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41.
Reglucosylation of the Benzoxazinoid DIMBOA with Inversion of Stereochemical Configuration is a Detoxification Strategy in Lepidopteran Herbivores 总被引:1,自引:0,他引:1 下载免费PDF全文
Felipe C. Wouters Dr. Michael Reichelt Dr. Gaétan Glauser Eugen Bauer Dr. Matthias Erb Prof. Jonathan Gershenzon Dr. Daniel G. Vassão 《Angewandte Chemie (International ed. in English)》2014,53(42):11320-11324
Benzoxazinoids are chemical defenses against herbivores and are produced by many members of the grass family. These compounds are stored as stable glucosides in plant cells and require the activity of glucosidases to release the corresponding toxic aglucones. In maize leaves, the most abundant benzoxazinoid is (2R)‐DIMBOA‐Glc, which is converted into the toxic DIMBOA upon herbivory. The ways in which three Spodoptera species metabolize this toxin were investigated. (2S)‐DIMBOA‐Glc, an epimer of the initial plant compound, was observed in the insect frass, and the associated glucosyltransferase activity was detected in the insect gut tissue. The epimeric glucoside produced by the insect was found to be no longer reactive towards plant glucosidases and thus cannot be converted into a toxin. Stereoselective reglucosylation thus represents a detoxification strategy in Spodoptera species that might help to explain their success as agricultural pests on benzoxazinoid‐containing crops. 相似文献
42.
Ancély F. dos Santos Daria Raquel Q. de Almeida Letícia F. Terra Rosangela A.M. Wailemann Vinícius M. Gomes Gabriel S. Arini Felipe G. Ravagnani Maurício S. Baptista Leticia Labriola 《Photochemistry and photobiology》2020,96(3):658-667
Photodynamic therapy (PDT) appears as a promising alternative in the treatment of breast cancer since it can be highly effective in curing cancer while preserving normal tissue. However, predicting outcomes in PDT still constitutes a great challenge. One of the parameters that are usually empirically determined is the rate of photon flux delivered to the tissue (light fluence rate). In the present study, we intended to understand why monolayers of human cells derived from mammary adenocarcinomas (MDA-MB-231 and MCF-7) respond quite differently to fluence rates (cells were irradiated either for 6 or for 16 min) at a fixed light dose (4.5 J cm−2) delivered with an array of LEDs in a typical methylene blue PDT protocol. While death rates of MDA-MB-231 cells were insensitive to the fluence rate, MCF-7 cells showed a quite impressive (three times) decrease in cell death levels in the shorter irradiation protocol. Independent on cell type cell death was invariably correlated with the depletion of reduced glutathione intracellular levels and consequently with widespread redox misbalance. Our data show the potential to optimize fluence rates to provide exhaustion of the cell antioxidant responses in order to circumvent therapy resistance of breast tumors. 相似文献
43.
Florian A. Mann Niklas Herrmann Felipe Opazo Sebastian Kruss 《Angewandte Chemie (International ed. in English)》2020,59(40):17732-17738
Single‐walled carbon nanotubes (SWCNTs) are a 1D nanomaterial that shows fluorescence in the near‐infrared (NIR, >800 nm). In the past, covalent chemistry was less explored to functionalize SWCNTs as it impairs NIR emission. However, certain sp3 defects (quantum defects) in the carbon lattice have emerged that preserve NIR fluorescence and even introduce a new, red‐shifted emission peak. Here, we report on quantum defects, introduced using light‐driven diazonium chemistry, that serve as anchor points for peptides and proteins. We show that maleimide anchors allow conjugation of cysteine‐containing proteins such as a GFP‐binding nanobody. In addition, an Fmoc‐protected phenylalanine defect serves as a starting point for conjugation of visible fluorophores to create multicolor SWCNTs and in situ peptide synthesis directly on the nanotube. Therefore, these quantum defects are a versatile platform to tailor both the nanotube's photophysical properties as well as their surface chemistry. 相似文献
44.
Felipe L. Oliveira Prof. Dr. Rodrigo B. Capaz Prof. Dr. Pierre M. Esteves 《Chemphyschem》2020,21(1):59-64
A structurally stable microporous metallic carbon allotrope, poly(spiro[2.2]penta-1,4-diyne) or, for short, spiro-carbon, with I41/amd (D4h) symmetry is predicted by first-principles calculations using density functional theory (DFT). The calculations of electronic, vibrational, and structural properties show that spiro-carbon has lower relative energy than other elusive carbon allotropes such as T-Carbon and 1-diamondyne (Y-Carbon). Its structure can be pictured as a set of trans-cisoid-polyacetylene chains tangled and interconnected together by sp3 carbon atoms. Calculations reveal a metallic electronic structure arising from an “intrinsic doping” of trans-cisoid-polyacetylene chains with sp3 carbon atoms. Possible synthetic routes and various simulated spectra (XRD, NMR, and IR absorption) are provided in order to guide future efforts to synthesize this novel material. 相似文献
45.
Selda Kabatas Paola Agüi‐Gonzalez Kim‐Ann Saal Sebastian Jhne Felipe Opazo Silvio O. Rizzoli Nhu T. N. Phan 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(11):3476-3481
Boron has been employed in materials science as a marker for imaging specific structures by electron energy loss spectroscopy (EELS) or secondary ion mass spectrometry (SIMS). It has a strong potential in biological analyses as well; however, the specific coupling of a sufficient number of boron atoms to a biological structure has proven challenging. Herein, we synthesize tags containing closo‐1,2‐dicarbadodecaborane, coupled to soluble peptides, which were integrated in specific proteins by click chemistry in mammalian cells and were also coupled to nanobodies for use in immunocytochemistry experiments. The tags were fully functional in biological samples, as demonstrated by nanoSIMS imaging of cell cultures. The boron signal revealed the protein of interest, while other SIMS channels were used for imaging different positive ions, such as the cellular metal ions. This allows, for the first time, the simultaneous imaging of such ions with a protein of interest and will enable new biological applications in the SIMS field. 相似文献
46.
Multi‐responses Methodology Applied in the Electroanalytical Determination of Hair Dye by Using Printed Carbon Electrode Modified with Graphene 下载免费PDF全文
Felipe Fantinato Hudari Sergio Luis Costa Ferreira Maria Valnice Boldrin Zanoni 《Electroanalysis》2016,28(5):1085-1092
This paper describes a rapid and sensitive method for determination of the hair dye Basic Blue 41 in wastewater samples using screen‐printed carbon electrodes modified with graphene (SPCE/Gr). The method is based on the reversible reduction of azo groups of the dye at potential of ?0.23 V/?0.26 V, where both the anodic and cathodic currents increased 1,300 % when compared to screen‐printed carbon (SPCE) and glassy carbon electrodes (GCE). The optimization of a square wave voltammetric method was performed by means of 23 factorial design, Doehlert matrix and multi‐response assays, and the best parameters were: frequency (54.8 Hz), step potential (6 mV), pulse amplitude (43.7 mV) and pH 4.5. The analytical curve was constructed from 3.00×10?8 to 2.01×10?6 mol L?1, with detection and quantification limits of 5.00×10?9 and 1.70×10?8 mol L?1, respectively. The repeatability of the method evaluated for 10 consecutive measurements at concentrations of 1.70×10?7 mol L?1 and 1.70×10?6 mol L?1, showed relative standard deviation of 3.56 and 0.57 %, respectively. The sensor based in SPCE/Gr was successfully applied in wastewater samples collected from a drinking water treatment plant and validated by comparison with HPLC‐DAD method with good accuracy. 相似文献
47.
48.
Dr. Renata Avena Maia Felipe Lopes Oliveira Prof. Vincent Ritleng Prof. Qiang Wang Dr. Benoît Louis Prof. Pierre Mothé Esteves 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(30):8048-8055
Covalent organic frameworks (COFs) RIO-13, RIO-12, RIO-11, and RIO-11m were investigated towards their CO2 capture properties by thermogravimetric analysis at 1 atm and 40 °C. These microporous COFs bear in common the azine backbone composed of hydroxy-benzene moieties but differ in the relative number of hydroxyl groups present in each material. Thus, their sorption capacities were studied as a function of their textural and chemical properties. Their maximum CO2 uptake values showed a strong correlation with an increasing specific surface area, but that property alone could not fully explain the CO2 uptake data. Hence, the specific CO2 uptake, combined with DFT calculations, indicated that the relative number of hydroxyl groups in the COF backbone acts as an adsorption threshold, as the hydroxyl groups were indeed identified as relevant adsorption sites in all the studied COFs. Additionally, the best performing COF was thoroughly investigated, experimentally and theoretically, for its CO2 capture properties in a variety of CO2 concentrations and temperatures, and showed excellent isothermal recyclability up to 3 cycles. 相似文献
49.
We study the static pricing problem for a network service provider in a loss system with a tree structure. In the network, multiple classes share a common inbound link and then have dedicated outbound links. The motivation is from a company that sells phone cards and needs to price calls to different destinations. We characterize the optimal static prices in order to maximize the steady-state revenue. We report new structural findings as well as alternative proofs for some known results. We compare the optimal static prices versus prices that are asymptotically optimal, and through a set of illustrative numerical examples we show that in certain cases the loss in revenue can be significant. Finally, we show that static prices obtained using the reduced load approximation of the blocking probabilities can be easily obtained and have near-optimal performance, which makes them more attractive for applications. 相似文献
50.
Alfonso J. Chirinos-Padrn Petra H. Hernndez Felipe A. Surez 《Polymer Degradation and Stability》1988,20(3-4):237-255
The effect of Cr(III), Fe(III) and Cu(II) ions, at trace levels, on the effectiveness of four commercial antioxidant systems, viz. Topanol, Santowhite, Hostanox 03 and Irganox 1425, in polypropylene (PP) films is examined using infra-red and second-order derivative uv spectroscopy. The results show that at these levels the metal ions have a minor effect on the unstabilised polymer. However, the ions can have a beneficial or adverse effect on antioxidant activity, particularly under oven ageing conditions. The observed effect depends on the metal/antioxidant system, and is attributed to an indirect interaction between the components which can delay or accelerate antioxidant decomposition in the polymer. An exception to this behaviour is the metal complex Irganox 1425, which interacts strongly with copper ions in the polymer matrix. The antioxidant is partially transformed by copper ions during the compression moulding stage. The beneficial effect present in some cases is in direct contrast with what has generally been observed in studies using unstabilised polymers. 相似文献