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Shafikov M.Z.,Ural Federal University | Kozhevnikov D.N.,Ural Federal University | Bodensteiner M.,Universitatsstrasse 31 | Brandl F.,University of Regensburg | Czerwieniec R.,University of Regensburg
Inorganic Chemistry | Year: 2016

Photophysical properties of four new platinum(II) complexes comprising extended ppy (Hppy = 2-phenylpyridine) and thpy (Hthpy = 2-(2′-thienyl)pyridine) cyclometalated ligands and acetylacetonate (acac) are reported. Substitution of the benzene ring of Pt-ppy complexes 1 and 2 with a more electron-rich thiophene of Pt-thpy complexes 3 and 4 leads to narrowing of the HOMO-LUMO gap and thus to a red shift of the lowest energy absorption band and phosphorescence band, as expected for low-energy excited states of the intraligand/metal-to-ligand charge transfer character. However, in addition to these conventional spectral shifts, another, at first unexpected, substitution effect occurs. Pt-thpy complexes 3 and 4 are dual emissive showing fluorescence about 6000 cm-1 (∼0.75 eV) higher in energy relative to the phosphorescence band, while for Pt-ppy complexes 1 and 2 only phosphorescence is observed. For dual-emissive complexes 3 and 4, ISC rates kISC are estimated to be in order of 109-1010 s-1, while kISC of Pt-ppy complexes 1 and 2 is much faster amounting to 1012 s-1 or more. The relative intensities of the fluorescence and phosphorescence signals of Pt-thpy complexes 3 and 4 depend on the excitation wavelength, showing that hyper-intersystem crossing (HISC) in these complexes is observably significant. © 2016 American Chemical Society.

Jirasek P.,Universitatsstrasse 31 | Jirasek P.,University of Regensburg | Amslinger S.,Universitatsstrasse 31 | Amslinger S.,University of Regensburg | Heilmann J.,Universitatsstrasse 31
Journal of Natural Products | Year: 2014

A strategy for the synthesis of natural and non-natural 5-deoxy-6,7-dihydrocurcuminoids (diarylheptanoids) was developed for the preparation of 14 compounds with varying aromatic substituent patterns and a different functionality in the aliphatic seven-carbon chain. The in vitro protective activity against glutamate-induced neuronal cell death was examined in the murine hippocampal cell line HT-22 to find structural motifs responsible for neuroprotective effects in vitro. Among the tested compounds the ferulic acid-like unit, present in the structures of (E)-1,7-bis(4-hydroxy-3-methoxyphenyl)hept-1-en-3-one (5) and (E)-1-(4-hydroxy-3-methoxyphenyl)-7-(4-hydroxyphenyl)hept-1-en-3-one (7), appeared to be an important feature for protection against glutamate-induced neurotoxicity. Both compounds demonstrated significant neuroprotective activity in a concentration range between 1 and 25 ∼M without showing toxic effects in a cytotoxicity assay with HT-22 cells. Furthermore, (E)-1,7-bis(3,4-dihydroxyphenyl)hept-1-en-3-one (9), exhibiting a caffeic acid-like structural motif, displayed a neuroprotective activity at a nontoxic concentration of 25 ∼M. In contrast, (1E,6E)-1,7-bis(3,4-dihydroxyphenyl)hepta-1,6-diene-3,5-dione (4, di-O-demethylcurcumin) showed mainly cytotoxic effects. A corresponding single-ring analogue that contains the ferulic acid-like unit as an enone was not active. © 2014 The American Chemical Society and American Society of Pharmacognosy.

Heinl S.,Universitatsstrasse 31 | Balazs G.,Universitatsstrasse 31 | Scheer M.,Universitatsstrasse 31
Phosphorus, Sulfur and Silicon and the Related Elements | Year: 2014

A new synthesis of [CpBIGFe(CO)2]2 3 (CpBIG = C5(4-nBuC6H4)5) was developed starting from CpBIGNa and FeCl2 in the presence of CO. Reaction of this product with P4 leads to the two new Pn ligand complexes [CpBIGFe(η5-P5)] 1b and [(CpBIGFe)2(,η4:4-P4)] (4) containing the highly sterically demanding CpBIG ligand. Depending on the solvent, different ratios of 1b:4 are obtained. The products 1b, 3, and 4 were characterized by spectroscopic methods as well as by X-ray diffraction. © 2014 Taylor & Francis Group, LLC.

Schweikhard E.S.,Max Planck Institute of Biophysics | Schweikhard E.S.,Universitatsstrasse 31 | Burckhardt B.C.,University of Gottingen | Joos F.,Max Planck Institute of Biophysics | And 7 more authors.
Biochemical Journal | Year: 2015

The osmolyte and folding chaperone betaine is transported by the renal Na+ -coupled GABA (γ -aminobutyric acid) symporter BGT-1 (betaine/GABA transporter 1), a member of the SLC6 (solute carrier 6) family. Under hypertonic conditions, the transcription, translation and plasma membrane (PM) insertion of BGT-1 in kidney cells are significantly increased, resulting in elevated betaine and GABA transport. Re-establishing isotonicity involves PM depletion of BGT-1. The molecular mechanism of the regulated PM insertion of BGT-1 during changes in osmotic stress is unknown. In the present study, we reveal a link between regulated PM insertion and N-glycosylation. Based on homology modelling, we identified two sites (Asn171 and Asn183) in the extracellular loop 2 (EL2) ofBGT-1,which were investigated with respect to trafficking, insertion and transport by immunogoldlabelling, electron microscopy (EM), mutagenesis and twoelectrode voltage clamp measurements in Xenopus laevis oocytes and uptake of radiolabelled substrate into MDCK (Madin-Darby canine kidney) and HEK293 (human embryonic kidney) cells. Trafficking and PM insertion of BGT-1 was clearly promoted by N-glycosylation in both oocytes and MDCK cells. Moreover, association with N-glycans at Asn171 and Asn183 contributed equally to protein activity and substrate affinity. Substitution of Asn171 andAsn183 by aspartate individually caused no loss of BGT- 1 activity, whereas the double mutant was inactive, suggesting that N-glycosylation of at least one of the sites is required for function. Substitution by alanine or valine at either site caused a dramatic loss in transport activity. Furthermore, in MDCK cells PMinsertion ofN183Dwas no longer regulated by osmotic stress, highlighting the impact of N-glycosylation in regulation of this SLC6 transporter. © 2015 Authors; published by Portland Press Limited.

Stokl J.,Max Planck Institute for Chemical Ecology | Stokl J.,Swedish University of Agricultural Sciences | Stokl J.,Universitatsstrasse 31 | Strutz A.,Max Planck Institute for Chemical Ecology | And 7 more authors.
Current Biology | Year: 2010

In deceptive pollination, insects are bamboozled into performing nonrewarded pollination. A prerequisite for the evolutionary stability in such systems is that the plants manage to generate a perfect sensory impression of a desirable object in the insect nervous system [1]. The study of these plants can provide important insights into sensory preference of their visiting insects. Here, we present the first description of a deceptive pollination system that specifically targets drosophilid flies. We show that the examined plant (Arum palaestinum) accomplishes its deception through olfactory mimicry of fermentation, a strategy that represents a novel pollination syndrome. The lily odor is composed of volatiles characteristic of yeast, and produces in Drosophila melanogaster an antennal detection pattern similar to that elicited by a range of fermentation products. By functional imaging, we show that the lily odors target a specific subset of odorant receptors (ORs), which include the most conserved OR genes in the drosophilid olfactome. Furthermore, seven of eight visiting drosophilid species show a congruent olfactory response pattern to the lily, in spite of comprising species pairs separated by ∼40 million years [2], showing that the lily targets a basal function of the fly nose, shared by species with similar ecological preference. © 2010 Elsevier Ltd. All rights reserved.

Osters O.,TU Munich | Nilges T.,TU Munich | Schoneich M.,Hochschule Lausitz FH | Schoneich M.,TU Dresden | And 5 more authors.
Inorganic Chemistry | Year: 2012

The ternary Laves phase Cd 4Cu 7As is the first intermetallic compound in the system Cu-Cd-As and a representative of a new substitution variant for Laves phases. It crystallizes orthorhombically in the space group Pnnm (No. 58) with lattice parameters a = 9.8833(7) Å b = 7.1251(3) Å c = 5.0895(4) Å. All sites are fully occupied within the standard deviations. The structure can be described as typical Laves phase, where Cu and As are forming vertex-linked tetrahedra and Cd adopts the structure motive of a distorted diamond network. Cd 4Cu 7As was prepared from stoichiometric mixtures of the elements in a solid state reaction at 1000 °C. Magnetic measurements are showing a Pauli paramagnetic behavior. During our systematical investigations within the ternary phase triangle Cd-Cu-As the cubic C15-type Laves phase Cd 4Cu 6.9(1)As 1.1(1) was structurally characterized. It crystallizes cubic in the space group Fd3m̄ with lattice parameter a = 7.0779(8) Å. Typically for quasi-binary Laves phases Cu and As are both occupying the 16c site. Chemical bonding, charge transfer and atomic properties of Cd 4Cu 7As were analyzed by band structure, ELF, and AIM calculations. On the basis of the general formula for Laves phases AB 2, Cd is slightly positively charged forming the A substructure, whereas Cu and As represent the negatively charged B substructure in both cases. The crystal structure distortion is thus related to local effects caused by Arsenic that exhibits a larger atomic volume (18 Å 3 compared to 13 Å 3 for Cu) and higher ionicity in bonding. © 2012 American Chemical Society.

PubMed | Universitatsstrasse 31
Type: Journal Article | Journal: Current medicinal chemistry | Year: 2011

In this article the design of hybrid molecules that covalently connect two distinct drug entities in one molecule, at least one part being a biologically active natural product will be discussed. In the quest for novel drug entities, the hybrid approach is a promising path to drug molecules that can effectively target multifactorial diseases including neurodegenerative disorders like Alzheimers and Parkinsons diseases (AD and PD). The hybrid approach can also be used to optimize certain biological properties like affinity and selectivity, but also to gain novel biological activities distinct from the ones of the components. Due to the high potential of natural products to exhibit pronounced biological activities, natural products have been one of the major sources of components in hybrid molecules. This review will cover their applications in developing drugs for neurodegenerative disorders, in the diverse field of anti-cancer agents (which represents the major application for natural products in medicinal chemistry), but also in miscellaneous areas of bioactive compounds including antioxidants, antimalarial drugs and estrogen-related hybrids to reach various therapeutic aims. The unique tasks of hybrid molecule design will be addressed, such as describing suitable ways to chemically connect the drug components, how to use the approach to enhance biological activity with respect to both activity and selectivity and potential drawbacks of the hybrid approach. It will be shown that hybrids can be more than the sum of their components, but in many cases should be considered as pharmacological entities in their own respect.

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