infection and PRKAA1 polymorphisms on gastric cancer risk in Koreans. In this hospital‐based case–control study, PRKAA1 genotypes were analyzed and H. pylori infection and CagA status were examined using a serologic method in 846 pairs of gastric cancer patients and controls matched for age and sex. H. pylori seropositivity was associated with a 1.43‐fold [95% confidence interval: 1.12–1.81] increase in the risk of gastric cancer, and CagA low‐positive titers during H. pylori infection increased the risk by 1.85‐fold (95% confidence interval, 1.38–2.48). Significant positive interaction between the PRKAA1 rs13361707 genotype and H. pylori infection was verified on an additive scale [relative excess risk due to interaction, 0.55; 95% confidence interval, 0.05–1.04; P = 0.030], and the gene‐environment interaction between PRKAA1 rs13361707 and CagA status was also statistically significant (relative excess risk due to interaction, 0.50; 95% confidence interval, 0.30–0.70; P < 0.001). Our results indicated that H. pylori infection, CagA status, and PRKAA1 polymorphisms were risk factors for gastric cancer in Koreans, and that the combination of two of these factors rather than their independent effects synergistically increased the risk.
First Report on Rare Unifloral Honey of Endemic Moltkia petraea (Tratt.) Griseb. from Croatia: Detailed Chemical Screening and Antioxidant Capacity
Authors: Jerković Igor , Marijanović Zvonimir , Zekić Marina , Tuberoso Carlo I. G.
Published: October 2016

Rare Moltkia petraea (Tratt.) Griseb. honey from Croatia was first time characterised. The spectrophotometric assays on CIE L*a*b*Cab*hab° colour coordinates, total phenol content and antioxidant capacity (FRAP, CUPRAC, DPPH• and ABTS•+ assays) determined higher honey values generally close to dark honeys ranges. Headspace solid‐phase microextraction (HS‐SPME) on two fibres after GC‐FID and GC/MS revealed the major compounds 2‐phenylacetaldehyde (12.8%; 15.6%), benzaldehyde (11.1%; 10.0%), octane (9.3%; 7.6%), nonane, propan‐2‐one, pentan‐2‐one, pentanal and nonanal (4.9%; 14.5%). Ultrasonic solvent extraction (USE) mainly isolated non‐specific higher molecular compounds characteristic of the comb environment. Targeted HLPC‐DAD analysis of the honey determined higher concentration of phenylalanine (212.08 mg/kg) and lumichrome (16.25 mg/kg) along with tyrosine and kojic acid. The headspace composition (chemical fingerprint) and high concentration of lumichrome can be considered particular for M. petraea honey.
Guide Strand 3′‐End Modifications Regulate siRNA Specificity
Authors: Valenzuela Rachel A. P. , Onizuka Kazumitsu , Ball‐Jones Alexi A. , Hu Tiannan , Suter Scott R. , Beal Peter A.
Published: October 2016

Short interfering RNA (siRNA)‐triggered gene knockdown through the RNA interference (RNAi) pathway is widely used to study gene function, and siRNA‐based therapeutics are in development. However, as the guide strand of an siRNA can function like a natural microRNA (miRNA), siRNAs often repress hundreds of off‐target transcripts with complementarity only to the seed region (nucleotides 2–8) of the guide strand. Here, we describe novel guide strand 3′‐end modifications derived from 1‐ethynylribose (1‐ER) and copper‐catalyzed azide–alkyne cycloaddition reactions and evaluate their impact on target versus miRNA‐like off‐target knockdown. Surprisingly, when positioned at the guide strand 3′‐end, the parent 1‐ER modification substantially reduced off‐target knockdown while having no measurable effect on on‐target knockdown potency. In addition, these modifications were shown to modulate siRNA affinity for the hAgo2 PAZ domain. However, the change in PAZ domain binding affinity was not sufficient to predict the modification's effect on miRNA‐like off targeting.
One‐Pot, Two‐Step Hydroxylation of the Macrocyclic Diterpenoid β‐Cembrenediol Catalyzed by P450 BM3 Mutants
Authors: Le‐Huu Priska , Petrović Dušan , Strodel Birgit , Urlacher Vlada B.
Published: October 2016

Cytochrome P450 monooxygenases (P450s) are involved in the biosynthesis of a wide range of bioactive secondary metabolites. They often introduce several oxy functionalities at different positions of a substrate through multiple steps and produce a range of oxidized derivatives. Herein, we describe a one‐pot two‐step hydroxylation of the diterpenoid β‐cembrenediol isolated from the plant Nicotiana tabacum. This 14‐membered macrocycle shows neuroprotective effects and is, along with its oxidized derivatives, of pharmaceutical interest. Sequential hydroxylations catalyzed by the regioselective P450 BM3 mutants F87A/I263L and V78A/F87G yielded the epimeric (9S,10R/S)‐β‐cembrenetetraols with a diastereomeric ratio of 48:52. The replacement of the mutant V78A/F87G with L75A/V78A/F87G in the second step improves the diastereomeric ratio up to 10:90. Absolute configurations of the newly introduced hydroxy groups were determined by quantum‐mechanical calculations of NMR spectra.
Superior Electrochemical Oxygen Evolution Enabled by Three‐Dimensional Layered Double Hydroxide Nanosheet Superstructures
Authors: Zhao Dandan , Jiang Kezhu , Pi Yecan , Huang Xiaoqing
Published: October 2016

Although extensive efforts have been devoted to the pursuit of promising electrocatalysts to lower the overpotential of the oxygen evolution reaction (OER), the design of low‐costing earth‐abundant OER electrocatalysts with desirable performance remains a formidable challenge. Herein, we demonstrate a facile strategy to create ultrathin NiFe layered double hydroxide (LDH) nanosheets grown on carbon nanotubes (CNTs) as superior OER electrocatalysts. Different from previously reported NiFe‐LDH nanomaterials, the newly generated NiFe‐LDH@CNTs exhibit distinct features, including ultrathin building blocks, a 1 D structure, 3 D hierarchical architecture, and the electron effect. Significantly, it was revealed that doping Fe into Ni‐LDH@CNTs optimized the performance for the OER; Ni8Fe‐LDH@CNTs was found to be the most active and is one of the best non‐noble metal catalysts for the OER to date. The catalysts are also highly stable for the OER with little potential shift after an 18 h test. Both X‐band electron spin resonance and X‐ray photoelectron spectroscopy indicated that optimized iron doping resulted in intense interaction between Nix+ and Fe3+ and electron transfer from Nix+ to Fe3+, which thus boosted the OER performance.
Unveiling the Reaction Machinery of the [AuI]‐Catalyzed Synthesis of Substituted Acenes by a [1,5]‐H Shift Cascade Reaction
Authors: Bandini Marco , Cera Gianpiero , Miscione Gian Pietro
Published: October 2016

The reaction mechanism of the gold‐catalyzed synthesis of functionalized acenes via cascade [3,3]‐oxo migration/[1,5]‐H shift is documented by DFT calculations. Interestingly, the overall reaction machinery displays a notable exothermic profile and the pivotal role played by the metal center in the initial [1,3]‐acyloxy migration of 1 was also discovered. Contrarily, contribution of the gold complex in the H shift was negligible as the energy profiles of the gold‐based and metal‐free protocols are very similar in the latest stage.
N‐Oxyl‐Radical‐Catalyzed Intermolecular Aminooxygenation of Styrenes and Inter/intramolecular Aminoalkoxylation of Homoallylic Alcohols
Authors: Weng Shiue‐Shien , Zhang Jia‐Wei
Published: October 2016

By taking advantage of the redox cycle between the reductive N‐oxyl radical and its oxidative oxoammonium counterpart, the N‐oxyl‐radical‐catalyzed intermolecular aminohydroxylation of styrenes with N‐fluorobenzenesulfonimide was developed. Various vinyl arenes were aminohydroxylated in moderate to excellent yields with high regio‐ and diastereoselectivities by using environmentally benign H2O as the oxygen source. In addition, the sequential inter/intramolecular aminoalkoxylation of homoallylic alcohols was also achieved under anhydrous conditions, which allowed the exclusive synthesis of pharmaceutically useful 2‐aryl‐3‐amino‐disubstituted tetrahydrofurans.
Artificial Neural Network Modeling of Hydrodynamics of Liquid‐Solid Circulating Fluidized Beds
Authors: Palkar Ritesh Ramesh , Shilapuram Vidyasagar
Published: October 2016

Solids holdup and solids circulation rate are the two important hydrodynamic variables affected by process conditions. These two variables have a significant influence on the performance of a liquid‐solid circulating fluidized bed (LSCFB). An artificial neural network (ANN) methodology was developed and simulated to predict the performance of the LSCFB for the experimental dataset collected under various process conditions. Different statistical parameters were applied to evaluate the prominent and unique characteristic features of the ANN‐predicted parameters. The ANN model successfully predicted the experimental observations and captured the actual nonlinear behavior noticed during the experiments. Model validation confirmed that this data‐driven technique can be used to model such nonlinear systems.
Electrochemical Properties and Reactions of Oxygen‐Containing Organotrifluoroborates and Their Boronic Acid Esters
Authors: Ohtsuka Kazuhiro , Inagi Shinsuke , Fuchigami Toshio
Published: October 2016

Electrochemical analyses of anisole, phenoxymethylboronic acid pinacol ester, tetra‐n‐butylammonium phenoxymethyltrifluoroborate, and their benzyloxy analogues were comparatively studied by using cyclic voltammetry measurements, and a marked β‐effect for organotrifluoroborates was found, which was indicated by experimental and theoretical aspects. Organotrifluoroborates were found to have much lower oxidation potentials than the corresponding boronic acid pinacol esters. The oxidation potentials of boronic acid pinacol esters were also significantly decreased in the presence of fluoride ions. This β‐effect is more pronounced than that of the corresponding organosulfur compounds reported previously. Anodic substitution reactions of organotrifluoroborates were successfully carried out in the presence of oxygen nucleophiles to provide regioselectively substituted products in moderate yields. Supporting‐electrolyte‐free electrolysis was also demonstrated.
A Nexus between Theory and Experiment: Non‐Empirical Quantum Mechanical Computational Methodology Applied to Cucurbit[n]uril⋅Guest Binding Interactions
Authors: Hostaš Jiří , Sigwalt David , Šekutor Marina , Ajani Haresh , Dubecký Matúš , Řezáč Jan , Zavalij Peter Y. , Cao Liping , Wohlschlager Christian , Mlinarić‐Majerski Kata , Isaacs Lyle , Glaser Robert , Hobza Pavel
Published: October 2016

A training set of eleven X‐ray structures determined for biomimetic complexes between cucurbit[n]uril (CB[7 or 8]) hosts and adamantane‐/diamantane ammonium/aminium guests were studied with DFT‐D3 quantum mechanical computational methods to afford ΔGcalcd binding energies. A novel feature of this work is that the fidelity of the BLYP‐D3/def2‐TZVPP choice of DFT functional was proven by comparison with more accurate methods. For the first time, the CB[n]⋅guest complex binding energy subcomponents [for example, ΔEdispersion, ΔEelectrostatic, ΔGsolvation, binding entropy (−TΔS), and induced fit Edeformation(host), Edeformation(guest)] were calculated. Only a few weeks of computation time per complex were required by using this protocol. The deformation (stiffness) and solvation properties (with emphasis on cavity desolvation) of cucurbit[n]uril (n=5, 6, 7, 8) isolated host molecules were also explored by means of the DFT‐D3 method. A high ρ2=0.84 correlation coefficient between ΔGexptl and ΔGcalcd was achieved without any scaling of the calculated terms (at 298 K). This linear dependence was utilized for ΔGcalcd predictions of new complexes. The nature of binding, including the role of high energy water molecules, was also studied. The utility of introduction of tethered [‐(CH2)nNH3]+ amino loops attached to N,N‐dimethyl‐adamantane‐1‐amine and N,N,N′,N′‐tetramethyl diamantane‐4,9‐diamine skeletons (both from an experimental and a theoretical perspective) is presented here as a promising tool for the achievement of new ultra‐high binding guests to CB[7] hosts. Predictions of not yet measured equilibrium constants are presented herein.
Can a Six‐Letter Alphabet Increase the Likelihood of Photochemical Assault to the Genetic Code?
Authors: Ashwood Brennan , Pollum Marvin , Crespo‐Hernández Carlos E.
Published: October 2016

In 2014, two unnatural nucleosides, d5SICS and dNaM, were shown to selectively base pair and replicate with high fidelity in a modified strain of E. coli, thus effectively expanding its genetic alphabet from four to six letters. More recently, a significant reduction in cell proliferation was reported in cells cultured with d5SICS, and putatively with dNaM, upon exposure to brief periods of near‐visible radiation. The photosensitizing properties of the lowest‐energy excited triplet state of both d5SICS and dNaM were implicated in their cytotoxicity. Importantly, however, the excited‐state mechanisms by which near‐visible excitation populates the triplet states of d5SICS and dNaM are currently unknown. In this study, steady‐state and time‐resolved spectroscopies are combined with quantum‐chemical calculations in order to reveal the excited‐state relaxation mechanisms leading to efficient population of the triplet states in these unnatural nucleosides in solution. It is shown that excitation of d5SICS or dNaM with near‐visible light leads overwhelmingly to ultrafast population of their triplet states on the femtosecond time scale. The results presented in this work lend strong support to the proposal that photoexcitation of these unnatural nucleosides can accelerate oxidatively generated damage to DNA and other biomolecules within the cellular environment.
Molecular Level Characterization of the Structure and Interactions in Peptide‐Functionalized Metal–Organic Frameworks
Authors: Todorova Tanya K. , Rozanska Xavier , Gervais Christel , Legrand Alexandre , Ho Linh N. , Berruyer Pierrick , Lesage Anne , Emsley Lyndon , Farrusseng David , Canivet Jérôme , Mellot‐Draznieks Caroline
Published: October 2016

We use density functional theory, newly parameterized molecular dynamics simulations, and last generation 15N dynamic nuclear polarization surface enhanced solid‐state NMR spectroscopy (DNP SENS) to understand graft–host interactions and effects imposed by the metal–organic framework (MOF) host on peptide conformations in a peptide‐functionalized MOF. Focusing on two grafts typified by MIL‐68‐proline (‐Pro) and MIL‐68‐glycine‐proline (‐Gly‐Pro), we identified the most likely peptide conformations adopted in the functionalized hybrid frameworks. We found that hydrogen bond interactions between the graft and the surface hydroxyl groups of the MOF are essential in determining the peptides conformation(s). DNP SENS methodology shows unprecedented signal enhancements when applied to these peptide‐functionalized MOFs. The calculated chemical shifts of selected MIL‐68‐NH‐Pro and MIL‐68‐NH‐Gly‐Pro conformations are in a good agreement with the experimentally obtained 15N NMR signals. The study shows that the conformations of peptides when grafted in a MOF host are unlikely to be freely distributed, and conformational selection is directed by strong host–guest interactions.
Formation of Long, Multicenter π‐[TCNE]22− Dimers in Solution: Solvation and Stability Assessed through Molecular Dynamics Simulations
Authors: Capdevila‐Cortada Marçal , Ribas‐Arino Jordi , Chaumont Alain , Wipff Georges , Novoa Juan J.
Published: October 2016

Purely organic radical ions dimerize in solution at low temperature, forming long, multicenter bonds, despite the metastability of the isolated dimers. Here, we present the first computational study of these π‐dimers in solution, with explicit consideration of solvent molecules and finite temperature effects. By means of force‐field and ab initio molecular dynamics and free energy simulations, the structure and stability of π‐[TCNE]22− (TCNE=tetracyanoethylene) dimers in dichloromethane have been evaluated. Although the dimers dissociate at room temperature, they are stable at 175 K and their structure is similar to the one in the solid state, with a cofacial arrangement of the radicals at an interplanar separation of approximately 3.0 Å. The π‐[TCNE]22− dimers form dissociated ion pairs with the NBu4+ counterions, and their first solvation shell comprises approximately 20 CH2Cl2 molecules. Among them, the eight molecules distributed along the equatorial plane of the dimer play a key role in stabilizing the dimer through bridging C−H⋅⋅⋅N contacts. The calculated free energy of dimerization of TCNE.− in solution at 175 K is −5.5 kcal mol−1. These results provide the first quantitative model describing the pairing of radical ions in solution, and demonstrate the key role of solvation forces on the dimerization process.
Low‐Symmetry Ω‐Shaped Zinc Phthalocyanine Sensitizers with Panchromatic Light‐Harvesting Properties for Dye‐Sensitized Solar Cells
Authors: Yamamoto Satoshi , Zhang Angel , Stillman Martin J. , Kobayashi Nagao , Kimura Mutsumi
Published: October 2016

Two low‐symmetry phthalocyanines (Pcs) substituted with thiophene units at the non‐peripheral (α) and peripheral (β) positions were synthesized and their optical, electronic‐structure, and electrochemical properties were investigated. The substitution of thiophene units at the α positions of the phthalocyanine skeleton resulted in a red shift of the Q band and significantly modified the molecular‐orbital electronic distributions just below the HOMO and just above the LUMO, with distortion of the typical Gouterman four‐orbital arrangement of MOs. Two amphiphilic Ω‐shaped ZnPcs (αPcS1 and αPcS2) bearing a π‐conjugated side chain with an adsorption site at an α position of the Pc macrocycle were synthesized as sensitizers for dye‐sensitized solar cells (DSSCs). The absorption spectra of αPcS1 and αPcS2 showed red shifted Q bands and a broad band from 350 to 550 nm assignable to the intramolecular charge‐transfer transition from the ZnPc core to the side chains. Time‐dependent DFT calculations provided a clear interpretation of the effect of the thiophene conjugation on the typical phthalocyanine core π MOs. Compound αPcS1 was used as a light‐harvesting dye on a TiO2 electrode for a DSSC, which showed a panchromatic response in the range 400–800 nm with a power conversion efficiency of 5.5 % under one‐sun conditions.
Triterpenoid‐Based Self‐Healing Supramolecular Polymer Hydrogels Formed by Host–Guest Interactions
Authors: Li Ying , Li Jianzuo , Zhao Xia , Yan Qiang , Gao Yuxia , Hao Jie , Hu Jun , Ju Yong
Published: October 2016

Pentacyclic triterpenoids, a class of naturally bioactive products having multiple functional groups, unique chiral centers, rigid skeletons, and good biocompatibility, are ideal building blocks for fabricating versatile supramolecular structures. In this research, the natural pentacyclic triterpenoid glycyrrhetinic acid (GA) was used as a guest molecule for β‐cyclodextrin (β‐CD) to form a GA/β‐CD (1:1) inclusion complex. By means of GA and β‐CD pendant groups in N,N′‐dimethylacrylamide copolymers, a supramolecular polymer hydrogel can be physically cross‐linked by host–guest interactions between GA and β‐CD moieties. Moreover, self‐healing of this hydrogel was observed and confirmed by step‐strain rheological measurements, whereby the maximum storage modulus occurred at a [GA]/[β‐CD] molar ratio of 1:1. Additionally, these polymers displayed outstanding biocompatibility. The introduction of a natural pentacyclic triterpenoid into a hydrogel system not only provides a biocompatible guest–host complementary GA/β‐CD pair, but also makes this hydrogel an attractive candidate for tissue engineering.
Redox‐Neutral Aromatization of Cyclic Amines: Mechanistic Insights and Harnessing of Reactive Intermediates for Amine α‐ and β‐C−H Functionalization
Authors: Ma Longle , Paul Anirudra , Breugst Martin , Seidel Daniel
Published: October 2016

Cyclic amines such as pyrrolidine and piperidine are known to undergo condensations with aldehydes to furnish pyrrole and pyridine derivatives, respectively. A combined experimental and computational study provides detailed insights into the mechanism of pyrrole formation. A number of reactive intermediates (e.g., azomethine ylides, conjugated azomethine ylides, enamines) were intercepted, outlining strategies for circumventing aromatization as a valuable pathway for amine C−H functionalization.
Highly Air‐Stable Electron‐Transport Material for Ink‐Jet‐Printed OLEDs
Authors: Wei Changting , Zhuang Jinyong , Chen Yali , Zhang Dongyu , Su Wenming , Cui Zheng
Published: October 2016

A novel cross‐linkable electron‐transport material has been designed and synthesized for use in the fabrication of solution‐processed OLEDs. The material exhibits a low LUMO level of −3.51 eV, a high electron mobility of 1.5×10−5 cm2 V−1 s−1, and excellent stability. An average 9.3 % shrinkage in film thickness was observed for the film after thermal curing. A maximum external quantum efficiency (EQE) of 15.6 % (35.0 cd A−1) was achieved for blue‐phosphorescent OLEDs by spin‐coating and 13.8 % (31.0 cd A−1) for an ink‐jet‐printed device, both of which are better than the EQE of a control device prepared by vacuum‐deposition (see figure).
Differential Solvation
Authors: Schreckenbach Georg
Published: October 2016

Solvation effects influence reaction equilibria by preferentially stabilizing reactants or products (differential solvation). We propose using simple electrostatic concepts to qualitatively interpret and understand these effects, applying the Born and Kirkwood–Onsager equations. Scenarios include, for charged species, redox potentials, different total absolute charges between reactants and products, and size differences between reactants and products. In addition, for neutral species, they are differences in total dipole moment and size differences. These scenarios are illustrated with several examples from different areas of chemistry.
Influence of the Headgroup of Azolium‐Based Lipids on Their Biophysical Properties and Cytotoxicity
Authors: Rühling Andreas , Wang Da , Ernst Johannes B. , Wulff Stephanie , Honeker Roman , Richter Christian , Ferry Angélique , Galla Hans‐Joachim , Glorius Frank
Published: October 2016

A series of (un‐)charged NHC derivatives bearing two pentadecyl chains in the backbone was studied in detail to find cooperative effects between the membrane and the NHC derivative. The tendency to show lipid‐like behavior is dependent on the properties of the NHC derivative headgroup, which can be modified on demand. The surface activity was investigated by film balance measurements, epifluorescence microscopy, and differential scanning calorimetry. Additionally the cytotoxicity was evaluated against different cell lines such as eukaryotic tumor cell lines. These novel lipid‐like NHC derivatives offer a broad spectrum for biological applications.
Nucleophilic Additions to Coordinated 1,10‐Phenanthroline: Intramolecular, Intermolecular, Reversible, and Irreversible
Authors: Arévalo Rebeca , Menéndez M. Isabel , López Ramón , Merino Isabel , Riera Lucía , Pérez Julio
Published: October 2016

KN(SiMe3)2 reacts with [Re(CO)3(phen)(PMe3)]OTf via reversible addition to the phen ligand and irreversible deprotonation of the PMe3 ligand followed by intramolecular attack to phen by the deprotonated phosphane, whereas MeLi irreversibly adds to phen. The addition of MeLi has been shown to be intermolecular, unlike previously known nucleophilic additions to pyridines.
Cyclopenta[b]annulation of Heteroarenes by Organocatalytic γ′[C(sp3)−H] Functionalization of Ynones
Authors: Raghu Moluguri , Grover Jagdeep , Ramasastry S. S. V.
Published: October 2016

A new approach for the cyclopenta[b]annulation of heteroarenes through metal‐free and directing‐group‐free γ′[C(sp3)−H] functionalization and intramolecular hydroalkylation of ynones has been developed. In an unprecedented event, nucleophilic addition of an organophosphine to the designed ynones triggers γ′[C(sp3)−H] functionalization, leading to the formation of heteroaryl‐based ortho‐quinodimethane (oQDM) intermediates that undergo carbocyclization to provide cyclopentannulated heteroarenes in good yields and excellent stereoselectivities. Deuterium‐labeling experiments substantiated the proposed reaction mechanism as well as the speculated epimerization.
Concomitant Carboxylate and Oxalate Formation From the Activation of CO2 by a Thorium(III) Complex
Authors: Formanuik Alasdair , Ortu Fabrizio , Inman Christopher J. , Kerridge Andrew , Castro Ludovic , Maron Laurent , Mills David P.
Published: October 2016

Improving our comprehension of diverse CO2 activation pathways is of vital importance for the widespread future utilization of this abundant greenhouse gas. CO2 activation by uranium(III) complexes is now relatively well understood, with oxo/carbonate formation predominating as CO2 is readily reduced to CO, but isolated thorium(III) CO2 activation is unprecedented. We show that the thorium(III) complex, [Th(Cp′′)3] (1, Cp′′={C5H3(SiMe3)2‐1,3}), reacts with CO2 to give the mixed oxalate‐carboxylate thorium(IV) complex [{Th(Cp′′)2[κ2‐O2C{C5H3‐3,3′‐(SiMe3)2}]}2(μ‐κ2:κ2‐C2O4)] (3). The concomitant formation of oxalate and carboxylate is unique for CO2 activation, as in previous examples either reduction or insertion is favored to yield a single product. Therefore, thorium(III) CO2 activation can differ from better understood uranium(III) chemistry.
Water‐Soluble, Thermostable, Photomodulated Color‐Switching Quantum Dots
Authors: Díaz Sebastián A. , Gillanders Florencia , Susumu Kimihiro , Oh Eunkeu , Medintz Igor L. , Jovin Thomas M.
Published: October 2016

Photoswitchable probes are of great utility in fluorescence microscopy, permitting numerous determinations, including molecular localization for super‐resolution, based on their modifiable emission intensity and spectra. We have coated a blue‐emitting (425 nm) quantum dot (QD) with a diheteroarylethene photochrome (PCf), the closed form isomer of which has absorption and emission maxima at 440 and 520–530 nm, respectively, and thus functions as a fluorescent acceptor for the QD donor in Förster resonance energy transfer (FRET). The transition from the non‐absorbing, non‐fluorescent open state to the fluorescent closed state is achieved by irradiation in the near‐UV and reversed by visible light. The PCf is coupled to an amphiphilic polymer that stably coats the QD, thereby creating a water‐soluble color‐switching QD (csQD) emitting in the blue after visible light irradiation and in the green after UV irradiation. Thus, csQDs photomodulate between two observable states, without the “off” state of previous constructs. The resulting change in the emission ratios of the QD and PCf is up to 180 %, and the csQD can undergo multiple photocycles with minimal fatigue.
ChemInform Abstract: Na2Co3[Fe(CN)6]2: A Promising Cathode Material for Lithium‐Ion and Sodium‐Ion Batteries.
Authors: Yuan Yan , Wang Junxiang , Hu Zongqian , Lei Haiping , Tian Donghua , Jiao Shuqiang
Published: October 2016

The nanocrystalline Prussian blue analogue of title is fabricated by co‐precipitation from an aqueous Na4Fe(CN)6 solution to which a CoCl2 solution is added dropwise at 25 °C.
ChemInform Abstract: Controllable Assembly of Vanadium‐Containing Polyoxoniobate‐Based Three‐Dimensional Organic—Inorganic Hybrid Compounds and Their Photocatalytic Properties.
Authors: Hu Jufang , Wang Yin , Zhang Xinning , Chi Yingnan , Yang Song , Li Jikun , Hu Changwen
Published: October 2016

Controllable synthesis of the two vanadium‐containing polyoxoniobate‐based three‐dimensional hybrid compounds (IV) and (V) is achieved by simply changing the hydrothermal temperature or adding N‐(aminoethyl)piperazine as an additive.
ChemInform Abstract: Solution 31P NMR Study of the Acid‐Catalyzed Formation of a Highly Charged {U24Pp12} Nanocluster, [(UO2)24(O2)24 (P2O7)12]48‐, and Its Structural Characterization in the Solid State Using Single‐Crystal Neutron Diffraction.
Authors: Dembowski Mateusz , Olds Travis A. , Pellegrini Kristi L. , Hoffmann Christina , Wang Xiaoping , Hickam Sarah , He Junhong , Oliver Allen G. , Burns Peter C.
Published: October 2016

Crystals of Na44K6 [(UO2)24(O2)24 (P2O7)12] [IO3]2·140H2O (triclinic space group P$\bar 1$, Z = 2) are obtained by evaporation of aqueous solutions containing UO2(NO3)2, H2O2, Na4P2O7, Et4NOH, and HIO3 (14 d, 19% yield).
ChemInform Abstract: Synthesis, Crystal Structure and Charge‐Distribution Validation of β‐Na4Cu(MoO4)3 Adopting the Alluadite Structure‐Type.
Authors: Dridi Wassim , Zid Mohamed Faouzi
Published: October 2016

Single crystals of the new β‐variety of Na4Cu(MoO4)3 are prepared by firing a 4:1:3 molar mixture of Na2CO3, Cu(OAc), and (NH4)6Mo7O24 in air (porcelain crucible, 873 K, 20 d; cooling to 823 K at a rate of 10 K/d).
ChemInform Abstract: YCu(TeO3)2(NO3) (H2O)3: A Novel Layered Tellurite.
Authors: Mills Stuart J. , Dunstan Maja A. , Christy Andrew G.
Published: October 2016

Dark blue prisms of the title tellurite are prepared by hydrothermal treatment of a 1:1:1 molar mixture of Y(NO3)3, Cu(NO3)2, and Te in H2O (autoclave, 473 K, 3 d).
ChemInform Abstract: Poly(hydroxamic acid) Functionalized Copper Catalyzed C—N Bond Formation Reactions.
Authors: Islam Md. Shaharul , Mandal Bablu Hira , Biswas Tapan Kumar , Rahman Md. Lutfor , Rashid S. S. , Tan Suat‐Hian , Sarkar Shaheen M.
Published: October 2016

The novel catalyst and its nanoparticle shape are utilized in click reactions and Michael addition reactions affording triazole derivatives and aliphatic amines, respectively.
ChemInform Abstract: Simple N‐Heterocyclic Carbenes as Ligands in Ullmann‐Type Ether and Thioether Formations.
Authors: Wu Jiang‐Ping , Saha Anjan K. , Haddad Nizar , Busacca Carl A. , Lorenz Jon C. , Lee Heewon , Senanayake Chris H.
Published: October 2016

A simple N‐heterocyclic carbene derived from imidazolium salt [enim]BF4 is found to be an efficient ligand in a range of Cu‐catalyzed cross‐coupling reactions furnishing aromatic ethers and thioethers.
ChemInform Abstract: Rhodium‐Catalyzed [5 + 2] Cycloaddition of 3‐Acyloxy‐1,4‐enyne with Alkene or Allene.
Authors: Song Wangze , Lynch John C. , Shu Xing‐zhong , Tang Weiping
Published: October 2016

Two novel types of [5 + 2] cycloaddition of 3‐acyloxy‐1,4‐enyne with a tethered alkene or a tethered allene are developed.
ChemInform Abstract: Titanium Dioxide Nanoparticles as Efficient Catalyst for the Synthesis of Pyran′s Annulated Heterocyclic Systems via Three‐Component Reaction.
Authors: Edjlali Ladan , Khanamiri Rahim Hosseinzdeh
Published: October 2016

The catalyst can be reused for six times without significant decrease in efficiency.
ChemInform Abstract: The Cyclopropylimine Rearrangement/Povarov Reaction Cascade for the Assembly of Pyrrolo[3,2‐c]quinoline Derivatives.
Authors: Cai Jinhui , Li Feifei , Deng Guo‐Jun , Ji Xiaochen , Huang Huawen
Published: October 2016

Pyrrolo[3,2‐c]quinoline derivatives are prepared using anilines and cyclopropyl aldehyde as starting material.
ChemInform Abstract: Investigation of Meyer—Schuster Rearrangement Promoted by a Samarium(III) Triflate/N‐Fluorobenzenesulfonimide Lewis Acid System.
Authors: Du Chuan , Wang Xiaoyu , Jin Shengfei , Shi Hui , Li Yangming , Pang Yadong , Liu Yang , Cheng Maosheng , Guo Chun , Liu Yongxiang
Published: October 2016

An acceleration effect is observed when catalytic amounts of N‐fluorobenzenesulfonimide is added to a microwave promoted samarium triflate catalyzed Meyer—Schuster rearrangement of propargylic alcohols.
ChemInform Abstract: Rapid Production of Benzazole Derivatives by a High‐Pressure and High‐Temperature Water Microflow Chemical Process.
Authors: Nagao I. , Ishizaka T. , Kawanami H.
Published: October 2016

Benzimidazoles, benzoxazoles, and benzothiazoles are prepared extremely rapidly.
ChemInform Abstract: Reductive N‐Methylation of Amines with Calcium Hydride and Pd/C Catalyst.
Authors: Guyon Carole , Duclos Marie‐Christine , Metay Estelle , Lemaire Marc
Published: October 2016

The monomethylation of amines with paraformaldehyde in proportions close to the stoichiometry in the presence of CaH2 as source of hydrogen and palladium on carbon as catalyst, is studied.
ChemInform Abstract: Copper‐Catalyzed Double Decarboxylative Coupling Reactions of Alkynyl Carboxylic Acid and Glyoxylic Acid: Synthesis of Propargyl Amines and Imidazopyridines.
Authors: Lee Sunwoo , et al.
Published: October 2016

The title coupling reaction proceeds in the presence of secondary amines to form propargyl amines.
ChemInform Abstract: A Mild Preparation of Alkynes from Alkenyl Triflates.
Authors: Yang Xiaowen , Wu Dimin , Lu Zhaohong , Sun Hongbin , Li Ang
Published: October 2016

A protocol for preparing alkynes from alkenyl triflates is reported.
ChemInform Abstract: anti‐Selective Aminofluorination of Alkenes with Amidines Mediated by Hypervalent Iodine(III) Reagents.
Authors: Chen Hui , Kaga Atsushi , Chiba Shunsuke
Published: October 2016

4‐Fluoroalkyl‐2‐imidazolines are synthesized by the anti‐selective aminofluorination of alkenes with amidines using hypervalent iodine(III) reagents.
ChemInform Abstract: The Reductive Cleavage of Picolinic Amides.
Authors: O' Donovan Daniel H. , De Fusco Claudia , Spring David R.
Published: October 2016

A facile procedure for the Zn/HCl promoted cleavage of picolinic amides is demonstrated.
ChemInform Abstract: Highly Stereoselective Cyclopropanation of Diazo Weinreb Amides Catalyzed by Chiral Ru(II)—Amm—Pheox Complexes.
Authors: Chanthamath Soda , Mandour Hamada S. A. , Tong Thu Minh Thi , Shibatomi Kazutaka , Iwasa Seiji
Published: October 2016

The first highly stereoselective cyclopropanation of diazo Weinreb amides with olefins using chiral Ru(II)—Pheox‐type catalysts is reported.
ChemInform Abstract: Amine‐Functionalized Metal‐Organic Frameworks: An Efficient and Recyclable Heterogeneous Catalyst for the Knoevenagel Condensation Reaction.
Authors: Taher Abu , Lee Dong‐Jin , Lee Byoung‐Ki , Lee Ik‐Mo
Published: October 2016

The novel efficient and reusable catalyst is applied for the Knoevenagel condensation of aldehydes and ketones with malononitrile or ethyl cyanoacetate.
ChemInform Abstract: Fluoroform‐Derived CuCF3 for Trifluoromethylation of Terminal and TMS‐Protected Alkynes.
Authors: He Lisi , Tsui Gavin Chit
Published: October 2016

Fluoroform derived air‐sensitive Cu(I)‐CF3 is oxidized to the much more electrophilic Cu(II)‐CF3 species upon treatment with air and the intermediate is directly employed for the trifluoromethylation process.
ChemInform Abstract: Cu(I)/Ag(I)‐Mediated Decarboxylative Trifluoromethylation of Arylpropiolic Acids with Me3SiCF3 at Room Temperature.
Authors: Yang Lingling , Jiang Linlin , Li Yaming , Fu Xinmei , Zhang Rong , Jin Kun , Duan Chunying
Published: October 2016

The method allows a direct approach to the target compounds and various functionalities are tolerated.
ChemInform Abstract: Synthesis of β‐Amino Alcohols Using the Tandem Reduction and Ring‐Opening Reaction of Nitroarenes and Epoxides.
Authors: Shi Chongyang , Ren Cheng , Zhang Erlei , Jin Huile , Yu Xiaochun , Wang Shun
Published: October 2016

The efficient procedure allows a mild access to various target compounds with a wide range of functionalities.
ChemInform Abstract: In(OTf)3/Acid Co‐Catalyzed Hydration of 1‐Haloalkynes to α‐Halomethyl Ketones.
Authors: Zeng Ming , Huang Rui‐Xue , Li Wen‐Yi , Liu Xiao‐Wen , He Fu‐Ling , Zhang Yi‐Yuan , Xiao Fang
Published: October 2016

A series of α‐bromoketones bearing functionalized aliphatic and aromatic substituents is readily available from simple, inexpensive starting materials.
ChemInform Abstract: Green Organocatalytic α‐Hydroxylation of Ketones.
Authors: Voutyritsa Errika , Theodorou Alexis , Kokotos Christoforos G.
Published: October 2016

Protected α‐hydroxy carbonyls or free α‐hydroxy ketones are prepared by an efficient and green method including the in situ conversion of various ketones into the corresponding silyl enol ethers and their oxidation to the corresponding α‐hydroxy ketones.
ChemInform Abstract: Studies of the Electronic Effects of Zinc Cluster Catalysts and Their Application to the Transesterification of β‐Keto Esters.
Authors: Agura Kazushi , Hayashi Yukiko , Wada Mari , Nakatake Daiki , Mashima Kazushi , Ohshima Takashi
Published: October 2016

Diverse β‐keto methyl esters, including amido and phosphate containing ones, as well as diesters, such as Meldrum′s acid, are efficiently transesterified with various primary, secondary, and tertiary alcohols which may contain a broad range of functional groups.
ChemInform Abstract: Carbene‐Catalyzed Desymmetrization of 1,3‐Diols: Access to Optically Enriched Tertiary Alkyl Chlorides.
Authors: Li Bao‐Sheng , Wang Yuhuang , Proctor Rupert S. J. , Jin Zhichao , Chi Yonggui Robin
Published: October 2016

The reaction has a broad substrate scope and tolerates diverse functional groups.