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Bonn, Germany

Calderon R.M.K.,The Interdisciplinary Center | Valero J.,Institute of Chemical Research of Catalonia | Valero J.,LIMES Institute | Grimm B.,The Interdisciplinary Center | And 2 more authors.
Journal of the American Chemical Society | Year: 2014

Herein, we report the synthesis of guanidinium bis-porphyrin tweezers 1 and fullerene carboxylate 3, their assembly into a novel supramolecular 1@3 electron donor-acceptor hybrid, and its characterization. In solution, the binding constant affording 1@3 is exceptionally high. 1@3, which features a highly confined topography, builds up from a combination of guanidinium- carboxylate hydrogen bonding and π-π stacking/charge-transfer motifs. The latter is governed by interactions between the electron-donating porphyrin and the electron-accepting fullerene. Importantly, positive cooperativity between the applied binding motifs is corroborated by a number of experimental techniques, such as NMR, absorption, fluorescence, etc. In addition, transient absorption experiments shed light onto electron-transfer processes taking place in the ground state and upon photoexcitation. In fact, porphyrin excitation powers an electron transfer to the fullerene yielding charge separated state lifetimes in the nanosecond regime. © 2014 American Chemical Society.

Valero J.,Institute of Chemical Research of Catalonia | Valero J.,LIMES Institute | Shiraishi T.,Copenhagen University | De Mendoza J.,Institute of Chemical Research of Catalonia | Nielsen P.E.,Copenhagen University
ChemBioChem | Year: 2015

A series of peptide nucleic acid-oligo(bicycloguanidinium) (PNA-BGn) conjugates were synthesized and characterized in terms of cellular antisense activity by using the pLuc750HeLa cell splice correction assay. PNA-BG4 conjugates exhibited low micromolar antisense activity, and their cellular activity required the presence of a hydrophobic silyl terminal protecting group on the oligo(BG) ligand and a minimum of four guanidinium units. Surprisingly, a nonlinear dose-response with an activity threshold around 3-4 μM, indicative of large cooperativity, was observed. Supported by light scattering and electron microscopy analyses, we propose that the activity, and thus cellular delivery, of these lipo-PNA-BG4 conjugates is dependent on self-assembled nanoaggregates. Finally, cellular activity was enhanced by the presence of serum. Therefore we conclude that the lipo-BG-PNA conjugates exhibit an unexpected mechanism for cell delivery and are of interest for further in vivo studies. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Draffehn A.M.,Max Planck Institute for Plant Breeding Research | Draffehn A.M.,LIMES Institute | Durek P.,Max Planck Institute of Molecular Plant Physiology | Durek P.,Charite - Medical University of Berlin | And 5 more authors.
Plant, Cell and Environment | Year: 2012

Biochemical, molecular and genetic studies emphasize the role of the potato vacuolar invertase Pain-1 in the accumulation of reducing sugars in potato tubers upon cold storage, and thereby its influence on the quality of potato chips and French fries. Previous studies showed that natural Pain-1 cDNA alleles were associated with better chip quality and higher tuber starch content. In this study, we focused on the functional characterization of these alleles. A genotype-dependent transient increase of total Pain-1 transcript levels in cold-stored tubers of six different genotypes as well as allele-specific expression patterns were detected. 3D modelling revealed putative structural differences between allelic Pain-1 proteins at the molecule's surface and at the substrate binding site. Furthermore, the yeast SUC2 mutant was complemented with Pain-1 cDNA alleles and enzymatic parameters of the heterologous expressed proteins were measured at 30 and 4°C. Significant differences between the alleles were detected. The observed functional differences between Pain-1 alleles did not permit final conclusions on the mechanism of their association with tuber quality traits. Our results show that natural allelic variation at the functional level is present in potato, and that the heterozygous genetic background influences the manifestation of this variation. © 2012 Blackwell Publishing Ltd.

Richter D.,University of Hohenheim | Richter D.,LIMES Institute | Katz B.,Hebrew University of Jerusalem | Oberacker T.,University of Hohenheim | And 4 more authors.
Journal of Biological Chemistry | Year: 2011

In Drosophila photoreceptors the transient receptor potential- like (TRPL), but not theTRPchannels undergo light-dependent translocation between the rhabdomere and cell body. Here we studied which of theTRPLchannel segments are essential for translocation and why the TRP channels are required for inducing TRPL translocation. We generated transgenic flies expressing chimeric TRP and TRPL proteins that formed functional light-activated channels. Translocation was induced only in chimera containing both the N- and C-terminal segments of TRPL. Using an inactive trp mutation and overexpressing the Na +/ Ca 2+ exchanger revealed that the essential function of the TRP channels in TRPL translocation is to enhance Ca 2+-influx. These results indicate that motifs present at both the N and C termini as well as sustained Ca 2+ entry are required for proper channel translocation. © 2011 by The American Society for Biochemistry and Molecular Biology, Inc.

Light microscopy image of a live Drosophila that was unable to produce enough growth factor idgf6 due to a genetic modification. As a result, defects can be seen in the respiratory organ as well as in the chitinous shell. Credit: Dr. Matthias Behr With their chitinous shells, insects seem almost invulnerable – but like Achilles' heel in Greek mythology, their impressive armor can still be attacked. Researchers at the universities of Bonn and Leipzig studied fruit flies (Drosophila) and discovered the molecular processes that are able to break through this protective casing. The enzyme chitinase 2 and growth factor idgf6 are especially important in correctly forming the insects' shells. These findings are relevant for fighting parasites, and will be published in the professional journal Scientific Reports. The same things that work with fruit flies (Drosophila) – one of developmental biologists' favorite animals to study – can generally also be applied to other insects. The deactivation of chitinase 2 and/or idgf6 genes results in a fragile shell that does not support adequate protection for larva of fruit flies and very likely other insects such as mosquitos. "Pathogens can then easily infiltrate the animals, and they usually die during the larval stage," says Assistant Professor Dr. Matthias Behr, who transferred from the Life & Medical Sciences (LIMES) Institute at his alma mater in Bonn to the Sächsische Inkubator für die klinische Translation (SIKT) at the University of Leipzig. The project was financed with funding from Special Research Area 645 at the University of Bonn. The current discovery offers completely new starting points for keeping agricultural parasites as well as dangerous disease-carrying insects in check. The enzyme chitinase 2 and growth factor idgf6 are essential for shell formation in nearly all insects, as well as in arthropods like crabs and spiders. "However, there are minor species-related differences that could allow us to develop tailor-made inhibitors that will prevent proper development of the chitinous shell in certain species," says first author Yanina-Yasmin Pesch from the LIMES Institute at the University of Bonn. Specially developed substances could be used to attack the chitinous covering of one arthropod species while leaving other species unharmed. Dr. Behr names two examples of possible applications: the spotted-wing drosophila (Drosophila suzukii) that recently migrated to Germany, and the new Zika virus pathogen. The spotted-wing drosophila causes enormous damage for the agricultural industry because it attacks a large volume of ripening fruit. The Zika virus is transmitted to people through mosquito bites. This virus is suspected of causing birth defects in Brazil, among other places. The researchers hope their discovery will make it easier to fight these kinds of dangerous insects in the future. The researchers from the universities of Bonn and Leipzig, as well as from the Max Planck Institute of Biophysical Chemistry in Göttingen, turned up one other surprising find: "Until now, scientists assumed that chitinase 2 was a degradation enzyme," reports Pesch. "But surprisingly, it has now been found that the enzyme is essential in forming the chitinous shell." When the protective casing is being created, chitinase shortens the chitin to the right length. The precisely tailored components are then combined with other materials to build the shell. As the team of researchers already showed in a previous study, the "Obstructor-A" protein plays a key role here. Like a construction-site manager, it makes sure that various building materials are added to the protective shell in the right places. "Step by step, our research is revealing molecular details about the insects' Achilles heel," says Dr. Behr. More information: Yanina-Yasmin Pesch et al. Chitinases and Imaginal disc growth factors organize the extracellular matrix formation at barrier tissues in insects, Scientific Reports (2016). DOI: 10.1038/srep18340

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