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排序方式: 共有114条查询结果,搜索用时 15 毫秒
1.
本工作研究了化合物13-SO_3Na-DDHA在不同pH的缓冲溶液中的电化学氧化还原行为.实验证明:化合物中羰基的还原电位与pH之间存在线性关系,其直线的斜率为60mV/pH.并证明了此过程为一步两电子、两质子还原过程:Q+2H ̄++2e=QH_2.DMF作为非质子溶剂,具有很好的稳定自由基的作用.向缓冲溶液中加入DMF后,化合物13-SO_3Na-DDHA为两步单电子还原过程,相应溶液中的光诱导电子转移吸收光谱证实了以上电化学的结果. 相似文献
2.
A previously described passive remote sensing fluorimeter (see companion paper) was modified to detect changes in the reflectance of vegetation. The utility of this remote sensing technique to measure the Physiological Reflectance Index (PRI) is shown at both leaf level under laboratory conditions and at the canopy level in the field. PRI, defined as the relative changes in reflectance at 531 nm with respect to those at 570 nm (PRI=R531−R570/R531+R570), is related to xanthophyll-related, dynamic changes of non-photochemical quenching of chlorophyll fluorescence. The robustness of this relationship by simultaneous remote sensing of PRI and chlorophyll fluorescence is strengthened. At the leaf level, the existence of two kinetically distinct components of PRI is shown. A fast (within seconds) component that is partly attributed to ΔpH induced chloroplast shrinkage, and a slow (within minutes), main component that is related to xanthophyll de-epoxidation, as demonstrated by its disappearance in the presence of DTT. Overall, PRI correlated better with non-photochemical quenching of chlorophyll fluorescence (NPQ) than with any other measured parameter, including the photochemical efficiency of PSII. Finally, at the canopy level and under field conditions, it is shown that PRI can be a useful tool for remote sensing of water stress in grapevines. 相似文献
3.
本文研究了蒽醌(AQ)及其衍生物以及氢化蒽醌对麦草烧碱法蒸煮的作用,用微型计算机处理蒸煮结果,得到7个关于添加剂用量与蒸煮效果关系的数学模型,并对蒸煮过程进行了分析。研究结果表明,氢化蒽醌是比较适合麦草制浆的蒸煮添加剂。 相似文献
4.
Takuya Akiyama Kengo Magara Gyosuke Meshitsuka Knut Lundquist Yuji Matsumoto 《木材化学与工艺学杂志》2015,35(1):8-16
In this study, we investigated the proportion of erythro- and threo-forms of β-O-4-ether structures and their enantiomeric compositions in hardwood lignin by applying the ozonation method to birch wood meal. Optical activity was not substantially observed in either the erythronic or threonic acids obtained as the ozonation products of β-O-4-structures in birch wood meal. The proportions of the four stereoisomeric forms {(αS,βR)-erythro, (αR,βR)-threo, (αS,βS)-threo, and (αR,βS)-erythro forms} were estimated to be 37-38%, 13-14%, 12-13%, and 36-37% based on the yields of erythronic and threonic acids, and on their optical activities. The proportions suggest that the entire components of β-O-4-ether structures in birch wood lignin have R- and S-configurations at the β-carbon in approximately the same quantities {(βR)-β-O-4-structure: (βS)-β-O-4-structure = 50–52:48–50}; i.e., that the β-ether structures are essentially racemic. This estimation implies that, during lignin biosynthesis, an equal number of enantiomeric forms of β-O-4-bonded quinone methides were formed by radical coupling reactions. 相似文献
5.
Satoshi Kubo Koh Hashida Shojiro Hishiyama Tatsuhiko Yamada Shuji Hosoya 《木材化学与工艺学杂志》2015,35(1):62-72
In the alkaline decomposition of a β-O-4 type lignin model compound (erythro-guaiacylglycerol-β-guaiacyl ether, compound 1), an isomeric pair of C6C2 enol-ether (2-methoxy-4-[2-(2-methoxyphenoxy)-vinyl]-phenol, compound 2) was detected as the main decomposition product with no trace of C6C3 enol-ether (4-[3-hydroxy-1-(2-methoxyphenoxy)-propenyl]-2-methoxy-phenol, compound 3) or other dimers. In contrast, compound 2 was not detected in the alkaline decomposition products of compound 3. Under alkaline conditions, the γ-hydroxymethyl group of compound 3 was reduced to form 2-methoxy-4-[1-(2-methoxyphenoxy)-propenyl]-phenol (compound 4). In the HSQC analysis of soda lignin, the formation of substructures of C6C2 type enol-ether (related to compound 2) was confirmed. However, no substructures related to compound 4, which could be formed if a substructure of C6C3 type enol-ether was formed under alkaline conditions, were detected. Therefore, it could be concluded that C6C3 type enol-ethers could not be intermediates of alkaline decomposition products of lignin. 相似文献
6.
Oxidative Metabolism of Ferrocene Analogues of Tamoxifen: Characterization and Antiproliferative Activities of the Metabolites 下载免费PDF全文
Dr. Marie‐Aude Richard Dr. Didier Hamels Dr. Pascal Pigeon Dr. Siden Top Dr. Patrick M. Dansette Hui Zhi Shirley Lee Dr. Anne Vessières Dr. Daniel Mansuy Prof. Gérard Jaouen 《ChemMedChem》2015,10(6):981-990
Ferrociphenols have been found to have high antiproliferative activity against estrogen‐independent breast cancer cells. The rat and human liver microsome‐mediated metabolism of three compounds of the ferrocifen ( FC ) family, 1,1‐bis(4‐hydroxyphenyl)‐2‐ferrocenyl‐but‐1‐ene ( FC1 ), 1‐(4‐hydroxyphenyl)‐1‐(phenyl)‐2‐ferrocenyl‐but‐1‐ene ( FC2 ), and 1‐[4‐(3‐dimethylaminopropoxy)phenyl]‐1‐(4‐hydroxyphenyl)‐2‐ferrocenyl‐but‐1‐ene ( FC3 ), was studied. Three main metabolite classes were identified: quinone methides ( QM s) deriving from two‐electron oxidation of FC s, cyclic indene products ( CP s) deriving from acid‐catalyzed cyclization of QM s, and allylic alcohols ( AA s) deriving from hydroxylation of FC s. These metabolites are generated by cytochromes P450 (P450s), as shown by experiments with either N‐benzylimidazole as a P450 inhibitor or recombinant human P450s. Such P450‐dependent oxidation of the phenol function and hydroxylation of the allylic CH2 group of FC s leads to the formation of QM and AA metabolites, respectively. Some of the new ferrociphenols obtained in this study were found to exhibit remarkable antiproliferative effects toward MDA‐MB‐231 hormone‐independent breast cancer cells. 相似文献
7.
Xuewen Mu Yun Xu Zheng Wang Dunyun Shi 《Frontiers of Chemical Science and Engineering》2023,17(2):123
The two-electron cytoplasmic reductase NAD(P)H:quinone oxidoreductase 1 is expressed in many tissues. NAD(P)H:quinone oxidoreductase 1 is well-known for being highly expressed in most cancers. Therefore, it could be a target for cancer therapy. Because it is a quinone reductase, many bioimaging probes based on quinone structures target NAD(P)H:quinone oxidoreductase 1 to diagnose tumours. Its expression is higher in tumours than in normal tissues, and using target drugs such as β-lapachone to reduce side effects in normal tissues can help. However, the physicochemical properties of β-lapachone limit its application. The problem can be solved by using nanosystems to deliver β-lapachone. This mini-review summarizes quinone-based fluorescent, near-infrared and two-photon fluorescent probes, as well as nanosystems for delivering the NAD(P)H:quinone oxidoreductase 1-activating drug β-lapachone. This review provides valuable information for the future development of probes and nano-delivery systems that target NAD(P)H:quinone oxidoreductase 1. 相似文献
8.
9.
An in vitro study on the dental caries preventing effect of oligomeric procyanidins in sorghum episperm 总被引:1,自引:0,他引:1
Procyanidins are abundant in sorghum episperm. In this study, the effects of procyanidins from Sorghum bicolor (L.) moench episperm (sorghum procyanidins, SPC) in preventing dental caries were investigated through analysis on SPCs’ effects on cariogenic bacteria and ability in scavenging superoxide anion free radicals. In addition, the SPC with activity in preventing dental caries were identified. The ESI-MS/MS analysis results revealed that the compositions of SPC purified by macroporous resin were dimmers, trimers, tetramers, pentamers and hexamers of procyanidins and catechin/epicatechin monomers. The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) of SPC on Streptococcus mutans (Ingbritt C) and Streptococcus sobrinus 6715 were 8 and 16 mg/ml, respectively. The SPC had a remarkable inhibition effect (P < 0.05) on acid production of S. sobrinus (Ingbritt C) and S. mutans 6715 compared with the control group, and a dose-dependent relationship was observed. By increasing the concentration of SPC in the experimental condition (200–600 mg/L), the scavenging ratio of superoxide anion radicals increased significantly, indicating that SPC could be used as a potential dental-caries-preventative medicine with its antibacterial and antioxidant ability. 相似文献
10.
Fluid Mixing for Low‐Power ‘Digital Microfluidics’ Using Electroactive Molecular Monolayers 下载免费PDF全文
Maria Serena Maglione Stefano Casalini Stamatis Georgakopoulos Marianna Barbalinardo Vitaliy Parkula Núria Crivillers Concepció Rovira Pierpaolo Greco Marta Mas‐Torrent 《Small (Weinheim an der Bergstrasse, Germany)》2018,14(10)
A switchable electrode, which relies on an indium‐tin oxide conductive substrate coated with a self‐assembled monolayer terminated with an anthraquinone group (AQ), is reported as an electrowetting system. AQ electrochemical features confer the capability of yielding a significant modulation of surface wettability as high as 26° when its redox state is switched. Hence, an array of planar electrodes for droplets actuation is fabricated and integrated in a microfluidic device to perform mixing and dispensing on sub‐nanoliter scale. Vehiculation of cells across microfluidic compartments is made possible by taking full advantage of surface electrowetting in culture medium. 相似文献