Oligoindole-based foldamers with a helical conformation induced by chloride

As a new type of foldamers, oligoindoles containing 4, 6, and 8 indole rings were synthesized, and their folding properties were characterized by a combination of 1H NMR techniques and UV/visible titration experiments. When chloride was added, the NH signals of the oligoindoles were downfield shifted as a result of hydrogen-bond formation, and the aromatic signals were upfield shifted by stacking between two indoles. Moreover, the ROESY experiment provided definitive NOE evidence for the helical stacking in the presence of chloride. Finally, the UV/visible titration experiments demonstrated that the oligoindoles formed 1:1 complexes with chloride, and the association constants greatly increased with increasing the number of the indole NHs. These observations are all consistent with the fact that oligoindoles adopt a helical conformation when complexed with chloride by hydrogen-bonding interactions.     

Cysteine carboxyl O-methylation of human placental 23 kDa protein

C-Terminal carboxyl methylation of a human placental 23 kDa protein catalyzed by membrane-associated methyltransferase has been investigated. The 23 kDa protein substrate methylated was partially purified by DEAE-Sephacel, hydroxyapatite and Sephadex G-100 gel filtration chromatographies. The substrate protein was eluted on Sephadex G-100 gel filtration chromatography as a protein of about 29 kDa. In the absence of Mg2+, the methylation was stimulated by guanine nucleotides (GTP, GDP and GTPgammaS), but in the presence of Mg2+, only GTPgammaS stimulated the methylation which was similar to the effect on the G25K/rhoGDI complex. AFC, an inhibitor of C-terminal carboxyl methylation, inhibited the methylation of human placental 23 kDa protein. These results suggests that the substrate is a small G protein different from the G25K and is methylated on C-terminal isoprenylated cysteine residue. This was also confirmed by vapor phase analysis. The methylated substrate protein was redistributed to membrane after in vitro methylation, suggesting that the methylation of this protein is important for the redistribution of the 23 kDa small G protein for its putative role in intracellular signaling.     

Thermal studies of some divalent metal chelates of croconic acid

The thermal properties of chelates of croconic acid and squaric acid with divalent copper, cobalt, nickel and zinc have been investigated by TG and DTA. The decreasing order of thermal stability for the decomposition of the croconate chelates was Ni > > Zn > Co=Cu and for the squarate complexes, Zn > Co=Cu > Ni. The copper croconate TG showed water loss in two distinct steps. This was rationalized on the basis of the already known Jahn-Teller effect for this molecule. The nickel squarate was thought to have a different structure than the other squarate chelates. Activation energies were calculated for the croconate chelates from their DTA curves.

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Zusammenfassung Die thermischen Eigenschaften der Chelate der Crocon- und Squarsäure mit zweiwertigem Kupfer, Cobalt, Nickel und Zink wurden durch TG und DTA untersucht. Die Abnahme der thermischen Stabilität bei der Zersetzung der Croconat-Chelate verlief von Ni>Zn>Co=Cu und der Squarat-Komplexe von Zn>Co=Cu>Ni. Die TG der Kupfercroconate wies eine Wasserabgabe in zwei deutlichen Stufen auf. Diese erklärt sich aufgrund des bereits bekannten Jahn-Teller Effekts für dieses Molekül. Für Nickelsquarat wurde eine andere Struktur angenommen als für die anderen Squaratkomplexe. Die Aktivierungsenergien für die Croconatchelate wurden aus ihren DTA-Kurven berechnet.

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Résumé Les propriétés thermiques des chélates formés par les acides croconique et squarique avec le cuivre, le cobalt, le nickel et le zinc ont été étudiées par TG et ATD. La stabilité thermique des chélates de l'acide croconique décroît dans l'ordre Ni>Zn>Co=Cu et pour l'acide squarique Zn>Co=Cu>Ni. L'étude TG du croconate de cuivre révèle une perte d'eau en deux étapes distinctes. Ceci s'explique par l'effet Jahn-Teller, déjà connu pour cette molécule. Le squarate de nickel possède sans dute une structure différente de celle des autres chélates de l'acide squarique. Les énergies d'activation des chélates de l'acide croconiqus ont été calculées à partir des courbes ATD.

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TGA DTA , , . Ni > > Zn > =u, — Zn > =Cu > Ni. TGA , . — . , , . DTA .

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Taken in part from a thesis submitted by D. A. L. to the Graduate School of the University of Notre Dame in partial fulfillment for the requirements of the Ph. D. degree.     

Antineoplastic anthraquinones. II. Design and synthesis of 1,2-Heteroannelated anthraquinones

Based on the “2-phenyinaphthalene-type” structural pattern hypothesis, a number of heterocycle-fused anthraquinones were designed by taking morindaparvin-A ( 2a ) as the lead structure. The compounds we synthesized and tested for antineoplastic activity include 1,2-alkylenedioxyanthraquinone, naphtho [2,3-f]-quinoxaline-7,12-dione, anthra[1,2-d]imidazole-6,11-dione and naphtho[2,3-f]quinoxaline-7,12-dione derivatives. Most of the synthesized anthraquinones possessed various degrees of anticancer activity. One of these compounds, 2-chloromethyl-1H-anthra[1,2-d]imidazole-6,11-dione ( 4b ), exhibited cytotoxic activity against all tested human carcinoma cell lines.     

Catalysts for the determination of oxygen in organic compounds

Summary Thermal decomposition of metal-organic complexes of nickel, cobalt and iron has given catalysts which are very effective at about 900° for the conversion of carbon dioxide, water and other oxygencontaining sample decomposition products to carbon monoxide in the direct determination of oxygen in organic compounds when using a modified Unterzaucher type apparatus. A copper catalyst similarly prepared required a temperature of 1030° whereas a manganese complex decomposition product was ineffective.

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Katalysatoren zur Sauerstoffbestimmung in organischen Substanzen

Zusammenfassung Durch thermische Zersetzung metallorganischer Komplexe von Ni, Co und Fe erhält man Katalysatoren, die die Umwandlung von CO₂, H₂O und anderen sauerstoffhältigen Zerfallsprodukten zu CO bei etwa 900° C bei der direkten Sauerstoffbestimmung in einer modifizierten Unterzaucher-Apparatur sehr wirksam fördern. Ein ähnlich hergestellter Cu-Katalysator erfordert 1030° C und das Zersetzungsprodukt eines Mn-Komplexes ist unwirksam.

     

利用高炉水淬渣制备(Ca/Y)-α-Sialon陶瓷的组织与性能

以高炉水淬渣合成的Ca-α-Sialon粉体为原料采用无压烧结技术制备了（Ca/Y）-α-Sialon陶瓷。通过用排水法、三点弯曲实验法、金相显微镜法、XRD法等手段研究了（Ca/Y）-α-Sialon陶瓷的烧结致密化过程、材料的力学性能、显微组织、相组成和材料的断裂特征。结果表明,适量的Y2O3促进材料的烧结致密化和提高材料的力学性能,但Y2O3过量（大于10%）时对材料的烧结和力学性能不利。掺杂Y^3＋的（Ca/Y）-α-Sialon呈柱状晶,随着Y2O3含量的增加和烧结温度的提高,（Ca/Y）-α-Sialon呈柱状晶出现粗化和等轴化。含10%Y2O3的材料在1700℃烧结时可获得较高的力学性能。     

Two New Steroidal Saponins from Tacca plantaginea

Two new C27 steroidal glycosides, named taccaoside A(1) and B(2), were isolated from the traditional Chinese herb Tacca plantaginea. The spectroscopic and chemical evidences revealed their structures to be 26-O-β-D-glucopyranosyl-(25R)-3β,26-dihydroxy furost-5,20-diene-3-O-[α-L-rhamnopyranosyl(1→2)]-[α-L-rhamnopyranosyl(1→3)]-β-D-glucopyranoside(1) and 26-O-β-D-glucopyranosyl-(25R)-3β,26-dihydroxy furost-5,20-diene-3-O-[α-L-rhamnopyranosyl-(1→2)]-[β-D-glucopyranosyl(1→3)-α-L-rhamnopyranosyl(1→3)]-β-D-glucopyranoside(2),respectively.     

Temporal Response of SERS to the Potential for 4-Cyanopyridine Adsorbed on Ag Electrode

Time-resolved surface-enhanced Raman scattering (SERS) was applied to study the response of Raman bands from 4-cyanopyridine (PyCN) adsorbed on a Ag electrode to variation of the potential; the temporal resolution was 0.1 s. The response of the SERS signals of PyCN was instantaneous to the oxidation potential of Ag electrode. However, delay of the SERS signals was observed while AgCl was reducing. The decay and growth of the SERS bands look place within 1 s in the cases of desorption and adsorption of PyCN on the electrode. It took much longer for PyCN to alter from one adsorption geometry to another on the electrode.     

硅胶担载四核羰基钴催化剂的EXAFS和IR研究

本文以透射法EXAFS和IR等手段研究了四核羰基钴金属簇Co_4(CO)_(10)(PPh)_2担载在SiO_2上以后及用于烯烃醛化反应前后的变化,确定了相应的结构参数并探讨了催化活性与结构的关系。     

Adsorption Kinetic Characteristics of H2S on Activated Carbon

This study compared H₂S adsorption kinetic parameters in both grain adsorption and column adsorption systems. Results indicated that when the nondimensional mass transfer parameter for adsorption column design was included, the axial dispersion (Pe > 1, < 1) and external film resistance (B 1) could be neglected, the fluid viscosity effect was small (Sc = 0.76), and the adsorbate affinity was fine (). Surface and pore diffusion controlled the adsorbent and fluid mass transfer. In addition, spent activated carbon could be treated by a thermal process and then impregnated with NaOH. After the pretreatment, the spent activated carbon could be used for H₂S adsorption. Furthermore, we also propose that the H₂S adsorption reaction on the carbon is due to the formation of sulfur crystals.