TY - JOUR A1 - Kastl, Johanna A1 - Braun, Joachim A1 - Prestel, Andreas A1 - Möller, Heiko Michael A1 - Huhn, Thomas A1 - Mayer, Thomas U. T1 - Mad2 Inhibitor-1 (M2I-1): A Small Molecule Protein-Protein Interaction Inhibitor Targeting the Mitotic Spindle Assembly Checkpoint JF - ACS chemical biology N2 - The genetic integrity of each organism depends on the faithful segregation of its genome during mitosis. To meet this challenge, a cellular surveillance mechanism, termed the spindle assembly checkpoint (SAC), evolved that monitors the correct attachment of chromosomes and blocks progression through mitosis if corrections are needed. While the central role of the SAC for genome integrity is well established, its functional dissection has been hampered by the limited availability of appropriate small molecule inhibitors. Using a fluorescence polarization-based screen, we identify Mad2 inhibitor-1 (M2I-1), the first small molecule inhibitor targeting the binding of Mad2 to Cdc20, an essential protein-protein interaction (PPI) within the SAC. Based on computational and biochemical analyses, we propose that M2I-1 disturbs conformational dynamics of Mad2 critical for complex formation with Cdc20. Cellular studies revealed that M2I-1 weakens the SAC response, indicating that the compound might be active in cells. Thus, our study identifies the SAC specific complex formation between Mad2 and Cdc20 as a protein-protein interaction that can be targeted by small molecules. Y1 - 2015 U6 - https://doi.org/10.1021/acschembio.5b00121 SN - 1554-8929 SN - 1554-8937 VL - 10 IS - 7 SP - 1661 EP - 1666 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Prestel, Andreas A1 - Möller, Heiko Michael T1 - Spatio-temporal control of cellular uptake achieved by photoswitchable cell-penetrating peptides JF - Chemical communications : ChemComm N2 - The selective uptake of compounds into specific cells of interest is a major objective in cell biology and drug delivery. By incorporation of a novel, thermostable azobenzene moiety we generated peptides that can be switched optically between an inactive state and an active, cell-penetrating state with excellent spatio-temporal control. Y1 - 2015 U6 - https://doi.org/10.1039/C5CC06848G SN - 1364-548X IS - 52 SP - 701 EP - 704 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Guha, S. A1 - Warsinke, A. A1 - Tientcheu, Ch. M. A1 - Schmalz, K. A1 - Meliani, C. A1 - Wenger, Ch. T1 - Label free sensing of creatinine using a 6 GHz CMOS near-field dielectric immunosensor JF - The analyst : the analytical journal of the Royal Society of Chemistry N2 - In this work we present a CMOS high frequency direct immunosensor operating at 6 GHz (C-band) for label free determination of creatinine. The sensor is fabricated in standard 0.13 μm SiGe:C BiCMOS process. The report also demonstrates the ability to immobilize creatinine molecules on a Si3N4 passivation layer of the standard BiCMOS/CMOS process, therefore, evading any further need of cumbersome post processing of the fabricated sensor chip. The sensor is based on capacitive detection of the amount of non-creatinine bound antibodies binding to an immobilized creatinine layer on the passivated sensor. The chip bound antibody amount in turn corresponds indirectly to the creatinine concentration used in the incubation phase. The determination of creatinine in the concentration range of 0.88–880 μM is successfully demonstrated in this work. A sensitivity of 35 MHz/10 fold increase in creatinine concentration (during incubation) at the centre frequency of 6 GHz is gained by the immunosensor. The results are compared with a standard optical measurement technique and the dynamic range and sensitivity is of the order of the established optical indication technique. The C-band immunosensor chip comprising an area of 0.3 mm2 reduces the sensing area considerably, therefore, requiring a sample volume as low as 2 μl. The small analyte sample volume and label free approach also reduce the experimental costs in addition to the low fabrication costs offered by the batch fabrication technique of CMOS/BiCMOS process. Y1 - 2015 U6 - https://doi.org/10.1039/c4an02194k SN - 0003-2654 SN - 1364-5528 VL - 9 IS - 140 SP - 3019 EP - 3027 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Bartoloni, Marco A1 - Jin, Xian A1 - Marcaida, Maria José A1 - Banha, Joao A1 - Dibonaventura, Ivan A1 - Bongoni, Swathi A1 - Bartho, Kathrin A1 - Gräbner, Olivia A1 - Sefkow, Michael A1 - Darbre, Tamis A1 - Reymond, Jean-Louis T1 - Bridged bicyclic peptides as potential drug scaffolds BT - synthesis, structure, protein binding and stability JF - Chemical Science N2 - Double cyclization of short linear peptides obtained by solid phase peptide synthesis was used to prepare bridged bicyclic peptides (BBPs) corresponding to the topology of bridged bicyclic alkanes such as norbornane. Diastereomeric norbornapeptides were investigated by 1H-NMR, X-ray crystallography and CD spectroscopy and found to represent rigid globular scaffolds stabilized by intramolecular backbone hydrogen bonds with scaffold geometries determined by the chirality of amino acid residues and sharing structural features of β-turns and α-helices. Proteome profiling by capture compound mass spectrometry (CCMS) led to the discovery of the norbornapeptide 27c binding selectively to calmodulin as an example of a BBP protein binder. This and other BBPs showed high stability towards proteolytic degradation in serum. Y1 - 2015 U6 - https://doi.org/10.1039/C5SC01699A SN - 2041-6520 SN - 2041-6539 VL - 10 IS - 6 SP - 5473 EP - 5490 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Meyer, S. A1 - Raber, G. A1 - Ebert, Franziska A1 - Leffers, L. A1 - Müller, Sandra Marie A1 - Taleshi, M. S. A1 - Francesconi, Kevin A. A1 - Schwerdtle, Tanja T1 - In vitro toxicological characterisation of arsenic-containing fatty acids and three of their metabolites JF - Toxicology research N2 - Arsenic-containing fatty acids are a group of fat-soluble arsenic species (arsenolipids) which are present in marine fish and other seafood. Recently, it has been shown that arsenic-containing hydrocarbons, another group of arsenolipids, exert toxicity in similar concentrations comparable to arsenite although the toxic modes of action differ. Hence, a risk assessment of arsenolipids is urgently needed. In this study the cellular toxicity of a saturated (AsFA 362) and an unsaturated (AsFA 388) arsenic-containing fatty acid and three of their proposed metabolites (DMAV, DMAPr and thio-DMAPr) were investigated in human liver cells (HepG2). Even though both arsenic-containing fatty acids were less toxic as compared to arsenic-containing hydrocarbons and arsenite, significant effects were observable at μM concentrations. DMAV causes effects in a similar concentration range and it could be seen that it is metabolised to its highly toxic thio analogue thio-DMAV in HepG2 cells. Nevertheless, DMAPr and thio-DMAPr did not exert any cytotoxicity. In summary, our data indicate that risks to human health related to the presence of arsenic-containing fatty acids in marine food cannot be excluded. This stresses the need for a full in vitro and in vivo toxicological characterisation of these arsenolipids. Y1 - 2015 U6 - https://doi.org/10.1039/c5tx00122f SN - 2045-4538 VL - 5 IS - 4 SP - 1289 EP - 1296 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Roder, Phillip A1 - Hille, Carsten T1 - A Multifunctional Frontloading Approach for Repeated Recycling of a Pressure-Controlled AFM Micropipette JF - PLoS ONE N2 - Fluid force microscopy combines the positional accuracy and force sensitivity of an atomic force microscope (AFM) with nanofluidics via a microchanneled cantilever. However, adequate loading and cleaning procedures for such AFM micropipettes are required for various application situations. Here, a new frontloading procedure is described for an AFM micropipette functioning as a force- and pressure-controlled microscale liquid dispenser. This frontloading procedure seems especially attractive when using target substances featuring high costs or low available amounts. Here, the AFM micropipette could be filled from the tip side with liquid from a previously applied droplet with a volume of only a few μL using a short low-pressure pulse. The liquid-loaded AFM micropipettes could be then applied for experiments in air or liquid environments. AFM micropipette frontloading was evaluated with the well-known organic fluorescent dye rhodamine 6G and the AlexaFluor647-labeled antibody goat anti-rat IgG as an example of a larger biological compound. After micropipette usage, specific cleaning procedures were tested. Furthermore, a storage method is described, at which the AFM micropipettes could be stored for a few hours up to several days without drying out or clogging of the microchannel. In summary, the rapid, versatile and cost-efficient frontloading and cleaning procedure for the repeated usage of a single AFM micropipette is beneficial for various application situations from specific surface modifications through to local manipulation of living cells, and provides a simplified and faster handling for already known experiments with fluid force microscopy. Y1 - 2015 U6 - https://doi.org/10.1371/journal.pone.0144157 SN - 1932-6203 VL - 10 IS - 12 PB - Public Library of Science CY - Lawrence, Kan. ER - TY - JOUR A1 - Megow, Jörg A1 - Röhr, Merle I. S. A1 - Schmidt am Busch, Marcel A1 - Renger, Thomas A1 - Mitrić, Roland A1 - Kirstein, Stefan A1 - Rabe, Jürgen P. A1 - May, Volkhard T1 - Site-dependence of van der Waals interaction explains exciton spectra of double-walled tubular J-aggregates JF - Physical chemistry, chemical physics : PCCP ; a journal of European chemical societies N2 - The simulation of the optical properties of supramolecular aggregates requires the development of methods, which are able to treat a large number of coupled chromophores interacting with the environment. Since it is currently not possible to treat large systems by quantum chemistry, the Frenkel exciton model is a valuable alternative. In this work we show how the Frenkel exciton model can be extended in order to explain the excitonic spectra of a specific double-walled tubular dye aggregate explicitly taking into account dispersive energy shifts of ground and excited states due to van der Waals interaction with all surrounding molecules. The experimentally observed splitting is well explained by the site-dependent energy shift of molecules placed at the inner or outer side of the double-walled tube, respectively. Therefore we can conclude that inclusion of the site-dependent dispersive effect in the theoretical description of optical properties of nanoscaled dye aggregates is mandatory. Y1 - 2015 U6 - https://doi.org/10.1039/c4cp05945j SN - 1463-9084 SN - 1463-9076 VL - 17 IS - 10 SP - 6741 EP - 6747 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Irungu, Beatrice N. A1 - Adipo, Nicholas A1 - Orwa, Jennifer A. A1 - Kimani, Francis A1 - Heydenreich, Matthias A1 - Midiwo, Jacob O. A1 - Bjoremark, Per Martin A1 - Hakansson, Mikael A1 - Yenesew, Abiy A1 - Erdelyi, Mate T1 - Antiplasmodial and cytotoxic activities of the constituents of Turraea robusta and Turraea nilotica JF - Journal of ethnopharmacology : an interdisciplinary journal devoted to bioscientific research on indigenous drugs N2 - Ethnopharmacological relevance: Turraea robusta and Turraea nilotica are African medicinal plants used for the treatment of a wide variety of diseases, including malaria. The genus Turraea is rich in limonoids and other triterpenoids known to possess various biological activities. Materials and methods: From the stem bark of T. robusta six compounds, and from various parts of T nilotica eleven compounds were isolated by the use of a combination of chromatographic techniques. The structures of the isolated compounds were elucidated using NMR and MS, whilst the relative configuration of one of the isolated compounds, toonapubesin F, was established by X-ray crystallography. The antiplasmodial activities of the crude extracts and the isolated constituents against the D6 and W2 strains of Plasmodium falciparum were determined using the semiautomated micro dilution technique that measures the ability of the extracts to inhibit the incorporation of (G-H-3, where G is guanine) hypoxanthine into the malaria parasite. The cytotoxicity of the crude extracts and their isolated constituents was evaluated against the mammalian cell lines African monkey kidney (vero), mouse breast cancer (4T1) and human larynx carcinoma (HEp2). Results: The extracts showed good to moderate antiplasmodial activities, where the extract of the stem bark of T. robusta was also cytotoxic against the 4T1 and the HEp2 cells (IC50 < 10 mu g/ml). The compounds isolated from these extracts were characterized as limonoids, protolimonoids and phytosterol glucosides. These compounds showed good to moderate activities with the most active one being azadironolide, IC50 2.4 +/- 0.03 mu M and 1.1 +/- 0.01 mu M against the D6 and W2 strains of Plasmodium falciparum, respectively; all other compounds possessed IC50 14.4-40.5 mu M. None of the compounds showed significant cytotoxicity against vero cells, yet four of them were toxic against the 4T1 and HEp2 cancer cell lines with piscidinol A having IC50 8.0 +/- 0.03 and 8.4 +/- 0.01 mu M against the 4T1 and HEp2 cells, respectively. Diacetylation of piscidinol A resulted in reduced cytotoxicity. Conclusion: From the medicinal plants T. robusta and T. nilotica, twelve compounds were isolated and characterized; two of the isolated compounds, namely 11-epi-toonacilin and azadironolide showed good antiplasmodial activity with the highest selectivity indices. (C) 2015 The Authors. Published by Elsevier Ireland Ltd. KW - Turraea robusta KW - Turraea nilotica KW - Antiplasmodial activity KW - Cytotoxicity KW - Limonoid KW - Toonapubesins F KW - Toonacilin KW - Azadironolide Y1 - 2015 U6 - https://doi.org/10.1016/j.jep.2015.08.039 SN - 0378-8741 VL - 174 SP - 419 EP - 425 PB - Elsevier CY - Clare ER - TY - JOUR A1 - Primus, Philipp-Alexander A1 - Menski, Antonia A1 - Yeste, Maria Pilar A1 - Cauqui, Miguel Angel A1 - Kumke, Michael Uwe T1 - Fluorescence Line-Narrowing Spectroscopy as a Tool to Monitor Phase Transitions and Phase Separation in Efficient Nanocrystalline CexZr1-xO2:Eu3+ Catalyst Materials JF - The journal of physical chemistry : C, Nanomaterials and interfaces N2 - Despite the wide range of industrial applications for ceria-zirconia mixed oxides (CexZr1-xO2), the complex correlation between their atomic structure and catalytic performance is still under debate. Catalytically interesting CexZr1-xO2 nanomaterials can form homogeneous solid solutions and, depending on the composition, show phase separation under the formation of small domains. The characterization of homogeneity and atomic structure of these materials remains a major challenge. High-resolution emission spectroscopy recorded under cryogenic conditions using Eu3+ as a structural probe in doped CeZrO2 nanoparticles offers an effective way to identify the different atomic environments of the Eu3+ dopants and, subsequently, to monitor structural parameters of the ceria-zirconia mixed oxides. It is found that, in stoichiometric CeZrO2:Eu3+, phase separation occurs at elevated temperatures beginning with the gradual formation of (pseudo)cubic crystallites in the amorphous materials at 500 degrees C and a sudden phase separation into tetragonal, zirconia-rich and cubic, ceria-rich domains over 900 degrees C. The presented technique allows us to easily monitor subtle changes even in amorphous, high surface area samples, yielding structural information not accessible by conventional techniques such as X-ray diffraction (XRD) and Raman. Moreover, in reference experiments investigating the reducibility of largely unordered Ce0.2Zr0.8O2:Eu3+, the main reduction peak in temperature-programmed reduction measurements appeared at exceptionally low temperatures below 200 degrees C, thus suggesting the outstanding potential of this oxide to activate catalytic oxidation reactions. This effect was found to be dependent on the amount of Eu3+ dopant introduced into the CeZrO2 matrix as well as to be connected to the atomic structure of the catalyst material. Y1 - 2015 U6 - https://doi.org/10.1021/acs.jpcc.5b01271 SN - 1932-7447 VL - 119 IS - 19 SP - 10682 EP - 10692 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Perez-Anes, Alexandra A1 - Rodrigues, Fernanda A1 - Caminade, Anne-Marie A1 - Stefaniu, Cristina A1 - Tiersch, Brigitte A1 - Turrin, Cedric-Olivier A1 - Blanzat, Muriel T1 - Influence of structural parameters on the self-association properties of anti-HIV catanionic dendrimers JF - ChemPhysChem : a European journal of chemical physics and physical chemistry N2 - The self-association properties of anti-HIV catanionic dendrimers as multivalent galactosylceramide (GalCer)-derived inhibitors are presented. The study was designed to elucidate the origin of the relatively high cytotoxicity values of these antiHIV catanionic dendrimers, which have previously been found to exhibit in vitro anti-HIV activity in the submicromolar range. The physicochemical properties of these catanionic dendrimers were studied to tentatively correlate the structural parameters with self-association and biological properties. We can conclude from this study that the absence of correlation between the hydrophobicity and the cytotoxicity of the catanionic systems could be explained by the partial segregation of the different partners of the catanionic entities. KW - anti-HIV KW - catanionic surfactants KW - dendrimers KW - galactosylceramide KW - glycolipids Y1 - 2015 U6 - https://doi.org/10.1002/cphc.201500484 SN - 1439-4235 SN - 1439-7641 VL - 16 IS - 16 SP - 3433 EP - 3437 PB - Wiley-VCH CY - Weinheim ER -