0IntroductionStudies of direct electrochemistry of proteins orenzymes at electrodes can serve as a basis for build-ing electrochemical biosensors,enzymatic bioreactors,and biomedical devices[1].This approach simplifiessuch devices without using mediators and is of partic-ular significance for fabricating the third generationbiosensors[2].For example,if a protein or enzyme im-mobilized on electrode surface is capable of directelectron transfer without loss of bioactivities,it can beused in the … 相似文献
Organic light emitting diodes with an interface of organic acceptor 3-, 4-, 9-,10-perylenetetracarboxylic dianhydride (PTCDA) and donor copper phthalocyanine (CuPc) involved in hole injection are fabricated. As compared to the conventional device using a 5 nm CuPc hole injection layer, the device using an interface of 10nm PTCDA and 5 nm CuPc layers shows much lower operating voltage with an increase of about 46% in the maximum power efficiency. The enhanced device performance is attributed to the efficient hole generation at the PTCDA/CuPc interface. This study provides a new way of designing hole injection. 相似文献
Qualitative characterization and quantitative analysis of labdane diterpenoids from Coleus forskohlii have been achieved by liquid chromatography hyphenated with photodiode-array detection and tandem electrospray ionization mass spectrometry (LC–DAD–ESI-MSn). By use of this method, thirteen forskolin-type diterpenoids were identified in the crude extract on the basis of their fragmentation mechanisms. Fragmentation rules were deduced from nine forskolin-type standards by ESI-MS in positive-ion mode. It was found that fragmentation behavior varied with the position and number of the substituents on the skeleton; this could be used for convenient identification of this type of compound. Six marker diterpenoids were also quantified, and the quality of both the cultivated and wild plants was evaluated.
Multidrug resistance (MDR) continues to be a major obstacle for successful anticancer therapy. In this work, fractions from 17 clinically used antitumour traditional Chinese medicinal herbs were tested for their potential to restore the sensitivity of MCF-7/ADR and A549/Taxol cells to a known antineoplastic agent. The effects of these fractions were evaluated by MTT method and an assay of the cellular accumulation of doxorubicin. Fractions from the PB group (herbs with the ability to promote blood circulation and remove blood stasis) showed more significant effects than fractions from the CH group (herbs with the ability to clear away heat and toxic materials). Fractions from CH?Cl? extracts were more effective than fractions from EtOAc extracts. Five herbs (Curcuma wenyujin, Chrysanthemum indicum, Salvia chinensis, Ligusticum chuanxiong Hort. and Cassia tora L.) could sensitise these resistant cancer cells at a non-toxic concentration (10?μg?mL?1), and markedly increased doxorubicin accumulation in MCF-7/ADR cells, which necessitates further investigations on the active ingredients of these herbs and their underlying mechanisms. 相似文献
Lathyranone A (1), a novel diterpenoid with a rearrangement skeleton, along with a known diterpenoid, Euphorbia factor L(11) (2), was isolated from the seeds of Euphorbia lathyris. The structure and relative stereochemistry of 1 were elucidated by extensive spectroscopic analysis. A possible biosynthetic pathway for lathyranone A (1) was proposed. 相似文献
Hostasinine A (1), a benzylphenethylamine alkaloid with an unprecedented skeleton featuring a C-4-C-6 linkage and a nitrone moiety, was isolated from Hosta plantaginea. Its structure was established on the basis of spectroscopic data, and was further confirmed by single-crystal X-ray diffraction. The alkaloid was postulated biogenetically from haemanthidine via N-oxidation and aza-aldol-type condensation and was synthesized biomimetically. The inhibitory activities of 1 on acetylcholinesterase (AChE) and two tumor cell lines (K562 and A549) were also evaluated. 相似文献
Eight new ring A-seco limonoids, aphanalides A–H (1–8) were isolated from the fruits of Aphanamixis polystachya. Aphanalides A–C (1–3) are the first examples of ring A-seco limonoids with an unusual oxetane ring between C-7 and C-14. The structures of aphanalide A (1) and aphanalide C (3) were confirmed by single-crystal X-ray studies. Their structures including absolute stereochemistry were established on the basis of extensive NMR spectroscopic analysis, by comparison of experimental and calculated electron circular dichroism (ECD) and by X-ray diffraction, representing the first report of assignment of absolute configuration of such type ring A-seco limonoids. The biogenetic origin of aphanalides A–D (1–4) from aphanalides E–H (5–8) was also postulated. 相似文献
A novel naphthalene glucoside, rheumone A (1), with an unprecedented skeleton containing a seven-membered lactone, and two new compounds, 1-O-phloroglucinyl-2-O-galloyl-6-O-cinnamoyl-β-D-glucoside (2) and chrysophanol 1-O-β-D-(6'-O-malonyl)glucoside (3), together with three known compounds (4-6) were isolated from the roots of Rheum palmatum. Their structures were elucidated mainly by spectroscopic analysis. These compounds were evaluated in vitro for their cytotoxicities towards human hepatocellular cancer cell lines Bel-7402 and Bel-7402/5Fu, and human gastric carcinoma cell line BGC-823. None of them showed cytotoxicity with IC(50) far beyond 50 μM. 相似文献