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151.
本文用微分脉冲极谱法研究了多酚氧化酶的活性测定和酶的反应动力学。应用于马铃薯等10余种植物样品的酶活力测定,结果良好。方法简便快速,重现性好。 相似文献
152.
Yan?Zhang Changchun?Wang Wuli?Yang Bin?Shi Shoukuan?FuEmail author 《Colloid and polymer science》2005,283(11):1246-1252
Biodegradable tri-component diblock copolymer was synthesized by bulk copolymerization of ε-caprolactone (CL) and D, L-lactide (LA) in the presence of methoxy poly(ethylene glycol) (MePEG), using stannous octoate as catalyst. Their chemical
structure and physical properties were investigated by GPC, NMR, DSC, TGAand XRD. The increase of CL/LA ratio in the diblock
copolymer leads to lower T
g, higher decomposition temperature and crystallinity. Nanoparticles formulated from MePEG–poly(CL-co-LA) (PCAE) possess spherical structure, which was characterized by dynamic light scattering (DLS) and transmission electron
microscopy (TEM). The DLS results indicate that the particle size increased with the increase of CL/LA ratio and the hydrophobic
fragment length in the copolymer. The drug encapsulation efficiency and the drug release behavior in vitro conditions of camptothecin
were measured by high performance liquid chromatography (HPLC). The encapsulation efficiency can be achieved as high as 84.4%
and the release behavior can be made well-controlled. MePEG–poly(CL-co-LA) nanoparticles might have a great potential as carriers for hydrophobic drugs. 相似文献
153.
A method has been developed for the speciation of trace dissolved Fe(II) and Fe(III) in water by coupling gallic acid (GA) modified nanometer-sized alumina micro-column separation with inductively coupled plasma mass spectrometry (ICP-MS). The separation of Fe(II) and Fe(III) was achieved based on the obvious difference in reaction kinetics between Fe(II) and Fe(III) with GA. Fe(III) was selectively retained on the micro-column at pH 5.5-6.5, while Fe(II) could not be retained by the micro-column at the whole tested pH range of 1.0-6.5, and passed through the micro-column. The Fe(II) can be determined by ICP-MS directly without preconcentration/separation procedure, while Fe(III) retained on the micro-column was then eluted with 1.0 mL of 1 mol L(-1) HCl and determined by ICP-MS. The parameters affecting the separation of Fe(II) and Fe(III) were investigated systematically and the optimum separation conditions were established. Under the optimized conditions, the detection limits of 0.48 microg L(-1) and 0.24 microg L(-1) with relative standard deviation of 5.6% and 4.3%(C= 5 microg L(-1), n= 7) for Fe(II) and Fe(III) were found, respectively. No obvious effect on the speciation of Fe(II) and Fe(III) was found with the change of the ratio of Fe(II) and Fe(III) from 0 ratio 10 to 10 ratio 0. The proposed method was applied for the determination of trace Fe(II) and Fe(III) in environmental water and the recoveries for spiked samples were found to be in the range of 97-105%. 相似文献
154.
采用示差脉冲伏安法,在乳酸脱氢酶(LDH)酶促体系“丙酮酸盐 + NADH +H+ (?) 乳酸盐 + NAD+”中,通过检测NAD+还原峰电流的变化,测定了不同条件下(不同酶用量、缓冲液pH值以及温度)LDH的活性、酶促体系的米氏常数KmNADH以及最大反应速率vmax。并且在最佳实验条件下,通过检测LDH活性的改变,实验考察了3种纳米物质(ZnS,TiO2(R)和TiO2(A))对乳酸脱氢酶酶促体系的影响。 相似文献
155.
In order to explore the transfer mechanism of chromium(III) in mammals, a novel complex [Cr(ASA)(en)2]Cl· 2H2O, bis(ethylenediamine‐ κ 2 N,N′)(4‐aminosalicylic acid‐ κ 2 O,O′) chromium(III) monochloride dihydrate was synthesized (4‐aminosalicylic acid=H2ASA, ethylenediamine=en). The crystal structure belongs to orthorhombic system with the space group P212121 by means of X‐ray diffraction. The characteristic for transfer of Cr3+ from the compound to the low‐molecular‐mass chelator EDTA and the iron‐binding protein apoovotransferrin (apoOTf) was followed by UV‐visible (UV‐Vis) and fluorescence spectra in 0.01 mol·L?1 Hepes at pH 7.4. The second order rate constants were calculated. Those spectra in conjunction were used to obtain more accurate information about the interaction of chromium complex with apoOTf. The experimental results indicate that Cr3+ can be transferred from the complex to apoOTf with the retention of the 4‐aminosalicylic acid acting as a synergistic anion. 相似文献
156.
Xiu Hui Lu Hai Bin Yu Wei Rong Wu Yue Hua Xu 《International journal of quantum chemistry》2007,107(2):451-457
Mechanisms of the cycloaddition reaction between singlet difluoromethylene carbene and acetone have been investigated with the second‐order Møller–Plesset (MP2)/6‐31G* method, including geometry optimization and vibrational analysis. Energies for the involved stationary points on the potential energy surface (PES) are corrected by zero‐point energy (ZPE) and CCSD(T)/6‐31G* single‐point calculations. From the PES obtained with the CCSD(T)//MP2/6‐31G* method for the cycloaddition reaction between singlet difluoromethylene carbene and acetone, it can be predicted that path B of reactions 2 and 3 should be two competitive leading channels of the cycloaddition reaction between difluoromethylene carbene and acetone. The former consists of two steps: (i) the two reactants first form a four‐membered ring intermediate, INT2, which is a barrier‐free exothermic reaction of 97.8 kJ/mol; (ii) the intermediate INT2 isomerizes to a four‐membered product P2b via a transition state TS2b with an energy barrier of 24.9 kJ/mol, which results from the methyl group transfer. The latter proceeds in three steps: (i) the two reactants first form an intermediate, INT1c, through a barrier‐free exothermic reaction of 199.4 kJ/mol; (ii) the intermediate INT1c further reacts with acetone to form a polycyclic intermediate, INT3, which is also a barrier‐free exothermic reaction of 27.4 kJ/mol; and (iii) INT3 isomerizes to a polycyclic product P3 via a transition state TS3 with an energy barrier of 25.8 kJ/mol. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 相似文献
157.
本文报道了一种新型三维亚磷酸锌[HO(CH2)2NH3]2•[Zn3(HPO3)4]的合成和晶体结构。在它的结构中,ZnO4和HPO3严格按照顶点连接的方式交替相连。骨架结构存在两个沿着不同方向无限延伸的由ZnO4和HPO3组成的四元环链,在[0 1 0]、[0 4 15]和[0 -4 15]三个方向形成了三个交叉8元环孔道,有机胺阳离子起着平衡电荷和稳定骨架的结构。它的晶体数据为:[HO(CH2)2NH3]2•[Zn3(HPO3)4],M=640.21, 正交晶系, Fdd2空间群, a=2.8528, b=0.8426, c=1.6159nm, Z=8, V=3.884nm3, R1=0.0219, wR2=0.0544。 相似文献
158.
QIN Jun XIE Ming-Gui JIANG Qing ZHAO Hua-Ming Department of Chemistry Sichuan University Chengdu Sichuan ChinaLIU Sheng-Chong Analytical Testing Center Sichuan University Chengdu Sichuan ChinaTAO Chang-Yuan Department of Chemistry Chongqing University Chongqing Sichuan China 《中国化学》1995,13(1):1-9
In view of the nature of orderness in structure and the mesomorphism in property of liquid crystal, the function of which is further exploited by integrating it with the feature of crown ether. The monoarmed crown ether liquid crystals are successfully applied to the imitation of biomembrane transport. Binary component membrane composed of crown ether liquid crystal and PVC was first developed. Such a novel model of biomimetic membrane is capable of imitating ingeniously the thermocontrolling transport of biomembrane, thus the essential function of liquid crystal in membane transport is more fully exploited. It was suggested, consequently, that the molecules of the crown ether liquid crystal could assemble themselves to form ionic channels, as they exist in mesophase.Of still more significance is that the thermocontrolling transport of ions through the membrane is found to be operative selectively and the permeation of ion is under the direct influence of the thermal turmoil of the crown ether liquid cr 相似文献
159.
由手性配体α-D-葡萄糖衍生物5,6,7以及薄荷醇(8)和葑醇(9),经 Ulmann偶联反应得到光学活性的(R)-和(S)-6,6′-二硝基联苯-2,2′- 二甲酸(4a),(R)-6,6′-二甲基联苯-2,2′-二甲酸(4b),(R)-1,1′-联萘-2 ,2′-二甲酸(13)。以三个手性膦酰胺16,17,18和CuCl组成的手性络合物为 催化剂,通过2-萘酚直接氧化偶联得到(S)-2,2′-联萘酚(15)。产物4, 13,15具有中等ee值的光学活性。 相似文献
160.