Observation of a Ξ*(2370) produced in 8.25 GeV/c K−p interactions

We observe production of a Ξ^*(2370) in the reactions K^?p→$[Y\overline{K}\pi ]$K, $[Y\overline{K}\pi ]$Kπ and [ΩK] (K or Kπ) at 8.25 GeV/c in a high statistics bubble chamber experiment. The mass and width are determined to be 2373 ± 8 MeV and 80 ± 25 MeV, respectively. The I = 1/2 assignment is strongly favoured.     

DNA cleavage by copper-ATCUN complexes. Factors influencing cleavage mechanism and linearization of dsDNA

The reactivity of two [peptide-Cu] complexes ([GGH-Cu](-) and [KGHK-Cu](+)) toward DNA cleavage has been quantitatively investigated. Neither complex promoted hydrolytic cleavage, but efficient oxidative cleavage was observed in the presence of a mild reducing agent (ascorbate) and dioxygen. Studies with scavengers of ROS confirmed hydrogen peroxide to be an obligatory diffusible intermediate. While oxidative cleavage of DNA was observed for Cu(2+)(aq) under the conditions used, the kinetics of cleavage and reaction products/pathway were distinct from those displayed by [peptide-Cu] complexes. DNA cleavage chemistry is mediated by the H(2)O-dependent pathway following C-4'H abstraction from the minor groove. Such a cleavage path also provides a ready explanation for the linearization reaction promoted by [KGHK-Cu](+). Kinetic activities and reaction pathways are compared to published results on other chemical nucleases. Both [peptide-Cu] complexes were found to display second-order kinetics, with rate constants k(2) approximately 39 and 93 M(-1) s(-1) for [GGH-Cu](-) and [KGHK-Cu](+), respectively. Neither complex displayed enzyme-like saturation behavior, consistent with the relatively low binding affinity and residence time expected for association with dsDNA, and the absence of a prereaction complex. However, the intrinsic activity of each is superior to other catalyst systems, as determined from relative k(2) or k(cat)/K(m) values. Linearization of DNA was observed for [KGHK-Cu](+) relative to [GGH-Cu](-), consistent with the increased positive charge and longer residency time on dsDNA.     

ESR Study of Trimethylsilane Plasma Polymer Part II; Effect of Consecutive Treatments and Mixed Gases

An ESR study has indicated that a second plasma treatment on plasma deposited films from trimethylsilane (TMS) monomer gas has the ability to modify the characteristics of the primary plasma polymer significantly in a favorable manner for many applications. The effect of the second plasma polymerization on the primary plasma polymer of TMS depends on the nature of the second monomer. Plasma of F-containing monomer, hexafluoroethane (HFE) and perfluoromethane (CF₄), decreases the ESR signal of TMS and no detectable signal due to F-containing monomer was found. The decay rate of the signal decreased significantly. In contrast to this situation, CH₄ plasma treatment yields an ESR signal that is a composite of that observed from TMS and CH₄ films individually. The overall signal increased in this instance, but didn't show appreciable decay in 24 hr period. A second treatment by nonpolymer forming plasmas also decreased the ESR signal of TMS, and decreased the decay rate, indicating that the second gas plasma treatment yields a somewhat similar effect found with the HFE plasma treatment. Plasma polymerization of mixtures of TMS and nonpolymer-forming gases increased the ESR signal but decreased the decay rate, except in the case of oxygen. A mixture of (TMS + O₂) behaved as a completely different monomer. No ESR signal was found in this system. The ESR analysis was supported by XPS data and an insight into the mechanisms occurring in these thin films are discussed.     

Interpenetrating supramolecular lattices in 4,4′-bi­pyridine–2,3,5,6-tetra­hydroxy-1,4-benzo­quinone (3/2)

4,4′-Bi­pyridine (BPY) and 2,3,5,6-tetra­hydroxy-1,4-benzo­quinone (THBQ) crystallize in a 3:2 ratio as a neutral molecular adduct, 3C₁₀H₈N₂·2C₆H₄O₆, in space group P. There are two independent and centrosymmetric THBQ mol­ecules and two different BPY mol­ecules in the asymmetric unit, one of which lies about an inversion centre. The molecules link together through O—H⃛O and O—H⃛N hydrogen bonds to form three interpenetrating networks which create a `superlattice' of three times the volume of the primitive cell.