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991.
992.
Zhang H Zhang H Qu C Bai L Ding L 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2007,68(3):474-477
The inclusion complex of beta-cyclodextrin (beta-CD) and osthole was studied by the electrospray ionization mass spectrometry (ESI-MS) and fluorescence spectrometry. From the mass spectrum, the 1:1 stoichiometric inclusion complex of beta-CD and osthole was observed. The tandem mass spectrum was performed. The fluorescence intensity of osthole increased in the present of beta-CD. According to the 1:1 beta-CD-osthole mode, the dissociation constant (KD) was obtained by ESI-MS and fluorescence spectrometry. The KD of beta-CD-osthole inclusion complex is 6.96 x 10(-3) mol L(-1) obtained by mass spectrometry and that is 8.14 x10 (-3) mol L(-1) obtained by fluorescence spectrometry, which is consistent with each other. 相似文献
993.
Covalent modification of glassy carbon electrode with aspartic acid for simultaneous determination of hydroquinone and catechol 总被引:1,自引:0,他引:1
Glassy carbon electrode (GCE) is covalently modified with aspartic acid (Asp). The modified electrode is used for the simultaneous electrochemical determination of hydroquinone (HQ) and catechol (CC) and shows an excellent electrocatalytical effect on the oxidation of HQ and CC by cyclic voltammetry (CV) in 0.1 mol/L acetate buffer solution (pH 4.5). In differential pulse voltammetric (DPV) measurements, the modified electrode could separate the oxidation peak potentials of HQ and CC present in binary mixtures by about 101 mV though the bare electrode gave a single broad response. A successful elimination of the fouling effect by the oxidized product of HQ on the response of CC has been achieved at the modified electrode. The determination limit of HQ in the presence of 0.1 mmol/L CC was 9.0 x 10(-7) mol/L and the determination limit of CC in the presence of 0.1 mmol/L HQ was 5.0 x 10(-7) mol/L. The proposed method has been applied to the simultaneous determination of HQ and CC in a water sample with simplicity and high selectivity. 相似文献
994.
Research to the racemization reaction of L-amino acids is performed through a laboratory-made 16-channel capillary array electrophoresis. The impact factors such as catalyst, solvent, and reactive time which influenced the racemization reaction are screened, the experimental results proved that the capillary array electrophoresis is qualified as combinatorial enantiomeric screening system. 相似文献
995.
Sun Q Wei M Bai Y He C Meng Q Duan C 《Dalton transactions (Cambridge, England : 2003)》2007,(36):4089-4094
A series of Ag(I) coordination compounds, from one-dimensional chains to 3D porous frameworks, were achieved from N,N'-bis[1-(2-pyrazinyl)ethylidene]benzil dihydrazone, L, via self-assembly, using helicates as effective secondary building units. Compound 2 [(Ag(2.75)L)(NO(3))(2.75)] was comprised of two opposite-handed 3D frameworks formed by connecting the 4(1) helical chains into (10(3)-b) nets. The pairs of the racemic 3D frameworks were connected through additional silver(I) centers and entangled each other forming a racemic 3D net. Compound 3 [(Ag(13)L(8))(BF(4))(13)(H(2)O)(12)] was comprised of a 3D framework that was constructed from double-helical building intermediates Ag(2)L(2) with one-dimensional infinite chains being threaded into the large voids of a 3D framework to form a weave structure. The ladder-like chains in compound 4 [(Ag(3)L(2))(ClO(3))(3)(CH(3)OH)(2)(CH(3)CN)] were formed by the addition of excess NaClO(3) into the methanol solution containing AgNO(3) and the ligand L, and the zigzag chains in compound 5 [(Ag(2)L(2))(ClO(4))(2)(CH(3)CN)(2)] were constructed by the addition of excess NaClO(4) into an acetonitrile solution containing AgNO(3) and the ligand L. 相似文献
996.
997.
998.
简谐振动实验中阻尼力作用的估算 总被引:1,自引:0,他引:1
根据振动振幅随时间的衰减来得到阻尼系数,并估算了阻尼力对振动周期和总机械能的影响。 相似文献
999.
胍变及脲变α-淀粉酶的研究 Ⅰ.用高效疏水色谱法研究变性机理和复性效率 总被引:2,自引:2,他引:0
用疏水性强弱不同的两种色谱柱对7.0mol/L盐酸胍及8.0mol/L脲变性的α-淀粉酶变体和在疏水色谱介质表面上折叠的中间体进行了分离和复性。通过研究和比较发现,两者的变性机理和形成折叠中间体的个数以及复性效率均不相同。在用疏水性较弱的疏水色谱柱对脲变α-淀粉酶的折叠中间体进行分离时,得到了疏水性接近连续的、数目很多的中间体。用疏水性较强的疏水色谱柱对胍变α-淀粉酶进行复性的效果较好。还研究了柱温变化对其折叠、分离效果和复性效率的影响。 相似文献
1000.
I.IntroductionInrecentdecades,thescholarsinphysicalmechanicscircleshavegivenmuchmoreattentiontothequestionsofthestressesanddeformationsoftheelasticbodiesunderthecoupledinfluenceofthemechanicalfieldandelectromagneticfield,whichresultsinthefoeinganddevelopm… 相似文献