@article{BullerLaschewskyWischerhoff2013, author = {Buller, Jens and Laschewsky, Andr{\´e} and Wischerhoff, Erik}, title = {Photoreactive oligoethylene glycol polymers - versatile compounds for surface modification by thin hydrogel films}, series = {Soft matter}, volume = {9}, journal = {Soft matter}, number = {3}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1744-683X}, doi = {10.1039/c2sm26879e}, pages = {929 -- 937}, year = {2013}, abstract = {Solid surfaces are modified using photo-crosslinkable copolymers based on oligo(ethylene glycol) methacrylate (OEGMA) bearing 2-(4-benzoylphenoxy) ethyl methacrylate (BPEM) as a photosensitive crosslinking unit. Thin films of about 100 nm are formed by spin-coating these a priori highly biocompatible copolymers onto silicon substrates. Subsequent UV-irradiation assures immobilization and crosslinking of the hydrogel films. Their stability is controlled by the number of crosslinker units per chain and the molar mass of the copolymers. The swelling of the hydrogel layers, as investigated by ellipsometry, can be tuned by the crosslinker content in the copolymer. If films are built from the ternary copolymers of OEGMA, BPEM and 2-(2-methoxyethoxy) ethyl methacrylate (MEO(2)MA), the hydrogel films exhibit a swelling/deswelling transition of the lower critical solution temperature (LCST) type. The observed thermally induced hydrogel collapse is fully reversible and the onset temperature of the transition can be tuned at will by the copolymer composition. Different from analogously prepared thermo-responsive hydrogel films of photocrosslinked poly(N-isopropylacrylamide), the swelling-deswelling transition occurs more gradually, but shows no hysteresis.}, language = {en} } @article{AdelsbergerGrilloKulkarnietal.2013, author = {Adelsberger, Joseph and Grillo, Isabelle and Kulkarni, Amit and Sharp, Melissa and Bivigou Koumba, Achille Mayelle and Laschewsky, Andr{\´e} and M{\"u}ller-Buschbaum, Peter and Papadakis, Christine M.}, title = {Kinetics of aggregation in micellar solutions of thermoresponsive triblock copolymers - influence of concentration, start and target temperatures}, series = {Soft matter}, volume = {9}, journal = {Soft matter}, number = {5}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1744-683X}, doi = {10.1039/c2sm27152d}, pages = {1685 -- 1699}, year = {2013}, abstract = {In aqueous solution, symmetric triblock copolymers with a thermoresponsive middle block and hydrophobic end blocks form flower-like core-shell micelles which collapse and aggregate upon heating through the cloud point (CP). The collapse of the micellar shell and the intermicellar aggregation are followed in situ and in real-time using time-resolved small-angle neutron scattering (SANS), while heating micellar solutions of a poly((styrene-d(8))-b-(N-isopropyl acrylamide)-b-(styrene-d(8))) triblock copolymer in D2O rapidly through their CP. The influence of polymer concentration as well as of the start and target temperatures is addressed. In all cases, the micellar collapse is very fast. The collapsed micelles immediately form small clusters which contain voids. They densify which slows down or even stops their growth. For low concentrations and target temperatures just above the CP, i.e. shallow temperature jumps, the subsequent growth of the clusters is described by diffusion-limited aggregation. In contrast, for higher concentrations and/or higher target temperatures, i.e. deep temperature jumps, intermicellar bridges dominate the growth. Eventually, in all cases, the clusters coagulate which results in macroscopic phase separation. For shallow temperature jumps, the cluster surfaces stay rough; whereas for deep temperature jumps, a concentration gradient develops at late stages. These results are important for the development of conditions for thermal switching in applications, e.g. for the use of thermoresponsive micellar systems for transport and delivery purposes.}, language = {en} } @article{WessigMatthes2013, author = {Wessig, Pablo and Matthes, Annika}, title = {Photochemical synthesis and properties of 1,6- and 1,8-Naphthalenophanes}, series = {Molecules}, volume = {18}, journal = {Molecules}, number = {1}, publisher = {MDPI}, address = {Basel}, issn = {1420-3049}, doi = {10.3390/molecules18011314}, pages = {1314 -- 1324}, year = {2013}, abstract = {Various 1,6- and 1,8-naphthalenophanes were synthesized by using the Photo-Dehydro-Diels-Alder (PDDA) reaction of bis-ynones. These compounds are easily accessible from omega-(3-iodophenyl)carboxylic acids in three steps. The obtained naphthalenophanes are axially chiral and the activation barrier for the atropisomerization could be determined in some cases by means of dynamic NMR (DNMR) and/or dynamic HPLC (DHPLC) experiments.}, language = {en} } @article{vonCzapiewskiKreyeMutluetal.2013, author = {von Czapiewski, Marc and Kreye, Oliver and Mutlu, Hatice and Meier, Michael A. R.}, title = {Cross-metathesis versus palladium-catalyzed C-H activation acetoxy ester functionalization of unsaturated fatty acid methyl esters}, series = {European journal of lipid science and technology}, volume = {115}, journal = {European journal of lipid science and technology}, number = {1}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {1438-7697}, doi = {10.1002/ejlt.201200196}, pages = {76 -- 85}, year = {2013}, abstract = {Two synthetic approaches to functionalize plant oil derived platform chemicals were investigated. For this purpose, methyl 10-undecenoate, which can be obtained by pyrolysis of castor oil, was used in olefin cross-metathesis under neat conditions forming an unsaturated a,?-acetoxy ester. A catalyst screening with 11 different ruthenium-based metathesis catalysts was performed, revealing that well-suited catalysts allow for full conversion and very good cross-metathesis selectivity at a loading of only 0.5?mol\%. An alternative possibility to the aforementioned synthetic method is a palladium-catalyzed reaction of methyl 10-undecenoate with acetic acid in the presence of dimethyl sulfoxide. Here, the formation of linear and branched unsaturated acetoxy esters as well as a ketone was observed. The conversion as well as the selectivity of this procedure was studied under different reaction conditions and compared to the cross-metathesis results. Based on the successful functionalization of methyl 10-undecenoate, methyl oleate was investigated in this palladium-catalyzed C?H activation reaction. Due to the lower reactivity of the internal double bond the desired acetoxy ester was only obtained in moderate conversion in this case. In summary, this study clearly shows that palladium-catalyzed functionalization of unsaturated fatty compounds via C?H activation is an attractive alternative to the well-established olefin cross-metathesis procedure.}, language = {en} } @article{HerderUtechtManickeetal.2013, author = {Herder, Martin and Utecht, Manuel Martin and Manicke, Nicole and Grubert, Lutz and P{\"a}tzel, Michael and Saalfrank, Peter and Hecht, Stefan}, title = {Switching with orthogonal stimuli electrochemical ring-closure and photochemical ring-opening of bis(thiazolyl) maleimides}, series = {Chemical science}, volume = {4}, journal = {Chemical science}, number = {3}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {2041-6520}, doi = {10.1039/c2sc21681g}, pages = {1028 -- 1040}, year = {2013}, abstract = {The photochemistry as well as electrochemistry of novel donor-acceptor bis(morpholinothiazolyl)maleimides has been investigated. Proper substitution of these diarylethene-type molecular switches leads to the unique situation in which their ring-closure can only be accomplished electrochemically, while ring-opening can only be achieved photochemically. Hence, these switches operate with orthogonal stimuli, i.e. redox potential and light, respectively. The switch system could be optimized by introducing trifluoromethyl groups at the reactive carbon atoms in order to avoid by-product formation during oxidative ring closure. Both photochemical and electrochemical pathways were investigated for methylated, trifluoromethylated, and nonsymmetrical bis(morpholinothiazolyl) maleimides as well as the bis(morpholinothiazolyl) cyclopentene reference compound. With the aid of the nonsymmetrical "mixed" derivative, the mechanism of electrochemically driven ring closure could be elucidated and seems to proceed via a dicationic intermediate generated by two-fold oxidation. All experimental work has been complemented by density functional theory that provides detailed insights into the thermodynamics of the ring-open and closed forms, the nature of their excited states, and the reactivity of their neutral as well as ionized species in different electronic configurations. The particular diarylethene systems described herein could serve in multifunctional (logic) devices operated by different stimuli (inputs) and may pave the way to converting light into electrical energy via photoinduced "pumping" of redox-active meta-stable states.}, language = {en} } @article{TomczykSobolewskaNagyetal.2013, author = {Tomczyk, Jaroslaw and Sobolewska, Anna and Nagy, Zsuzsanna T. and Guillon, Daniel and Donnio, Bertrand and Stumpe, Joachim}, title = {Photo- and thermal-processing of azobenzene-containing star-shaped liquid crystals}, series = {Journal of materials chemistry : C, Materials for optical and electronic devices}, volume = {1}, journal = {Journal of materials chemistry : C, Materials for optical and electronic devices}, number = {5}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {2050-7526}, doi = {10.1039/c2tc00627h}, pages = {924 -- 932}, year = {2013}, abstract = {A new class of star-shaped, liquid crystalline, low-molecular weight compounds functionalized with photochromic azobenzene and mesogenic groups was investigated in terms of light-induced anisotropy. The behaviour of the materials under the action of light with simultaneous or subsequent thermal treatment was examined with respect to the induction of anisotropy. The unconventional UV light treatment prior to the irradiation with linearly polarized light allowed induction of very high values of anisotropy (D = 0.77) at room temperature. Moreover, the simultaneous action of light and temperature led to the induction of higher values of dichroism in comparison with anisotropy generated by the standard procedure. Subsequent thermal treatment led to dewetting and the formation of 3D macroscopic stripe- and dome-like structures for one of the investigated compounds. Despite photoinduction of anisotropy by a single beam, the formation of polarization and surface relief gratings by two-beam interference pattern was also investigated.}, language = {en} } @article{ThielZehbeRoeseretal.2013, author = {Thiel, Kerstin and Zehbe, Rolf and R{\"o}ser, Jerome and Strauch, Peter and Enthaler, Stephan and Thomas, Arne}, title = {A polymer analogous reaction for the formation of imidazolium and NHC based porous polymer networks}, series = {Polymer Chemistry}, volume = {4}, journal = {Polymer Chemistry}, number = {6}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1759-9954}, doi = {10.1039/c2py20947k}, pages = {1848 -- 1856}, year = {2013}, abstract = {A polymer analogous reaction was carried out to generate a porous polymeric network with N-heterocyclic carbenes (NHC) in the polymer backbone. Using a stepwise approach, first a polyimine network is formed by polymerization of the tetrafunctional amine tetrakis(4-aminophenyl)methane. This polyimine network is converted in the second step into polyimidazolium chloride and finally to a polyNHC network. Furthermore a porous Cu(II)-coordinated polyNHC network can be generated. Supercritical drying generates polymer networks with high permanent surface areas and porosities which can be applied for different catalytic reactions. The catalytic properties were demonstrated for example in the activation of CO2 or in the deoxygenation of sulfoxides to the corresponding sulfides.}, language = {en} } @article{ChechkinZaidLomholtetal.2013, author = {Chechkin, Aleksei V. and Zaid, I. M. and Lomholt, M. A. and Sokolov, Igor M. and Metzler, Ralf}, title = {Bulk-mediated surface diffusion on a cylinder in the fast exchange limit}, series = {Mathematical modelling of natural phenomena}, volume = {8}, journal = {Mathematical modelling of natural phenomena}, number = {2}, publisher = {EDP Sciences}, address = {Les Ulis}, issn = {0973-5348}, doi = {10.1051/mmnp/20138208}, pages = {114 -- 126}, year = {2013}, abstract = {In various biological systems and small scale technological applications particles transiently bind to a cylindrical surface. Upon unbinding the particles diffuse in the vicinal bulk before rebinding to the surface. Such bulk-mediated excursions give rise to an effective surface translation, for which we here derive and discuss the dynamic equations, including additional surface diffusion. We discuss the time evolution of the number of surface-bound particles, the effective surface mean squared displacement, and the surface propagator. In particular, we observe sub- and superdiffusive regimes. A plateau of the surface mean-squared displacement reflects a stalling of the surface diffusion at longer times. Finally, the corresponding first passage problem for the cylindrical geometry is analysed.}, language = {en} } @article{SchmidtElizarovBergeretal.2013, author = {Schmidt, Bernd and Elizarov, Nelli and Berger, Ren{\´e} and Hoelter, Frank}, title = {Scope and limitations of the Heck-Matsuda-coupling of phenol diazonium salts and styrenes a protecting-group economic synthesis of phenolic stilbenes}, series = {Organic \& biomolecular chemistry : an international journal of synthetic, physical and biomolecular organic chemistry}, volume = {11}, journal = {Organic \& biomolecular chemistry : an international journal of synthetic, physical and biomolecular organic chemistry}, number = {22}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1477-0520}, doi = {10.1039/c3ob40420j}, pages = {3674 -- 3691}, year = {2013}, abstract = {4-Phenol diazonium salts undergo Pd-catalyzed Heck reactions with various styrenes to 4'-hydroxy stilbenes. In almost all cases higher yields and fewer side products were observed, compared to the analogous 4-methoxy benzene diazonium salts. In contrast, the reaction fails completely with 2- and 3-phenol diazonium salts. For these substitution patterns the methoxy-substituted derivatives are superior.}, language = {en} } @article{TentschertDraudeJungnickeletal.2013, author = {Tentschert, J. and Draude, F. and Jungnickel, H. and Haase, A. and Mantion, Alexandre and Galla, S. and Thuenemann, Andreas F. and Taubert, Andreas and Luch, A. and Arlinghaus, H. F.}, title = {TOF-SIMS analysis of cell membrane changes in functional impaired human macrophages upon nanosilver treatment}, series = {Surface and interface analysis : an international journal devoted to the development and application of techniques for the analysis surfaces, interfaces and thin films}, volume = {45}, journal = {Surface and interface analysis : an international journal devoted to the development and application of techniques for the analysis surfaces, interfaces and thin films}, number = {1}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {0142-2421}, doi = {10.1002/sia.5155}, pages = {483 -- 485}, year = {2013}, abstract = {Silver nanoparticles (SNP) are among the most commercialized nanoparticles. Here, we show that peptide-coated SNP cause functional impairment of human macrophages. A dose-dependent inhibition of phagocytosis is observed after nanoparticle treatment, and pretreatment of cells with N-acetyl cysteine (NAC) can counteract the phagocytosis disturbances caused by SNP. Using the surface-sensitive mode of time-of-flight secondary ion mass spectrometry, in combination with multivariate statistical methods, we studied the composition of cell membranes in human macrophages upon exposure to SNP with and without NAC preconditioning. This method revealed characteristic changes in the lipid pattern of the cellular membrane outer leaflet in those cells challenged by SNP. Statistical analyses resulted in 19 characteristic ions, which can be used to distinguish between NAC pretreated and untreated macrophages. The present study discusses the assignments of surface cell membrane phospholipids for the identified ions and the resulting changes in the phospholipid pattern of treated cells. We conclude that the adverse effects in human macrophages caused by SNP can be partially reversed through NAC administration. Some alterations, however, remained.}, language = {en} } @article{DraudeGallaPelsteretal.2013, author = {Draude, F. and Galla, S. and Pelster, Axel and Tentschert, J. and Jungnickel, H. and Haase, Alfred and Mantion, Alexandre and Thuenemann, Andreas F. and Taubert, Andreas and Luch, A. and Arlinghaus, H. F.}, title = {ToF-SIMS and Laser-SNMS analysis of macrophages after exposure to silver nanoparticles}, series = {Surface and interface analysis : an international journal devoted to the development and application of techniques for the analysis surfaces, interfaces and thin films}, volume = {45}, journal = {Surface and interface analysis : an international journal devoted to the development and application of techniques for the analysis surfaces, interfaces and thin films}, number = {1}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {0142-2421}, doi = {10.1002/sia.4902}, pages = {286 -- 289}, year = {2013}, abstract = {Silver nanoparticles (SNPs) are among the most commercialized nanoparticles because of their antibacterial effects. Besides being employed, e. g. as a coatingmaterial for sterile surfaces in household articles and appliances, the particles are also used in a broad range of medical applications. Their antibacterial properties make SNPs especially useful for wound disinfection or as a coating material for prostheses and surgical instruments. Because of their optical characteristics, the particles are of increasing interest in biodetection as well. Despite the widespread use of SNPs, there is little knowledge of their toxicity. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) and laser post-ionization secondary neutral mass spectrometry (Laser-SNMS) were used to investigate the effects of SNPs on human macrophages derived from THP-1 cells in vitro. For this purpose, macrophages were exposed to SNPs. The SNP concentration ranges were chosen with regard to functional impairments of the macrophages. To optimize the analysis of the macrophages, a special silicon wafer sandwich preparation technique was employed; ToF-SIMS was employed to characterize fragments originating from macrophage cell membranes. With the use of this optimized sample preparation method, the SNP-exposed macrophages were analyzed with ToF-SIMS and with Laser-SNMS. With Laser-SNMS, the three-dimensional distribution of SNPs in cells could be readily detected with very high efficiency, sensitivity, and submicron lateral resolution. We found an accumulation of SNPs directly beneath the cell membrane in a nanoparticular state as well as agglomerations of SNPs inside the cells.}, language = {en} } @article{SchmidtHauke2013, author = {Schmidt, Bernd and Hauke, Sylvia}, title = {Cross metathesis of allyl alcohols how to suppress and how to promote double bond isomerization}, series = {Organic \& biomolecular chemistry : an international journal of synthetic, physical and biomolecular organic chemistry}, volume = {11}, journal = {Organic \& biomolecular chemistry : an international journal of synthetic, physical and biomolecular organic chemistry}, number = {25}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1477-0520}, doi = {10.1039/c3ob40167g}, pages = {4194 -- 4206}, year = {2013}, abstract = {Under standard conditions the cross metathesis of allyl alcohols and methyl acrylate is accompanied by the formation of ketones, resulting from uncontrolled and undesired double bond isomerization. By conducting the CM in the presence of phenol, the catalyst loading and the reaction time required for quantiative conversion can be reduced, and isomerization can be suppressed. On the other hand, consecutive isomerization can be deliberately promoted by evaporating excess methyl acrylate after completing cross metathesis and by adding a base or silane as chemical triggers.}, language = {en} } @article{JungingerKuebelSchacheretal.2013, author = {Junginger, Mathias and K{\"u}bel, Christian and Schacher, Felix H. and M{\"u}ller, Axel H. E. and Taubert, Andreas}, title = {Crystal structure and chemical composition of biomimetic calcium phosphate nanofibers}, series = {RSC Advances}, volume = {3}, journal = {RSC Advances}, number = {28}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {2046-2069}, doi = {10.1039/c3ra23348k}, pages = {11301 -- 11308}, year = {2013}, abstract = {Calcium phosphate nanofibers with a diameter of only a few nanometers and a cotton-ball-like aggregate morphology have been reported several times in the literature. Although fiber formation seems reproducible in a variety of conditions, the crystal structure and chemical composition of the fibers have been elusive. Using scanning transmission electron microscopy, low dose electron (nano) diffraction, energy-dispersive X-ray spectroscopy, and energy-filtered transmission electron microscopy, we have assigned crystal structures and chemical compositions to the fibers. Moreover, we demonstrate that the mineralization process yields true polymer/calcium phosphate hybrid materials where the block copolymer template is closely associated with the calcium phosphate.}, language = {en} } @article{TheteRojasNeumeyeretal.2013, author = {Thete, Aniket and Rojas, Oscar and Neumeyer, David and Koetz, Joachim and Dujardin, Erik}, title = {Ionic liquid-assisted morphosynthesis of gold nanorods using polyethyleneimine-capped seeds}, series = {RSC Advances}, volume = {3}, journal = {RSC Advances}, number = {34}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {2046-2069}, doi = {10.1039/c3ra22112a}, pages = {14294 -- 14298}, year = {2013}, abstract = {Seed-mediated gold nanorods with tunable lengths are prepared using new polyethyleneimine-capped gold nanoparticles synthesized in ionic liquid. The effect of polyethyleneimine and ionic liquid during nanorod growth is investigated and shows a marked effect on their final aspect ratio.}, language = {en} } @article{MondalBhuniaBaburinetal.2013, author = {Mondal, Suvendu Sekhar and Bhunia, Asamanjoy and Baburin, Igor A. and J{\"a}ger, Christian and Kelling, Alexandra and Schilde, Uwe and Seifert, Gotthard and Janiak, Christoph and Holdt, Hans-J{\"u}rgen}, title = {Gate effects in a hexagonal zinc-imidazolate-4-amide-5-imidate framework with flexible methoxy substituents and CO2 selectivity}, series = {Chemical communications}, volume = {49}, journal = {Chemical communications}, number = {69}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1359-7345}, doi = {10.1039/c3cc42156b}, pages = {7599 -- 7601}, year = {2013}, abstract = {A new imidazolate-4-amide-5-imidate based MOF, IFP-7, is generated, having flexible methoxy groups, which act as molecular gates for guest molecules. This allows highly selective CO2 sorption over N-2 and CH4 gases.}, language = {en} } @article{MenSiebenbuergerQiuetal.2013, author = {Men, Yongjun and Siebenb{\"u}rger, Miriam and Qiu, Xunlin and Antonietti, Markus and Yuan, Jiayin}, title = {Low fractions of ionic liquid or poly(ionic liquid) can activate polysaccharide biomass into shaped, flexible and fire-retardant porous carbons}, series = {Journal of materials chemistry : A, Materials for energy and sustainability}, volume = {1}, journal = {Journal of materials chemistry : A, Materials for energy and sustainability}, number = {38}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {2050-7488}, doi = {10.1039/c3ta12302b}, pages = {11887 -- 11893}, year = {2013}, abstract = {Sugar-based molecules and polysaccharide biomass can be turned into porous functional carbonaceous products at comparably low temperatures of 400 degrees C under a nitrogen atmosphere in the presence of an ionic liquid (IL) or a poly(ionic liquid) (PIL). The IL and PIL act as "activation agents" with own structural contribution, and effectively promote the conversion and pore generation in the biomaterials even at a rather low doping ratio (7 wt\%). In addition, this "induced carbonization" and pore forming phenomenon enables the preservation of the biotemplate shape to the highest extent and was employed to fabricate shaped porous carbonaceous materials from carbohydrate-based biotemplates, exemplified here with cellulose filter membranes, coffee filter paper and natural cotton. These carbonized hybrids exhibit comparably good mechanical properties, such as bendability of membranes or shape recovery of foams. Moreover, the nitrogen atoms incorporated in the final products from the IL/PIL precursors further improve the oxidation stability in the fire-retardant tests.}, language = {en} } @article{MondalDeyBaburinetal.2013, author = {Mondal, Suvendu Sekhar and Dey, Subarna and Baburin, Igor A. and Kelling, Alexandra and Schilde, Uwe and Seifert, Gotthard and Janiak, Christoph and Holdt, Hans-J{\"u}rgen}, title = {Syntheses of two imidazolate-4-amide-5-imidate linker-based hexagonal metal-organic frameworks with flexible ethoxy substituent}, series = {CrystEngComm}, volume = {15}, journal = {CrystEngComm}, number = {45}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1466-8033}, doi = {10.1039/c3ce41632a}, pages = {9394 -- 9399}, year = {2013}, abstract = {A rare example of in situ linker generation with the formation of soft porous Zn- and Co-MOFs (IFP-9 and -10, respectively) is reported. The flexible ethoxy groups of IFP-9 and -10 protrude into the 1D hexagonal channels. The gas-sorption behavior of both materials for H-2, CO2 and CH4 showed wide hysteretic isotherms, typical for MOFs having a flexible substituent which can give rise to a gate effect.}, language = {en} } @article{VanBelProostVanNesteetal.2013, author = {Van Bel, Michiel and Proost, Sebastian and Van Neste, Christophe and Deforce, Dieter and Van de Peer, Yves and Vandepoele, Klaas}, title = {TRAPID - an efficient online tool for the functional and comparative analysis of de novo RNA-Seq transcriptomes}, series = {Genome biology : biology for the post-genomic era}, volume = {14}, journal = {Genome biology : biology for the post-genomic era}, number = {12}, publisher = {BioMed Central}, address = {London}, issn = {1465-6906}, doi = {10.1186/gb-2013-14-12-r134}, pages = {10}, year = {2013}, abstract = {Transcriptome analysis through next-generation sequencing technologies allows the generation of detailed gene catalogs for non-model species, at the cost of new challenges with regards to computational requirements and bioinformatics expertise. Here, we present TRAPID, an online tool for the fast and efficient processing of assembled RNA-Seq transcriptome data, developed to mitigate these challenges. TRAPID offers high-throughput open reading frame detection, frameshift correction and includes a functional, comparative and phylogenetic toolbox, making use of 175 reference proteomes. Benchmarking and comparison against state-of-the-art transcript analysis tools reveals the efficiency and unique features of the TRAPID system.}, language = {en} } @article{MoskalikShainyanAstakhovaetal.2013, author = {Moskalik, Mikhail Yu and Shainyan, Bagrat A. and Astakhova, Vera V. and Schilde, Uwe}, title = {Oxidative addition of trifluoromethanesulfonamide to cycloalkadienes}, series = {Tetrahedron}, volume = {69}, journal = {Tetrahedron}, number = {2}, publisher = {Elsevier}, address = {Oxford}, issn = {0040-4020}, doi = {10.1016/j.tet.2012.10.099}, pages = {705 -- 711}, year = {2013}, abstract = {In the oxidative system (t-BuOCl+NaI) trifluoromethanesulfonamide is regio- and stereoselectively added to only one double bond of cyclopentadiene and 1,3-cyclohexadiene giving rise to 1,1,1-trifluoro-N-(5-iodocyclopent-2-en-1-yl)methanesulfonamide 7 and trans-N,N'-cyclohex-3-en-1,2-diylbis(1,1,1-trifluoromethanesulfonamide) 8. The structure of 7 and 8 was determined by X-ray, NMR, and MS. With 1,4-cyclohexadiene, addition to both double bonds occurs with the formation of N,N'-(4-chloro-5-iodocyclohexan-1,2-diyl)bis(1,1,1-trifluoromethanesulfonamide) 9. Under the action of sodium iodide in acetone, the latter product undergoes halogenophilic attack with the reduction of the CHI group and elimination of HCl to give trans-N,N'-cyclohex-4-en-1,2-diylbis(1,1,1-trifluoromethanesulfonamide) 10, whose structure was also determined by X-ray analysis. 1,3,5-Cycloheptatriene under these conditions is oxidized to benzaldehyde and does not react with trifluoromethanesulfonamide.}, language = {en} } @article{UnuabonahOluOwolabiTaubertetal.2013, author = {Unuabonah, Emmanuel Iyayi and Olu-Owolabi, Bamidele I. and Taubert, Andreas and Omolehin, Elizabeth B. and Adebowale, Kayode O.}, title = {SAPK a novel composite resin for water treatment with very high Zn2+, Cd2+, and Pb2+ adsorption capacity}, series = {Industrial \& engineering chemistry research}, volume = {52}, journal = {Industrial \& engineering chemistry research}, number = {2}, publisher = {American Chemical Society}, address = {Washington}, issn = {0888-5885}, doi = {10.1021/ie3024577}, pages = {578 -- 585}, year = {2013}, abstract = {A new sulfonated aniline-modified poly(vinyl alcohol)/K-feldspar (SAPK) composite was prepared. The cation-exchange capacity of the composite was found to be S times that of neat feldspar. The specific surface area and point of zero charge also changed significantly upon modification, from 15.6 +/- 0.1 m(2)/g and 2.20 (K-feldspar) to 73.6 +/- 0.3 m(2)/g and 1.91 (SAPK). Zn2+, Cd2+, and Pb2+ adsorption was found to be largely independent of pH, and the metal adsorption rate on SAPK was higher than that on neat feldspar. This particularly applies to the initial adsorption rates. The adsorption process involves both film and pore diffusion; film diffusion initially controls the adsorption. The Freundlich and Langmuir models were found to fit metal-ion adsorption on SAPK most accurately. Adsorption on neat feldspar was best fitted with a Langmuir model, indicating the formation of adsorbate monolayers. Both pure feldspar and SAPK showed better selectivity for Pb2+ than for Cd2+ or Zn2+.}, language = {en} } @article{BertzWoehlBruhnMietheetal.2013, author = {Bertz, Andreas and W{\"o}hl-Bruhn, Stefanie and Miethe, Sebastian and Tiersch, Brigitte and Koetz, Joachim and Hust, Michael and Bunjes, Heike and Menzel, Henning}, title = {Encapsulation of proteins in hydrogel carrier systems for controlled drug delivery influence of network structure and drug size on release rate}, series = {Journal of biotechnology}, volume = {163}, journal = {Journal of biotechnology}, number = {2}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0168-1656}, doi = {10.1016/j.jbiotec.2012.06.036}, pages = {243 -- 249}, year = {2013}, abstract = {Novel hydrogels based on hydroxyethyl starch modified with polyethylene glycol methacrylate (HES-P(EG)(6)MA) were developed as delivery system for the controlled release of proteins. Since the drug release behavior is supposed to be related to the pore structure of the hydrogel network the pore sizes were determined by cryo-SEM, which is a mild technique for imaging on a nanometer scale. The results showed a decreasing pore size and an increase in pore homogeneity with increasing polymer concentration. Furthermore, the mesh sizes of the hydrogels were calculated based on swelling data. Pore and mesh size were significantly different which indicates that both structures are present in the hydrogel. The resulting structural model was correlated with release data for bulk hydrogel cylinders loaded with FITC-dextran and hydrogel microspheres loaded with FITC-IgG and FITC-dextran of different molecular size. The initial release depended much on the relation between hydrodynamic diameter and pore size while the long term release of the incorporated substances was predominantly controlled by degradation of the network of the much smaller meshes.}, language = {en} } @article{GeisslerStuflerLoehmannsroebenetal.2013, author = {Geissler, Daniel and Stufler, Stefan and L{\"o}hmannsr{\"o}ben, Hans-Gerd and Hildebrandt, Niko}, title = {Six-color time-resolved forster resonance energy transfer for ultrasensitive multiplexed biosensing}, series = {Journal of the American Chemical Society}, volume = {135}, journal = {Journal of the American Chemical Society}, number = {3}, publisher = {American Chemical Society}, address = {Washington}, issn = {0002-7863}, doi = {10.1021/ja310317n}, pages = {1102 -- 1109}, year = {2013}, abstract = {Simultaneous monitoring of multiple molecular interactions and multiplexed detection of several diagnostic biomarkers at very low concentrations have become important issues in advanced biological and chemical sensing. Here we present an optically multiplexed six-color Forster resonance energy transfer (FRET) biosensor for simultaneous monitoring of five different individual binding events. We combined simultaneous FRET from one Tb complex to five different organic dyes measured in a filter-based time-resolved detection format with a sophisticated spectral crosstalk correction, which results in very efficient background suppression. The advantages and robustness of the multiplexed FRET sensor were exemplified by analyzing a 15-component lung cancer immunoassay involving 10 different antibodies and five different tumor markers in a single 50 mu L human serum sample. The multiplexed biosensor offers clinically relevant detection limits in the low picomolar (ng/mL) concentration range for all five markers, thus providing an effective early screening tool for lung cancer with the possibility of distinguishing small-cell from non-small-cell lung carcinoma. This novel technology will open new doors for multiple biomarker diagnostics as well as multiplexed real-time imaging and spectroscopy.}, language = {en} } @article{SchmidtBerger2013, author = {Schmidt, Bernd and Berger, Ren{\´e}}, title = {A deacetylation-diazotation-coupling sequence - palladium-catalyzed CC bond formation with acetanilides as formal leaving groups}, series = {Advanced synthesis \& catalysis}, volume = {355}, journal = {Advanced synthesis \& catalysis}, number = {2-3}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1615-4150}, doi = {10.1002/adsc.201200929}, pages = {463 -- 476}, year = {2013}, abstract = {Acetanilides can be deacetylated and diazotized in situ, and subsequently used in Pd-catalyzed coupling reactions without isolation of the diazonium intermediate. Heck reactions, Suzuki cross-coupling reactions, and a Pd-catalyzed [2+2+1]cycloaddition have been investigated as terminating CC bond-forming steps of this one-flask sequence. The sequence does not require the exchange of solvents or removal of by-products between the individual steps, but proceeds by addition of reagents and catalysts in due course.}, language = {en} } @article{GrimmMeyerCzaplaetal.2013, author = {Grimm, Christiane and Meyer, Thomas and Czapla, Sylvia and Nikolaus, J{\"o}rg and Scheidt, Holger A. and Vogel, Alexander and Herrmann, Andreas and Wessig, Pablo and Huster, Daniel and M{\"u}ller, Peter}, title = {Structure and dynamics of molecular rods in membranes application of a Spin-Labeled rod}, series = {Chemistry - a European journal}, volume = {19}, journal = {Chemistry - a European journal}, number = {8}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {0947-6539}, doi = {10.1002/chem.201202500}, pages = {2703 -- 2710}, year = {2013}, abstract = {Molecular rods consisting of a hydrophobic backbone and terminally varying functional groups have been synthesized for applications for the functionalization of membranes. In the present study, we employ a spin-labeled analogue of a recently described new class of molecular rods to characterize their dynamic interactions with membranes. By using the different approaches of ESR and NMR spectroscopy, we show that the spin moiety of the membrane-embedded spin-labeled rod is localized in the upper chain/glycerol region of membranes of different compositions. The rod is embedded within the membrane in a tilted orientation to adjust for the varying hydrophobic thicknesses of these bilayers. This orientation does not perturb the membrane structure. The water solubility of the rod is increased significantly in the presence of certain cyclodextrins. These cyclodextrins also allow the rods to be extracted from the membrane and incorporated into preformed membranes. The latter will improve the future applications of these rods in cellular systems as stable membrane-associated anchors for the functionalization of membrane surfaces.}, language = {en} } @article{BeschererMunzkeReichetal.2013, author = {Bescherer, Klaus and Munzke, Dorit and Reich, Oliver and Loock, Hans-Peter}, title = {Fabrication and modeling of multimode fiber lenses}, series = {Applied optics}, volume = {52}, journal = {Applied optics}, number = {4}, publisher = {Optical Society of America}, address = {Washington}, issn = {1559-128X}, doi = {10.1364/AO.52.000B40}, pages = {B40 -- B45}, year = {2013}, abstract = {We report on the fabrication, modeling, and experimental verification of the emission of fiber lenses fabricated on multimode fibers in different media. Concave fiber lenses with a radius of 150 mu m were fabricated onto a multimode silica fiber (100 mu m core) by grinding and polishing against a ruby sphere template. In our theoretical model we assume that the fiber guides light from a Lambertian light source and that the emission cone is governed solely by the range of permitted emission angles. We investigate concave and convex lenses at 532 nm with different radii and in a variety of surrounding media from air (n(0) = 1.00) to sapphire (n(0) = 1.77). It was found that noticeable focusing or defocusing effects of a silica fiber lens in ethanol (n(0) = 1.36) and dimethyl sulfoxide (DMSO) (n(0) = 1.48) are only observed when the fiber lens radius was less than the fiber diameter.}, language = {en} } @article{KeruboMidiwoDereseetal.2013, author = {Kerubo, Leonidah Omosa and Midiwo, Jacob Ogweno and Derese, Solomon and Langat, Moses K. and Akala, Hoseah M. and Waters, Norman C. and Peter, Martin and Heydenreich, Matthias}, title = {Antiplasmodial activity of compounds from the surface exudates of senecio roseiflorus}, series = {Natural product communications : an international journal for communications and reviews}, volume = {8}, journal = {Natural product communications : an international journal for communications and reviews}, number = {2}, publisher = {NPC}, address = {Westerville}, issn = {1934-578X}, pages = {175 -- 176}, year = {2013}, abstract = {From the surface exudates of Senecio roseiflorus fourteen known methylated flavonoids and one phenol were isolated and characterized. The structures of these compounds were determined on the basis of their spectroscopic analysis. The surface exudate and the flavonoids isolated showed moderate to good antiplasmodial activity with 5,4'-dihydroxy-7-dimethoxyflavanone having the highest activity against chloroquine-sensitive (D6) and resistant (W2) strains of Plasmodium falciparum, with IC50 values of 3.2 +/- 0.8 and 4.4 +/- 0.01 mu g/mL respectively.}, language = {en} } @article{KleinpeterKoch2013, author = {Kleinpeter, Erich and Koch, Andreas}, title = {(Anti)aromaticity of dehydroannulenes of various ring size proved by the ring current effect in H-1 NMR spectra}, series = {Tetrahedron}, volume = {69}, journal = {Tetrahedron}, number = {5}, publisher = {Elsevier}, address = {Oxford}, issn = {0040-4020}, doi = {10.1016/j.tet.2012.12.019}, pages = {1481 -- 1488}, year = {2013}, abstract = {The spatial magnetic properties (Through-Space NMR Shieldings-TSNMRS) of already synthesized dehydro[n]annulenes of various ring size (from C-12 to C-20) have been computed, visualized as Isochemical Shielding Surfaces (ICSS) of various size and direction, and were examined subject to present (anti)aromaticity. For this purpose the thus quantified ring current effect of the macro cycles on proximate protons in proton NMR spectra was employed.}, language = {en} } @article{HassMuenzbergBresseletal.2013, author = {Hass, Roland and M{\"u}nzberg, Marvin and Bressel, Lena and Reich, Oliver}, title = {Industrial applications of photon density wave spectroscopy for in-line particle sizing [Invited]}, series = {Applied optics}, volume = {52}, journal = {Applied optics}, number = {7}, publisher = {Optical Society of America}, address = {Washington}, issn = {1559-128X}, doi = {10.1364/AO.52.001423}, pages = {1423 -- 1431}, year = {2013}, abstract = {Optical spectroscopy in highly turbid liquid material is often restricted by simultaneous occurrence of absorption and scattering of light. Photon Density Wave (PDW) spectroscopy is one of the very few, yet widely unknown, technologies for the independent quantification of these two optical processes. Here, a concise overview about modern PDW spectroscopy is given, including all necessary equations concerning the optical description of the investigated material, dependent light scattering, particle sizing, and PDW spectroscopy itself. Additionally, it is shown how the ambiguity in particle sizing, arising from Mie theory, can be correctly solved. Due to its high temporal resolution, its applicability to highest particle concentrations, and its purely fiber-optical probe, PDW spectroscopy possesses all fundamental characteristics for optical in-line process analysis. Several application examples from the chemical industry are presented. (C) 2013 Optical Society of America}, language = {en} } @article{HarmaPihlasaloCywinskietal.2013, author = {Harma, Harri and Pihlasalo, Sari and Cywinski, Piotr J. and Mikkonen, Piia and Hammann, Tommy and L{\"o}hmannsr{\"o}ben, Hans-Gerd and Hanninen, Pekka}, title = {Protein quantification using resonance energy transfer between donor nanoparticles and acceptor quantum dots}, series = {Analytical chemistry}, volume = {85}, journal = {Analytical chemistry}, number = {5}, publisher = {American Chemical Society}, address = {Washington}, issn = {0003-2700}, doi = {10.1021/ac303586n}, pages = {2921 -- 2926}, year = {2013}, abstract = {A homogeneous time-resolved luminescence resonance energy transfer (TR-LRET) assay has been developed to quantify proteins. The competitive assay is based on resonance energy transfer (RET) between two luminescent nanosized particles. Polystyrene nanoparticles loaded with Eu3+ chelates (EuNPs) act as donors, while protein-coated quantum dots (QDs), either CdSe/ZnS emitting at 655 nm (QD655-strep) or CdSeTe/ZnS with emission wavelength at 705 nm (QD705-strep), are acceptors. In the absence of analyte protein, in our case bovine serum albumin (BSA), the protein-coated QDs bind nonspecifically to the EuNPs, leading to RET. In the presence of analyte proteins, the binding of the QDs to the EuNPs is prevented and the RET signal decreases. RET from the EuNPs to the QDs was confirmed and characterized with steady-state and time-resolved luminescence spectroscopy. In accordance with the Forster theory, the approximate average donor acceptor distance is around 15 nm at RET efficiencies, equal to 15\% for QD655 and 13\% for QD705 acceptor, respectively. The limits of detection are below 10 ng of BSA with less than a 10\% average coefficient of variation. The assay sensitivity is improved, when compared to the most sensitive commercial methods. The presented mix-and-measure method has potential to be implemented into routine protein quantification in biological laboratories.}, language = {en} } @article{JulichGrunerLoewenbergNeffeetal.2013, author = {Julich-Gruner, Konstanze K. and L{\"o}wenberg, Candy and Neffe, Axel T. and Behl, Marc and Lendlein, Andreas}, title = {Recent trends in the chemistry of shape-memory polymers}, series = {Macromolecular chemistry and physics}, volume = {214}, journal = {Macromolecular chemistry and physics}, number = {5}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1022-1352}, doi = {10.1002/macp.201200607}, pages = {527 -- 536}, year = {2013}, abstract = {Shape-memory polymers (SMPs) are stimuli-sensitive materials capable of performing complex movements on demand, which makes them interesting candidates for various applications, for example, in biomedicine or aerospace. This trend article highlights current approaches in the chemistry of SMPs, such as tailored segment chemistry to integrate additional functions and novel synthetic routes toward permanent and temporary netpoints. Multiphase polymer networks and multimaterial systems illustrate that SMPs can be constructed as a modular system of different building blocks and netpoints. Future developments are aiming at multifunctional and multistimuli-sensitive SMPs.}, language = {en} } @article{LemkePrietzelKoetz2013, author = {Lemke, Karina and Prietzel, Claudia Christina and Koetz, Joachim}, title = {Fluorescent gold clusters synthesized in a poly(ethyleneimine) modified reverse microemulsion}, series = {Journal of colloid and interface science}, volume = {394}, journal = {Journal of colloid and interface science}, publisher = {Elsevier}, address = {San Diego}, issn = {0021-9797}, doi = {10.1016/j.jcis.2012.11.057}, pages = {141 -- 146}, year = {2013}, abstract = {This paper is focused on the formation of gold clusters in a tailor-made polyelectrolyte-modified reverse microemulsion using poly(ethyleneimine) (PEI) as a cationic polyelectrolyte. PEI incorporated into a ternary w/o microemulsion consisting of water/heptanol/zwitterionic surfactant 3-(N,N-dimethyl-dodecylammonio)-propanesulfonate (SB) acts as a reducing and stabilizing agent and shows an additional template effect. The nanoparticle synthesis is performed by a simple mixing of two microemulsions, one containing the PEI and the other one containing the gold chloride precursor. UV-vis measurements in the microemulsion show two pronounced absorption maxima, one at 360 nm and the other one at 520 nm, indicating two particle fractions. The absorption maximum at 360 nm in combination to the unique fluorescence properties indicate the formation of gold clusters. After a complete solvent evaporation the redispersed nanoparticles have been characterized by using UV-vis and fluorescence spectroscopy, in combination to dynamic light scattering and transmission electron microscopy (TEM). In addition to the gold nanoparticle fraction (>5 nm) the fluorescent gold cluster fraction (<2 nm) can be redispersed without particle aggregation. By means of asymmetric flow field flow fractionation (AF-FFF) two different cluster fractions with particle diameter (<2 nm) can be identified.}, language = {en} } @article{KleinpeterWernerKoch2013, author = {Kleinpeter, Erich and Werner, Peter and Koch, Andreas}, title = {Push-pull allenes-conjugation, (anti)aromaticity and quantification of the push-pull character}, series = {Tetrahedron}, volume = {69}, journal = {Tetrahedron}, number = {11}, publisher = {Elsevier}, address = {Oxford}, issn = {0040-4020}, doi = {10.1016/j.tet.2013.01.027}, pages = {2436 -- 2445}, year = {2013}, abstract = {Structures, H-1/C-13 chemical shifts, and pi electron distribution/conjugation of an experimentally available and theoretically completed set of push-pull allenes Acc(2)C=C=CDon(2) (Acc=F, CHO, CF3, C N; Don=t-Bu, OMe, OEt, SMe, SEt, NCH2R) have been computed at the OFT level of theory. Both orthogonal linear and orthogonal bent structures have been obtained. In the latter case the push-pull character could be quantified by the quotient method. The C-13 chemical shift of the central allene carbon atom C-2 and chemical shift differences Delta delta(C-1, C-2) and Delta delta(C-2, C-3) of allene carbon atoms proved to be a quantitative alternative. TSNMRS of ring-closed push-pull allenes have been computed in addition and were employed to identify polar, carbene-like and carbone-like canonical structures of these molecules.}, language = {en} } @article{DodooBalzerHugeletal.2013, author = {Dodoo, Samuel and Balzer, Bizan N. and Hugel, Thorsten and Laschewsky, Andr{\´e} and von Klitzing, Regine}, title = {Effect of ionic strength and layer number on swelling of polyelectrolyte multilayers in water vapour}, series = {Soft materials}, volume = {11}, journal = {Soft materials}, number = {2}, publisher = {Taylor \& Francis Group}, address = {Philadelphia}, issn = {1539-445X}, doi = {10.1080/1539445X.2011.607203}, pages = {157 -- 164}, year = {2013}, abstract = {The swelling behavior of polyelectrolyte multilayers (PEMs) of poly(sodium-4 styrene sulfonate) (PSS) and poly(diallyl dimethyl ammonium chloride) (PDADMAC) prepared from aqueous solution of 0.1 M and 0.5 M NaCl are investigated by ellipsometry and Atomic Force Microscopy (AFM). From 1 double-layer up to 4 double-layers of 0.1 M NaCl, the amount of swelling water in the PEMs decreases with increasing number of adsorbed double layers due to an increase in polyelectrolyte density as a result of the attraction between the positively charged outermost PDADMAC layer and the Si substrate. From 6 double layers to 30 double layers, the attraction is reduced due to a much larger distance between substrate and outermost layer leading to a much lower polyelectrolyte density and higher swelling water. In PEMs prepared from aqueous solution of 0.5 M NaCl, the amount of water constantly increases which is related to a monotonically decreasing polyelectrolyte density with increasing number of polyelectrolyte layers. Studies of the surface topology also indicate a transition from a more substrate affected interphase behavior to a continuum properties of the polyelectrolyte multilayers. The threshold for the transition from interphase to continuum behavior depends on the preparation conditions of the PEM.}, language = {en} } @article{WessigMatthesSchildeetal.2013, author = {Wessig, Pablo and Matthes, Annika and Schilde, Uwe and Kelling, Alexandra}, title = {Asymmetric synthesis of (1,5)Naphthalenophanes by Dehydro-Diels-Alder reaction}, series = {European journal of organic chemistry}, journal = {European journal of organic chemistry}, number = {11}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1434-193X}, doi = {10.1002/ejoc.201201594}, pages = {2123 -- 2129}, year = {2013}, abstract = {An asymmetric variant of the dehydro-Diels-Alder (DDA) reaction has been developed and applied in the atropselective synthesis of various (1,5)naphthalenophanes. Whereas the suitability of the photochemically induced DDA (PDDA) was limited, the thermally induced DDA provided the desired product, depending on the chiral auxiliary used and the length of the linker, with nearly perfect stereoselectivity. Furthermore, the mechanism of the DDA was investigated by means of DFT calculations, and a stepwise mechanism involving 1,4-biradicals was suggested.}, language = {en} } @article{ShainyanKirpichenkoKleinpeteretal.2013, author = {Shainyan, Bagrat A. and Kirpichenko, Svetlana V. and Kleinpeter, Erich and Shlykov, Sergey A. and Osadchiy, Dmitriy Yu and Chipanina, Nina N. and Oznobikhina, Larisa P.}, title = {1,3-Dimethy1-3-silapiperidine - synthesis, molecular structure, and conformational analysis by gas-phase electron diffraction, low temperature NMR, IR and Raman Spectroscopy, and quantum chemical calculations}, series = {The journal of organic chemistry}, volume = {78}, journal = {The journal of organic chemistry}, number = {8}, publisher = {American Chemical Society}, address = {Washington}, issn = {0022-3263}, doi = {10.1021/jo400289g}, pages = {3939 -- 3947}, year = {2013}, abstract = {The first Si-H-containing azasilaheterocycle, 1,3-dimethyl-3-silapiperidine 1, was synthesized, and its molecular structure and conformational properties were studied by gas-phase electron diffraction (GED), low temperature NMR, IR and Raman spectroscopy and quantum chemical calculations. The compound exists as a mixture of two conformers possessing the chair conformation with the equatorial NMe group and differing by axial or equatorial position of the SiMe group. In the gas phase, the SiMeax conformer predominates (GED: ax/eq = 65(7):35(7)\%,Delta G = 0.36(18) kcal/mol; IR: ax/eq = 62(5):38(5)\%,Delta G = 0.16(7) kcal/mol). In solution, at 143 k the SiMeeq conformer predominates' in the frozen equilibrium (NMR: ax/eq = 31.5(1.5):68.5(1.5)\%, Delta G = -0.22(2) kcal/mol). Thermodynamic parameters of the ring inversion are determined (Delta G(double dagger) = 8.9-9.0 kcal/mol, Delta H-double dagger = 9.6 kcal/mol, Delta S-double dagger = 2.1 eu). High-level quantum chemical calculations :(MP2, G2, CCSD(T)) nicely reproduce the experimental geometry and the predominance of the axial conformer in the gas phase.}, language = {en} } @article{NestLudwigUlusoyetal.2013, author = {Nest, Mathias and Ludwig, M. and Ulusoy, I. and Klamroth, Tillmann and Saalfrank, Peter}, title = {Electron correlation dynamics in atoms and molecules}, series = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr}, volume = {138}, journal = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr}, number = {16}, publisher = {American Institute of Physics}, address = {Melville}, issn = {0021-9606}, doi = {10.1063/1.4801867}, pages = {6}, year = {2013}, abstract = {In this paper, we present quantum dynamical calculations on electron correlation dynamics in atoms and molecules using explicitly time-dependent ab initio configuration interaction theory. The goals are (i) to show that in which cases it is possible to switch off the electronic correlation by ultrashort laser pulses, and (ii) to understand the temporal evolution and the time scale on which it reappears. We characterize the appearance of correlation through electron-electron scattering when starting from an uncorrelated state, and we identify pathways for the preparation of a Hartree-Fock state from the correlated, true ground state. Exemplary results for noble gases, alkaline earth elements, and selected molecules are provided. For Mg we show that the uncorrelated state can be prepared using a shaped ultrashort laser pulse.}, language = {en} } @article{SchmidtElizarovBergeretal.2013, author = {Schmidt, Bernd and Elizarov, Nelli and Berger, Ren{\´e} and Petersen, Monib H.}, title = {From paracetamol to rolipram and derivatives - application of deacetylation-diazotation sequences and palladium-catalyzed matsuda-heck reaction}, series = {Synthesis}, volume = {45}, journal = {Synthesis}, number = {9}, publisher = {Thieme}, address = {Stuttgart}, issn = {0039-7881}, doi = {10.1055/s-0032-1316874}, pages = {1174 -- 1180}, year = {2013}, abstract = {A six-step synthesis of the antidepressant rolipram from the popular analgetic 4-acetamidophenol (paracetamol) is described. The steps include oxidative functionalization of the aromatic core, diazonium salt formation via deacetylation-diazotation, Matsuda-Heck reaction, conjugate addition of nitromethane, and hydrogenative cyclization.}, language = {en} } @article{AbdissaInduliAkalaetal.2013, author = {Abdissa, Negera and Induli, Martha and Akala, Hoseah M. and Heydenreich, Matthias and Midiwo, Jacob O. and Ndakala, Albert and Yenesew, Abiy}, title = {Knipholone cyclooxanthrone and an anthraquinone dimer with antiplasmodial activities from the roots of Kniphofia foliosa}, series = {Phytochemistry letters}, volume = {6}, journal = {Phytochemistry letters}, number = {2}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1874-3900}, doi = {10.1016/j.phytol.2013.02.005}, pages = {241 -- 245}, year = {2013}, abstract = {A new phenylanthrone, named knipholone cyclooxanthrone and a dimeric anthraquinone, 10-methoxy-10,7'-(chrysophanol anthrone)-chrysophanol were isolated from the roots of Kniphofia foliosa together with the rare naphthalene glycoside, dianellin. The structures were determined by NMR and mass spectroscopic techniques. The compounds showed antiplasmodial activities against the chloroquine-resistant (W2) and chloroquine-sensitive (D6) strains of Plasmodium falciparum with 10-methoxy-10,7'-(chrysophanol anthrone)-chrysophanol being the most active with IC50 values of 1.17 +/- 0.12 and 4.07 +/- 1.54 mu g/ml, respectively.}, language = {en} } @article{KlinkuschKlamroth2013, author = {Klinkusch, Stefan and Klamroth, Tillmann}, title = {Simulations of pump-probe exitations of electronic wave packets for a large qusi-rigid molecular system by means of an extension to the time-dependent configuration interaction singles method}, series = {Journal of theoretical and computational chemistry}, volume = {12}, journal = {Journal of theoretical and computational chemistry}, number = {3}, publisher = {World Scientific}, address = {Singapore}, issn = {0219-6336}, doi = {10.1142/S0219633613500053}, pages = {17}, year = {2013}, abstract = {In this paper, we report simulations of laser-driven many-electron dynamics by means of the time-dependent configuration interaction singles (TD-CIS) approach. Photoionization is included by a heuristic model within calculations employing standard Gaussian basis sets. Benzo[g]-N-methyl-quinolinium-7-hydroxylate (BMQ7H) serves as a test system to generate predefined wave packets, i.e. a superposition between the ground and fifth excited state, in a large molecule. For this molecule, these two states have a very similar geometry, which enables us to use the fixed nuclei approximation. Furthermore, this geometric stability would also prevent a dephasing of the electron wave packet due to nuclear dynamics in an experimental realization of our simulations. We also simulate the possible detection of such a wave packet by ultra short probe laser pulses, i.e. pump-probe spectra.}, language = {en} } @article{FuechselTremblayKlamrothetal.2013, author = {F{\"u}chsel, Gernot and Tremblay, Jean Christophe and Klamroth, Tillmann and Saalfrank, Peter}, title = {Quantum dynamical simulations of the femtosecond-laser-induced ultrafast desorption of H2 and D2 from Ru(0001)}, series = {ChemPhysChem : a European journal of chemical physics and physical chemistry}, volume = {14}, journal = {ChemPhysChem : a European journal of chemical physics and physical chemistry}, number = {7}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1439-4235}, doi = {10.1002/cphc.201200940}, pages = {1471 -- 1478}, year = {2013}, abstract = {We investigate the recombinative desorption of hydrogen and deuterium from a Ru(0001) surface initiated by femtosecond laser pulses. We adopt a quantum mechanical two-state model including three molecular degrees of freedom to describe the dynamics within the desorption induced by electronic transition (DIET) limit. The energy distributions as well as the state-resolved and ensemble properties of the desorbed molecules are analyzed in detail by using the time-energy method. Our results shed light on the experimentally observed 1) large isotopic effects regarding desorption yields and translational energies and 2) the nonequal energy partitioning into internal and translational modes. In particular, it is shown that a single temperature is sufficient to characterize the energy distributions for all degrees of freedom. Further, we confirm that quantization effects play an important role in the determination of the energy partitioning.}, language = {en} } @article{ShalomInalFettkenhaueretal.2013, author = {Shalom, Menny and Inal, Sahika and Fettkenhauer, Christian and Neher, Dieter and Antonietti, Markus}, title = {Improving Carbon Nitride Photocatalysis by Supramolecular Preorganization of Monomers}, series = {Journal of the American Chemical Society}, volume = {135}, journal = {Journal of the American Chemical Society}, number = {19}, publisher = {American Chemical Society}, address = {Washington}, issn = {0002-7863}, doi = {10.1021/ja402521s}, pages = {7118 -- 7121}, year = {2013}, abstract = {Here we report a new and simple synthetic pathway to form ordered, hollow carbon nitride structures, using a cyanuric acid melamine (CM) complex in ethanol as a starting product. A detailed analysis of the optical and photocatalytic properties shows that optimum hollow carbon nitride structures are formed after 8 h of condensation. For this condensation time, we find a significantly reduced fluorescence intensity and lifetime, indicating the formation of new, nonradiative deactivation pathways, probably involving charge-transfer processes. Enhanced charge transfer is seen as well from a drastic increase of the photocatalytic activity in the degradation of rhodamine B dye, which is shown to proceed via photoinduced hole transfer. Moreover, we show that various CM morphologies can be obtained using different solvents, which leads to diverse ordered carbon nitride architectures. In all cases, the CM-C3N4 structures exhibited superior photocatalytic activity compared to the bulk material. The utilization of CM hydrogen-bonded complexes opens new opportunities for the significant improvement of carbon nitride synthesis, structure, and optical properties toward an efficient photoactive material for catalysis.}, language = {en} } @article{DolyaRojasKosmellaetal.2013, author = {Dolya, Natalya and Rojas, Oscar and Kosmella, Sabine and Tiersch, Brigitte and Koetz, Joachim and Kudaibergenov, Sarkyt}, title = {"One-Pot" in situ frmation of Gold Nanoparticles within Poly(acrylamide) Hydrogels}, series = {Macromolecular chemistry and physics}, volume = {214}, journal = {Macromolecular chemistry and physics}, number = {10}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1022-1352}, doi = {10.1002/macp.201200727}, pages = {1114 -- 1121}, year = {2013}, abstract = {This paper focuses on two different strategies to incorporate gold nanoparticles (AuNPs) into the matrix of polyacrylamide (PAAm) hydrogels. Poly(ethyleneimine) (PEI) is used as both reducing and stabilizing agent for the formation of AuNPs. In addition, the influence of an ionic liquid (IL) (i.e., 1-ethyl-3-methylimidazolium ethylsulfate) on the stability of the nanoparticles and their immobilization in the hydrogel is investigated The results show that AuNPs surrounded by a shell containing PEI and IL, synthesized according to the one-pot approach, are much better immobilized within the PAAm hydrogel. Hereby, the IL is responsible for structural changes in the hydrogel as well as the improved stabilization and embedding of the AuNPs into the polymer gel matrix.}, language = {en} } @article{ZhongMetwalliRawolleetal.2013, author = {Zhong, Qi and Metwalli, Ezzeldin and Rawolle, Monika and Kaune, Gunar and Bivigou Koumba, Achille Mayelle and Laschewsky, Andr{\´e} and Papadakis, Christine M. and Cubitt, Robert and M{\"u}ller-Buschbaum, Peter}, title = {Structure and Thermal Response of Thin Thermoresponsive Polystyrene-block-poly(methoxydiethylene glycol acrylate)-block-polystyrene Films}, series = {Macromolecules : a publication of the American Chemical Society}, volume = {46}, journal = {Macromolecules : a publication of the American Chemical Society}, number = {10}, publisher = {American Chemical Society}, address = {Washington}, issn = {0024-9297}, doi = {10.1021/ma400627u}, pages = {4069 -- 4080}, year = {2013}, abstract = {Thin thermoresponsive films of the triblock copolymer polystyrene-block-poly(methoxydiethylene glycol acrylate)-block-polystyrene (P(S-b-MDEGA-b-S)) are investigated on silicon substrates. By spin coating, homogeneous and smooth films are prepared for a range of film thicknesses from 6 to 82 nm. Films are stable with respect to dewetting as investigated with optical microscopy and atomic force microscopy. P(S-b-MDEGA-b-S) films with a thickness of 39 nm exhibit a phase transition of the lower critical solution temperature (LCST) type at 36.5 degrees C. The swelling and the thermoresponsive behavior of the films with respect to a sudden thermal stimulus are probed with in-situ neutron reflectivity. In undersaturated water vapor swelling proceeds without thickness increase. The thermoresponse proceeds in three steps: First, the film rejects water as the temperature is above LCST. Next, it stays constant for 600 s, before the collapsed film takes up water again. With ATR-FTIR measurements, changes of bound water in the film caused by different thermal stimuli are studied. Hydrogen bonds only form between C=O and water in the swollen film. Above the LCST most hydrogen bonds with water are broken, but some amount of bound water remains inside the film in agreement with the neutron reflectivity data. Grazing-incidence small-angle X-ray scattering (GISAXS) shows that the inner lateral structure is not significantly influenced by the different thermal stimuli.}, language = {en} } @article{ZhongAdelsbergerNiedermeieretal.2013, author = {Zhong, Qi and Adelsberger, Joseph and Niedermeier, M. A. and Golosova, Anastasi and Bivigou Koumba, Achille Mayelle and Laschewsky, Andr{\´e} and Funari, S. S. and Papadakis, Christine M. and M{\"u}ller-Buschbaum, Peter}, title = {The influence of selective solvents on the transition behavior of poly(styrene-b-monomethoxydiethylenglycol-acrylate-b-styrene) thick films}, series = {Colloid and polymer science : official journal of the Kolloid-Gesellschaft}, volume = {291}, journal = {Colloid and polymer science : official journal of the Kolloid-Gesellschaft}, number = {6}, publisher = {Springer}, address = {New York}, issn = {0303-402X}, doi = {10.1007/s00396-012-2879-4}, pages = {1439 -- 1451}, year = {2013}, abstract = {Thick poly(styrene-b-monomethoxydiethylenglycol-acrylate-b-styrene) [P(S-b-MDEGA-b-S)] films (thickness 5 mu m) are prepared from different solvents on flexible substrates by solution casting and investigated with small-angle X-ray scattering. As the solvents are either PS- or PMDEGA-selective, micelles with different core-shell micellar structures are formed. In PMDEGA-selective solvents, the PS block is the core and PMDEGA is the shell, whereas in PS-selective solvents, the order is reversed. After exposing the films to liquid D2O, the micellar structure inside the films prepared from PMDEGA-selective solvents remains unchanged and only the PMDEGA (shell part) swells. On the contrary, in the films prepared from PS-selective solvents, the micelles revert the core and the shell. This reversal causes more entanglements of the PMDEGA chains between the micelles. Moreover, the thermal collapse transition of the PMDEGA block in liquid D2O is significantly broadened. Irrespective of the solvent used for film preparation, the swollen PMDEGA shell does not show a prominent shrinkage when passing the phase transition, and the transition process occurs via compaction. The collapsed micelles have a tendency to densely pack above the transition temperature.}, language = {en} } @article{EichSchmaelzlinLoehmannsroeben2013, author = {Eich, Susanne and Schm{\"a}lzlin, Elmar and L{\"o}hmannsr{\"o}ben, Hans-Gerd}, title = {Distributed fiber optical sensing of Oxygen with optical time domain reflectometry}, series = {Sensors}, volume = {13}, journal = {Sensors}, number = {6}, publisher = {MDPI}, address = {Basel}, issn = {1424-8220}, doi = {10.3390/s130607170}, pages = {7170 -- 7183}, year = {2013}, abstract = {In many biological and environmental applications spatially resolved sensing of molecular oxygen is desirable. A powerful tool for distributed measurements is optical time domain reflectometry (OTDR) which is often used in the field of telecommunications. We combine this technique with a novel optical oxygen sensor dye, triangular-[4] phenylene (TP), immobilized in a polymer matrix. The TP luminescence decay time is 86 ns. The short decay time of the sensor dye is suitable to achieve a spatial resolution of some meters. In this paper we present the development and characterization of a reflectometer in the UV range of the electromagnetic spectrum as well as optical oxygen sensing with different fiber arrangements.}, language = {en} } @article{SchmidtKrehlHauke2013, author = {Schmidt, Bernd and Krehl, Stefan and Hauke, Sylvia}, title = {Assisted tandem catalytic cross metathesis-oxidation in one flask from styrenes to 1,2-Diketones and further to quinoxalines}, series = {The journal of organic chemistry}, volume = {78}, journal = {The journal of organic chemistry}, number = {11}, publisher = {American Chemical Society}, address = {Washington}, issn = {0022-3263}, doi = {10.1021/jo4005684}, pages = {5427 -- 5435}, year = {2013}, abstract = {1,2-Diketones were synthesized from styrenes by combining a cross metathesis and a Ru-catalyzed alkene oxidation to an assisted tandem catalytic sequence. The synthesis relies on the use of just one metathesis precatalyst, which was in situ converted to the oxidation catalyst by addition of an alkyl hydroperoxide as a chemical trigger and oxidant. The one-flask sequence can be extended beyond 1,2-diketones to quinoxalines, by condensation of the oxidation products with ortho-phenylenediamine.}, language = {en} } @article{RojasTierschRabeetal.2013, author = {Rojas, Oscar and Tiersch, Brigitte and Rabe, Christian and Stehle, Ralf and Hoell, Armin and Arlt, Bastian and Koetz, Joachim}, title = {Nonaqueous Microemulsions Based on N,N '-Alkylimidazolium Alkylsulfate Ionic Liquids}, series = {Langmuir}, volume = {29}, journal = {Langmuir}, number = {23}, publisher = {American Chemical Society}, address = {Washington}, issn = {0743-7463}, doi = {10.1021/la401080q}, pages = {6833 -- 6839}, year = {2013}, abstract = {The ternary system composed of the ionic liquid surfactant (IL-S) 1-butyl-3-methylimidazolium dodecylsulfate ([Bmim][DodSO(4)]), the room temperature ionic liquid (RTIL) 1-ethyl-3-methylimidazolium ethylsulfate ([Emim][EtSO4]), and toluene has been investigated. Three major mechanisms guiding the structure of the isotropic phase were identified by means of conductometric experiments, which have been correlated to the presence of oil-in-IL, bicontinuous, and IL-in-oil microemulsions. IL-S forms micelles in toluene, which swell by adding RTIL as to be shown by dynamic light scattering (DLS) and small-angle X-ray scattering (SAXS) experiments. Therefore, it is possible to form water free IL-in-oil reverse microemulsions <= 10 nm in size as a new type of nanoreactor.}, language = {en} } @article{GhobadiHeuchelKratzetal.2013, author = {Ghobadi, Ehsan and Heuchel, Matthias and Kratz, Karl and Lendlein, Andreas}, title = {Simulating the shape-Memory behavior of amorphous switching domains of Poly(L-lactide) by molecular dynamics}, series = {Macromolecular chemistry and physics}, volume = {214}, journal = {Macromolecular chemistry and physics}, number = {11}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1022-1352}, doi = {10.1002/macp.201200450}, pages = {1273 -- 1283}, year = {2013}, abstract = {The thermally induced shape-memory effect of polymers is typically characterized by cyclic uniaxial thermomechanical tests. Here, a molecular-dynamics (MD) simulation approach of such a cyclic uniaxial thermomechanical test is presented for amorphous switching domains of poly(L-lactide) (PLLA). Uniaxial deformation of the constructed PLLA models is simulated with a Parinello-Rahman scheme, as well as a pragmatic geometrical approach. We are able to describe two subsequent test cycles using the presented simulation approach. The obtained simulated shape-memory properties in both test cycles are similar and independent of the applied deformation protocols. The simulated PLLA shows high shape fixity ratios (Rf 94\%), but only a moderate shape recovery ratio is obtained (Rr 30\%). Finally, the structural changes during the simulated test are characterized by analysis of the changes in the dihedral angle distributions.}, language = {en} } @article{LendleinSauter2013, author = {Lendlein, Andreas and Sauter, Tilman}, title = {Shape-memory effect in polymers}, series = {Macromolecular chemistry and physics}, volume = {214}, journal = {Macromolecular chemistry and physics}, number = {11}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1022-1352}, doi = {10.1002/macp.201300098}, pages = {1175 -- 1177}, year = {2013}, language = {en} } @article{FechnerKoetz2013, author = {Fechner, Mabya and Koetz, Joachim}, title = {Polyampholyte/Surfactant complexes at the water-air interface a surface tension study}, series = {Langmuir}, volume = {29}, journal = {Langmuir}, number = {25}, publisher = {American Chemical Society}, address = {Washington}, issn = {0743-7463}, doi = {10.1021/la401576q}, pages = {7600 -- 7606}, year = {2013}, abstract = {The present paper is related to interactions between strongly alternating polyampholytes, i.e., copolymers of N,N'-diallyl-N,N'-dimethylammonium chloride and maleamic acid derivatives, varying in hydrophobicity and excess charges and the oppositely charged anionic surfactant sodium dodecyl sulfate (SDS). Surface tension measurements have revealed a complex behavior with the formation of polyampholyte-SDS complexes at water air interfaces which depends on both the hydrophobic character of the polyampholyte and electrostatic attractive forces between the polyampholyte and the anionic surfactant in dependence on pH. Hereby, maleamic acid copolymers with additional carboxylic groups in the phenylic side chain show a significant lower surface tension at the critical association concentration (CAC) due to the formation of surface-active SDS complexes and multicomplexes. In the presence of only one carboxylic group in the p-position the CAC can be strongly shifted by varying the pH due to repulsive electrostatic interactions.}, language = {en} }