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51.
In this work, we have developed a novel hybrid two-dimensional counter-current chromatography and liquid chromatography (2D CCC × LC) system for the continuous purification of arctiin from crude extract of Arctium lappa. The first dimensional CCC column has been designed to fractionalize crude complex extract into pure arctiin effluent using a one-component organic/salt-containing system, and the second dimensional LC column has been packed with macroporous resin for on-line adsorption, desalination and desorption of arctiin which was effluent purified from the first CCC dimension. Thus, the crude arctiin mixture has been purified efficiently and conveniently by on-line CCC × LC in spite of the use of a salt-containing solvent system in CCC separation. As a result, high purity (more than 97%) of arctiin has been isolated by repeated injections both using the ethyl acetate–8% sodium chloride aqueous solution and butanol–1% sodium chloride aqueous solution. By contrast with the traditional CCC processes using multi-component organic/aqueous solvent systems, the present on-line CCC × LC process only used a one-component organic solvent and thus the solvent is easier to recover and regenerate. All of used solvents such as ethyl acetate, n-butanol and NaCl aqueous solution are low toxicity and environment-friendly. Moreover, the lower phase of salt-containing aqueous solution used as mobile phase, only contained minor organic solvent, which will save much organic solvent in continuous separation. In summary, our results indicated that the on-line hybrid 2D CCC × LC system using one-component organic/salt-containing aqueous solution is very promising and powerful tool for high-throughput purification of arctiin from fruits of A. lappa. 相似文献
52.
Jiayi Chen Dr. Dashuai Wang Xiaoxuan Yang Wenjun Cui Prof. Dr. Xiahan Sang Zilin Zhao Dr. Liguang Wang Dr. Zhongjian Li Dr. Bin Yang Prof. Dr. Lecheng Lei Prof. Dr. Jinyang Zheng Prof. Dr. Liming Dai Prof. Dr. Yang Hou 《Angewandte Chemie (International ed. in English)》2023,62(10):e202215406
Cu-based catalysts have been widely applied in electroreduction of carbon dioxide (CO2ER) to produce multicarbon (C2+) feedstocks (e.g., C2H4). However, the high energy barriers for CO2 activation on the Cu surface is a challenge for a high catalytic efficiency and product selectivity. Herein, we developed an in situ *CO generation and spillover strategy by engineering single Ni atoms on a pyridinic N-enriched carbon support with a sodalite (SOD) topology (Ni-SOD/NC) that acted as a donor to feed adjacent Cu nanoparticles (NPs) with *CO intermediate. As a result, a high C2H4 selectivity of 62.5 % and an industrial-level current density of 160 mA cm−2 at a low potential of −0.72 V were achieved. Our studies revealed that the isolated NiN3 active sites with adjacent pyridinic N species facilitated the *CO desorption and the massive *CO intermediate released from Ni-SOD/NC then overflowed to Cu NPs surface to enrich the *CO coverage for improving the selectivity of CO2ER to C2H4. 相似文献
53.
Ye Gong Rui Liu Hongjing Zha Ding Dong Dr. Nihong Lu Hui Yan Dr. Luosheng Wan Dr. Yin Nian 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2024,136(1):e202313461
Low-voltage-gated calcium channels (LVGCCs; Cav3.1-3.3) represent promising drug targets for epilepsy, pain, and essential tremor. At present, modulators with heightened selectivity for a subtype of LVGCCs are still highly desired. In this study we explored three classes of Buxus alkaloids and identified 9(10/19)abeo-artanes Buxusemine H and Buxusemine L (BXSL) as an unprecedented type of Cav3.2 inhibitors. Particularly, BXSL exhibited Cav3.2 inhibition comparable to Z944, a non-subtype-selective LVGCCs inhibitor under clinical trial. While lacking specificity for Cav3.3, BXSL showed a 30-fold selectivity of Cav3.2 over Cav3.1. As compared to several well-known inhibitors, the experimental and computational studies suggested BXSL exhibits a distinct binding mode to Cav3.2, notably through the essential interaction with serine-1543 in domain III. Furthermore, BXSL showed minimal impact on various recombinant and native nociceptive ion channels, while significantly reducing the excitability of isolated mouse dorsal root ganglion neurons. Animal studies in wild-type and Cav3.2 knock-out mice revealed that BXSL (5 mg/kg), by inhibiting Cav3.2, exhibits an analgesic effect equivalent to Z944 (10 mg/kg) or mibefradil (10 mg/kg). Moreover, we proposed a structural rationale for the high selectivity of 9(10/19)abeo-artane-type alkaloids towards Cav3.2 over Cav3.1. This study introduces a novel analgesic agent and valuable molecular insight for structure-based innovative Cav3.2 drug development. 相似文献
54.
55.
56.
Managing environmental contamination with Benz[a]anthracene (B[a]A) is essential due to its carcinogenic, teratogenic and mutagenic effects on humans and the environment. At present, the mainly B[a]A degradation methods used are photodegradation, bioremediation and traditional advanced oxidation, although they all have disadvantages. In this study, B[a]A was degraded by hydrodynamic cavitation (HC), chlorine dioxide (ClO2), or an innovative combination of the two methods. According to high performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC–MS) analysed the degradation products and degradation pathway of B[a]A, with the kinetics of different degradation methods discussed. Under optimal conditions, HC combined with ClO2 oxidation can further degrade products to achieve ring cleavage. Compared with the two separate degradation process methods, the combined method exerts a synergistic effect on the degradation of B[a]A, with an enhancement factor of 1.48. Experimental results showed that the combination method can realize enhanced complete degradation of B[a]A, reduce ClO2 requirements, improve efficiency, reduce energy consumption and produce less harmful products with ring cleavage achieved. 相似文献
57.
给定Hilbert空间L2[a,∞)上两个由2n阶对称微分算式生成的微分算子Li(i=1,2),该文给出了乘积算子L2L1是自伴算子的一个充分必要条件. 相似文献
58.
Squares of characters and finite groups 总被引:1,自引:0,他引:1
Let G be a finite group and χ be an irreducible complex character. We study the character χ2 in the case that χ(1) is a prime power. 相似文献
59.
Let S be the multiplicative semigroup of q×q matrices with positive entries such that every row and every column contains a strictly positive element. Denote by (X
n
)
n≥1 a sequence of independent identically distributed random variables in S and by X
(n)=X
n
⋅⋅⋅
X
1, n≥1, the associated left random walk on S. We assume that (X
n
)
n≥1 satisfies the contraction property
where S° is the subset of all matrices which have strictly positive entries. We state conditions on the distribution of the random
matrix X
1 which ensure that the logarithms of the entries, of the norm, and of the spectral radius of the products X
(n), n≥1, are in the domain of attraction of a stable law.
相似文献