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181.
Alexander K. Mengele Dominik Weixler Avinash Chettri Maite Maurer Fabian Lukas Huber Prof. Gerd M. Seibold Prof. Benjamin Dietzek Prof. Bernhard J. Eikmanns Prof. Sven Rau 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(68):16840-16845
A series of three Ru(II) polypyridine complexes was investigated for the selective photocatalytic oxidation of NAD(P)H to NAD(P)+ in water. A combination of (time-resolved) spectroscopic studies and photocatalysis experiments revealed that ligand design can be used to control the mechanism of the photooxidation: For prototypical Ru(II) complexes a 1O2 pathway was found. Rudppz ([(tbbpy)2Ru(dppz)]Cl2, tbbpy=4,4'-di-tert-butyl-2,2'-bipyridine, dppz=dipyrido[3,2-a:2′,3′-c]phenazine), instead, initiated the cofactor oxidation by electron transfer from NAD(P)H enabled by supramolecular binding between substrate and catalyst. Expulsion of the photoproduct NAD(P)+ from the supramolecular binding site in Rudppz allowed very efficient turnover. Therefore, Rudppz permits repetitive selective assembly and oxidative conversion of reduced naturally occurring nicotinamides by recognizing the redox state of the cofactor under formation of H2O2 as additional product. This photocatalytic process can fuel discontinuous photobiocatalysis. 相似文献
182.
Towards a microchannel‐based X‐ray detector with two‐dimensional spatial and time resolution and high dynamic range
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Bernhard W. Adams Anil U. Mane Jeffrey W. Elam Razib Obaid Matthew Wetstein Matthieu Chollet 《Journal of synchrotron radiation》2015,22(5):1202-1206
X‐ray detectors that combine two‐dimensional spatial resolution with a high time resolution are needed in numerous applications of synchrotron radiation. Most detectors with this combination of capabilities are based on semiconductor technology and are therefore limited in size. Furthermore, the time resolution is often realised through rapid time‐gating of the acquisition, followed by a slower readout. Here, a detector technology is realised based on relatively inexpensive microchannel plates that uses GHz waveform sampling for a millimeter‐scale spatial resolution and better than 100 ps time resolution. The technology is capable of continuous streaming of time‐ and location‐tagged events at rates greater than 107 events per cm2. Time‐gating can be used for improved dynamic range. 相似文献
183.
184.
Ioku Norisuke Ruf Bernhard Terraneo Elide 《Mathematical Physics, Analysis and Geometry》2015,18(1):1-19
We consider a semilinear heat equation with exponential nonlinearity in ?2. We prove that local solutions do not exist for certain data in the Orlicz space exp L 2(?2), even though a small data global existence result holds in the same space exp L 2(?2). Moreover, some suitable subclass of exp L 2(?2) for local existence and uniqueness is proposed.
相似文献185.
Atom‐Economic,Regiodivergent, and Stereoselective Coupling of Imidazole Derivatives with Terminal Allenes
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Kun Xu Niels Thieme Prof. Dr. Bernhard Breit 《Angewandte Chemie (International ed. in English)》2014,53(8):2162-2165
New Rh‐ and Pd‐catalyzed regiodivergent and stereoselective intermolecular coupling reactions of imidazole derivatives with mono‐substituted allenes are herein reported. Using a RhI/Josiphos system, perfect regioselectivities and high enantiomeric excess were obtained, while a PdII/dppf system gave linear products with high regioselectivities and high E/Z selectivities. This method permits the atom economic synthesis of valuable branched and linear allylic imidazole derivatives. 相似文献
186.
A Deadly Organometallic Luminescent Probe: Anticancer Activity of a ReI Bisquinoline Complex
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Dr. Igor Kitanovic Suzan Can Dr. Hamed Alborzinia Dr. Ana Kitanovic Vanessa Pierroz Anna Leonidova Dr. Antonio Pinto Priv. Doz. Dr. Bernhard Spingler Priv. Doz. Dr. Stefano Ferrari Roberto Molteni Dr. Andreas Steffen Prof. Dr. Nils Metzler‐Nolte Prof. Dr. Stefan Wölfl Prof. Dr. Gilles Gasser 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(9):2496-2507
The photophysical properties of [Re(CO)3(L ‐N3)]Br (L ‐N3=2‐azido‐N,N‐bis[(quinolin‐2‐yl)methyl]ethanamine), which could not be localized in cancer cells by fluorescence microscopy, have been revisited in order to evaluate its use as a luminescent probe in a biological environment. The ReI complex displays concentration‐dependent residual fluorescence besides the expected phosphorescence, and the nature of the emitting excited states have been evaluated by DFT and time‐dependent (TD) DFT methods. The results show that fluorescence occurs from a 1LC/MLCT state, whereas phosphorescence mainly stems from a 3LC state, in contrast to previous assignments. We found that our luminescent probe, [Re(CO)3(L ‐N3)]Br, exhibits an interesting cytotoxic activity in the low micromolar range in various cancer cell lines. Several biochemical assays were performed to unveil the cytotoxic mechanism of the organometallic ReI bisquinoline complex. [Re(CO)3(L ‐N3)]Br was found to be stable in human plasma indicating that [Re(CO)3(L ‐N3)]Br itself and not a decomposition product is responsible for the observed cytotoxicity. Addition of [Re(CO)3(L ‐N3)]Br to MCF‐7 breast cancer cells grown on a biosensor chip micro‐bioreactor immediately led to reduced cellular respiration and increased glycolysis, indicating a large shift in cellular metabolism and inhibition of mitochondrial activity. Further analysis of respiration of isolated mitochondria clearly showed that mitochondrial respiratory activity was a direct target of [Re(CO)3(L ‐N3)]Br and involved two modes of action, namely increased respiration at lower concentrations, potentially through increased proton transport through the inner mitochondrial membrane, and efficient blocking of respiration at higher concentrations. Thus, we believe that the direct targeting of mitochondria in cells by [Re(CO)3(L ‐N3)]Br is responsible for the anticancer activity. 相似文献
187.
Tuning Thiophene with Phosphorus: Synthesis and Electronic Properties of Benzobisthiaphospholes
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Yunyan Qiu Joshua C. Worch Danielle N. Chirdon Aman Kaur Andrew B. Maurer Samuel Amsterdam Christopher R. Collins Prof. Tomislav Pintauer Prof. David Yaron Prof. Stefan Bernhard Prof. Kevin J. T. Noonan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(25):7746-7751
1,4‐Dimercapto‐2,5‐diphosphinobenzene and 3,6‐bis(hexyloxy)‐1,4‐dimercapto‐2,5‐diphosphinobenzene were synthesized and combined with various acid chlorides to obtain a series of benzobisthiaphospholes. Electrochemical and photophysical properties of the substituted benzobisthiaphospholes have been evaluated, and the observed reductions are more facile than the related benzothiaphospholes and 2,6‐diphenylbenzobisthiazole. A benzobisthiaphosphole with C6H4‐p‐CN substituents was reduced at E1/2=?1.08 V (vs. saturated calomel electrode (SCE)). X‐ray diffraction data for several of these phosphorus heterocycles has been obtained, and DFT calculations at the B3LYP level have been performed. 相似文献
188.
Hydroxymethylated Phyllobilins: A Puzzling New Feature of the Dioxobilin Branch of Chlorophyll Breakdown
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Iris Süssenbacher Dr. Bastien Christ Prof. Dr. Stefan Hörtensteiner Prof. Dr. Bernhard Kräutler 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(1):87-92
Colorless nonfluorescent chlorophyll (Chl) catabolites (NCCs) are formyloxobilin‐type phyllobilins, which are considered the typical products of Chl breakdown in senescent leaves. However, in degreened leaves of some plants, dioxobilin‐type Chl catabolites (DCCs) predominate, which lack the formyl group of the NCCs, and which arise from Chl catabolites by oxidative removal of the formyl group by a P450 enzyme. Here a structural investigation of the DCCs in the methylesterase16 mutant of Arabidopsis thaliana is reported. Eight new DCCs were identified and characterized structurally. Strikingly, three of these DCCs carry stereospecifically added hydroxymethyl groups, and represent bilin‐type linear tetrapyrroles with an unprecedented modification. Indeed, DCCs show a remarkable structural parallel, otherwise, to the bilins from heme breakdown. 相似文献
189.
How Many Molecules are Required to Obtain a Steady Faradaic Current from Mediated Electron Transfer at a Single Nanoparticle on a Supporting Surface?
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Enno Kätelhön Kay J. Krause Prof. Dr. Bernhard Wolfrum Prof. Dr. Richard G. Compton 《Chemphyschem》2014,15(5):872-875
We investigate the chronoamperometric noise characteristics of electron‐transfer reactions occurring on single nanoparticles (NPs) and assemblies of well‐separated NPs on a supporting surface. To this end, we combine a formerly described expression for the steady‐state current of a single particle with the shot‐noise model and derive an expression for the signal‐to‐noise ratio as a function of bulk concentration and particle radius. Our findings are supported by random‐walk simulations, which closely match the analytical results. 相似文献
190.
Dr. Christoph Kieninger Dr. Klaus Wurst Dr. Maren Podewitz Dr. Maria Stanley Dr. Evelyne Deery Dr. Andrew D. Lawrence Prof. Dr. Klaus R. Liedl Prof. Dr. Martin J. Warren Prof. Dr. Bernhard Kräutler 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(45):20304-20311
The (formal) replacement of Co in cobalamin ( Cbl ) by NiII generates nibalamin ( Nibl ), a new transition-metal analogue of vitamin B12. Described here is Nibl , synthesized by incorporation of a NiII ion into the metal-free B12 ligand hydrogenobalamin ( Hbl ), itself prepared from hydrogenobyric acid ( Hby ). The related NiII corrin nibyric acid ( Niby ) was similarly synthesized from Hby , the metal-free cobyric acid ligand. The solution structures of Hbl , and Niby and Nibl , were characterized by spectroscopic studies. Hbl features two inner protons bound at N2 and N4 of the corrin ligand, as discovered in Hby . X-ray analysis of Niby shows the structural adaptation of the corrin ligand to NiII ions and the coordination behavior of NiII. The diamagnetic Niby and Nibl , and corresponding isoelectronic CoI corrins, were deduced to be isostructural. Nibl is a structural mimic of four-coordinate base-off Cbls , as verified by its ability to act as a strong inhibitor of bacterial adenosyltransferase. 相似文献