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121.
The computational results for curcumin at the B3LYP/6-31G(d,p) level show that the enol form of curcumin is more stable than the diketo form because of an intramolecular hydrogen bond, which extends the conjugation effect in the enol chain, formed in the enol structure. Cis-diketone form can not be obtained, presumably due to the strong repulsion between the carbonyl dipoles aligned in parallel. According to the phenolic O-H bond dissociation enthalpy, curcumin in its most stable form can be suggested to be a relatively good antioxidant. In order to avoid overcoming H-bond interaction and to improve the antioxidant activity of curcumin, a catechol moiety was incorporated into curcumin for designing a novel antioxidant. It is found that the designed molecule is much more efficient to scavenge radical than curcumin, comparable to vitamin E. Moreover, the ionization potential of the designed molecule is similar to that of curcumin, indicating that the designed molecule can not display the prooxidant effect. 相似文献
122.
铂(Ⅳ)—钼酸盐—丁基罗丹明B缔合显色反应的研究 总被引:7,自引:0,他引:7
本文研究在聚乙烯醇(PVA)存在下,铂与钼酸铵和丁基罗丹明B(BRB)形成离子缔合物,该缔合物的最大吸收位于570nm,摩尔吸光系数ε值为9.26×10~5L·mol~(-1)·cm~(-1),服从比耳定律范围0~3.0μg Pt/25ml,缔合物至少稳定3周。测定铂的条件为C_(HClO_4)=1.4mol/L,C_(MoO_4~(2-)=1.1×10~(-3)mol/L,C_(BRB)=3.8×10~(-5)mol/L,0.08%PVA。考察了40多种共存离子的影响,除形成杂多酸的元素外,大多数不干扰。本法已用于催化剂和某些铂矿中铂的测定,结果较满意。 相似文献
123.
本文提出了一种快速、简便、灵敏检测痕量多胺的新方法。用对酞内酰胺苯甲酰氯同多胺进行柱前衍生反应,以反相高效液相色谱定量测定多胺含量。在4~500 pmol范围内有良好的定量线性关系,腐胺、精脒和精胺的检测限均为0.1 pmol。 相似文献
124.
HongBingJI DuGuiHE JunSONG YuQIAN 《中国化学快报》2004,15(10):1241-1244
Clean liquid oxidation of aldehydes can be accomplished using solid catalyst in the presence of molecular oxygen at room temperature, which is a valuable alternative to traditional counterparts. 相似文献
125.
Introduction Tremendous advances have been witnessed during the last decade in the syntheses and application of Group 4 metal complexes because of the motivity which comes from both academic and industrial field. Among them, studies have been dominated by the complexes supported by bis or mono cyclopentadienyl ligands, such as Cp2MX2 or half sandwich amide (CGC) com-plexes.1-6 At that time chemists paid a little attention to the non-cyclopentadienyl complexes, but in recent years, many chem… 相似文献
126.
A natural CXN zeolite (stilbite, type code-STI) discovered in China was modified with NH4^ exchange by using ammonium salt and calcinations (procedure Ⅰ), or with NH4 exchange followed by treatment with acid (procedure Ⅱ). The coordination state of Si and A1 atoms in the framework, the property of ion exchange, and the adsorption of the H-STI zeolite samples prepared by different modification procedure were investigated with XRD,EDX,^29Si and ^27Al MAS NMR, Ag^ ion exchange and Ne adsorption. The results of the investigations indicate that different procedure of the modification made variety on the distribution of the framework Si atoms and A1 atoms,the content of non-framework aluminum, and the blocking channels and the shielding effect to the positions of the exchangeable cations. The H-STI zeolite prepared by the procedure Ⅱ possesses high ion exchange capacity, open and perfect pore system, and high thermal stability. 相似文献
127.
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129.
Li Qiu WANG Xiao Jun PENG* Rong ZHANG Guo Quan XU Jing Nan CUI State Key Laboratory of Fine Chemicals Dalian University of Technology Dalian 《中国化学快报》2003,(1)
Indocyanine dyes as fluorescent labeling reagents have been used in bioanalysis1,2. Arylsulfonate indocyanine dyes 1d and 1e developed by Waggoner A. S. et al.3,4 have excellent fluorescent properties combined with good aqueous solubility, are a new generation of fluorescent label compounds for proteins, oligonucleotides and other compounds containing hydroxyl, mercaptol or primary amine groups5. However, photostability of these dyes has been a problem. Z. G. YAO et al.6 reported that p… 相似文献
130.
SHEN Yehua WANG Haibo BAI Quan & GENG Xindu Institute of Modern Separation Science Shaanxi Key Laboratory of Modern Separation Science Northwest University Xi''''an China 《中国科学B辑(英文版)》2005,(Z1)
The renaturation of the denaturedα-chymotrypsin (α-Chy) with 1.7 mol·L-1 gua-nidine hydrochloride (GuHCI) by three kinds of stationary phase of high performance hydropho-bic interaction chromatography (STHIC) with a comparable hydrophobicity but different ligand structures was investigated. The obtained result indicates that the ligand structures of the three STHIC contribute to the renaturation efficiency ofα-Chy in the order of the end ligands PEG-600< phenyl group < tetrahydrofurfuryl alcohol (THFA). 相似文献