bluuebunny/crossref_metadata_2025 huggingface dataset:
Molekulare Studien an Ameisenbäumen
Authors: Guicking Daniela , Fiala Brigitte , Weising Kurt
Published: December 2013

Myrmekophyten sind ständig von Ameisen besiedelte Pflanzen. Die Ameisen erhalten eine Wohnstatt und Futter von der Pflanze, im Gegenzug beschützen sie ihren Wirt vor Herbivoren und pflanzlichen Konkurrenten. Die vielfältigen Beziehungen zwischen tropischen Pionierbäumen der Gattung Macaranga und ihren Partnerameisen der Gattung Crematogaster stellen die bedeutendste und artenreichste mutualistische Ameisen‐Pflanzen‐Assoziation der Altwelttropen dar. Mit Hilfe vergleichender DNA‐Sequenzierung und molekularer Marker‐Technologien analysieren wir die Verwandtschaftsverhältnisse innerhalb der etwa 30 myrmekophytischen Macaranga‐Arten und ihre Co‐Evolution mit Ameisen sowie die Populationsgenetik und historische Biogeografie einzelner Artengruppen. Ausmaß und Strukturierung der genetischen Diversität dieser Pionierbaumarten zeigen interessante Korrelationen mit ihrer Reproduktionsbiologie und der Besiedlung von zunehmend fragmentierten Pionierhabitaten im tropischen Regenwald.
Formfleisch selbstgemacht
Authors: Högermann Christiane
Published: December 2013

Am Beispiel des “Klebeenzyms” (mikrobielle) Transglutaminase, das vorwiegend zum “Verschmelzen” von Fleischstücken – auch von Schlachttieren unterschiedlicher Herkunft – dient, wird neben dem fachlichen Hintergrund eine einfache Versuchsreihe mit dem Ergebnis eines schnittfesten, aus Hackfleisch hergestellten Hackfleischblocks vorgestellt. Die drei Experimente veranschaulichen die grundlegende Wirkungsweise einer der industriell verwendeten Transglutaminase‐Mischungen.
Aal‐grün: Eine neue Farbe in der Fluoreszenz‐Toolbox
Authors: Kronberg Inge
Published: December 2013

Fluoreszenz‐Proteine haben die experimentelle Biologie in den vergangenen Jahren revolutioniert: Ihr Aufleuchten zeigt, wann, wo und oft auch wozu entsprechend markierte Proteine in einer Zelle auftauchen. Neben dem grün fluoreszierenden Protein GFP (green fluorescent protein) aus der Qualle Aequorea verwenden Labore inzwischen modifizierte GFP‐artige Proteine mit anderen Fluoreszenzspektren und NIR‐Proteine (near infrared) aus Bakterien. Jetzt wurde im Aal ein Fluoreszenz‐Protein mit vollkommen neuen Eigenschaften und Einsatzmöglichkeiten entdeckt.
Der Kampf um die Seen in den fünf “neuen Ländern”
Authors: Oehler Jochen
Published: December 2013

Seen sind komplex vernetzte und sensible ökologische Systeme, die durch eine Vielzahl anthropogener Einflüsse oder gar als Renditeobjekte Gefahr laufen, ihren natürlichen Charakter zu verlieren. Bis heute wurden schon etwa 14.000 ha Wasserfläche in der ehemaligen DDR an private Eigentümer verkauft – ohne dass die Öffentlichkeit viel davon erfuhr. Bürgerproteste sorgten für ein Umdenken, sodass nun viele Seen wieder im Besitz von Bundesländern wie Mecklenburg‐Vorpommern und Brandenburg sind.
Der BundesUmweltWettbewerb (BUW) –Wissen über und Handeln für die Umwelt
Authors: Eckhardt Marc
Published: December 2013

Seit 1990 motiviert der BundesUmweltWettbewerb Jugendliche und junge Erwachsene, sich eines Umweltproblems anzunehmen und für dieses eigenständig Lösungen zu erarbeiten. Ein Blick auf die in den vergangenen 23 Jahren eingereichten Projekte zeigt, dass es sie tatsächlich gibt, die umweltengagierten und talentierten Nachwuchsforscher, die ihr Wissen auch in Handeln umsetzen. Bis zum 15. März 2014 werden noch Projekte für die nächste Wettbewerbsrunde angenommen.
Klein, aber oho: Mykoplasmen in der Zellkultur
Authors: Hauk Andrea
Published: December 2013

Welcher Zellbiologe kennt sie nicht. Mykoplasmen fühlen sich in Zellkulturen so wohl wie Langschläfer im warmen, kuscheligen Bett. Was genau sind aber eigentlich Mykoplasmen? Und warum sind sie in Zellkulturlaboratorien so ungern gesehen?
Treffpunkt Futterplatz: Von Invasionsvögeln und anderen Wintergästen
Authors: Petrischak Hannes
Published: December 2013

Eine winterliche Futterstelle im Garten lockt eine große Vielfalt an Standvögeln, Durchzüglern und Wintergästen an. Recht bequem lassen sich dann vom Fenster aus auch Arten beobachten, die im Sommer sehr versteckt oder außerhalb der Ortschaften leben. Besonders spannend wird es in den Jahren, in denen es nordische Arten invasionsartig nach Mitteleuropa zieht.
Quantitative determination of alkannins and shikonins in endemic Mediterranean Alkanna species
Authors: Tappeiner Jasmin , Vasiliou Alexandra , Ganzera Markus , Fessas Dimitrios , Stuppner Hermann , Papageorgiou Vassilios P. , Assimopoulou Andreana N.
Published: December 2013

The optical antipodes alkannin/shikonin (A/S) and their esters are potent pharmaceutical substances found in the roots of 150 Boraginaceous species. This study estimated and compared total and free A/S content and A/S enantiomeric ratio in roots of 11 Alkanna species (A. corcyrensis, A. tinctoria, A. pindicola, A. orientalis, A. methanaea, A. calliensis, A. graeca, A. primuliflora, A. stribrnyi, A. sieberi and A. noneiformis) growing wild in various Greek regions, to compare with cultivated species. It also re‐characterized the chirality of A/S commercial samples, since most of them were misnamed by the providers. Several Alkanna species were collected (groups 1 and 3) and botanically identified, whereas some Alkanna species were cultivated from collected seeds (group 2). Free A/S and derivatives were extracted from the dried roots of Alkanna species and analyzed by high performance liquid chromatography‐diode array detection (HPLC‐DAD). For total A/S content the hexane extracts of Alkanna roots were hydrolyzed and analyzed by HPLC‐DAD. Chirality determination and A/S enantiomeric ratio estimation was performed for several commercial samples by polarimetry,chiral LC‐DAD and circular dichroism studies. Quantitative analysis revealed that A/S content varied from one region to another even within the same species. Most of the cultivated samples contained greater amounts of free and total A/S compared with the wild ones, wheras no difference was observed in A/S enantiomeric ratio. All the Alkanna samples tested contain mainly alkannin derivatives. Some of the examined Alkanna species of the Greek flora that are endemic to the Mediterranean area could serve as alternative sources for medicinally valuable A/S derivatives. Most of the commercial A/S samples tested were misnamed in terms of chirality and re‐characterized. Copyright © 2013 John Wiley & Sons, Ltd.
Selected ASIS&T board members discuss research trends in information science: A summary
Authors: Gainor Rhiannon
Published: December 2013

Editor's Summary

A symposium organized by McGill University's iSchool students and director brought together past, current and future ASIS&T presidents and board members to discuss trends in information science research. The discussion revealed diverse opinions on the definition of information science, concerns about research practices and expected directions for future research. Definitions of the field focused on social questions in an information society, the intersection of information and technology and strategies to better connect information with users. Panelists exhorted attendees, many being students, to tackle big questions, consider the applications of their research and collaborate with other disciplines. The critical role and strength of information science should drive robust and compelling research, addressing areas of need from the personal to the national level. Specific topics needing investigation include big data, information security, information as a stimulus for creativity, personal information management and better integration with technology.
The discipline of organizing
Authors: Glushko Robert J.
Published: December 2013

Editor's Summary

It is normal to organize our world, but doing so systematically is key and the subject of the book The Discipline of Organizing (TDO). The driving concept is that, while organization of resources is fundamental to library and information science, it is a central issue for many professional fields employing different organizational strategies and descriptive vernacular. To bring the diverse perspectives together, a broadly applicable, abstract framework can be used, based on an assessment of what is being organized, why, how much, when and by what means. These points of analysis of the resources to be organized inform organizational design decisions, considerations of stakeholders and costs and strategic planning for tools and methods. Principles underlying an organization system's design may draw on frequency of resource use or coordination of items, alphabetic or chronological ordering or unique approaches to manage hybrid and novel resources. The TDO philosophy reflects an information management approach that spans disciplinary silos and avoids field‐limited terminology, while building the critical skills of resource organization and management.
Learning and teaching information architecture: The current state of IA education
Authors: MacDonald Craig M.
Published: December 2013

Editor's Summary

Hitting the mainstream in the late 1990s, the concept of information architecture (IA) grew within library and information science, but it is closely tied to multiple fields, making an organized approach to learning and teaching a challenge. A World IA Day 2013 session explored IA through a survey and town hall meeting for insight into how and where people learn the craft. Survey responses showed four in five information architects come from other than information and library disciplines, but about half took a college course in the field. The vast majority of survey respondents and town hall attendees cited practical experience as critical. Without a consensus on core concepts and skills in IA, educators have no clear direction as they try to prepare students for work. Until agreement is established, input from multiple disciplines and on‐the‐job learning will remain key, though inconsistent, parts of IA education.
Strategic action: Information architecture in platform migrations
Authors: Heffernan John R.
Published: December 2013

Editor's Summary

Information architects (IAs) have a strategic role to play, especially in firms that appreciate the need for clear and efficient user experiences. To support the end user, information must have value and be organized and understandable. An information domain model is a useful starting point to set the parameters of an organization's collection of online information resources. It provides a shared basis for stakeholders to analyze and discuss the domain, working toward a common and well‐developed mental model and foundation for information architecture work. For the IA, it becomes the basis for sorting and mapping pieces of information during a platform migration or other transition. The IA's focus is on deep understanding of content to define and strategically manage knowledge units. Developing and implementing an information domain model supports the goal of enhancing the user's experience through content structure and findability.
Chemosystematic Analyses of Gingidia Volatiles
Authors: Sansom Catherine E. , Heenan Peter B. , Perry Nigel B. , Smallfield Bruce M. , van Klink John W.
Published: December 2013

The leave volatiles of six Gingidia species from New Zealand and Australia and the seed volatiles of G. grisea were characterized by solid‐phase microextraction (SPME)‐GC/MS analysis. This technique, using a small quantity of samples and automated extraction, gave repeatable results, with maximum sensitivity for medium volatility compounds. The major monoterpenes among the volatiles, i.e., β‐phellandrene (4), limonene (6), and γ‐terpinene (5), and phenylpropanoids, i.e., estragole (3), (E)‐anethole (7), and myristicin (1), showed to be useful chemotaxonomic markers. For G. grisea leaves and seeds, similar compositions were detected, characterized by high contents of 4. As leaves were more readily available for study than seeds, they were used for further investigations. The G. grisea leaf volatiles showed infraspecific variation in the ratio of 4/5 between and within sites of collection. The G. montana leaf volatiles also showed infraspecific variation, with high contents of 3 at one site and high contents of 7 at another. The SPME‐GC/MS analysis of G. montana herbarium voucher specimens resulted in the identification of further chemotypes for this species. The volatiles of the G. amphistoma samples were all dominated by 7 and those of the G. haematitica samples were rich in 5. Moreover, single plants of two Australian Gingidia species were analyzed; the volatiles of G. harveyana showed high concentrations of 5 and 7, whereas those of G. rupicola were dominated by 5 and 1.
The Creation of Proton Hopping from a DrugReceptor Encounter
Authors: Kier Lemont B. , Hall Lowell H.
Published: December 2013

We extend recent modeling studies of proton hopping, used to describe the functioning of membrane channels and axon nerve conduction, to offer an explanation of the initiation of the nerve impulse at an effectorligand encounter. This encounter is proposed to create a hydronium ion in the vicinity of the effector and ligand, which leads to a continuous flow of protons, called proton hopping, through water adjacent to this encounter. This proton hopping is proposed to be the message carried from the encounter to the axon of a particular nerve system associated with that particular effectorligand system.
Synthesis of 5‐Fluorouridine Nucleolipid Derivatives and Their Cytostatic/Cytotoxic Activities on Human HT‐29 Colon Carcinoma Cells
Authors: Malecki Edith , Farhat Anisa , Bonaterra Gabriel A. , Röthlein Doris , Wolf Martin , Schmitt Jürgen , Kinscherf Ralf , Rosemeyer Helmut
Published: December 2013

One of the major drawbacks of chemotherapeutics is their insufficient penetration through cell membranes due to a high hydrophobicity. Thus, we have synthesized a series of selected nucleolipid derivatives of 5‐fluorouridine (5‐FUrd; 2a), carrying lipophilic moieties at N(3) and/or in the 2′,3′‐O‐position (i.e., 3a–7a and 3c), and tested their cytostatic/cytotoxic activities using HT‐29 human colon carcinoma cells, in comparison with, e.g., 5‐FU (1) and 5‐FUrd (2a). Incorporation and intracellular localization of the substances under test were performed after conjugation with the fluorochrome Atto 425. We showed that all 5′‐O‐labelled Atto 425 derivatives were incorporated by the human HT‐29 cells and accumulated in their cytoplasm. Moreover, after 24‐h treatment of HT‐29 human colon carcinoma cells, 1 or 2a (10, 20, 40, or 80 μM) revealed a significant (14–23 or 33–45%, resp.) decrease of the viability in comparison with the (negative) control. Interestingly, derivatives 3a and 3c (40 and 80 μM) led to a significant (77–95 or 89–96%, resp.) inhibition of survival of human HT29 cells, i.e., these two substances were ca. 63–72% or ca. 75%, respectively more effective than 5‐FU (1; positive control). Furthermore, derivative 5a showed a significant, i.e., 30 and 86%, inhibition of the survival at 40 and 80 μM, respectively in comparison with the (negative) control. Some synthesized 5‐FUrd derivatives turned out to be more effective than 5‐FU (1) or 5‐FUrd (2a).
Syntheses, Receptor Bindings, in vitro and in vivo Stabilities and Biodistributions of DOTA‐Neurotensin(8–13) Derivatives Containing β‐Amino Acid Residues – A Lesson about the Importance of Animal Experiments
Authors: Sparr Christof , Purkayastha Nirupam , Yoshinari Tomohiro , Seebach Dieter , Maschauer Simone , Prante Olaf , Hübner Harald , Gmeiner Peter , Kolesinska Beata , Cescato Renzo , Waser Beatrice , Reubi Jean Claude
Published: December 2013

Neurotensin(8–13) (NTS(8–13)) analogs with C‐ and/or N‐terminal β‐amino acid residues and three DOTA derivatives thereof have been synthesized (i.e., 1–6). A virtual docking experiment showed almost perfect fit of one of the 1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetraacetic acid (DOTA) derivatives, 6a, into a crystallographically identified receptor NTSR1 (Fig. 1). The affinities for the receptors of the NTS analogs and derivatives are low, when determined with cell‐membrane homogenates, while, with NTSR1‐exhibiting cancer tissues, affinities in the single‐digit nanomolar range can be observed (Table 2). Most of the β‐amino acid‐containing NTS(8–13) analogs (Table 1 and Fig. 2), including the 68Ga complexes of the DOTA‐substituted ones (6; Figs. 2 and 5), are stable for ca. 1 h in human serum and plasma, and in murine plasma. The biodistributions of two 68Ga complexes (of 6a and 6b) in HT29 tumor‐bearing nude mice, in the absence and in the presence of a blocking compound, after 10, 30, and 60 min (Figs. 3 and 4) lead to the conclusion that the amount of specifically bound radioligand is rather low. This was confirmed by PET‐imaging experiments with the tumor‐bearing mice (Fig. 6). Comparison of the in vitro plasma stability (after 1 h) with the ex vivo blood content (after 10–15 min) of the two 68Ga complexes shows that they are rapidly cleaved in the animals (Fig. 5).
Leucine improves protein nutritional status and regulates hepatic lipid metabolism in calorie‐restricted rats
Authors: Pedroso João Alfredo B. , Nishimura Luciana Sigueta , de Matos‐Neto Emídio Marques , Donato Jose , Tirapegui Julio
Published: December 2013

Several studies have highlighted the potential of leucine supplementation for the treatment of metabolic diseases including type 2 diabetes and obesity. Caloric restriction is a common approach to improve the health in diabetic and obese subjects. However, very few studies assessed the effects of leucine supplementation in calorie‐restricted animals. Rats were subjected to a 30% calorie‐restricted diet for 6 weeks to study the effects of leucine supplementation on protein status markers and lipid metabolism. Caloric restriction reduced the body weight. However, increased leucine intake preserved body lean mass and protein mass and improved protein anabolism as indicated by the increased circulating levels of albumin and insulin‐like growth factor‐1 (IGF‐1), and the liver expression of albumin and IGF‐1 messenger RNA. Leucine supplementation also increased the circulating levels of interleukin‐6 and leptin but did not affect the tumour necrosis factor‐α and monocyte chemotactic protein‐1 concentrations. Ketone bodies were increased in rats consuming a leucine‐rich diet, but we observed no changes in cholesterol or triglycerides concentrations. Caloric restriction reduced the liver expression of peroxisome proliferator activated receptor‐α and glucose‐6‐phosphatase, whereas leucine supplementation increased the liver expression of 3‐hydroxy‐3‐methyl‐glutaryl‐CoA reductase (HMG‐CoA) reductase and sterol regulatory element‐binding transcription factor 1. A leucine‐rich diet during caloric restriction preserved whole body protein mass and improved markers of protein anabolism. In addition, leucine modulated the hepatic lipid metabolism. These results indicate that increased leucine intake may be useful in preventing excessive protein waste in conditions of large weight loss. Copyright © 2013 John Wiley & Sons, Ltd.
Structural and Mutational Studies on the Unusual Substrate Specificity of meso‐Diaminopimelate Dehydrogenase from Symbiobacterium thermophilum
Authors: Liu Weidong , Li Zhe , Huang Chun‐Hsiang , Guo Rey‐Ting , Zhao Leiming , Zhang Dalong , Chen Xi , Wu Qiaqing , Zhu Dunming
Published: December 2013

Wild‐type meso‐diaminopimelate dehydrogenase (DAPDH) is usually specific to the native substrate, meso‐2,6‐diaminopimelate. Recently, a DAPDH from Symbiobacterium thermophilum (StDAPDH) was found to exhibit expanded substrate specificity. As such, its crystal structures in apo form and in complex with NADP+ and both NADPH and meso‐DAP were investigated to reveal the structural basis of its unique catalytic properties. Structural analysis results show that StDAPDH should prefer an ordered kinetic catalytic mechanism. A second substrate entrance tunnel with Met152 at its bottleneck was found, through which pyruvate/D‐alanine might bind and enter the catalytic cavity, providing some structural insights into its high activity toward pyruvate. The side chain of Met152 might interact with Asp92 and Asn253, thus affecting the domain motion and catalysis. These results offer useful information for understanding the unique catalytic properties of StDAPDH and guiding further engineering of this enzyme.
Percutaneous balloon dilation of severe pulmonary valve stenosis in patients with cyanosis and congestive heart failure
Authors: Tefera Endale , Qureshi Shakeel A. , Bermudez‐Cañete Ramón , Rubio Lola
Published: December 2013

Objectives

This article reports outcomes of percutaneous balloon dilation in patients with severe pulmonary valve stenosis, in particular in those treated late with cyanosis, congestive heart failure, and pericardial effusion.

Background

Percutaneous balloon dilation is the treatment of choice for pulmonary valve stenosis. Although earlier intervention may produce better results, patients may present late with congestive heart failure and cyanosis.

Methods

Fifty‐five patients who underwent pulmonary valve balloon dilation, were grouped into two groups, based on the presence or absence of congestive right heart failure and/or central cyanosis. Group I included 33 patients with severe pulmonary valve stenosis, but without clinical evidence of congestive right heart failure in the form of liver enlargement, raised jugular venous pressure, and peripheral edema and/or central cyanosis and group II included 22 patients with severe pulmonary valve stenosis and congestive right heart failure and/or central cyanosis. Their outcomes were compared.

Results

Doppler measured transvalvar pressure gradient decreased from 110.2 ± 34.0 mm Hg before to 52.5 ± 28.7 mm Hg in group I after dilation (P < 0.001), and from 138.4 ± 32.3 mm Hg to 53.9 ± 19.3 mm Hg in group II, (P < 0.001). Complications included ventricular tachycardia/fibrillation in three patients and severe bradycardia in one patient in group II. Twelve patients in group II developed clinical and radiologic evidence of reperfusion injury/pulmonary edema within the first 24 hr of intervention and needed ventilation for 2–9 days. Three of these patients died from intractable pulmonary edema. On follow up, clinical and echocardiographic improvement parameters were similar in the two groups.

Conclusion

Those patients with severe pulmonary valve stenosis with congestive right heart failure, especially those with pericardial effusion, ascites and cyanosis, represent an important technical and clinical challenge. They are a high‐risk group with or without treatment. If they survive the procedure, they may still remain at a high risk in the first few days afterward. Maintaining their ventilator and inotropic support after balloon dilation may increase survival. However, excellent results can be obtained. © 2013 Wiley Periodicals, Inc.
Safety of percutaneous left atrial appendage closure with the amplatzer cardiac plug in patients with atrial fibrillation and contraindications to anticoagulation
Authors: Wiebe Jens , Bertog Stefan , Franke Jennifer , Wettstein Olga , Lehn Katharina , Hofmann Ilona , Vaskelyte Laura , Sievert Horst
Published: December 2013

Objective

To evaluate the safety of percutaneous left atrial appendage (LAA) closure with the Amplatzer Cardiac Plug (ACP) in patients with nonvalvular atrial fibrillation (AF) who are not eligible for oral anticoagulation with warfarin.

Background

Anticoagulation is the treatment of choice for prevention of strokes in patients with AF, but some patients have contraindications to anticoagulation.

Methods

A total of 60 patients with a CHA2DS2‐VASc score of at least 1 and contraindications to warfarin who underwent percutaneous LAA closure with the ACP were included. Stroke risk assessment was performed with the CHADS2 and CHA2DS2‐VASc score and the bleeding risk was calculated with the HAS‐BLED‐score. Follow‐up included office visits, telephone inquiries, and mail contact.

Results

Mean CHADS2‐, CHA2DS2‐VASc‐, and HAS‐BLED scores were 2.6 (± 1.4), 4.3 (± 1.7), and 3.3 (± 1.0), respectively. Twenty‐five percent had a history of previous bleeding without oral anticoagulation and 63.3% while receiving oral anticoagulation. In 36.7% other contraindications to warfarin were present. Procedural success was achieved in 95%. Mean follow‐up time was 1.8 (1.0–2.8) years. The estimated annual stroke risk based on the CHADS2‐score was 5.8%. The estimated annual bleeding risk on warfarin based on the HAS‐BLED score was 3.7%. During follow‐up, the annual incidence of stroke was 0%. Major bleeding complications occurred in 1.9% annually.

Conclusions

Percutaneous LAA closure with the ACP in patients with contraindications to oral anticoagulation is safe. The stroke and bleeding risk after percutaneous LAA closure is lower than predicted by conventional risk scores. © 2013 Wiley Periodicals, Inc.
Stepwise Solid‐Phase Synthesis and Solid‐State Electrochemistry of Redox‐Active Viologen Core/Shell‐Structured Modified Silica Materials
Authors: Passon Monika , Ruff Adrian , Schuler Paul , Speiser Bernd , Dreiling Ines
Published: December 2013

Core/shell‐structured viologen‐modified Stöber silica particles with diameters of approximately 235 nm are prepared in a stepwise, solid‐phase synthesis. The nonporous and spherical silica base particles are obtained through a sol–gel process from tetraethoxysilane followed by a post‐synthetic calcination step and characterized by means of scanning electron microscopy, nitrogen adsorption/desorption experiments, diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, Gay‐Lussac pycnometry in water, and dynamic light scattering. Coating with triethoxysilane yields SiH‐terminated particles, which are further reacted with the linker, 11‐bromo‐1‐undecene, in a thermally induced hydrosilylation. The resulting kinetically inert and thermodynamically stable SiC bond ensures strong attachment to the silica surface. The viologen units are generated by alkylation with 1‐methyl[4,4′]bipyridinium iodide directly on the particle surface. The successful attachment is confirmed by diffuse reflectance UV/Vis, DRIFT, and 13C cross‐polarization/magic‐angle spinning nuclear magnetic resonance spectroscopy. The viologen shell of the particles is electrochemically addressable. In cyclic voltammetry experiments, under three‐phase junction conditions with modified gold and paraffin‐impregnated graphite electrodes, the immobilized viologen units are reduced to the neutral state in two consecutive electron‐transfer reactions via a mono radical cation species. The in situ electrolysis of suspended particles leads to a material with a diamagnetic core (silica) and a paramagnetic shell (viologen mono radical cations). Electron paramagnetic resonance experiments demonstrate that the radical cations are strongly attached to the particle surface. The material and electrochemical properties of the particles are compared to amorphous silica and to a viologen‐modified Stöber material based on a well‐established immobilization strategy (condensation of alkoxysilane to surface silanol groups).
Transalkylation of Higher Trifluoromethylated Fullerenes with C70: A Pathway to New Addition Patterns of C70(CF3)8
Authors: Belov Nikita M. , Apenova Marina G. , Rybalchenko Alexey V. , Borkovskaya Eugenia V. , Lukonina Natalia S. , Goryunkov Alexey A. , Ioffe Ilya N. , Troyanov Sergey I. , Sidorov Lev N.
Published: December 2013

We report three new isomers of C70(CF3)8, structurally related to p7mp‐C70(CF3)10, that are inaccessible by direct trifluoromethylation, but can be easily identified among the products of the transalkylation of higher trifluoromethylfullerenes with C70. The reported compounds are characterized by UV/Vis, 1 D and 2 D COSY 19F NMR spectroscopy, and DFT calculations. A rather unusual addition pattern is observed in p6,i‐C70(CF3)8 in which one addend is attached remotely from the others; polarization of the adjacent unsaturated bonds by the addend makes the molecule readily oxidizable.
Self‐Assembly of a Highly Organized, Hexameric Supramolecular Architecture: Formation, Structure and Properties
Authors: Schaeffer Gaël , Fuhr Olaf , Fenske Dieter , Lehn Jean‐Marie
Published: December 2013

Two derivatives, 3L and 9L, of a ditopic, multiply hydrogen‐bonding molecule, known for more than a decade, have been found, in the solid state as well as in solvents of low polarity at room temperature, to exist not as monomers, but to undergo a remarkable self‐assembly into a complex supramolecular species. The solid‐state molecular structure of 3L, determined by single‐crystal X‐ray crystallography, revealed that it forms a highly organized hexameric entity 3L6 with a capsular shape, resulting from the interlocking of two sets of three monomolecular components, linked through hydrogen‐bonding interactions. The complicated 1H NMR spectra observed in o‐dichlorobenzene (o‐DCB) for 3L and 9L are consistent with the presence of a hexamer of D3 symmetry in both cases. DOSY measurements confirm the hexameric constitution in solution. In contrast, in a hydrogen‐bond‐disrupting solvent, such as DMSO, the 1H NMR spectra are very simple and consistent with the presence of isolated monomers only. Extensive temperature‐dependent 1H NMR studies in o‐DCB showed that the L6 species dissociated progressively into the monomeric unit on increasing th temperature, up to complete dissociation at about 90 °C. The coexistence of the hexamer and the monomer indicated that exchange was slow on the NMR timescale. Remarkably, no species other than hexamer and monomer were detected in the equilibrating mixtures. The relative amounts of each entity showed a reversible sigmoidal variation with temperature, indicating that the assembly proceeded with positive cooperativity. A full thermodynamic analysis has been applied to the data.
Gold Nanocage Assemblies for Selective Second Harmonic Generation Imaging of Cancer Cell
Authors: Demeritte Teresa , Fan Zhen , Sinha Sudarson Sekhar , Duan Jinsong , Pachter Ruth , Ray Paresh C.
Published: December 2013

Second harmonic generation (SHG) imaging using near infrared laser light is the key to improving penetration depths, leading to biological understanding. Unfortunately, currently SHG imaging techniques have limited capability due to the poor signal‐to‐noise ratio, resulting from the low SHG efficiency of available dyes. Targeted tumor imaging over nontargeted tissues is also a challenge that needs to be overcome. Driven by this need, in this study, the development of two‐photon SHG imaging of live cancer cell lines selectively by enhancement of the nonlinear optical response of gold nanocage assemblies is reported. Experimental results show that two‐photon scattering intensity can be increased by few orders of magnitude by just developing nanoparticle self‐assembly. Theoretical modeling indicates that the field enhancement values for the nanocage assemblies can explain, in part, the enhanced nonlinear optical properties. Our experimental data also show that A9 RNA aptamer conjugated gold nanocage assemblies can be used for targeted SHG imaging of the LNCaP prostate cancer cell line. Experimental results with the HaCaT normal skin cell lines show that bioconjugated nanocage‐based assemblies demonstrate SHG imaging that is highly selective and will be able to distinguish targeted cancer cell lines from other nontargeted cell types. After optimization, this reported SHG imaging assay could have considerable application for biology.
Antimicrobial Activity of Water‐Soluble Triazole Phenazine Clickamers against E. coli
Authors: Hayden Steven C. , Bryant Jonathan J. , Mackey Megan A. , Höfer Katharina , Lindner Benjamin D. , Nguyen Vanessa P. , Jäschke Andres , Bunz Uwe H. F.
Published: December 2013

The antimicrobial potency of phenazine derivatives is attenuated by their inherently hydrophobic nature, complicating their use as antibiotic drugs. We have analyzed the cytotoxicity and mode of action of water‐soluble bis‐triazolyl phenazines against E. coli and a human epithelial (HaCat) cell line. We observed complete inhibition of bacterial growth over concentration ranges that do not affect the viability of human epithelial cells. Confocal fluorescence microscopy revealed a high degree of interaction between the phenazine compounds and E. coli, as well as evidence of membrane damage in phenazine‐treated E. coli. Additional data suggests that the potency of these particular water‐soluble phenazine compounds does not result from the production of reactive oxygen species, but rather from cytotoxic interference with metabolic electron‐transfer cascades.
Composite PET Membrane with Nanostructured Ag/AgTCNQ Schottky Junctions: Electrochemical Nanofabrication and Charge‐Transfer Properties
Authors: Huang Li , Chen Yong , Bian Shujuan , Huang Yi‐Fan , Tian Zhong‐Qun , Zhan Dongping
Published: December 2013

Large‐area nanostructured Ag/Ag‐tetracyanoquinodimethane (TCNQ) Schottky junctions are fabricated electrochemically on a mesoporous polyethylene terephthalate (PET) membrane‐supported water/1, 2‐dichloroethane (DCE) interface. When the interface is polarized, Ag+ ions transfer across the PET membrane from the aqueous phase and are reduced to form metallic Ag on the PET membrane, which reacts further with tetracyanoquinodimethane (TCNQ) in the DCE phase to form nanostructured Ag/AgTCNQ Schottky junctions. Once the mesoporous membrane is blocked by metallic Ag, a bipolar mechanism is proposed to explain the successive growth of AgTCNQ nanorods and Ag film on each side of the PET membrane. Due to the well‐formed nanostructure of Ag/AgTCNQ Schottky junctions, the direct electrochemical behavior is observed, which is essential to explain the physicochemical mechanism of its electric performance. Moreover, the composite PET membrane with nanostructured Ag/AgTCNQ Schottky junctions is tailorable and can be assembled directly into electric devices without any pretreatment.
Enantioselective Aziridination of Cyclic Enals Facilitated by the Fluorine‐Iminium Ion Gauche Effect
Authors: Molnár István Gábor , Tanzer Eva‐Maria , Daniliuc Constantin , Gilmour Ryan
Published: December 2013

The enantioselective, organocatalytic aziridination of small, medium and macro‐cyclic enals is reported using (S)‐2‐(fluorodiphenyl methyl)‐pyrrolidine. Central to the reaction design is the reversible formation of a β‐fluoroiminium ion intermediate, which is pre‐organised on account of the fluorine‐iminium ion gauche effect. This conformational effect positions the fluorine substituent synclinal‐endo to the electropositive nitrogen centre thus benefiting from favourable stereoelectronic and electrostatic interactions (σC−H→σC−F*; Fδ−…︁N+). Consequently, one of the shielding groups on the fluorine‐bearing carbon atom is positioned above the π‐system, forming the basis of an enantioinduction strategy. Treatment of this intermediate with a “nitrene” source furnished a series of novel, optically active aziridines (e.r. up to 99.5:0.5). Further derivatisation of the product aziridines gives facile access to various amino acid derivatives, including β‐fluoroamino acids. Crystallographic analyses of both the aziridines and their derivatives are disclosed.
Fluorescent Probes Based on Nucleophilic Substitution–Cyclization for Hydrogen Sulfide Detection and Bioimaging
Authors: Peng Bo , Chen Wei , Liu Chunrong , Rosser Ethan W. , Pacheco Armando , Zhao Yu , Aguilar Hector C. , Xian Ming
Published: December 2013

The design, synthesis, properties, and cell imaging applications of a series of 2‐pyridyl disulfide based fluorescent probes (WSP1, WSP2, WSP3, WSP4 and WSP5) for hydrogen sulfide detection are reported. The strategy is based on the dual‐nucleophilicity of hydrogen sulfide. A hydrogen sulfide mediated tandem nucleophilic substitution‐cyclization reaction is used to release the fluorophores and turn on the fluorescence. The probes showed high sensitivity and selectivity for hydrogen sulfide over other reactive sulfur species, including cysteine and glutathione.
Achieving a Rare Breathing Behavior in a Polycatenated 2 D to 3 D Net through a Pillar‐Ligand Extension Strategy
Authors: Zhao Xiaoliang , Liu Fuling , Zhang Liangliang , Sun Di , Wang Rongming , Ju Zhangfeng , Yuan Daqiang , Sun Daofeng
Published: December 2013

Through a pillar‐ligand extension strategy, a rare breathing behavior in polycatenated 2D→3D nets has been achieved. Three variants exhibit interesting sorption properties that range from non‐breathing to breathing behaviors, which is influenced by the angles between the pillars and the single honeycomb layers. The increase in pillar length does not lead to an increase in polycatenation multiplicity, which is controlled by the length of intralayer tripodal carboxylate. It also does not induce obviously expanded interlayer separations but occupies much more the free voids, and as a consequence, a smaller pore volume is obtained. This suggests that in 2D→3D polycatenated bilayer metal–organic frameworks, the porosity is not always enhanced by increasing the length of the interlayer pillars with the intralayer linker remaining unchanged.
Studies on Enantioselective Liquid–Liquid Extraction of Amino‐(4‐nitro‐phenyl)‐acetic Acid Enantiomers: Modeling and Optimization
Authors: Zhang Panliang , Liu Chang , Tang Kewen , Liu Jiajia , Zhou Congshan , Yang Changan
Published: December 2013

BINAP‐metal complexes were prepared as extractant for enantioselective liquid–liquid extraction (ELLE) of amino‐(4‐nitro‐phenyl)‐acetic acid (NPA) enantiomers. The influence of process variables, including types of organic solvents and metal precursor, concentration of ligand, pH, and temperature on the efficiency of the extraction, were investigated experimentally. An interfacial reaction model was established for insightful understanding of the chiral extraction process. Important parameters required for the model were determined. The experimental data were compared with model predictions to verify the model prediction, It was found that the interfacial reaction model predicted the experimental results accurately. By modeling and experiment, an optimal extraction condition with pH of 7 and host (extractant) concentration of 1 mmol/L was obtained and high enantioselectivity (αop) of 3.86 and performance factor (pf) of 0.1949 were achieved. Chirality 26:79–87, 2014. © 2013 Wiley Periodicals, Inc.
Diastereoselective Synthesis of Functionalized Tetrahydropyrimidin‐2‐thiones via ZnCl2 Promoted One‐pot Reactions
Authors: Liu Zhenming , Zhang Lili , Sun Jing , Yan Chaoguo
Published: December 2013

In the presence of zinc chloride, the in situ generated β‐enamino ester from the reaction of morpholine, piperidine and pyrrolidine with methyl propiolate reacted, with aromatic aldehydes and thiourea in ethanol resulting in the functionalized tetrahydropyrimidin‐2‐thiones in satisfactory yields and with good diastereoselectivity. When aromatic aldehydes bearing electron‐withdrawing group were used in the reaction, the 4‐hydroxytetrahydropyrimidin‐2‐thione derivatives were obtained as the main product.
A Photo‐responsive Catalytic Vesicle with GPx Activity
Authors: Xiao Ruiqing , Zhou Lipeng , Dong Zeyuan , Gao Yuzhou , Liu Junqiu
Published: December 2013

Glutathione peroxidase (GPx) is a vital antioxidant enzyme involved in the reduction of reactive oxygen species and protects cells from oxidative damage. Consequently enormous efforts have been devoted to developing artificial catalysts with GPx function. Besides the research on enhancing the catalytic activity of GPx mimics, the design and construction of smart GPx models has also inspired great interest. Herein, a novel photo‐responsive selenium‐containing vesicular GPx model was successfully constructed by supramolecular self‐assembly of the cationic surfactant PyC10AzoC10Py with benzeneseleninic acid (PhSeO2H) through hydrophobic and electrostatic interactions in aqueous media. This selenium‐containing vesicular catalyst showed remarkable GPx‐like activity, which is 692 times more effective than PhSeO2H for the reduction of cumene hydroperoxide (CUOOH) by 4‐nitrobenzenethiol (NBT). Interestingly, when an equimolar amount of α‐CD was added, the GPx‐like activity of the catalytic vesicle declines remarkably due to the vesicle disaggregation in the presence of α‐CD. Whereas the biomimetic system was irradiated by UV light at 365 nm, the catalytic vesicle was formed again and the GPx‐like activity recovered.
Deposition of SnO2 on the Anatase TiO2 {105} Facets with High Photocatalytic Performance
Authors: Jiang Haibo , Xing Jun , Wang Chongwu , Yang Huagui
Published: December 2013

Anatase TiO2 as a promising photocatalyst has been widely employed in the decontamination treatment of polluted water, air purification and water splitting. Coupling TiO2 with other semiconductor materials could further enhance the photocatalytic activity. Here, we successfully synthesized the SnO2/TiO2 catalyst by depositing SnO2 particles on the anatase TiO2 {105} facets through a gas phase oxidation process. The SnO2/TiO2 catalyst shows higher photocatalytic activity for decomposition of MB than that of the pure TiO2 catalyst. The enhanced photocatalytic activity can be attributed to the efficient charge separation since TiO2 and SnO2 catalyst have staggered energy level.
Multiresponsive Polymer Assemblies Achieved by a Subtle Chain Terminal Modification
Authors: Liu Weiwei , Wang Yucai , Li Yang , Wang Feng , Yang Xianzhu , Sun Tianmeng , Du Jinzhi , Wang Jun
Published: December 2013

Inspired by the influence of chemical structure of end groups on the phase transition temperature of thermoresponsive polymers, we demonstrated a strategy to control the multi‐responsiveness of polymer assemblies via subtle modification of end groups of thermoresponsive polymer segments and revealed its potential application for drug delivery. By developing polymer assemblies composed of poly(aliphatic ester) as the inner core and thermoresponsive polyphosphoester as the outer shell, we showed that end groups of thermoresponsive polyphosphoester segments controlled the surface property of assemblies and further determined the stimuli‐responsive behavior. The phase‐transition temperatures of the unmodified polymer assemblies are tightly controlled by their surface properties due to the hydrophilic to hydrophobic transitions of end groups in response to an environmental stimulus (e.g. pH or light irradiation). External control over these surface properties can by asserted by adjusting the chemical structure and composition of the terminal groups of the thermoresponsive polyphosphoesters.
Synthesis of a Pillar[5]arene with Both Hydroxyl and Methoxycarbonyl‐Methoxy Groups and Its Host‐Guest Complexation with a Bis(imidazolium) Salt
Authors: Pan Mingguang , Xue Min
Published: December 2013

By the introduction of methoxycarbonyl‐methoxy groups and hydroxyl groups into a pillar structure, a pillararene entirely with two types of functional groups was successfully prepared, which can form a stable 1:1 complex with a bis(imidazolium) salt in CHCl3/acetone solution (V:V=1:1).
Fluorine NMR‐Based Screening on Cell Membrane Extracts
Authors: Veronesi Marina , Romeo Elisa , Lambruschini Chiara , Piomelli Daniele , Bandiera Tiziano , Scarpelli Rita , Garau Gianpiero , Dalvit Claudio
Published: December 2013

The possibility of measuring the action of inhibitors of specific enzymatic reactions in intact cells, cell lysates or membrane preparations represents a major advance in the lead discovery process. Despite the relevance of assaying in physiological conditions, only a small number of biophysical techniques, often requiring complex set‐up, are applicable to these sample types. Here, we demonstrate the first application of n‐fluorine atoms for biochemical screening (n‐FABS), a homogeneous and versatile assay based on 19F NMR spectroscopy, to the detection of high‐ and low‐affinity inhibitors of a membrane enzyme in cell extracts and determination of their IC50 values. Our approach can allow the discovery of novel binding fragments against targets known to be difficult to purify or where membrane‐association is required for activity. These results pave the way for future applications of the methodology to these relevant and complex biological systems.
Surface‐Modified TiO2 Photocatalysts Prepared by a Photosynthetic Route: Mechanism, Enhancement, and Limits
Authors: Neubert Susann , Ramakrishnan Ayyappan , Strunk Jennifer , Shi Haoyu , Mei Bastian , Wang Lidong , Bledowski Michal , Guschin Dmitrii A. , Kauer Max , Wang Yuemin , Muhler Martin , Beranek Radim
Published: December 2013

Surface‐modified TiO2 photocatalysts were synthesized by a photosynthetic route involving visible‐light‐induced (λ>455 nm) activation of benzene and toluene at the surface of TiO2 leading to the formation of carbonaceous polymeric deposits. IR spectroscopic and photoelectrochemical experiments showed that the mechanism of the photosynthetic reactions involves intra‐bandgap surface states at TiO2 related to surface OH groups interacting with adsorbed aromatic molecules. The photosynthesized surface‐modified TiO2 materials exhibited enhanced activity, relative to pristine TiO2, in photocatalytic degradation (and complete mineralization) of 4‐chlorophenol. The improvement was pronounced particularly under visible‐light (λ>455 nm) irradiation with the relative initial photodegradation rate enhanced by a factor of four. The surface‐modified photocatalysts exhibited good stability under the operating conditions, and the optimum carbon content was approximately 0.5 wt %. Mechanistic studies showed that the enhanced visible‐light photodegradation of 4‐chlorophenol is due to modified surface‐adsorption properties that facilitate formation of a surface complex between titania and 4‐chlorophenol, rather than due to any sensitizing effect of the carbonaceous deposits. The study highlights the importance of considering the interaction between pollutant molecules and the photocatalyst surface in heterogeneous photocatalysis, and possibly opens up a route for photosynthesis of further surface‐modified photocatalysts with tuned surface properties.
Synthesis of Hybrid Cyclic Peptoids and Identification of Autophagy Enhancer
Authors: Rajasekhar Kolla , Narayanaswamy Nagarjun , Mishra Piyush , Suresh S. N. , Manjithaya Ravi , Govindaraju T.
Published: December 2013

Cyclic peptoids are potential candidates for diverse biological activities. However, applications of cyclic peptoids are limited by the synthetic difficulties, conformational flexibility of large cyclic peptoids, and lack of secondary amide in the backbone. Herein, an elegant methodology for the synthesis of small and medium‐size cyclic hybrid peptoids is developed. αN‐Alkyl and αN‐acyl substituents in N‐(2‐aminoethyl)glycine monomers enforce intra‐ and intermolecular cyclization to form stable six‐ and 12‐membered cyclic products, respectively. NMR studies show inter‐ and intramolecular hydrogen bonding in six‐ and 12‐membered cyclic peptoids, respectively. Screening of a cyclic peptoid library resulted in the identification of a potential candidate that enhanced autophagic degradation of cargo in a live cell model. Such upregulation of autophagy using small molecules is a promising approach for elimination of intracellular pathogens and neurodegenerative protein aggregates.