Cyclic Voltammetry in a Perfluorocarbon Emulsion Blood Substitute

Cyclic voltammetry in a perfluorocarbon emulsion based blood substitute (PEBS) was evaluated. The intent was to determine how PEBS affects the voltammetry of four representative electroactive compounds: potassium ferricyanide, ruthenium(II) trisbipyridine (rutris), hydroquinone, and 2,6‐dichloroindophenol (DCIP). Voltammograms in 0–20% PEBS‐Tris buffer mixtures are affected by PEBS, but reasonably well‐defined voltammograms are obtained in as much as 20% v/v. This report also shows that PEBS has only a small effect on amperometric detection of the reaction between DCIP and nicotinamide adenine dinucleotide (NADH), which has importance in clinical homogeneous immunoassays. Results support continued exploration of voltammetry/amperometry for quantitative analysis in this medium.     

General deoxyribozyme-catalyzed synthesis of native 3'-5' RNA linkages

An elusive goal for nucleic acid enzymology has been deoxyribozymes that ligate RNA rapidly, sequence-generally, with formation of native 3'-5' linkages, and in preparatively useful yield. Using in vitro selection, we have identified Mg2+- and Zn2+-dependent deoxyribozymes that simultaneously fulfill all four of these criteria. The new deoxyribozymes operate under practical incubation conditions and have modest RNA substrate sequence requirements, specifically D downward arrowRA for 9DB1 and A downward arrowR for 7DE5 (D = A, G, or U; R = A or G). These requirements are comparable to those of deoxyribozymes such as 10-23 and 8-17, which are already widely used as biochemical tools for RNA cleavage. We anticipate that the 9DB1 and 7DE5 deoxyribozymes will find immediate practical application for RNA ligation.     

A Preparatively Simple Access to Homochiral Heterocyclic α-Hydroxy Acids and their Derivatives

 The synthesis of homochiral heterocyclic α-hydroxy acids starting from (S)- and (R)-malic acid using hexafluoroacetone as protecting and activating agent is described. The new compounds are useful building blocks for peptide and depsipeptide modification.     

Synthesis of an isomer of the germacranolide isoaristolactone

Photocycloadditlon of (+)-isoplperltenone and cyclobutene-1-carboxylic acid gives an adduct which upon reduction with NaCNBH₃ followed by thermolysis yields an isomer of isoaristolactone in an overall yield of 26%.     

The Bohlmann-Rahtz route to functionalised pyridine scaffolds and their use in library synthesis

The Bohlmann-Rahtz reaction has been used to prepare 2,3,6-trisubstituted pyridines suitable for use in library synthesis. The synthesis of piperidine substituted nicotinic acid derivative 9 has been optimised and carried out on a large scale to give ca. 500 g of scaffold which was used in the generation of the pyridine library 11.     

Preparation and Properties of Composite Polypyrrole/Pt Catalyst Systems

Three different methods for the preparation and modification of conducting polymer/noble metal catalyst systems consisting of polypyrrole (PPy) and platinum (Pt) are described for the anodic oxidation of methanol. The first method consists of the electrochemical deposition of a thin PPy film on glassy carbon substrate, which is modified with Pt either by electroreduction of hexachloroplatinate, codeposition from a nanodispersed Pt solution, or incorporation of tetrachloroplatinate as counterion followed by cathodic reduction. A second method is based on the preparation of nanoscale PPy(PSS) particles by chemical polymerization with polystyrenesulfonate PSS^– as the counterion. This material is a favorable catalyst support for nanodispersed Pt due to its mixed electronic and cationic conductivity. To study the electrochemical properties, the particulate system PPy(PSS)/Pt is fixed in a carbon fiber electrode. A third method was developed which brings the polypyrrole in close contact to a proton exchanger membrane (Nafion) using a special chemical deposition procedure. This method is useful for preparing a membrane electrode assembly (MEA) consisting of Nafion/PPy/Pt. The structural, morphological, and electrocatalytic properties for methanol oxidation were studied depending on the preparation method applied using surface analytical techniques (TEM, SEM, and EDX) and electrochemical measurements (cyclic voltammetry and transient techniques).     

Gitterschwingungsspektren. LXIII. Be(lO3)2 · 4 H2O,ein Hydrat mit ungewöhnlicher Bindungsstruktur und Gitterdynamik

Lattice Vibration Spectra. LXIII. Be(IO₃)₂ · 4 H₂O, a Hydrate with Unusual Bonding and Lattice Dynamics The IR and Raman spectra (4000–50 cm^?1) of Be(IO₃)₂ · 4 H₂O and of deuterated specimens are recorded at 90 and 300 K and discussed in terms of the unusual relations of the masses of the atoms involved and the large polarization power of the beryllium ions. Thus, the translatory modes of the Be²⁺ ions (BeO₄ skeleton vibrations), the librations of the H₂O molecules, and the internal vibrations of the IO₃^? ions in the spectral regions of 300–400 and 600–1000 cm^?1 couple and coincide producing unusual v_H/v_D isotopic ratios of partly < 1. The H-bond donor strengths of the water molecules is so much increased (due to the very large ionic potential of Be²⁺ ions, viz. 49 e nm^?1) (synergetic effect) that the H-bonds formed are similar in strength as those in hydrates of hydroxides with the very strong H-bond acceptor group OH^? (v_OD of matrix isolated HDO molecules 2 074 and 2 244 (H₂O I) and 2 206 and 2 349 cm^?1 (H₂O II))     

Ultraviolet photochemistry of ethane: implications for the atmospheric chemistry of the gas giants

Chemical processing in the stratospheres of the gas giants is driven by incident vacuum ultraviolet (VUV) light. Ethane is an important constituent in the atmospheres of the gas giants in our solar system. The present work describes translational spectroscopy studies of the VUV photochemistry of ethane using tuneable radiation in the wavelength range 112 ≤ λ ≤ 126 nm from a free electron laser and event-triggered, fast-framing, multi-mass imaging detection methods. Contributions from at least five primary photofragmentation pathways yielding CH₂, CH₃ and/or H atom products are demonstrated and interpreted in terms of unimolecular decay following rapid non-adiabatic coupling to the ground state potential energy surface. These data serve to highlight parallels with methane photochemistry and limitations in contemporary models of the photoinduced stratospheric chemistry of the gas giants. The work identifies additional photochemical reactions that require incorporation into next generation extraterrestrial atmospheric chemistry models which should help rationalise hitherto unexplained aspects of the atmospheric ethane/acetylene ratios revealed by the Cassini–Huygens fly-by of Jupiter.

The vacuum ultraviolet photodissociation dynamics of ethane provide clues for modelling the atmospheric chemistry of the gas giants.     

INDUCTION OF CHROMOSOME ABERRATIONS IN ICR 2A FROG CELLS EXPOSED TO265–313 nm MONOCHROMATIC ULTRAVIOLET WAVELENGTHS and PHOTOREACTIVATING LIGHT

Abstract— Exposure of ICR 2A cells to either 265, 289, 302 or 313 nm monochromatic UV wavelengths caused the induction of chromosome aberrations with chromatid gaps and breaks being the most common type of aberration detected. Treatment of U V-irradiated cells with photoreactivating light (PRL) resulted in a lower yield of aberrations demonstrating that pyrimidine dimers are involved in the formation of chromosome aberrations induced by the UV wavelengths tested. However, the decrease in the level of aberrations resulting from PRL treatment of 313 nm-irradiated cells was significantly less than for the other wavelengths indicating that non-dimer photoproducts may have played an important additional role in the induction of chromosome aberrations by this UV wavelength.