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121.
Total Synthesis of Tambromycin by Combining Chemocatalytic and Biocatalytic C−H Functionalization 下载免费PDF全文
Dr. Xiao Zhang Emma King‐Smith Prof. Dr. Hans Renata 《Angewandte Chemie (International ed. in English)》2018,57(18):5037-5041
A combination of genomic and metabolomic approaches recently resulted in the identification of a nonribosomal tetrapeptide tambromycin, which possesses promising antiproliferative activity and several unusual structural features, including a densely substituted indole, a methyloxazoline ring, and an unusual pyrrolidine‐containing amino acid called tambroline. In this work, we identify a concise synthetic route to access tambromycin, which relies on the strategic use of biocatalytic and chemocatalytic C?H functionalization methods to prepare two key precursors to the natural product in an efficient and scalable manner. The success of our study highlights the benefits of applying the principles of biocatalytic retrosynthesis as well as C?H functionalization logic to the synthesis of complex molecular scaffolds. 相似文献
122.
Danuta Wróbel Izabela Hanyż Renata Bartkowiak Rodica M. Ion 《Journal of fluorescence》1998,8(3):191-198
Porphyrin dyes fulfill an essential function in photosynthesis and are important in photodynamic therapy and in a range of electronic devices. Their spectroscopic characteristics may play a crucial role in these processes. The spectral properties of two porphyrin dyes: tetraphenylporphyrin and tetraphenysulfporphyrin in organic solvents (acetone, chloroform, methyl alcohol, and dimethyl-sulfoxide) and in polyvinyl alcohol and poly(methylmethacrylate) films have been investigated. Absorption, fluorescence, and microsecond time-resolved delayed luminescence spectra have been measured at room temperature. The existence of different aggregated dye forms in the ground and excited states has been demonstrated. The manifold of dye species depends on the solvent/polymer. In the case of the polymers, it also depends on the solvent used to coat the polymer film. Delayed luminescence spectra and decay times of the two porphyrins in the different solutions and in polymeric matrices suggest that different mechanisms of deexcitation of the singlet excited states may be responsible for their generation in these and other porphyrin dyes. 相似文献
123.
124.
Nazaruk E Bilewicz R Lindblom G Lindholm-Sethson B 《Analytical and bioanalytical chemistry》2008,391(5):1569-1578
Incorporation of membrane proteins with retained activity in artificial membranes for use in membrane-based sensors has attracted
scientists for decades. This review briefly summarises general concepts on relevant cubic phases with and without incorporated
proteins and provides some insight into the development of biosensors where bicontinuous cubic phases are used for incorporation
of an enzyme. Some new data on impedance characterisation of a supported cubic phase are also shown. An efficient membrane-based
electrochemical biosensor requires that the analyte has free access to the immobilised membrane protein and that regeneration
of the catalysing enzyme is fast. Long-term stability of the system is also necessary for the biosensor to find applications
outside the research laboratory. These basic concepts are discussed in the review along with presentation of those biosensing
systems based on cubic phases that are reported in the literature. 相似文献
125.
Brimble MA Kowalczyk R Harris PW Dunbar PR Muir VJ 《Organic & biomolecular chemistry》2008,6(1):112-121
Mannose-binding proteins on the surface of antigen-presenting cells (APCs) are capable of recognizing and internalizing foreign agents in the early stages of immune response. These receptors offer a potential target for synthetic vaccines, especially vaccines designed to stimulate T cells. We set out to synthesize a series of fluorescein-labelled O-mannosylated peptides using manual solid phase peptide synthesis (SPPS) on pre-loaded Wang resin, in order to test their ability to bind mannose receptors on human APCs in vitro. A flexible and reliable method for the synthesis of fluorescein-labelled O-mannosylated glycopeptides was desired in order to study their lectin-binding properties using flow cell cytometry. Two synthetic strategies were investigated: incorporation of a fluorescein label into the peptide chain via a lysine side chain epsilon-amino group at the final stage of standard Fmoc solid phase peptide synthesis or attachment of the fluorescein label to the N(alpha)-amino group of a lysine with further incorporation of a mannosylated peptide unit through the side chain N(epsilon)-amino group. The latter strategy proved more effective in that it facilitated SPPS by positioning the growing mannosylated peptide chain further removed from the fluorescein label. 相似文献
126.
The following paper compares several procedures of in-capillary bienzymatic derivatization with regard to glucose determination with the use of glucose oxidase and horseradish peroxidase. The procedures discussed below include continuous contact in the capillary, plug-plug injection, and sequential injection with incubation in the capillary inlet. The reaction of hydrogen peroxide catalyzed by peroxidase was performed using two different substrates. The best results were achieved for nicotinamide adenine dinucleotide, reduced disodium salt (NADH) acting both as a chromogenic reagent and a substrate for peroxidase, while the method employed was sequential injection and incubation at the capillary inlet. The LOD was estimated to be 25 nM with a linear response up to 0.1 microM. 相似文献
127.
A 4-component Ugi reaction with a suitable isocyanide, followed by a novel secondary transformation involving a Pd(II)-mediated (R5 = H) or a Pd(0)-mediated (R5 = CO2Me) SN2' cyclization to give highly functionalized N-acyl-2-vinylpyrrolidines, is reported. The overall yields are usually good and in most cases the Pd(0)-catalyzed reaction gave the final product in almost quantitative yield. 相似文献
128.
Renata Karpicz Vytautas Getautis Karolis Kazlauskas Saulius Jurnas Vidmantas Gulbinas 《Chemical physics》2008,351(1-3):147-153
Excited state relaxation of indan-1,3-dione derivatives with different substituents attached to the phenyl ring and with the bridged amino group was investigated by means of the steady-state fluorescence and femtosecond time-resolved absorption pump–probe spectroscopy. Bridging of the amino group increases the fluorescence quantum yield and the excited state lifetime. Analysis of the results indicates that the phenyl ring twisting around a single central bond leads to the nonradiative state formation and to subsequent fast relaxation to the ground state. Double bond twisting takes place in molecules with the bridged amino group and causes a large Stokes shift and slightly slower excited state relaxation. 相似文献
129.
Renata Gudiukaitė Audrius Gegeckas Mikas Sadauskas Donaldas Citavicius 《Applied biochemistry and biotechnology》2016,178(4):654-669
GD-95-10 and GD-95-20 lipases are modified GD-95 lipase variants, which lack 10 and 20 C-terminal amino acids, respectively. Previous analysis showed that GD-95-10 lipase has higher activity than GD-95 lipase, while GD-95-20 lipase almost completely loses its activity. Analysis in silico suggested three conservative amino acids at region between 369 and 378 amino acids which can be relevant to the activity of GD-95-10 lipase. These amino acids have direct contacts with residues involved in substrate binding, stabilization of the serine loop or form oxyanion hole. In this work, the role of Asp371, Phe375, and Tyr376 on activity, functionality, and structure of GD-95-10 lipase was analyzed by Ala scanning mutagenesis. We showed that even a single mutation can impact the main structure and activity of Geobacillus lipases. Our experiments provide new knowledge about lipases from thermophilic Geobacillus bacteria and are important for protein engineering and synthetic biology. These enzymes and their engineering can be basis for future biocatalysts applied in production of biofuel or other industrial esters. 相似文献
130.
Renata Jastrzab Martyna Nowak Monika Skrobanska Michał Zabiszak 《Journal of Coordination Chemistry》2016,69(14):2174-2181
Results of potentiometric and spectral studies have shown that in d-glucuronic acid (GluA) with Cu2+ or Mg2+ systems, the complexes ML and ML(OH)x are formed. Overall stability constants (log β) and equilibrium constants (log Ke) were calculated for all complex forms. The mode of coordination for each form was concluded on the basis of spectral values, Vis, EPR, and chemical shifts in the 13C NMR. According to spectral analysis, Cu(GluA) exists in two possible forms, which confirm the occurrence of the coordination dichotomy in the system. The main center of interactions in the hydroxyl complexes Cu(GluA)(OH)x and MgGluA are oxygens from the carboxyl group. Differences in the coordination mode in the copper(II) and magnesium systems at low pH were observed. 相似文献