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991.
Dan M.J. Doble Richard D. Kay Colin H. Benison Alexander J. Blake Xiang Lin Claire Wilson Martin Schröder 《Journal of inclusion phenomena and macrocyclic chemistry》2001,41(1-4):23-30
Reaction of tris-(2-aminoethyl)amine (tren) andthe sodium salt of an -ketocarboxylic acid, typically sodium pyruvate, affordsin the presence of a lanthanide ion aseries of complexes and aggregates includingmononuclear, cyclic tetranuclear and polymerspecies of [L1]3- ([L1]3-=N[CH2CH2N=C(CH3)COO-]3).The aggregation of these and related d-block elementcomplexes with Na+ ions leadsto the formation of polymeric materials, and thefactors influencing the formation and controlof these various aggregation states are discussed.Metal cations also template the aggregationof the fragment [Ni(L2)] ([L2]2- =CH2[CH2N = C(CH3)COO-]2)to give, in high yield, the polynuclearaggregates {[Ni(L2)]6M}x+(M = Nd, Pr, Ce, La, x = 3; M = Sr, Ba, x = 2). The structures of{[Ni(L2)]6M}x+ show aninterstitial twelve co-ordinate, icosahedralcation Mx+ encapsulated by six [Ni(L2)]fragments. In the presence ofNa+, aggregation of [Ni(L2)] fragments affords {[Ni(L2)]9Na4(H2O)(MeOH)(ClO4)}3+ thestructure of whichshows four Na+ ions templating the formation ofa distorted tricapped trigonal prismatic[Ni(L2)]9 cage. Thus, control overconstruction of various polynuclear cages viaself-assembly at octahedral junctions can beachieved using main group, transition metaland lanthanide ion templates. 相似文献
992.
Weizhen Lin Tiecheng Tu Jirong Dong Jiashang Zhang Nianyun Lin 《Radiation Physics and Chemistry》1998,53(6):651-655
ESR spectrum of neat histone H3 γ-irradiated and observed at 77 K with low microwave power and modulation amplitude showed multiple resolved structure depicting nonequivalent interaction of the unpaired electron located at amido-carbonyl radical anion [–
)NH–] of the peptide backbone with adjacent –NH– group and the β-proton of –CH group. The predominance of amido-carbonyl radical anion is in good accord with the expected partition of secondary electrons amongst the various electrophilic groups including peptide carbonyl and aromatic acid residues. Following a gradual rise of annealing temperature to room temperature, a double splitting spectrum from the well known -carbon amido radical was evolved. 相似文献
993.
钴(Ⅱ)-5-取代邻菲罗啉-α-氨基酸三元配合物的稳定性研究 总被引:5,自引:1,他引:5
本文在25.0±0.1℃,I=0.1mol·dm-3KNO3存在下,采用pH法测得了5-取代邻菲罗啉的质子化常数以及钴(Ⅱ)与5-取代邻菲罗啉、α-氨基酸的二元、三元配合物的稳定常数。结果表明三元配合物的稳定性与5-取代邻菲罗啉的质子化常数、取代基常数均存在直线自由能关系。并用三元配合物稳定性的表征值logKM、△logK,讨论了三元配合物的稳定性,发现钴(Ⅱ)与配体5-取代邻菲罗啉之间也存在着d-p反馈π键。该π健的强度对三元配合物稳定性有着显著影响。 相似文献
994.
To investigate the pharmacokinetics of adefovir as an anti-hepatitis B virus drug, a sensitive and specific liquid chromatography/tandem mass spectrometry method was developed and validated. After a simple protein precipitation using methanol, the post-treatment samples were analyzed on a C(18) column interfaced with a triple-quadrupole tandem mass spectrometer using positive electrospray ionization. A structural analogue, PMPA, was used as the internal standard. The method was linear in the concentration range 0.25-100 ng/mL. The lower limit of quantification was 0.25 ng/mL. The intra- and inter-day relative standard deviation over the entire concentration range was 5.7% or less. The accuracy determined at three concentrations (0.75, 10 and 80 ng/mL for adefovir) was within +/-2.5% relative error. The method described here was successfully applied for the evaluation of pharmacokinetic profiles of adefovir after single oral administration doses of 5, 10 and 20 mg adefovir dipivoxil to ten healthy volunteers. 相似文献
995.
Biosorption of copper(II) and zinc(II) from aqueous solution by Pseudomonas putida CZ1 总被引:1,自引:0,他引:1
Chen XC Wang YP Lin Q Shi JY Wu WX Chen YX 《Colloids and surfaces. B, Biointerfaces》2005,46(2):101-107
To study Pseudomonas putida CZ1, having high tolerance to copper and zinc on the removal of toxic metals from aqueous solutions, the biosorption of Cu(II) and Zn(II) by living and nonliving P. putida CZ1 were studied as functions of reaction time, initial pH of the solution and metal concentration. It was found that the optimum pH for Zn(II) removal by living and nonliving cells was 5.0, while it was 5.0 and 4.5, respectively, for Cu(II) removal. At the optimal conditions, metal ion biosorption was increased as the initial metal concentration increased. The adsorption data with respect to both metals provide an excellent fit to the Langmuir isotherm. The binding capacity of living cells is significantly higher than that of nonliving cells at tested conditions. It demonstrated that about 40-50% of the metals were actively taken up by P. putida CZ1, with the remainder being passively bound to the bacterium. Moreover, desorption efficiency of Cu(II) and Zn(II) by living cells was 72.5 and 45.6% under 0.1M HCl and it was 95.3 and 83.8% by nonliving cells, respectively. It may be due to Cu(II) and Zn(II) uptake by the living cells enhanced by intracellular accumulation. 相似文献
996.
文中采用机械合金化(MA)和氢化燃烧法(HCS)制备了Mg1.9Al0.1Ni,通过对它们储氢性能的对比研究发现,MA优于HCS.采用MA制得的Mg1.9Al0.1Ni储氢合金具有较高的活性和高储氢量,对PCT结果进行计算,得出温度和氢平衡压的关系式.Mg1.9Al0.1Ni(MA)553K时100s内吸放氢量分别为2.67和2.54 mass%H.用XRD方法进行物相分析,表明添加适量Al没有改变Mg2Ni的物相结构,由于MA能够制备出纳米晶粒,使得Mg1.9Al0.1Ni合金具有更好的储放氢动力学性能. 相似文献
997.
新型两亲性壳聚糖衍生物的合成、表征及对难溶性药物的增溶性 总被引:3,自引:0,他引:3
以天然可生物降解的壳聚糖为原料, 通过在壳聚糖6位羟基上引入羧甲基, 在2位氨基上引入疏水烷基链, 制得N-辛基-O,N-羧甲基壳聚糖(OCC)两亲性衍生物, 分别用FTIR、1H NMR和元素分析等技术对其结构进行表征, 用广角X射线衍射(WAXD)和差示扫描量热法(DSC)对其物理性质进行分析, 并考察其在各种溶剂中的溶解性能及其对难溶性药物的增溶能力. 所制备的OCC羧甲基取代度为115.9%, 取代主要发生在6位羟基上; 辛基取代度58.0%, 取代主要发生在2位氨基上; 与壳聚糖相比, OCC分子间/内氢键作用减弱; OCC在常用的有机溶剂中不溶, 但在水中溶解度增加, 能够形成具有淡蓝色乳光的纳米胶体溶液, 对难溶性抗肿瘤药物紫杉醇具有优越的增溶能力, 使紫杉醇在水中的溶解度提高近500倍, 载药量为34.6%(质量分数), 包封率为89.9%. OCC是潜在的优良的难溶性药物增溶载体材料. 相似文献
998.
Ya‐Ping Du Ya‐Wen Zhang Prof. Dr. Zheng‐Guang Yan Dr. Ling‐Dong Sun Prof. Dr. Song Gao Prof. Dr. Chun‐Hua Yan Prof. Dr. 《化学:亚洲杂志》2007,2(8):965-974
We report the synthesis of single‐crystalline and near‐monodispersed NaMF3 (M=Mn, Co, Ni, Mg), LiMAlF6 (M=Ca, Sr), and NaMgF3:Yb,Er nanocrystals (quasisquare nanoplates, nanorods, and nanopolygons) by the cothermolysis of multiple trifluoroacetates in hot combined organic solvents (oleic acid, oleylamine, and 1‐octadecene). The nanocrystals were characterized by XRD, TEM, superconductive quantum interference device (SQUID), and upconversion luminescence spectroscopy. By regulating the polarity of the dispersant, the NaMF3 (M=Mn, Co, Ni) nanoplates were partially aligned to form nanoarrays on copper TEM grids. The sizes of the NaMF3 nanocrystals were easily tuned by the use of proper synthetic conditions such as reaction temperature and time and solvent composition. On the basis of a series of experiments in which the reaction conditions were varied, together with GC–MS and FTIR analysis, the reaction pathways for the formation of these nanocrystals from trifluoroacetate precursors were proposed. The magnetic measurements showed that the differently sized NaMnF3 square plates displayed interesting weak ferromagnetic behavior on the nanometer scale. The strong red upconversion luminescence emitted from the NaMgF3:Yb,Er nanorods under 980‐nm near‐IR laser excitation suggests that NaMgF3 may be a good candidate host material for red upconversion luminescence. 相似文献
999.
In this study, we developed an analytical method for the enantioseparation of ofloxacin, using capillary electrophoresis with fluorescence detection. The optimum background electrolyte was obtained to be 60 mM hydroxylpropyl‐β‐cyclodextrin (HP‐β‐CD) in 50 mM phosphate buffer at pH 2.30. Under these conditions, the (+) and (‐) ofloxacin were completely separated, with the detection limit of 10 nM when the sample was prepared in deionized water. The linear ranges of levofloxacin in deionized water and untreated urine were 10?7 to 5 × 10?3 M with R2 = 0.9989 and 5 × 10?6to 5 × 10?3 M with R2 = 0.9943, respectively. We also applied this method to investigate the purity of a commercial drug. The results revealed that the ratio between (+)‐ofloxacin and (‐)‐ofloxacin (levofloxacin) was 99.9:0.1, and there is about 93 mg levofloxacin per tablet (200 mg). The concentration of levofloxacin in patient's urine was founded to be 7.9 × 10?4M, and the ratio between the two optical isomers was 99.3:0.7. 相似文献
1000.
羧基功能化的聚[(9,9-二辛基芴基-2,7-二基)-co-(1,4-苯并-{2,1′,3}-噻二唑)]聚合物点(PFBT-COOH)在无外加共反应试剂的条件下具有高的电致化学发光(ECL)信号,且过氧化氢(H_2O_2)对其ECL具有高效猝灭作用。采用PFBT-COOH修饰玻碳电极,进一步交联葡萄糖氧化酶(GOD)以构建酶传感器(GOD/PFBT-COOH/GCE)。随着检测底液中葡萄糖浓度的增加,葡萄糖在GOD催化下原位产生的H_2O_2量增加,导致传感器的ECL信号逐渐减弱,从而实现葡萄糖的准确、快速、灵敏检测。此方法测得葡萄糖的线性范围为1.0×10~(-7)~3.0×10~(-3) mol/L,检出限为3.0×10~(-8) mol/L。血清样品中葡萄糖的加标回收率为98.5%~106%。该策略为酶传感器的构建提供了新思路,为葡萄糖的检测提供了新方法。 相似文献