Synthesis and Structural Characterization of cis- and trans-bis(4,4′-dimethyl-2,2′-bipyridine)cadmium(II) Nitrates Prepared in a One-pot Reaction

The cis and trans isomers of [Cd(dmbpy)₂](NO₃)₂] (dmbpy = 4,4′-dimethyl-2,2′-bipyridine) have been synthesized simultaneously via a one-pot reaction of Cd(NO₃)₂ · 4H₂O with the dmbpy ligand in a MeOH/H₂O mixture; they can be obtained individually by means of the mechanical separation due to their different growing habit of the single-crystals. Different π-stacking interactions are observed in the cis and trans isomers forming different one-dimensional networks. The outcome of the DFT calculations agrees well with the experimental results.     

Models of steroid binding based on the minimum deviation of structurally assigned 13C NMR spectra analysis (MiDSASA)

This paper develops a quantitative k-nearest neighbors modeling technique. The technique is used to demonstrate that a compound's biological binding activity to a receptor can be calculated from the minimum of the square root of the sum of squared deviations (SSSD) of a structurally assigned chemical shift on a template between the unknown compound to be predicted and a set of known compounds with known activities. When building models of biological activity, nonlinear relationships are built into the input training data. If a model is developed by selecting only compounds with minimum structurally assigned chemical shift deviations from the unknown compound, some of the nonlinear relationships can be removed. The smaller the total chemical shift deviation between a compound with known activity and another compound with unknown activity, the more likely it will have similar biological, chemical, and physical properties. This means that a model can be produced without rigorous statistics or neural networks. This technique is similar to structure-activity relationship (SAR) modeling, but instead of relying on substructure fragments to produce a model, this new model is based on minimum chemical shift differences on those substructure fragments. We refer to this method as minimum deviation of structurally assigned spectra analysis (MiDSASA) modeling. Modeling by the minimum deviation concept can be applied to other chemoinformatic data analyses such as metabolite concentrations in metabolic pathways for metabolomics research. A MiDSASA template model for 30 steroids binding the corticosterone binding globulin based on the activity factors of the two nearest compounds had a correlation of 0.88. A MiDSASA template model for 50 steroids binding the aromatse enzyme based on the average activity of the four nearest compounds had a correlation of 0.71.     

5C + 1S] annulation: a facile and efficient synthetic route toward functionalized 2,3-dihydrothiopyran-4-ones

[reaction: see text] A facile and efficient synthetic route toward highly substituted 2,3-dihydrothiopyran-4-ones 2 has been developed via a formal [5C + 1S] annulation of readily available alpha-alkenoyl ketene-(S,S)-acetals 1 with sodium sulfide nonahydrated salt (Na2S x 9H2O) and utilized in the synthesis of 2-(4-chlorophenyl)-6-(morpholin-4-yl)-4H-thiopyran-4-one 5l, an inhibitor of DNA-dependent protein kinase (DNA-PK).     

Valence Bond Study of Dissociation Behavior and Spectroscopic Constants for the Ground States of LiF and NaF

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端羟丁腈聚氨酯/聚甲基丙烯酸甲酯互穿网络高聚物的T_g和形态研究——Ⅰ.组分比和交联程度的影响

用同步法合成了端羟丁腈聚氨酯/聚甲基丙烯酸甲酯互穿网络高聚物[PU(HTBN)/PMMA-IPN]。用动态力学方法和透射电镜研究了它们的T_(?)转变行为和形态。理论计算和实验结果表明,样品具有两个明显相互分离但又各自连续的相结构,呈现出分属于组分聚合物的两个Tg转变(Tg_1,Tg_2)。在全IPN中,PMMA相区的尺寸(1000—2000?),比在接枝共聚物(3000—6000?)和半IPN(—3000?)中的明显变小。适当的交联程度可使相区进一步变小,变均匀,相连续性增加。这是网络互穿造成的“强迫互容”所致。部分丁腈羟(HTBN)分子同PMMA的反应,使一些样品出现了Tg_2升高的现象。     

Effect of thermal history on crystallization and melting behaviour of lldpe

In this paper two LLDPE samples with their own structural parameters were studied by means of DSC. Experimental results show that DSC was good for revealing slight structural difference between these two samples. Furthermore, the effect of thermal history on crystallization and melting behaviour of LLDPE was observed clearly through varying conditions of thermal treatment.

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Zusammenfassung Mittels DSC werden zwei LLDPE-Proben mit ihren eigenen Strukturparametern untersucht. Die Versuchsergebnisse zeigen, da\ sich DSC gut eignet, um gering fügige Unterschiede dieser zwei Proben nachzuweisen. Weiterhin wurde unter verschiedenen Bedingungen der Einflu\ der thermischen Vorgeschichte auf das Kristallisations-und Schmelzverhalten von LLDPE untersucht.

     

Structures and stability of N7+ and N7− clusters

Ab initio molecular orbital theory and density functional theory have been used to study nine isomers of N₇ ionic clusters with low spin at the HF/6-31G*, MP2/6-31G*, B3LYP/6-31G*, and B3LYP/6-311(+)G* levels of theory. All stationary points are examined with harmonic vibrational frequency analyses. Four N₇ ⁺ isomers and five N₇ ⁻ isomers are determined to be local minima or very close to the minima on their potential-energy hypersurfaces, respectively. For N₇ ⁺ and N₇ ⁻, the energetically low lying isomers are open-chain structures (C _{2 v} and C _{2 v} or C₂). The results are very similar to those of other known odd-number nitrogen ions, such as N₅ ⁺, N₉ ⁺, and N₉ ⁻, for which the open-chain structures are also the global minima. This research suggests that the N₇ ionic clusters are likely to be stable and to be potential high-energy-density materials if they could be synthesized. Received: 16 July 2001 / Accepted: 8 October 2001 / Published online: 21 January 2002     

硫代草酸二乙二胺铬(Ⅲ)配合物的光化学

制备了铬(Ⅲ)的一个新配合物cis-[Cr(en)_2SC_2O_3·Cl·H_2O,这里en表示乙二胺.在酸性水溶液中进行光照.释放H_2S,生成cis-Cr(en)_2(C_2O_4)~+,测定了光分解反应的准一级速度常数,配合物消失的量子产率取决于照射波长和溶液的酸度,还讨论了光反应机制.     

Selective dye-labeling of newly synthesized proteins in bacterial cells

We describe fluorescence labeling of newly synthesized proteins in Escherichia coli cells by means of Cu(I)-catalyzed cycloaddition between alkynyl amino acid side chains and the fluorogenic dye 3-azido-7-hydroxycoumarin. The method involves co-translational labeling of proteins by the non-natural amino acids homopropargylglycine (Hpg) or ethynylphenylalanine (Eth) followed by treatment with the dye. As a demonstration, the model protein barstar was expressed and treated overnight with Cu(I) and 3-azido-7-hydroxycoumarin. Examination of treated cells by confocal microscopy revealed that strong fluorescence enhancement was observed only for alkynyl-barstar treated with Cu(I) and the reactive dye. The cellular fluorescence was punctate, and gel electrophoresis confirmed that labeled barstar was localized in inclusion bodies. Other proteins showed little fluorescence. Examination of treated cells by fluorimetry demonstrated that cultures supplemented with Eth or Hpg showed an 8- to 14-fold enhancement in fluorescence intensity after labeling. Addition of a protein synthesis inhibitor reduced the emission intensity to levels slightly above background, confirming selective labeling of newly synthesized proteins in the bacterial cell.