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991.
Marcel Ritter Vincensius S. P. Oetama Daniel Schulze Katrin Muetzlaff Anja K. Meents Dr. Raphael A. Seidel Dr. Helmar Görls Prof. Dr. Matthias Westerhausen Prof. Dr. Wilhelm Boland Prof. Dr. Georg Pohnert 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(28):6205-6213
The degradation of chlorophyll, the omnipresent green pigment, has been investigated intensively over the last 30 years resulting in many elucidated tetrapyrrolic degradation products. With a comparison to the degradation of the structurally similar heme, we hereby propose a novel additional chlorophyll degradation mechanism to mono- and dipyrrolic products. This is the first proof of the occurrence of a family of mono- and dipyrrols in leaves that are previously only known as heme degradation products. This product family is also found in spit and feces of herbivores with specific metabolomic patterns reflecting the origin of the samples. Based on chromatographic and mass spectrometric evidence as well as on mechanistic considerations we also suggest several tentative new degradation products. One of them, dihydro BOX A, was fully confirmed as a novel natural product by synthesis and comparison of its spectroscopic data. 相似文献
992.
Shai Rahimipour Georg Gescheidt Itzhak Bilkis Mati Fridkin Lev Weiner 《Applied magnetic resonance》2010,37(1-4):629-648
In this review article, the structure, properties, stability and biological application of redox-active quinones are presented. A series of quinoid molecules is evaluated in terms of their ability to act as electron-transfer active compounds using cyclovoltammetric, electron paramagnetic resonance (EPR) and spin-trapping techniques. Redox potentials and electron distribution of the intermediate radical anions are shown to be decisive factors for the generation of reactive oxygen species (ROS). Mechanisms of ROS generation in dark by biological electron-transfer reaction or under photoexcitation have been proposed and experimentally verified. For site-specific damage of tumors, some quinone derivatives were covalently bound with the luteinizing hormone-releasing hormone (LH–RH or GnRH) that produces specific complexes with receptors on the surface of cancer cells. The properties of obtained conjugates to be bound with the different lines of cancer cells (αT3-1, M2R, LNCaP) were tested. EPR was used for the estimation of efficacy of ROS production by the conjugates in solution and in the complex with cancer cells. The toxicity of these conjugates as well as their stability in the stimulated oxidative stress were tested. The proposed approach could be useful in creating a new family of addressed anticancer drugs, including compounds for the treatment of tumors by photodynamic therapy. 相似文献
993.
Dr. Xin Chen Peter Denninger Dr. Tanja Stimpel-Lindner Prof. Erdmann Spiecker Prof. Georg S. Duesberg Dr. Claudia Backes Dr. Kathrin C. Knirsch Prof. Andreas Hirsch 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(29):6535-6544
Two-dimensional (2D) molybdenum disulfide (MoS2) holds great promise in electronic and optoelectronic applications owing to its unique structure and intriguing properties. The intrinsic defects such as sulfur vacancies (SVs) of MoS2 nanosheets are found to be detrimental to the device efficiency. To mitigate this problem, functionalization of 2D MoS2 using thiols has emerged as one of the key strategies for engineering defects. Herein, we demonstrate an approach to controllably engineer the SVs of chemically exfoliated MoS2 nanosheets using a series of substituted thiophenols in solution. The degree of functionalization can be tuned by varying the electron-withdrawing strength of substituents in thiophenols. We find that the intensity of 2LA(M) peak normalized to A1g peak strongly correlates to the degree of functionalization. Our results provide a spectroscopic indicator to monitor and quantify the defect engineering process. This method of MoS2 defect functionalization in solution also benefits the further exploration of defect-free MoS2 for a wide range of applications. 相似文献
994.
In this work an innovative method for heat exchanger network (HEN) synthesis is introduced and examined. It combines a genetic
algorithm (GA) with a heuristic based optimization procedure. The novel algorithm removes appearing heat load loops from the
HEN structures when profitable, throughout the evolution. Two examples were examined with the new HEN synthesis method and
for both better results were obtained. Thus, a positive effect of heuristic based optimization methods on the HEN synthesis
with GA could be located. 相似文献
995.
Dr. Hans‐Wilhelm Engels Dr. Hans‐Georg Pirkl Dr. Reinhard Albers Dr. Rolf W. Albach Dr. Jens Krause Dr. Andreas Hoffmann Dr. Holger Casselmann Dr. Jeff Dormish 《Angewandte Chemie (International ed. in English)》2013,52(36):9422-9441
Polyurethanes are the only class of polymers that display thermoplastic, elastomeric, and thermoset behavior depending on their chemical and morphological makeup. In addition to compact polyurethanes, foamed variations in particular are very widespread, and they achieve their targeted properties at very low weights. The simple production of sandwich structures and material composites in a single processing step is a key advantage of polyurethane technology. The requirement of energy and resource efficiency increasingly demands lightweight structures. Polyurethanes can serve this requirement by acting as matrix materials or as flexible adhesives for composites. Polyurethanes are indispensable when it comes to high‐quality decorative coatings or maintaining the value of numerous objects. They are extremely adaptable and sustainable problem solvers for today’s challenges facing our society, all of which impose special demands on materials. 相似文献
996.
997.
998.
Peyton W. Roth Ahlam M. Armaly Ian McCraw James H. Tryon Hayden M. Rudd Brian C. Goess 《Tetrahedron letters》2018,59(39):3586-3588
The first total syntheses of the furanosesquiterpenoids hibiscone B and acyl hibiscone B are reported. The chemistry used to prepare hibiscone B solves an important challenge to the synthesis of other members of the furanosesquiterpenoid family of natural products, for which the parent molecule, hibiscone C, has shown promising biological activity. 相似文献
999.