@article{SchulzeKoetz2017, author = {Schulze, Nicole and Koetz, Joachim}, title = {Kinetically controlled growth of gold nanotriangles in a vesicular template phase by adding a strongly alternating polyampholyte}, series = {Journal of dispersion science and technology}, volume = {38}, journal = {Journal of dispersion science and technology}, number = {8}, publisher = {Taylor \& Francis}, address = {Philadelphia}, issn = {0193-2691}, doi = {10.1080/01932691.2016.1220318}, pages = {1073 -- 1078}, year = {2017}, abstract = {This paper is focused on the temperature-dependent synthesis of gold nanotriangles in a vesicular template phase, containing phosphatidylcholine and AOT, by adding the strongly alternating polyampholyte PalPhBisCarb. UV-vis absorption spectra in combination with TEM micrographs show that flat gold nanoplatelets are formed predominantly in the presence of the polyampholyte at 45°C. The formation of triangular and hexagonal nanoplatelets can be directly influenced by the kinetic approach, i.e., by varying the polyampholyte dosage rate at 45°C. Corresponding zeta potential measurements indicate that a temperature-dependent adsorption of the polyampholyte on the {111} faces will induce the symmetry breaking effect, which is responsible for the kinetically controlled hindered vertical and preferred lateral growth of the nanoplatelets.}, language = {en} } @article{OlejkoBald2017, author = {Olejko, Lydia and Bald, Ilko}, title = {FRET efficiency and antenna effect in multi-color DNA origami-based light harvesting systems}, series = {RSC Advances}, volume = {7}, journal = {RSC Advances}, number = {39}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {2046-2069}, doi = {10.1039/c7ra02114c}, pages = {23924 -- 23934}, year = {2017}, abstract = {Artificial light harvesting complexes find applications in artificial photosynthesis, photovoltaics and light harvesting chemical sensors. They are used to enhance the absorption of light of a reaction center which is often represented by a single acceptor. Here, we present different light harvesting systems on DNA origami structures and analyze systematically the light harvesting efficiency. By changing the number and arrangement of different fluorophores (FAM as donor, Cy3 as transmitter and Cy5 as acceptor molecules) the light harvesting efficiency is optimized to create a broadband absorption and to improve the antenna effect 1 (including two energy transfer steps) from 0.02 to 1.58, and the antenna effect 2 (including a single energy transfer step) from 0.04 to 8.7, i.e. the fluorescence emission of the acceptor is significantly higher when the light-harvesting antenna is excited at lower wavelength compared to direct excitation of the acceptor. The channeling of photo energy to the acceptor proceeds by Forster Resonance Energy Transfer (FRET) and we carefully analyze also the FRET efficiency of the different light harvesting systems. Accordingly, the antenna effect can be tuned by modifying the stoichiometry of donor, transmitter and acceptor dyes, whereas the FRET efficiency is mainly governed by the spectroscopic properties of dyes and their distances.}, language = {en} } @article{AtilawDuffyHeydenreichetal.2017, author = {Atilaw, Yoseph and Duffy, Sandra and Heydenreich, Matthias and Muiva-Mutisya, Lois and Avery, Vicky M. and Erdelyi, Mate and Yenesew, Abiy}, title = {Three Chalconoids and a Pterocarpene from the Roots of Tephrosia aequilata}, series = {Molecules}, volume = {22}, journal = {Molecules}, number = {2}, publisher = {MDPI}, address = {Basel}, issn = {1420-3049}, doi = {10.3390/molecules22020318}, pages = {11}, year = {2017}, abstract = {In our search for new antiplasmodial agents, the CH2Cl2/CH3OH (1:1) extract of the roots of Tephrosia aequilata was investigated, and observed to cause 100\% mortality of the chloroquine-sensitive (3D7) strain of Plasmodium falciparum at a 10 mg/mL concentration. From this extract three new chalconoids, E-2,6-dimethoxy-3,4-(2,2-dimethyl)pyranoretrochalcone (1, aequichalcone A), Z-2,6-dimethoxy-3,4-(2,2-dimethyl)pyranoretrochalcone (2, aequichalcone B), 4-ethoxy-3-hydroxypraecansone B (3, aequichalcone C) and a new pterocarpene, 3,4:8,9-dimethylenedioxy-6a,11a-pterocarpene (4), along with seven known compounds were isolated. The purified compounds were characterized by NMR spectroscopic and mass spectrometric analyses. Compound 1 slowly converts into 2 in solution, and thus the latter may have been enriched, or formed, during the extraction and separation process. The isomeric compounds 1 and 2 were both observed in the crude extract. Some of the isolated constituents showed good to moderate antiplasmodial activity against the chloroquine-sensitive (3D7) strain of Plasmodium falciparum.}, language = {en} } @article{SchmidtKorbAbell2017, author = {Schmidt, Marco F. and Korb, Oliver and Abell, Chris}, title = {Antagonists of the miRNA-Argonaute 2 Protein Complex}, series = {Drug Target miRNA: Methods and Protocols}, volume = {1517}, journal = {Drug Target miRNA: Methods and Protocols}, publisher = {Springer}, address = {New York}, isbn = {978-1-4939-6563-2}, issn = {1064-3745}, doi = {10.1007/978-1-4939-6563-2_17}, pages = {239 -- 249}, year = {2017}, abstract = {microRNAs (miRNAs) have been identified as high-value drug targets. A widely applied strategy in miRNA inhibition is the use of antisense agents. However, it has been shown that oligonucleotides are poorly cell permeable because of their complex chemical structure and due to their negatively charged backbone. Consequently, the general application of oligonucleotides in therapy is limited. Since miRNAs' functions are executed exclusively by the Argonaute 2 protein, we therefore describe a protocol for the design of a novel miRNA inhibitor class: antagonists of the miRNA-Argonaute 2 protein complex, so-called anti-miR-AGOs, that not only block the crucial binding site of the target miRNA but also bind to the protein's active site. Due to their lower molecular weight and, thus, more drug-like chemical structure, the novel inhibitor class may show better pharmacokinetic properties than reported oligonucleotide inhibitors, enabling them for potential therapeutic use.}, language = {en} } @article{YouBehlLoewenbergetal.2017, author = {You, Zewang and Behl, Marc and L{\"o}wenberg, Candy and Lendlein, Andreas}, title = {pH-sensitivity and conformation change of the n-terminal methacrylated peptide VK20}, series = {MRS advances : a journal of the Materials Research Society (MRS)}, volume = {2}, journal = {MRS advances : a journal of the Materials Research Society (MRS)}, publisher = {Cambridge University Press}, address = {Cambridge}, issn = {2059-8521}, doi = {10.1557/adv.2017.491}, pages = {2571 -- 2579}, year = {2017}, abstract = {N-terminal methacrylation of peptide MAXI, which is capable of conformational changes variation of the pH, results in a peptide, named VK20. Increasing the reactivity of this terminal group enables further coupling reactions or chemical modifications of the peptidc. However, this end group functionalization may influence the ability of confonnational changes of VK20; as well as its properties. In this paper; the influence of pH on the transition between random coil and beta-sheet conformation of VK20; including the transition kinetics, were investigated. At pH values of 9 and higher, the kinetics beta-sheet formation increased tor VK(2 0, compared to MAXI. The self-assembly into beta-sheets recognized by the formation of a physically crosslinked gel was furthermore indicated by a significant increase of G. An increase in pH (from 9 to 9.5) led to a faster gelation of the peptide VK20. Simultaneously, G was increased from 460 +/- 70 Pa (at pH 9) to 1520 +/- 180 Pa (at pH 9.5). At the nanoscale, the gel showed a highly interconnected fibrillar/network structure with uniform fibril widths of approximately 3.4 +/- 0.5 nm (N=30). The recovery of the peptide conformation back to random coil resulted in the dissolution of the gel; whereby the kinetics of the recovery depended on the pH. Conclusively, the ability of MAXI to undergo confommtional changes was not affected by N-terminal methacrylation whereas the kinetics of pH-sensitive beta-sheet formations has been increased.}, language = {en} } @article{MuthauraKerikoMutaietal.2017, author = {Muthaura, Charles N. and Keriko, Joseph M. and Mutai, Charles and Yenesew, Abiy and Heydenreich, Matthias and Atilaw, Yoseph and Gathirwa, Jeremiah W. and Irungu, Beatrice N. and Derese, Solomon}, title = {Antiplasmodial, cytotoxicity and phytochemical constituents of four maytenus species used in traditional medicine in Kenya}, series = {The natural products journal}, volume = {7}, journal = {The natural products journal}, number = {2}, publisher = {Bentham Science Publ.}, address = {Sharjah}, issn = {2210-3155}, doi = {10.2174/2210315507666161206144050}, pages = {144 -- 152}, year = {2017}, abstract = {Background: In Kenya, several species of the genus Maytenus are used in traditional medicine to treat many diseases including malaria. In this study, phytochemical constituents and extracts of Maytenus undata, M. putterlickioides, M. senegalensis and M. heterophylla were evaluated to determine compound/s responsible for antimalarial activity. Objective: To isolate antiplasmodial compounds from these plant species which could be used as marker compounds in the standardization of their extracts as a phytomedicine for malaria. Methods: Constituents were isolated through activity-guided fractionation of the MeOH/CHCl3 (1:1) extracts and in vitro inhibition of Plasmodium falciparum. Cytotoxicity was evaluated using Vero cells and the compounds were elucidated on the basis of NMR spectroscopy. Results: Fractionation of the extracts resulted in the isolation of ten known compounds. Compound 1 showed promising antiplasmodial activity with IC50, 3.63 and 3.95 ng/ml against chloroquine sensitive (D6) and resistant (W2) P. falciparum, respectively and moderate cytotoxicity (CC50, 37.5 ng/ml) against Vero E6 cells. The other compounds showed weak antiplasmodial (IC50 > 1.93 mu g/ml) and cytotoxic (CC50 > 39.52 mu g/ml) activities against P. falciparum and Vero E6 cells, respectively. Conclusion: (20 alpha)-3-hydroxy-2-oxo-24-nor-friedela-1(10),3,5,7-tetraen-carboxylic acid-(29)-methyl-ester (pristimerin) (1) was the most active marker and lead compound that warrants further investigation as a template for the development of new antimalarial drugs. Pristimerin is reported for the first time in M. putterlickioides. 3-Hydroxyolean-12-en-28-oic acid (oleanolic acid) (5), stigmast-5-en-3-ol (beta-sitosterol) (6), 3-oxo-28-friedelanoic acid (7), olean-12-en-3-ol (beta-amyrin) (8), lup-20(29)-en-3-ol (lupeol) (9) and lup-20(29)-en-3-one (lupenone) (10) are reported for the first time in M. undata.}, language = {en} } @article{PengBehlZhangetal.2017, author = {Peng, Xingzhou and Behl, Marc and Zhang, Pengfei and Mazurek-Budzyńska, Magdalena and Feng, Yakai and Lendlein, Andreas}, title = {Synthesis and characterization of multiblock poly(ester-amide-urethane)s}, series = {MRS advances : a journal of the Materials Research Society (MRS)}, volume = {2}, journal = {MRS advances : a journal of the Materials Research Society (MRS)}, publisher = {Cambridge University Press}, address = {Cambridge}, issn = {2059-8521}, doi = {10.1557/adv.2017.486}, pages = {2551 -- 2559}, year = {2017}, abstract = {In this study, a multiblock copolymer containing oligo(3-methyl-morpholine-2, 5-dione) (oMMD) and oligo(3-sec-butyl-morpholine-2, 5-dione) (oBMD) building blocks obtained by ring-opening polymerization (ROP) of the corresponding monomers, was synthesized in a polyaddition reaction using an aliphatic diisocyanate. The multiblock copolymer (pBMD-MMD) provided a molecular weight of 40, 000 g·mol-1, determined by gel permeation chromatography (GPC). Incorporation of both oligodepsipeptide segments in multiblock copolymers was confirmed by 1H NMR and Matrix Assisted Laser Desorption/Ionization Time Of Flight Mass Spectroscopy (MALDI-TOF MS) analysis. pBMD-MMD showed two separated glass transition temperatures (61 °C and 74 °C) indicating a microphase separation. Furthermore, a broad glass transition was observed by DMTA, which can be attributed to strong physical interaction i.e. by H-bonds formed between amide, ester, and urethane groups of the investigated copolymers. The obtained multiblock copolymer is supposed to own the capability to exhibit strong physical interactions.}, language = {en} } @article{ParamonovKuehnBandrauk2017, author = {Paramonov, Guennaddi K. and K{\"u}hn, Oliver and Bandrauk, Andr{\´e} D.}, title = {Excitation of H+ 2 with one-cycle laser pulses}, series = {Molecular physics : MP ; an international journal in the field of chemical physics}, volume = {115}, journal = {Molecular physics : MP ; an international journal in the field of chemical physics}, number = {15/16}, publisher = {Taylor \& Francis}, address = {London}, issn = {0026-8976}, doi = {10.1080/00268976.2017.1288938}, pages = {1846 -- 1860}, year = {2017}, abstract = {Non-Born-Oppenheimer quantum dynamics of H+ 2 excited by shaped one-cycle laser pulses linearly polarised along the molecular axis have been studied by the numerical solution of the time-dependent Schr{\"o}dinger equation within a three-dimensional model, including the internuclear separation, R, and the electron coordinates z and ρ. Laser carrier frequencies corresponding to the wavelengths λ l = 25 nm through λ l = 400 nm were used and the amplitudes of the pulses were chosen such that the energy of H+ 2 was close to its dissociation threshold at the end of any laser pulse applied. It is shown that there exists a characteristic oscillation frequency ωosc ≃ 0.2265 au (corresponding to the period of τosc ≃ 0.671 fs and the wavelength of λosc ≃ 201 nm) that manifests itself as a 'carrier' frequency of temporally shaped oscillations of the time-dependent expectation values ⟨z ⟩ and ⟨∂V/∂z ⟩ that emerge at the ends of the laser pulses and exist on a timescale of at least 50 fs. Time-dependent expectation values ⟨ρ⟩ and ⟨∂V /∂ρ⟩ of the optically passive degree of freedom, ρ, demonstrate post-laser-field oscillations at two basic frequencies ωρ 1 ≈ ωosc and ωρ 2 ≈ 2ωosc. Power spectra associated with the electronic motion show higher- and lower-order harmonics with respect to the driving field.}, language = {en} } @article{MorgnerBennemannCywińskietal.2017, author = {Morgner, Frank and Bennemann, Mark and Cywiński, Piotr J. and Kollosche, Matthias and G{\´o}rski, Krzysztof and Pietraszkiewicz, Marek and Geßner, Andr{\´e} and L{\"o}hmannsr{\"o}ben, Hans-Gerd}, title = {Elastic FRET sensors for contactless pressure measurement}, series = {RSC Advances : an international journal to further the chemical sciences}, volume = {7}, journal = {RSC Advances : an international journal to further the chemical sciences}, publisher = {RSC Publishing}, address = {Cambridge}, issn = {2046-2069}, doi = {10.1039/c7ra06379b}, pages = {50578 -- 50583}, year = {2017}, abstract = {Contactless pressure monitoring based on Forster resonance energy transfer between donor/acceptor pairs immobilized within elastomers is demonstrated. The donor/acceptor energy transfer is employed by dispersing terbium(III) tris[(2-hydroxybenzoyl)-2-aminoethyl] amine complex (LLC, donor) and CdSe/ZnS quantum dots (QD655, acceptor) in styrene-ethylene/buthylene-styrene (SEBS) and poly(dimethylsiloxane) (PDMS). The continuous monitoring of QD luminescence showed a reversible intensity change as the pressure signal is alternated between two stable states indicating a pressure sensitivity of 6350 cps kPa(-1). Time-resolved measurements show the pressure impact on the FRET signal due to an increase of decay time (270 ms up to 420 ms) for the donor signal and parallel drop of decay time (170 mu s to 155 mu s) for the acceptor signal as the net pressure applied. The LLC/QD655 sensors enable a contactless readout as well as space resolved monitoring to enable miniaturization towards smaller integrated stretchable opto-electronics. Elastic FRET sensors can potentially lead to developing profitable analysis systems capable to outdo conventional wired electronic systems (inductive, capacitive, ultrasonic and photoelectric sensors) especially for point-of-care diagnostics, biological monitoring required for wearable electronics.}, language = {en} } @article{ShainyanBelyakovSigolaevetal.2017, author = {Shainyan, Bagrat A. and Belyakov, Alexander V. and Sigolaev, Yurii F. and Khramov, Alexander N. and Kleinpeter, Erich}, title = {Molecular Structure and Conformational Analysis of 1-Phenyl-1-X-1-Silacyclohexanes (X = F, Cl) by Electron Diffraction, Low-Temperature NMR, and Quantum Chemical Calculations}, series = {The journal of organic chemistry}, volume = {82}, journal = {The journal of organic chemistry}, number = {1}, publisher = {American Chemical Society}, address = {Washington}, issn = {0022-3263}, doi = {10.1021/acs.joc.6b02538}, pages = {461 -- 470}, year = {2017}, abstract = {The molecular structure and conformational preferences of 1-phenyl-1-X-1-silacyclohexanes C5H10Si(Ph,X) (X = F (3), Cl (4)) were studied by gas-phase electron diffraction, low-temperature NMR spectroscopy, and high-level quantum chemical calculations. In the gas phase only three (3) and two (4) stable conformers differing in the axial or equatorial location of the phenyl group and the angle of rotation about the Si-C-ph bond (axi and axo denote the Ph group lying in or out of the X-Si-C-ph plane) contribute to the equilibrium. In 3 the ratio Ph-eq:Ph-axo:Ph-axi is 40(12):55(24):5 and 64:20:16 by experiment and theory, respectively. In 4 the ratio Ph-eq:Ph-axo is 79(15):21(15) and 71:29 by experiment and theory (M06-2X calculations), respectively. The gas-phase electron diffraction parameters are in good agreement with those obtained from theory at the M06-2X/aug-ccPVTZ and MP2/aug-cc-pVTZ levels. Unlike the case for M06-2X, MP2 calculations indicate that 3-Ph-eq conformer lies 0.5 kcal/mol higher than the 3-Ph-axo, conformer. As follows from QTAIM analysis, the phenyl group is more stable when it is located in the axial position but produces destabilization of the silacyclohexane ring: By low temperature NMR spectroscopy the six-membered ring interconversion could be frozen, at 103 K and the present conformational equilibria of 3 and 4 could be determined. The ratio of the conformers is 3-Ph-eq:3-Ph-ax = (75-77):(23-25) and 4-Ph-eq:4-Ph-ax = 82:18.}, language = {en} }