[n-C_(12)H_(25)NH_3]_2ZnCl_4配合物相变拉曼光谱研究

通式为[C_nH_(2n+1)NH_3]_2MX_4(M=Cu,Mn,Zn…、X=Cl,Br)(简写C_nM)四卤合金属酸二烷基铵系列化合物一般具有二维层结构。它是由薄的无机层阴离子MX_4~(2-)和厚的烷基铵阳离子[R-NH_3]~+组成的碳氢层规则交替构成的“夹心面包”型体系。这类化合物常存在固-固相变,并且有较大的相变潜热,有可能成为很有应用前景的一类新的低温储能材

杂多酸PMo_(12-x)V_x和PMo_(12-x)W_x的XPS研究 Ⅱ.氧的双电离能及轫致辐射诱导的磷、钼俄歇谱

利用式E_Ⅱ(min)=E_B(K)-E_i(L_(23)~+L_(23)~+)可以从OKL_(23)L_(23)价态型俄歇跃迁能量求出氧的双电离能,它与杂多酸的Bronsted质子酸有一定的对应关系。本文利用铝靶的轫致辐射诱导MoL_3M_(45)M_(45)和PKL_(23)L_(23)俄歇跃迁,实现了在一个阳极和同一次实验情况下,既测得Mo、P特征的电光电子峰,又记录了高动能的俄歇峰。Mo、P的俄歇谱可表明杂原子与杂多配位原子的关系。

稀土在催化剂中的应用

有关稀土催化剂的国内文献概况 根据历年《全国报刊索引》科技版“物理化学”中的“催化作用”部分及“试剂与纯化学品的生产”中的“催化剂”部分所作的调查统计,在1980年至1988年的9年间国内发表的有关稀土催化剂方面的文献共有112篇。

Ho~(3+):Gd_3Ga_5O_(12)晶体的光谱性质及强度参数

本文详细地研究了Ho~(3+):Gd_3Ga_5O_(12)(以下简称Ho~(3+):GGG)中Ho~(3+)离子在0.5～3.0μm波段内的室温及77K温度下的荧光光谱。根据Judd—Ofelt理论,计算了Ho~(3+)离子的自发辐射电偶跃迁几率与辐射寿命等光谱强度参数。

Er_(3x)~(3+):Y_(3-3x)Al_5O_(12)和Er_x~(3+)Yb_(1-x)P_5O_(14)晶体的光谱强度参数

本文报道了用J-O理论计算的Er_(3x)~(3+):Y_(3-3x)A_5O_(12)和Er_x~(3+)Yb_(1-x)P_5O_(14)两种晶体中Er~(3+)五种浓度的振子强度、Ω_λ参数、辐射跃迁几率与荧光分支比。并观察了这些参数的变化规律。

杂多酸催化性能的研究——Ⅱ.12-钼和12-钨杂多酸催化烯烃环氧化物与苯甲醇的醚化

研究了12-钼和12-钨磷酸在环氧乙烷和环氧(?)烷与苯甲醇的醚化反应中的催化作用。考查了反应条件对杂多酸催化活性的影响。实验结果表明,除了杂多酸中的质子在该反应中起着必要的作用外,杂多阴离子也有重要的催化作用。

杂多化合物催化性能的研究——Ⅲ.12-钼和12-钨系杂多酸催化的烷基苯与苯乙烯的烷基化反应

研究了 Keggin 型结构的12-钼和12-钨系杂多酸催化的烷基苯与苯乙烯的烷基化反应。实验发现,在12-铝磷酸存在下,烷基苯的烷基化活性序列为:间二甲苯>邻二甲苯>1,3,5-三甲苯>甲苯>对二甲苯;Keggin 型结构的杂多酸的中心原子和配位原子对其催化活性有明显影响,其中,12-钼磷酸给出最好的催化活性和选择性。根据动力学试验,求得了反应温度为 40—80℃时的苯乙烯反应的表观活化能为78.3kJ/mol.

RESEARCHES ON CHEMICALLY MODIFIED ELECTRODES - ELECTROCHEMISTRY OF 1-12 PHOSPHOMOLYBDIC HETEROPOLY ANION FILM MODIFIED ELECTRODE

A monolayer of 1:12 phosphomolybdic anion (PMo_(12)) was modified electrochemically on a glassy carbon electrode and its electrochemical behavior was studied with cyclic voltammetry (CV). It is shown that PMo_(12) film is adsoibed strongly on the surface of glassy carbon electrodes, H~+ ions in the solution plays an important role in the electrochemical processes of PMo_(12) film modified electrodes, whereas other anions, such as Cl~-, NO_3~-, SO_4~(2-), ClO_4~- and PO_4~(3-) etc., do not take par...

ELECTROCHEMICAL TRANSFER OF 12-SILICOTUNGSTATE ANION ACROSS THE WATER NITROBENZENE INTERFACE

It has been firstly found by means of cyclic voltammetry (CV) and chronopotentiometry with linear current-scanning (CLC)that 12-silicotungstate anion (SiW_(12)O_(40)~(4-)) with high charge numbers, large molecular volume and symmetric structure can cross

12-硅钨酸根离子在水/硝基苯界面的电化学转移

用循环伏安(CV)法和线性循环扫描电流计时电位(CLC)法首次研究发现带有高价电荷、体积大和高对称性的12-硅钨酸根离子(SiW_(12)O_(40)~(4-))可以在水/硝基苯界面进行电化学转移。SiW_(12)O_(40)~(4-)离子的CV曲线的特征

化学修饰电极的研究——1:12磷钼杂多阴离子薄膜修饰电极的电化学性质

自从化学修饰电极问世以来,在电极反应过程、电极效应以及扩展修饰薄膜类型方面进展较快。目前研究较多的是聚合物薄膜修饰电极,由于结构和化学性能的特点,对无机物修饰电极的研究也已引起重视。杂多酸具有很好的氧化还原性能,而且可通过改变化学组成的方法使杂多酸的氧化还原电位在很宽范围内变动。杂多酸可发生多电子还原反应形成“杂多蓝”,所以杂多酸或其盐类修饰在电极上有可能发生电催化和电色效应。目前杂多酸修饰电极的报道甚少。本文研

Molecular cloning and stress-dependent expression of a gene encoding Delta(12)-fatty acid desaturase in the Antarctic microalga Chlorella vulgaris NJ-7

The psychrotrophic Antarctic alga, Chlorella vulgaris NJ-7, grows under an extreme environment of low temperature and high salinity. In an effort to better understand the correlation between fatty acid metabolism and acclimation to Antarctic environment, we analyzed its fatty acid compositions. An extremely high amount of Delta(12) unsaturated fatty acids was identified which prompted us to speculate about the involvement of Delta(12) fatty acid desaturase in the process of acclimation. A full-length cDNA sequence, designated CvFAD2, was isolated from C. vulgaris NJ-7 via reverse transcription polymerase chain reaction (RT-PCR) and RACE methods. Sequence alignment and phylogenetic analysis showed that the gene was homologous to known microsomal Delta(12)-FADs with the conserved histidine motifs. Heterologous expression in yeast was used to confirm the regioselectivity and the function of CvFAD2. Linoleic acid (18:2), normally not present in wild-type yeast cells, was detected in transformants of CvFAD2. The induction of CvFAD2 at an mRNA level under cold stress and high salinity is detected by real-time PCR. The results showed that both temperature and salinity motivated the upregulation of CvFAD2 expression. The accumulation of CvFAD2 increased 2.2-fold at 15A degrees C and 3.9-fold at 4A degrees C compared to the alga at 25A degrees C. Meanwhile a 1.7- and 8.5-fold increase at 3 and 6% NaCl was detected. These data suggest that CvFAD2 is the enzyme responsible for the Delta(12) fatty acids desaturation involved in the adaption to cold and high salinity for Antarctic C. vugaris NJ-7.

Fatty acid biosynthesis in eukaryotic photosynthetic microalgae: Identification of a microsomal delta 12 desaturase in Chlamydomonas reinhardtii

Polyunsaturated fatty acids (PUFAs) are important components of infant and adult nutrition because they serve as structural elements of cell membranes. Fatty acid desaturases are responsible for the insertion of double bonds into pre-formed fatty acid chains in reactions that require oxygen and reducing equivalents. In this study, the genome-wide characterization of the fatty acid desaturases from seven eukaryotic photosynthetic microalgae was undertaken according to the conserved histidine-rich motifs and phylogenetic profiles. Analysis of these genomes provided insight into the origin and evolution of the pathway of fatty acid biosynthesis in eukaryotic plants. In addition, the candidate enzyme from Chlamydomonas reinhardtii with the highest similarity to the microsomal Delta 12 desaturase of Chlorella vulgaris was isolated, and its function was verified by heterologous expression in yeast (Saccharomyces cerevisiae).

Cys-92, Cys-95, and the C-terminal 12 residues of the Vibrio harveyi ferric uptake regulator (Fur) are functionally inessential

Ferric uptake regulator (Fur) is a global regulator involved in multiple aspects of bacterial life. The gene encoding the Vibrio harveyi Fur (Fur(vh)) was cloned from a pathogenic V. harveyi strain isolated from diseased fish. Furvh shares 77% overall sequence identity with the Escherichia coli Fur (Fur(Ec)) and could complement a mutant of Fur(Ec). Like Fur(Ec), Fur(Vh), possesses two cysteine residues at positions 92 and 95, yet unlike Fur(Ec), in which these cysteine residues constitute part of the metal ion coordination site and hence are vital to the repressor activity, C92 and C95 of Fur(Vh) proved to be functionally inessential. Further study identified a Vibrio Fur signature sequence, which is preserved in all the ten Vibrio Fur proteins that have been discovered to date but in none of the non-vibrio Fur proteins. Site-directed and random mutation analyses of the signature residues, the cysteine residues, and seven highly charged amino acid residues indicated that D9, H32, C137, and K138 of Fur(vh) are functionally important but D9, C137, and K138 can be replaced by more than one functional substitutes. Systematic deletion analysis demonstrated that the C-terminal 12 residues of Fur(Vh) are functionally inessential. These results (i) indicated that the activation mechanism, or certain aspects of which, of Fur(Vh) is possibly different from that of Fur(Ec); and (ii) suggested that it is not very likely that the C-terminal 12 residues play any significant role in the activation or stability of Fur(Vh); and (iii) provided insights into the potential function of the local structure involving C137 and K138.