Synthesis,crystal structure and magnetic properties of [RBzPy] [Fe(mnt)2] complexes ([RBzPy]+ = 1-(4′-R-benzyl)pyridinium,R = NO2 and CL; mnt2− = maleonitriledithiolate)

Ion-pair complexes consisting of the [Fe(mnt)₂]^– anion and [RBzPy]⁺ cations [R = NO₂ (1) or Cl (2)] have been prepared and characterized by elemental analysis and i.r. spectroscopy. The single crystal structure of (1) shows that the [Fe(mnt)₂]^– anions are dimeric, and that the coordination geometry of each Fe atom is square pyramidal. The most significant structural feature of (1) is that anions and cations form completely separate columns and – interactions occur within the cation columns. Thermal variations of _m T for the complexes indicated antiferromagnetic coupling within the dimer.     

Structure and magnetic properties of diaqua(4,4′-bipyridine) terbium(III) and the zinc(II) carboxylate dimer [Tb2Zn2(CH2C(CH3)COO)10(bipy)(H2O)2]2

A novel heteronuclear complex, [Tb₂Zn₂L₁₀(bipy)(H₂O)₂]₂ (HL = -methylacrylic acid, bipy = 4,4-bipyridine), was synthesized and characterized by elemental analysis and i.r. absorption spectra. Its structure, determined by X-ray diffraction, is a discrete octanuclear molecule, in which two Zn^II ions are linked by a bipy molecule and between Tb^III ions, or Tb^III and Zn^II ions are bridged by bidentate -methylacrylato groups. The temperature dependence of the magnetic susceptibility of the complex shows strong ferromagnetic interaction between the terbium atoms.     

RAMPED-UP NMR: multiplexed NMR-based screening for drug discovery

The crucial step in drug discovery is the identification of a lead compound from a vast chemical library by any number of screening techniques. NMR-based screening has the advantage of directly detecting binding of a compound to the target. The spectra resulting from these screens can also be very complex and difficult to analyze, making this an inefficient process. We present here a method, RAMPED-UP NMR, (Rapid Analysis and Multiplexing of Experimentally Discriminated Uniquely Labeled Proteins using NMR) which generates simple spectra which are easy to interpret and allows several proteins to be screened simultaneously. In this method, the proteins to be screened are uniquely labeled with one amino acid type. There are several benefits derived from this unique labeling strategy: the spectra are greatly simplified, resonances that are most likely to be affected by binding are the only ones observed, and peaks that yield little or no information upon binding are eliminated, allowing the analysis of multiple proteins easily and simultaneously. We demonstrate the ability of three different proteins to be analyzed simultaneously for binding to two different ligands. This method will have significant impact in the use of NMR spectroscopy for both the lead generation and lead optimization phases of drug discovery by its ability to increase screening throughput and the ability to examine selectivity. To the best of our knowledge, this is the first time in any format that multiple proteins can be screened in one tube.     

Novel design of a pentacyclic scaffold as structural mimic of saframycin A

The design, synthesis and evaluation of a pentacyclic scaffold, CWO-324 to mimic saframycin A is described. CWO-324 is readily synthesized in five steps from 1,4-diacetyl-piperazine-2,5-dione and 2,5-dimethoxybenzaldehyde. CWO-324 was found to scission DNA, binds to bases 69-83(5′-GCAGTCAGG CACCGT-3′) of Hind III/Rsa I from plasmid pBR322 DNA in a foot-printing study and possesses anti-tumor activity.     

Metal complex-substituted polysiloxanes as novel coatings for capillary electrophoresis and capillary electrochromatography

Two novel polysiloxane-based polymers, which contain metal complexes, have been prepared. To prepare the Co(TACN)3+(2) (TACN= 1,4,7-triazacyclononane) based polymers, an orthoamide derivative of TACN was added to bromobutane-substituted methylpolysiloxane and hydrolyzed with base. Co(II) was then coordinated to the TACN, followed by cobalt oxidation to make polymer A or followed by N-octyl TACN coordination and cobalt oxidation to make polymer B. In both materials, TACN forms thermodynamically and kinetically stable Co(TACN)3+(2) complexes in which the six coordination sites of the Co(III) are occupied by nitrogens from the TACN. The polymers were coated on fused-silica capillary columns and spherical silica particles, which were used for capillary electrophoresis and capillary electrochromatography, respectively. The open and packed columns showed strong and pH-independent reversed electroosmotic flow.     

笼形聚偕胺肟树脂的研究─—H_2PtCl_6在酸处理树脂上的吸附过程

H2PtCl6可被一系列的酸处理定形聚偕胺肟树脂所吸附，吸附容量的大小与处理树脂的质子酸的Pka值有关．认为是解高度低的酸所处理的树脂上的伯胺基成盐的机会较少，即树脂的吸附中心保留着较多的空穴，有利于H2PtCl6的接近而被吸附下来．吸附动力学的研究表明化学反应是吸附速度的控制因素。     

用傅里叶变换红外光谱法研究聚对苯二甲酸乙二酯的结构

用傅里叶变换红外光谱法,将一系列不同温度下退火的PET光谱与熔融淬火的PET光谱进行数字吸光度相减,得到不同结晶状态的“反式构象光谱”。进一步将不同温度退火的“反式构象光谱”(240℃和120℃)彼此相减,可得到“纯晶区的光谱”和“非晶区的反式构象光谱”。通过差示光谱的比较,发现一些新的谱带和谱带的变化。可用PET 的晶区和非晶区中其分子链的内旋转构象的变化解释。     

ALTERATION IN CHROMATIN CONFORMATION OF PROLIFERATING AND DIFFERENTIATING ENZYME GENES IN NORMAL MOUSE LIVER AND ASCITES HEPATOMA CELLS AND ITS RELATION TO THE GENE EXPRESSION OF ENZYMES

Nuclei from the normal mouse liver were partially digested with micrococcal nuclease, followed by DNA extraction, agarose gel clectrophoresis and dot blot hybridization with ~(32)P-labeled cDNA probes of CPS_1 and ACT complex, It was clearly shown that the CPS_1 genes were distributed on the monomer, dimer. and trimer of nucleosomes, while the genes coding for ACT complex were distributed on the condensed oligonucleosomes. An opposite manner of distribution of CPS_1 and ACT complex genes was, however, noted in the case of ascites hepatoma cells, in which the specific activity of ACT was 13 times higher than that in the normal liver, while that of CPS_1 was remarkably reduced. Similar patterns of change in mRNA level of CPS_1 and ACT complex were observed in the normal mouse liver and ascites hepatoma cells, indicating a close relationship between chromatin structure and gene expression of these enzymes.     

Enantioselective synthesis of nitroalkanes bearing all-carbon quaternary stereogenic centers through Cu-catalyzed asymmetric conjugate additions

The first examples of catalytic asymmetric conjugate addition (ACA) of alkylzinc reagents to trisubstituted nitroalkenes, leading to the formation of nitroalkanes bearing a quaternary carbon stereogenic center, are reported. Reactions are promoted in the presence of 4 mol % of a readily available amino acid-based phosphine and 2 mol % (CuOTf).C6H6. Cu-catalyzed reactions proceed efficiently in up to 98% ee and can be carried out with a variety of dialkylzinc reagents and trisubstituted nitroolefins. We highlight the synthetic utility of the products obtained by efficient conversion of optically enriched nitroalkanes to the corresponding carboxylic acids.     

铬酸引发丙烯腈与苎麻纤维接枝共聚反应

棉、麻类织物通过与乙烯类单体接枝共聚可以提高染色性、皱折回复性、耐磨性、防污性等［‘j．纤维素接枝共聚物的合成始于50年代，目前研究最多的是乙烯类单体通过自由基活性中间体与纤维素进行接技共聚，但此法存在一个突出的问题是在接技共聚的同时生成大量均聚物．铬酸（下文用Cr’“表示）是公认的强氧化剂，据报道［’－‘j，它单独存在时并不能引发乙烯类单体聚合，如果用Cr‘”引发乙烯类单体与纤维素接技共聚，均聚物的生成量将会减少．本文以Cr’”为引发剂，将丙烯睛（AN）与艺麻纤维进行接技共聚，考查不同条件对接技率及均聚…