Investigation of Aconitine-type Alkaloids from Processed Tuber of Aconitum carmiechaeli by HPLC-ESI-MS/MS~n

Introduction Aconitine-type alkaloids isolated from the roots of Aconitum carmiechaeli show a potential toxicity and a broad spectrum of bioactivity[1-4].On the basis of the C8-substituent of C19-diterpenoid skeleton,aconitine-type alkaloids can be divided into diester-diterpenoid alkaloids(DDAs),monoester-diterpenoid alkaloids(MDAs),and lipo-alkaloids(Fig.1).     

A new serratane-type triterpene from Lycopodium phlegmaria

A new serratane-type triterpene, lycophlegmarin (1), has been isolated from Lycopodium phlegmaria L. Four known related triterpenoids were also found from the title plant. The structure of the new compound was elucidated on the basis of detailed spectroscopic analysis and chemical method. Lycophlegmarin exhibited modest growth-inhibitory activity in vitro against human hepatoma cells BEL 7402.     

A Novel Asymmetric Synthesis of （-）-cis-1, 3-Dibenzylhexahydrofuro[3, 4-d]imidazole-2,4-dione

(-)-cis-1, 3-Dibenzyl-hexahydrofuro[3, 4-d]imidazole-2, 4-dione was prepared by a new synthesis method from meso dicarboxylic acid and dehydroabietylamine by asymmetric reduction in good yield with up to 91.6% e.e. value.     

Enantioseparation in capillary electrophoresis using 2-O-(2-hydroxybutyl)-beta-CD as a chiral selector

The resolving ability of 2-O-(2-hydroxybutyl)-beta-CD (HB-beta-CD) with different degrees of substitution (DS = 2.9 and 4.0) as a chiral selector in CZE is reported in this work. Fourteen chiral drugs belonging to different classes of compounds of pharmaceutical interest such as beta-agonists, antifungal agents, ageneric agents, etc., were resolved. The effects of the DS of HB-beta-CD on separations were also investigated. The chiral resolution (R(s)) was strongly influenced by the concentrations of the CD derivative, the BGE, and the pH of the BGE. Under the conditions of 50 mmol/L Tris-phosphate buffer at pH 2.5 containing 5 mmol/L HB-beta-CD, all 14 analytes were separated. The very low concentration necessary to obtain separation was particularly impressive. The DS had a significant effect on the resolution of the chiral drugs and the ionic strength of the separation media; hence, the use of a well-characterized CD derivative is crucial.     

Luminescence in NaLn(SO4)2H2O: A host lattice with high-energy vibrations

The luminescence of Ce³⁺, Sm³⁺, Eu³⁺, Gd³⁺, Tb³⁺, and Dy³⁺ in NaLn(SO₄)₂H₂O (Ln = lanthanide) is reported. Only Ce³⁺, Gd³⁺, and Tb³⁺ show efficient emission. This is explained in terms of an energy-gap law. Energy transfer is studied in several codoped compositions. The mutual transfer between Gd³⁺ ions is the only one encountered with high probability. The several transfers are discussed and where possible their rates are calculated.     

Cu-Mg/Al复合氧化物催化碳颗粒物燃烧性能的研究

恒定二价与三价阳离子比为3(nM2+/nM3+=3),采用共沉淀法制备不同Cu含量的系列水滑石前驱物, 800 ℃焙烧4 h形成复合氧化物(CuO质量百分数分别为0％、5％、10％、15％、20％、30％、40％)用作柴油车排放碳颗粒物燃烧的催化剂,并采用XRD、BET、TG-DSC、FT-IR、TPR等表征手段研究了Cu、Mg含量对材料前驱物物化性能的影响及对其衍生复合氧化物催化碳颗粒物燃烧性能的影响．结果表明,Cu、Mg含量对材料的热稳定性、比表面和催化氧化活性有显著的影响. Mg有助于提高催化剂的热稳定性; Cu含量增加,催化剂比表面下降,但比表面不是影响催化剂活性的主要因素. CuO含量为15％时,催化剂具有最好的催化活性和稳定性,碳颗粒物的起燃温度(T10)和半转化温度(T50)分别为336 ℃和409 ℃.在CuO含量≤30％时可以形成结构完整的水滑石前驱物, CuO含量为40％时出现Cu(OH)2杂相; CuO含量< 20％时,经高温焙烧可得到均匀的复合氧化物, CuO含量≥20％时出现CuO偏析． TPR结果表明焙烧温度和复合氧化物的组成决定了材料的可还原性能．     

Structures of E. coli peptide deformylase bound to formate: insight into the preference for Fe2+ over Zn2+ as the active site metal

E. coli peptide deformylase (PDF) catalyzes the deformylation of nascent polypeptides generated during protein synthesis. While PDF was originally thought to be a zinc enzyme, subsequent studies revealed that the active site metal is iron. In an attempt to understand this unusual metal preference, high-resolution structures of Fe-, Co-, and Zn-PDF were determined in complex with its deformylation product, formate. In all three structures, the formate ion binds the metal and forms hydrogen-bonding interactions with the backbone nitrogen of Leu91, the amide side chain of Gln50, and the carboxylate side chain of Glu133. One key difference, however, is how the formate binds the metal. In Fe-PDF and Co-PDF, formate binds in a bidentate fashion, while in Zn-PDF, it binds in a monodentate fashion. Importantly, these structural results provide the first clues into the origins of PDF's metal-dependent activity differences. On the basis of these structures, we propose that the basis for the higher activity of Fe-PDF stems from the better ability of iron to bind and activate the tetrahedral transition state required for cleavage of the N-terminal formyl group.     

Electrospray ionization tandem mass spectrometric study of salt cluster ions. Part 1--investigations of alkali metal chloride and sodium salt cluster ions

Salt cluster ions of alkali metal chlorides ACl (A = Li(+), Na(+), K(+), Rb(+) and Cs(+)) and sodium salts NaB (B = I(-), HCOO(-), CH(3)COO(-), NO(2)(-), and NO(3)(-)), formed by electrospray ionization, were studied systematically by mass spectrometry. The influences on the total positive ion and negative ion currents of variation of solvent, solution concentration, desolvation temperature, solution flow-rate, capillary voltage and cone voltage were investigated. Only cone voltage was found to influence dramatically the distribution of salt cluster ions in the mass spectra observed. Under conditions of normal cone voltage of approximately 70 V, cluster ions having magic numbers of molecules are detected with high relative signal intensity. Under conditions of low cone voltage of approximately 10 V, the distribution of cluster ions detected is characterized by a relatively low average mass/charge ratio due to the presence of multiply charged cluster ions; in addition, there is a marked reduction in cluster ions having a magic number of molecules. Product ion mass spectra obtained by tandem mass spectrometry of cluster ions are characterized by a base peak having a magic number of molecules that is less than and closest to the number of molecules in the precursor ion. Structures have been proposed for some dications and some quadruply charged ions. At pH 3 and 11, the mass spectra of NaCl clusters show the presence of mixed clusters of NaCl with HCl and NaOH, respectively. The effects of ionic radius on 20 distributions of cluster ions for 10 salts were investigated; however, the fine structure of these effects is not readily discerned.     

Intermolecular potential energy surface and spectra of He-HCl with generalization to other rare gas-hydrogen halide complexes

A two-dimensional (rigid monomer) intermolecular potential energy surface (PES) of the He-HCl complex has been obtained from ab initio calculations utilizing the symmetry-adapted perturbation theory (SAPT) and an spdfg basis set including midbond functions. The bond length in HCl was chosen to be equal to the expectation value in the ground vibrational state of isolated HCl. The rigid-monomer potential should be a very good approximation to the complete (three-dimensional) potential for H-Cl distances corresponding to the lowest vibrational levels of the monomer since the He-HCl interaction energy was found to be only weakly dependent on the HCl bond length in this region, at least as compared to systems such as Ar-HF. The calculated points were fitted using an analytic function with ab initio computed asymptotic coefficients. As expected, the complex is loosely bound, with the dispersion energy providing the majority of the attraction. Our SAPT PES agrees with the semiempirical PES of Willey et al. [J. Chem. Phys. 96, 898 (1992)], in finding that, atypically for rare gas-hydrogen halide complexes including the lighter halide atoms, the global minimum is on the Cl side (with intermonomer separation 3.35 A and depth of 32.8 cm(-1)), rather than on the H side, where there is only a local minimum (3.85 A, 30.8 cm(-1)). The ordering of the minima was confirmed by single-point calculations in larger basis sets and complete basis set extrapolations, and also using higher levels of theory. We show that the opposite findings in the recent calculations of Zhang and Shi [J. Mol. Struct: THEOCHEM 589, 89 (2002)] are due to the lack of midbond functions in their basis set. Despite the closeness in depth of the two linear minima, the existence of a relatively high barrier between them invalidates the assumption of isotropy, a feature of some literature potentials. The trends concerning the locations of minima within the family of rare gas-hydrogen halide complexes are rationalized in terms of the physical components of the intermolecular forces and related to monomer properties. The accuracy of the SAPT PES was tested by performing calculations of rovibrational levels. The transition frequencies obtained were found to be in excellent agreement (to within 0.02 cm(-1)) with the measurements of Lovejoy and Nesbitt [J. Chem. Phys. 93, 5387 (1990)]. The SAPT PES predicts a dissociation energy for the complex of 7.74 cm(-1) which is probably more accurate than the experimental value of 10.1+/-1.2 cm(-1). Our analysis of the ground-state rovibrational wave function shows that the He-HCl configuration is favored over the He-ClH configuration despite the ordering of minima. This is due to the greater volume of the well in the former case. We have also determined positions and widths of three low-lying resonance states through scattering calculations. These predictions are expected to be more accurate than values derived from experiment.     

Synthesis of a Tweezer—like Bis（Phenylthiapropoxy）calix[4]—arene as a Cation／π Enhanced Sensor for Ion—Selective Electrodes

Two novel 25,27-dihydroxy-26,28-bis(3-phenylthiapropxy)-calix[4]arene(3) and 25,27-dihydroxy-26,28-bis(3-phenylthiapropoxy)-5,11,17,23-tetra-tert-butylcalix[4] arene (4) were synthesized for the evaluation of their ion-selectivity in ion-selective electrodes(ISEs).ISEs based on 3 and 4 as neutral ionophores were prepared,and their selectivity coefficients for Ag^ (lg KAg,M^pot)were investigated against other alkali metal,alkaline-earth metal,aluminum,thallium(Ⅰ）,Lead and some transition metal ions using the separate solution method (SSM).These ISEs showed excellent Ag^ seletivity over most of the interfering cations examined,except for Hg^2 and Fe^2 having relative smaller interference(lg KAg,M^pot≤-2.1).