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991.
Distribution of rare earth elements among chloroplast components of hyperaccumulator<Emphasis Type="Italic"> Dicranopteris dichotoma</Emphasis> 总被引:3,自引:0,他引:3
A rare earth element (REE) hyperaccumulator, Dicranopteris dichotoma, that accumulates more than 0.1% REEs dry leaf mass has been discovered in southern China. The different components of chloroplast were isolated and the concentration of REEs in each component was determined by ICP-MS. The experimental data indicated that about 8% of total leaf REEs was present in the chloroplast of Dicranopteris dichotoma. In order to thoroughly study the distribution of REEs among different components of chloroplast, the membrane of chloroplast, the intact thylakoid and the photosystem II (PS II system) of D. dichotoma were isolated from the chloroplast. It was found that half of total chloroplast REEs was stored at the membrane of the chloroplast and another half was in the thylakoid. And 25% of total chloroplast REEs was bound with PS II system of D.dichotoma. The concentration of REEs in chlorophyll a was only at the level of g/g on the bases of chlorophylls. These data are useful for understanding of both the storage of REEs in chloroplast and the effect of REEs on the photosynthesis of plants. 相似文献
992.
A series of copolylactones was synthesized by ring‐opening copolymerization of glycolide, L ‐lactide and ?‐caprolactone, using stannous octoate as catalyst. The in vitro degradation behaviors of them were studied and data demonstrated different degradation rates which mainly depended on the compositions. Investigation of the 5‐fluorouracil (5‐Fu) release from these copolylactones revealed that the composition, degradation rate and the morphology of the polymeric matrix played an important role on the drug release kinetics. A sustained 5‐Fu release without initial time lag was obtained from random poly(lactide‐co‐glycolide‐co‐caprolactone) (r‐PGLC) drug carrier, and it differed from the cases of polylactide (PLA) or random poly(lactide‐co‐glycolide) (PLGA), which usually showed an initial time lag or biphasic drug release behavior. It was due to the low glass transition temperature (T g) of the r‐PGLC and the drug would diffuse faster in rubbery state under the experimental temperature. Furthermore, a significant change in the drug release behavior of r‐PGLC was observed when the temperatures were changed around the T g of the drug carrier, which implied that the drug release behavior could be regulated by adjusting the morphology of the drug carrier. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
993.
BeiJIANG HuiYANG 《中国化学快报》2002,13(11):1083-1086
Two new ent-kauranc dierpenoids,sculponcatins L(1) and M (2) ,were isolated from the EtOAc extract of Isodon sculponeata.Their structures,were clucidated by spectroscopic cvidences.The cytotoxicities of 1 and 2 against human tumor cells k562 and T24 were tested. 相似文献
994.
995.
4,6-二硝基苯并氧化呋咱的制备、晶体结构及热分解机理 总被引:7,自引:0,他引:7
通过2,4,6-三硝基叠氮苯(TNAB)在冰醋酸中的关环反应,制备了4,6-二硝基苯并氧化呋咱(DNBF)、并培养出了DNBF的单晶.利用X射线单晶衍射、元素分析和红外光谱对其进行了结构表征.测试结果表明:DNBF晶体属单斜晶系,空间群为P21, a=0.7408(2) nm, b=0.6185(1) nm, c=0.9796(2) nm, β=107.99(2)°, V=0.4269(16) nm3, Z=2, Dc=1.759 g·cm-3, F(000)=228, μ(Mo Kα)=0.161 mm-1, R1=0.0483, wR2=0.1240, DNBF分子呈平面构型,其晶体为层状晶体.用TG-DTG和DSC研究了DNBF的热分解过程,在5 K·min-1的升温条件下,其熔点为173 ℃,在206~246 ℃之间发生剧烈分解反应,至429 ℃分解完全. 相似文献
996.
Photocatalytic reduction of CO2 to hydrocarbon compounds is a promising method for addressing energy shortages and environmental pollution. Considerable efforts have been devoted to exploring valid strategies to enhance photocatalytic efficiency. Among various modification methods, the hybridization of different photocatalysts is effective for addressing the shortcomings of a single photocatalyst and enhancing its CO2 reduction performance. In addition, metal-free materials such as g-C3N4 and black phosphorus (BP) are attractive because of their unique structures and electronic properties. Many experimental results have verified the superior photocatalytic activity of a BP/g-C3N4 composite. However, theoretical understanding of the intrinsic mechanism of the activity enhancement is still lacking. Herein, the geometric structures, optical absorption, electronic properties, and CO2 reduction reaction processes of 2D/2D BP/g-C3N4 composite models are investigated using density functional theory calculations. The composite model consists of a monolayer of BP and a tri-s-triazine-based monolayer of g-C3N4. Based on the calculated work function, it is inferred that electrons transfer from g-C3N4 to BP owing to the higher Fermi level of g-C3N4 compared with that of BP. Furthermore, the charge density difference suggests the formation of a built-in electric field at the interface, which is conducive to the separation of photogenerated electron-hole pairs. The optical absorption coefficient demonstrates that the light absorption of the composite is significantly higher than that of its single-component counterpart. Integrated analysis of the band edge potential and interfacial electronic interaction indicates that the migration of photogenerated charge carriers in the BP/g-C3N4 hybrid follows the S-scheme photocatalytic mechanism. Under visible-light irradiation, the photogenerated electrons on BP recombine with the photogenerated holes on g-C3N4, leaving photogenerated electrons and holes in the conduction band of g-C3N4 and the valence band of BP, respectively. Compared with pristine g-C3N4, this S-scheme heterojunction allows efficient separation of photogenerated charge carriers while effectively preserving strong redox abilities. Additionally, the possible reaction path for CO2 reduction on g-C3N4 and BP/g-C3N4 is discussed by computing the free energy of each step. It was found that CO2 reduction on the composite occurs most readily on the g-C3N4 side. The reaction path on the composite is different from that on g-C3N4. The heterojunction reduces the maximum energy barrier for CO2 reduction from 1.48 to 1.22 eV, following the optimal reaction path. Consequently, the BP/g-C3N4 heterojunction is theoretically proven to be an excellent CO2 reduction photocatalyst. This work is helpful for understanding the effect of BP modification on the photocatalytic activity of g-C3N4. It also provides a theoretical basis for the design of other high-performance CO2 reduction photocatalysts.
相似文献
997.
The catalytic combustion of various organic compounds has been investigated over noble and non-noble metal catalysts using
a fixed bed. It was concluded that the activity order of different organic compounds on a noble metal catalyst, is toluene
> 2-butanone > benzene >n-heptane≈isopropyl alcohol > acrylonitrile > cyclohexane. On non-noble metal catalyst, it is isopropyl alcohol > 2-butanone
> acrylonitrile > toluene >n-heptane > cyclohexane > benzene. In order to compare the thermal stability of catalysts, the catalytic reaction of toluene
has been studied over noble and non-noble metal catalysts which were calcined at various temperatures up to 900°C for 3 h. 相似文献
998.
Bei Ran Yuyu Yuan Wenxi Xia Mingle Li Qichao Yao Zuokai Wang Lili Wang Xiaoyu Li Yongping Xu Xiaojun Peng 《Chemical science》2021,12(3):1054
Antibiotic abuse causes the emergence of bacterial resistance. Photodynamic antibacterial chemotherapy (PACT) has great potential to solve serious bacterial resistance, but it suffers from the inefficient generation of ROS and the lack of bacterial targeting ability. Herein, a unique cationic photosensitizer (NB) and bacteriophage (ABP)-based photodynamic antimicrobial agent (APNB) is developed for precise bacterial eradication and efficient biofilm ablation. Thanks to the structural modification of the NB photosensitizer with a sulfur atom, it displays excellent reactive oxygen species (ROS)-production ability. Moreover, specific binding to pathogenic microorganisms can be provided by bacteriophages. The developed APNB has multiple functions, including bacteria targeting, near-infrared fluorescence imaging and combination therapy (PACT and phage therapy). Both in vitro and in vivo experiments prove that APNB can efficiently treat A. baumannii infection. Particularly, the recovery from A. baumannii infection after APNB treatment is faster than that with ampicillin and polymyxin B in vivo. Furthermore, the strategy of combining bacteriophages and photosensitizers is employed to eradicate bacterial biofilms for the first time, and it shows the excellent biofilm ablation effect as expected. Thus, APNB has huge potential in fighting against multidrug-resistant bacteria and biofilm ablation in practice.APNB for multidrug-resistant A. Baumannii therapy and biofilms ablation. 相似文献
999.
By employing one bridging ligand, 2,5‐pyridinedicarboxylate (2,5‐pda2?), in the presence or absence of another bridging ligand, 4,4′‐bipyridine (4,4′‐bpy), one one‐dimensional (1D) {[Co2(2,5‐pda)(2,5‐Hpda)2(4,4′‐bpy)(H2O)3]·6H2O}∞ ( 1 ) and two two‐dimensional (2D) coordination polymers, {[Cu3(2,5‐pda)3(H2O)3]·6H2O}∞ ( 2 ) and {[Co(2,5‐pda)(H2O)]·2H2O}∞ ( 3 ) were synthesized. Complexes 2 and 3 are characterized as concomitant polymorphs from a one‐pot reaction at ambient temperature. A comparison of the coordination geometries of all neutral and anionic coordination polymers containing {Mx(2,5‐pda)y(H2O)z}∞ available to date is presented. 相似文献
1000.
Bei Yan Guang-ji Wang Jian-guo Sun Fen-zhi Sun Xiao-yu Li Xiao-ming Wu Jin-yi Xu Yuan-ting Zheng Hua Lv 《Chromatographia》2007,66(1-2):55-61
A simple and sensitive reversed-phase LC-ESI-MS method to identify and quantitate 5-n-butyl-4-{4-[2-(1H-tetrazole-5-yl)-1H-pyrrol-1-yl]phenylmethyl}-2,4-dihydro-2-(2,6-dichloridephenyl)-3H-1,2,4-triazol-3-one (1b), a new Angiotensin II type 1 receptor antagonist in rat plasma has been developed and validated.
Sample preparation used a simple liquid–liquid extraction with ethyl acetate. Separation was achieved by gradient elution
on a C18 column. The mobile phase consisted of acetonitrile and water (0.05% triethylamine and 0.05% acetic acid) at a flow rate of
0.2 mL min−1. The detection utilized selected ion monitoring (SIM) in the negative mode at m/z 507.1 and m/z 407.2 for the deprotonated molecular ions of 1b and the internal standard irbesartan, respectively. The lower limit of quantification
was reproducible at 5 ng mL−1 with 100 μL of plasma and the good linear was observed in the 5–500 ng mL−1 range. This concentration range corresponded well with the plasma concentrations of 1b in pharmacokinetic studies. Recoveries
of 1b in rat plasma were 76.1, 74.6 and 79.0% at 5, 50 and 500 ng mL−1. The RSD of intra-assay and inter-assay variations were all less than 5%. This validated LC-ESI-MS assay is an economic,
quick, precise and reliable method for the analysis of 1b in pharmacokinetic studies. 相似文献