Hydrogen-bonded assembly and binding affinity of the multi-point acceptor and isophthalic acid

Supermolecular complexes formed by oligophenyleneethynylene derivatives and isophthalic acid were studied using AM1 method to obtain binding energy. Electronic spectra and IR spectra of the complexes were calculated by INDO/CIS and AM1 methods based on AM1 geometries. Results indicated that the dimer could be formed by the monomers via hydrogen bonding because of the negative binding energy. Binding energy of the complexes was affected by electronegativity and steric effects of the substituents. The first UV absorptions and IR frequencies of N-H bonds of the complexes were both red-shifted compared with those of the monomers. The complexes could bind small molecules via hydrogen bonds, resulting in the change in UV absorptions and an increase in IR frequencies of N-H bonds.     

Expression and Purification of ZNF191（243-368） in Three Expression Systems

ZNF191 （243-368）, a new human zinc finger protein, probably relates to some hereditary diseases and cancers, To obtain adequate amount of ZNF191（243-368） for the study of its property, structure and function, three different expression systems of inclusion-body, glutathione S-transferase （GST）, and hexahistidine （6 × His） were used and compared. Among these systems, the expression level of ZNFI91（243-368） was increased in inclusion body system under a higher isopropylthio-β-D-galactoside （IPTG） concentration, but the non-target proteins were also increased more, which made its purification more difficult and the yield lower. The expression of His-tag fusion protein was almost not affected by IPTG concentration, temperature and inducing time. At a high IPTG concentration the highest expression yield for GST fusion protein was obtained. And the fusion proteins can be partially purified by a single affinity chromatography step. The fusion protein systems show advantages for expression of these proteins.     

单分散交联聚甲基丙烯酸环氧丙酯树脂的制备及亲合纯化伴刀豆球蛋白-A

采用一步种子溶胀聚合法制备了颗粒呈单分散的交联聚甲基丙烯酸环氧丙南树脂，对其环氧基的组成比进行了表征，并以氨基葡萄糖为配基，首次制备了纯化粗品伴刀豆球蛋白-A(Ⅲ）(Con-A，Ⅲ)的聚合物基质的高效亲合色谱柱。配基在树脂上的键合量为8．2mg／g，对纯化后的Con-A（Ⅲ）的吸附量为13．4mg／g。使用该亲合色谱介质成功地从粗品Con-A中快速纯化了Con-A，电泳分析显示为一个主要的谱带，纯度从15％提高到95％。     

Use of cluster expansion techniques in quantum chemistry. A linear response model for calculating energy differences

In this paper we have reviewed the theoretical framework of the coupled-cluster (cc) based linear response model as a tool for directly calculating energy differences of spectroscopic interest like excitation energy (ee), ionisation potential (ip) or electron affinity (ea). In this model, the ground state of a many-electron system is described as in a coupled cluster theory for closed shells. The electronic ground state is supposed to interact with an external photon field of frequencyw, and the poles of the linear response function as a function ofw furnish with the elementary excitations of the system. Depending on the general form of the coupling term chosen, appropriate difference energies like ee, ip or EA may be generated. Pertinent derivations of the general working equations are reviewed, and specific details as well as approximations for ee, ip or ea are indicated. It is shown that the theory bears a close resemblance to the equation of motion (eom) method but is superior to the latter in that the ground state correlation is taken to all orders and may be looked upon as essentially a variant of renormalisedtda. A perturbative analysis elucidating the underlying perturbative structure of the formulation is also given which reveals that the theory has a hybrid structure: the correlation terms are treated akin to an open shellmbpt, while the relaxation terms are treated akin to a Green function theory. A critique of the methodvis-a-vis other cc-based approaches for difference energies forms the concluding part of our review.     

自由体积与亲水性对环氧涂层防护性能的影响

报道了涂层聚合物自由体积和亲水性对涂层腐蚀防护性能影响的初步研究结果.实验表明,相对于自由体积,树脂的亲水性是决定树脂吸水率的更主要因素.低亲水性涂层腐蚀防护性能的提高主要源自到达涂层/金属界面的水量的显著降低.但由于采用活性酯固化的环氧树脂涂层中水通道的尺寸相对较大,水合离子扩散较容易,因此该类涂层覆盖下的金属基体被润湿部分的腐蚀趋势反而较一般涂层为大.     

极化效应指数与脂肪族胺、醇和醚气相碱性的关系

脂肪族胺、醇和醚的气相质子亲合能(PA)与N, O原子所带电荷(qx)以及烷基的极化效应指数(PEI)的关系可表示为其中a、b、c为系数。回归分析结果表明, 上式较好地表达了脂肪族胺、醇和醚的气相碱性变化规律。     

Carbonylation of Benzyl Halides Over Two-Phase Catalyst of Iron Pentacarbonyl

Carbonylation of benzyl halides to phenylacetic acid was studied in a two-phase system with iron pentacarbonyl as the catalyst precursor. The solutions consisted of a benzyl halide and iron pentacarbonyl in benzene and tetrabutylammonium hydrogen sulfate in aqueous sodium hydroxide. Stirring under carbon monoxide readily produced phenylacetic salts in aqueous phase which were then acidified and extracted with ether. The yields of phenylacetic acid from benzyl iodide and from benzyl bromide were similar at a evel of about 50percnt;, that of the latter being higher by 1%. The yield from benzyl chloride was far less, at a level of only 21%. The rate as studied with gas chromatography was found to decrease in the order benzyl iodide>benzyl bromide>benzyl chloride.     

The unimolecular chemistry of protonated glycine and the proton affinity of glycine: a computational model

The potential energy hypersurface of protonated glycine, GH⁺, has been investigated. The calculated G2(MP2) value for the proton affinity (PA) of glycine, PA _calc=895kJ mol⁻¹, is in good agreement with the experimental value which has been estimated to lie in the range 864kJ mol⁻¹ < PA _exp <891kJ mol⁻¹. Ab initio quantum chemical calculations of relevant parts of the potential energy surface of GH⁺ give a reaction model which is consistent with the observed mass spectrometric fragmentation pattern. The lowest energy unimolecular reactions of GH⁺ are two distinct processes: (1) loss of CO, which has a substantial barrier for the reverse reaction, and (2) loss of CO plus H₂O, which has no barrier for the reverse reaction. Received: 15 November 1996 / Accepted: 6 May 1997     

PREPARATION OF MICROGEL-EPOXY RESIN TWO-PHASE POLYMERS BY IN SITU POLYMERIZATION~*

Microgel-epoxy resin two-phase polymers were prepared by in situ copolymerization of ethylenic monomers with unsaturated polyesters. The choice of monomers and the effect of monomer concentration on microgel particle size were discussed. Agglomeration of particles played a significant role in the early stage of polymerization. The microgel dispersion in epoxy resin was stable after the finish of polymerization. Upon curing the particles remained well dispersed.