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981.
First separation of four aromatic acids and two analogues with similar structures and polarities from Clematis akebioides by high‐speed counter‐current chromatography
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Chengcheng Gong Tao Chen Huifeng Chen Shanshan Zhang Xinzhu Wang Weiqing Wang Jing Sun Yulin Li Zhixin Liao 《Journal of separation science》2016,39(23):4660-4666
In this paper, we report an efficient method by high‐speed counter‐current chromatography for the first separation of four aromatic acids and two analogs with similar structures and polarities from Clematis akebioides. First, the ethyl acetate extract was treated by silica gel column chromatography to enrich the target compounds. And then the fraction with target compounds were purified by high‐speed counter‐counter chromatography using a two‐phase solvent system consisting of chloroform/acetonitrile/water (10:6:4, v/v). The results showed high‐speed counter‐current chromatography could be a powerful technology for the separation of compounds with similar structures and polarities. Besides, it was found acetonitrile could be a good methanol substitute when a chloroform/methanol/water system could not provide a good separation factor. This study provides a reference for the separation of compounds from Clematis akebioides. 相似文献
982.
Room-Temperature Phosphorescence Turn-on Detection of DNA Based on Riboflavin-Modulated Manganese Doped Zinc Sulfide Quantum Dots 总被引:1,自引:0,他引:1
A sensitive phosphorescent sensor based on riboflavin (RF)-modulated mercaptopropionic acid (MPA)-capped Mn-doped ZnS quantum dots (QDs) was developed and utilized as room-temperature phosphorescence (RTP) sensor for DNA detection. The RTP of the MPA-capped Mn-doped ZnS QDs was stored via photoinduced electron transfer by RF, and formed an electrochemically nonactive QDs/RF nanohybrids through electrostatic attraction. In the presence of DNA, RF could bind with DNA, which has a double helical structure, via electrostatic interaction and intercalation. RF can be removed from the surface of the QDs, thus releasing the RTP of the QDs. On the basis of this principle, an RTP sensor for DNA detection was developed. Under optimal conditions, the detection limit for DNA was 15 μg mL?1, the relative standard deviation was 1.9 %, and the method recovery ranged from 97 % to 103 %. The proposed method was applied to biological fluids, in which satisfactory results were obtained. 相似文献
983.
Hui Li ShuJiang Zhang ChenLiang Gong JianZhi Wang Feng Wang 《Journal of fluorescence》2016,26(5):1555-1561
A new 4,5-diazafluorene-based fluorescent chemosensor has been synthesized by Schiff base condensation of 9,9-bis(3,5-dimethyl-4-aminophenyl)-4,5-diazafluorene with salicylaldehyde. The interaction of Schiff base with different metal ions has been studied over photofluorescent spectra. The results showed that Schiff base exhibited 194-fold enhancements in fluorescence at 465 nm after Zn2+ ions. Such fluorescent responses could be detected by naked eye under UV-lamp. The complex solution (L-Zn2+) exhibited reversibility with EDTA. 相似文献
984.
Huijuan Xie Yubing Gong Qi Wang 《The European Physical Journal B - Condensed Matter and Complex Systems》2016,89(7):161
In this paper, we numerically study how time delay induces multiple coherence resonance (MCR) and synchronization transitions (ST) in adaptive Hodgkin-Huxley neuronal networks with spike-timing dependent plasticity (STDP). It is found that MCR induced by time delay STDP can be either enhanced or suppressed as the adjusting rate Ap of STDP changes, and ST by time delay varies with the increase of Ap, and there is optimal Ap by which the ST becomes strongest. It is also found that there are optimal network randomness and network size by which ST by time delay becomes strongest, and when Ap increases, the optimal network randomness and optimal network size increase and related ST is enhanced. These results show that STDP can either enhance or suppress MCR and optimal STDP can enhance ST induced by time delay in the adaptive neuronal networks. These findings provide a new insight into STDP’s role for the information processing and transmission in neural systems. 相似文献
985.
Xiaozhuang Wang Yuekun Heng Zhi Wu Cheng Li Yongjie Sun Hongliang Dai Shengsen Sun Rongxing Yang Zhen Liu Ping Cao Jie Zhang Yun Wang Weijia Sun Siyu Wang Xiaolu Ji Jinzhou Zhao Wenxuan Gong Mei Ye Xiaoyan Ma Mingming Chen Meihang Xu Xiaolan Luo Kejun Zhu Zhenan Liu Xiaoshan Jiang 《The European Physical Journal C - Particles and Fields》2016,76(4):211
986.
987.
Lu W Du L Wang M Jia X Wen J Huang Y Guo Y Gong W Bao H Yang J Sun B 《Applied biochemistry and biotechnology》2007,142(1):17-28
A new method for breeding the hydrocortisone overproducing strain Curvularia lunata by screening ketoconazole-resistance mutant was developed. A hydrocortisone overproducing mutant C. lunata KA-91 with ketoconazole-resistance marker was obtained from protoplasts treated with ultraviolet radiation. The hydrocortisone
conversion rate of C. lunata KA-91 was increased by 42.1% compared to the original strain CL-114 at the substrate 17α-hydroxypregn-4-en-3, 20-dione-21-acetate
addition concentration of 1.0 g/L. The by-products produced by KA-91 were fewer than those of the original strain. It was
assumed that the higher cytochrome P450 content of ketoconazole-resistance mutant resulted in the increase of 11β-hydroxylation
capacity. The culture conditions for biotransformation of 17α-hydroxypregn-4-en-3, 20-dione-21-acetate to hydrocortisone were
optimized by response surface methodology. Plackett–Burman design was applied to elucidate the key factors affecting the hydrocortisone
production, and the results indicated that glucose, initial pH, and glucose to total nitrogen sources ratio (ω) had significant effects on hydrocortisone production. Box–Behnken design was employed to search for the optimal parameters
of those three key factors. According to the model, the trial checking at the optimal conditions showed a high hydrocortisone
conversion rate of 82.67%. 相似文献
988.
989.
990.
Gong J Vaidyanathan VG Yu X Kensler TW Peterson LA Sturla SJ 《Journal of the American Chemical Society》2007,129(7):2101-2111
Acylfulvenes (AFs) are a class of semisynthetic agents with high toxicity toward certain tumor cells, and for one analogue, hydroxymethylacylfulvene (HMAF), clinical trials are in progress. DNA alkylation by AFs, mediated by bioreductive activation, is believed to contribute to cytotoxicity, but the structures and chemical properties of corresponding DNA adducts are unknown. This study provides the first structural characterization of AF-specific DNA adducts. In the presence of a reductive enzyme, alkenal/one oxidoreductase (AOR), AF selectively alkylates dAdo and dGuo in reactions with a monomeric nucleoside, as well as in reactions with naked or cellular DNA, with 3-alkyl-dAdo as the apparently most abundant AF-DNA adduct. Characterization of this adduct was facilitated by independent chemical synthesis of the corresponding 3-alkyl-Ade adduct. In addition, in naked or cellular DNA, evidence was obtained for the formation of an additional type of adduct resulting from direct conjugate addition of Ade to AF followed by hydrolytic cyclopropane ring-opening, indicating the potential for a competing reaction pathway involving direct DNA alkylation. The major AF-dAdo and AF-dGuo adducts are unstable under physiologically relevant conditions and depurinate to release an alkylated nucleobase in a process that has a half-life of 8.5 h for 3-alkyladenine and less than approximately 2 h for dGuo adducts. DNA alkylation further leads to single-stranded DNA cleavage, occurring exclusively at dGuo and dAdo sites, in a nonsequence-specific manner. In AF-treated cells that were transfected with either AOR or control vectors, the DNA adducts identified match those from in vitro studies. Moreover, a positive correlation was observed between DNA adduct levels and cell sensitivity to AF. The potential contributing roles of AOR-mediated bioactivation and adduct stability to the cytotoxicity of AF are discussed. 相似文献