石墨炉原子吸收分光光度法测定大气颗粒物中锡

介绍了用石墨炉原子吸收分光光度法测定大气颗粒物中的锡,并进行了全程序空白值的测定、精密度测定,准确度测定,以及加标回收率实验,各项指标均符合实际要求。     

A novel three‐dimensional copper(II) network via hydrogen bonds: diaquabis[bis(pyrazol‐1‐yl‐κN2)methane]copper(II) diperchlorate

The crystal structure of the title complex, [Cu(C₇H₈N₄)₂(H₂O)₂](ClO₄)₂, consists of a discrete centrosymmetric [Cu(C₇H₈N₄)₂(H₂O)₂]²⁺ cation and two perchlorate anions. The Cu^II centre is six‐coordinated by four N donors from the two pyrazole rings [Cu—N 1.998 (2) and 2.032 (3) Å] and two O atoms from the water mol­ecules occupying the apical sites [Cu—O 2.459 (3) Å]. The coordination geometry of the complex can be described as octahedral. There is a unique three‐dimensional network in which the perchlorate units are linked by a combination of strong O—H?O and weak C—H?O hydrogen bonds.     

Chloro(2‐{[5‐(2‐hydroxy­benzyl‐O)‐1,5‐di­aza‐1‐cyclo­octyl‐N,N′]­methyl}phenolato‐O)­cadmium(II)

The crystal structure of the title complex, [Cd(C₂₀H₂₅­N₂­O₂)­Cl], reveals a hydrogen‐bonded dimer composed of neutral molecules. The Cd^II center is five‐coordinated by two O atoms of the pendant arms, two nitro­gen donors of the 1,5‐di­aza­cyclo­octane ring and a chloride anion. The coordination geometry of the complex could be described as a distorted square pyramid. The 1,5‐di­aza­cyclo­octane backbone adopts a boat/chair configuration and the two phenol/phenolato groups have a dihedral angle of 101.3 (2)° between them. The coordinated phenolate and phenolic groups of inversion‐related mol­ecules form strong intermolecular O—H?O hydrogen bonds.     

X射线光谱与神经网络中单组分型神经群结构研究

研究、比较了神经群结构与常规神经网络算法的预测性能,考察了过拟合与最佳拟合态等的关系。结果表明,在多元体系中,将神经网络单组分预测模型应用于Ｘ射线荧光光谱分析时,在预测准确度、模型稳定性和外推预测能力方面,神经群结构优于常规神经网络模型。     

Adaptive optical properties of ER fluid incorporating composite particles

Electrorheological (ER) fluid is one of the popular materials used in smart materials and structures. The material properties of ER fluid can be changed markedly while an external electric field is imposed on ER fluid domain. In this paper, the optical properties of ER suspensions consisting of composite particles dispersed in silicone oil are investigated. Both dc and ac electric fields are utilized to be imposed on ER fluid. The transmissivity of light through ER fluid under various electric fields is detected and analyzed. It is shown that the transmissivity of light increases with the increasing electric field strength and time. The change of transmissivity is caused by the formation of particle chains. The higher the particle concentration, the faster the change occurs. When an ac electric field is applied, the transmissivity can be affected by the frequency of electric field.     

单纵模Nd:YAG激光泵浦H2气中的受激喇曼散射

用单纵模Nd:YAG激光(波长1.06μm,脉宽9ns,线宽0.003cm-1)泵浦氢气中的受激喇曼散射,产生很强的后向一级斯托克斯.当泵浦能量为120mJ,压力为1.5MPaH2时,后向和前向喇曼的光子转化效率分别为66%和15%,而在4MPa时两个数值分别为46%和39%.由于后向喇曼与前向喇曼和泵浦光的传播方向相反,二者的相互竞争产生了张弛振荡,使得后向和前向喇曼的时间波形都分裂为两个峰,后向喇曼的两个峰都被压窄到1ns,使峰值功率达到了泵浦光功率的二倍,这在前向喇曼是不可能的.而且后向喇曼的光束质量要大大优于泵浦光和前向喇曼的光束质量,在4MPaH2和脉冲重复频率为10Hz时,喇曼过程的放热使前向喇曼的光束质量变坏,但对后向喇曼的光束质量影响不大.计算表明,该实验条件下受激喇曼过程没有达到稳态,所有实验结果都可以而且只能用相关的瞬态受激喇曼理论解释.     

稀土元素对磷钼钒杂多酸催化氧化活性的影响

讨论了镧的置換度和稀土元素对含氧有机化合物在杂多酸催化剂上的氧化反应的影响,并与催化剂的结构进行了关联。镧的引入不影响氧化脱氢反应,而明显削弱插入氧反应。其它稀土元素的影响与镧相同。     

Determination of the Protein-Protein Interactions within Acyl Carrier Protein (MmcB)-Dependent Modifications in the Biosynthesis of Mitomycin

Mitomycin has a unique chemical structure and contains densely assembled functionalities with extraordinary antitumor activity. The previously proposed mitomycin C biosynthetic pathway has caused great attention to decipher the enzymatic mechanisms for assembling the pharmaceutically unprecedented chemical scaffold. Herein, we focused on the determination of acyl carrier protein (ACP)-dependent modification steps and identification of the protein–protein interactions between MmcB (ACP) with the partners in the early-stage biosynthesis of mitomycin C. Based on the initial genetic manipulation consisting of gene disruption and complementation experiments, genes mitE, mmcB, mitB, and mitF were identified as the essential functional genes in the mitomycin C biosynthesis, respectively. Further integration of biochemical analysis elucidated that MitE catalyzed CoA ligation of 3-amino-5-hydroxy-bezonic acid (AHBA), MmcB-tethered AHBA triggered the biosynthesis of mitomycin C, and both MitB and MitF were MmcB-dependent tailoring enzymes involved in the assembly of mitosane. Aiming at understanding the poorly characterized protein–protein interactions, the in vitro pull-down assay was carried out by monitoring MmcB individually with MitB and MitF. The observed results displayed the clear interactions between MmcB and MitB and MitF. The surface plasmon resonance (SPR) biosensor analysis further confirmed the protein–protein interactions of MmcB with MitB and MitF, respectively. Taken together, the current genetic and biochemical analysis will facilitate the investigations of the unusual enzymatic mechanisms for the structurally unique compound assembly and inspire attempts to modify the chemical scaffold of mitomycin family antibiotics.     

硫醚与2-甲基-1,5-己二烯反应的机理研究

采用密度泛函理论对硫醚与2-甲基-1,5-己二烯的反应机理进行了详细的理论探究.计算结果表明,该反应历程主要包含活性物种的生成、2-甲基-1,5-己二烯的插入、另一分子的硫醚的碳氢键活化三部分.在2-甲基-1,5-己二烯插入步骤中,发现其采用6-5-re-插入时需要克服的活化能垒最低,反应时更为占优,在进行烯烃分子内碳碳双键插入完成闭环反应时相对比较容易.通过能量对比探明硫醚的C-H键活化需要克服的能垒最高,为该反应的速控步.     

Single-Shot Solid-Phase Synthesis of Full-Length H2 Relaxin Disulfide Surrogates

Chemical synthesis of insulin superfamily proteins (ISPs) has recently been widely studied to develop next-generation drugs. Separate synthesis of multiple peptide fragments and tedious chain-to-chain folding are usually encountered in these studies, limiting accessibility to ISP derivatives. Here we report the finding that insulin superfamily proteins (e.g. H2 relaxin, insulin itself, and H3 relaxin) incorporating a pre-made diaminodiacid bridge at A-B chain terminal disulfide can be easily and rapidly synthesized by a single-shot automated solid-phase synthesis and expedient one-step folding. Our new H2 relaxin analogues exhibit almost identical structures and activities when compared to their natural counterparts. This new synthetic strategy will expediate production of new ISP analogues for pharmaceutical studies.