NMR Diffusion Measurements as a Simple Method to Examine Solvent–Solvent and Solvent–Solute Interactions in Mixtures of the Ionic Liquid [Bmim][N(SO2CF3)2] and Acetonitrile

The self‐diffusion coefficients of each component in mixtures of 1‐butyl‐3‐methylimidazolium bis(trifluoromethanesulfonyl)imide ([Bmim][N(SO₂CF₃)₂]) and acetonitrile were determined. The results suggest that the hydrodynamic boundary conditions change from “stick” to “slip” as the solvent composition transitions from “ionic liquid dissolved in acetonitrile” (χ_IL<0.4) to “acetonitrile dissolved in ionic liquid” (χ_IL>0.4). At higher χ_IL, the acetonitrile species are affected by “cage” and “jump” events, as the acetonitrile molecules reside nearer to the charged centre on the ions than in the “non‐polar” regions. The self‐diffusion coefficients of hexan‐1‐amine, dipropylamine, 1‐hexanol and dipropylether in mixtures of [Bmim][N(SO₂CF₃)₂] and acetonitrile were determined. In general, the nitrogen‐containing solutes were found to diffuse slower than the oxygen‐containing solutes; this indicates that there are greater ionic liquid–N interactions than ionic liquid–O interactions. This work demonstrates that the self‐diffusion coefficients of species can provide valuable information about solvent–solvent and solvent–solute interactions in mixtures containing an ionic liquid.     

Diazonium-functionalized horseradish peroxidase immobilized via addressable electrodeposition: direct electron transfer and electrochemical detection

A simple one-step procedure is introduced for the preparation of diazonium-enzyme adducts. The direct electrically addressable deposition of diazonium-modified enzymes is examined for electrochemical sensor applications. The deposition of diazonium-horseradish peroxidase leads to the direct electron transfer between the enzyme and electrode exhibiting a heterogeneous rate constant, ks, of 10.3 +/- 0.7 s-1 and a DeltaEp of 8 mV (v = 150 mV/s). The large ks and low DeltaEp are attributed to the intimate contact between enzyme and electrode attached by one to three phenyl molecules. Such an electrode shows high nonmediated catalytic activity toward H2O2 reduction. Future generations of arrayed electrochemical sensors and studies of direct electron transfer of enzymes can benefit from protein electrodes prepared by this method.     

Do (pentaarylcyclopentadienyl)molybdenum(VI) dioxo species catalyse alkene epoxidations? Insights from kinetics data

A (perarylcyclopentadienyl)molybdenum(VI) dioxo complex is shown to catalyse epoxidation of cyclooctene by t-butylhydroperoxide, but decomposition to a much more active non-cyclopentadienyl containing catalyst occurs as the reaction proceeds.     

Reagentless electrochemical immunoassay using electrocatalytic nanoparticle-modified antibodies

We describe a new approach for reagentless electrochemical immunoassay sensing in which Au/Pd NPs can be "loaded" onto antibodies to create an electrocatalytic antibody that is sensitive to the oxygen reduction reaction.     

Predicting Trigger Bonds in Explosive Materials through Wiberg Bond Index Analysis

Understanding the explosive decomposition pathways of high‐energy‐density materials (HEDMs) is important for developing compounds with improved properties. Rapid reaction rates make the detonation mechanisms of HEDMs difficult to understand, so computational tools are used to predict trigger bonds—weak bonds that break, leading to detonation. Wiberg bond indices (WBIs) have been used to compare bond densities in HEDMs to reference molecules to provide a relative scale for the bond strength to predict the activated bonds most likely to break to trigger an explosion. This analysis confirms that X?NO₂ (X=N,C,O) bonds are trigger linkages in common HEDMs such as TNT, RDX and PETN, consistent with previous experimental and theoretical studies. Calculations on a small test set of substituted tetrazoles show that the assignment of the trigger bond depends upon the functionality of the material and that the relative weakening of the bond correlates with experimental impact sensitivities.     

Anti-inflammatory and antimalarial meroterpenoids from the New Zealand ascidian Aplidium scabellum

Bioassay-directed fractionation of an extract of the New Zealand ascidian Aplidium scabellum has afforded the anti-inflammatory secondary metabolite 2-geranyl-6-methoxy-1,4-hydroquinone-4-sulfate (1) and a family of pseudodimeric meroterpenoids scabellones A (2)-D (5). The benzo[c]chromene-7,10-dione scaffold contained within scabellones A-D is particularly rare among natural products. The structures were elucidated by interpretation of NMR data. Scabellone B was also identified as a moderately potent, nontoxic inhibitor of Plasmodium falciparum.     

Araiosamines A-D: tris-bromoindole cyclic guanidine alkaloids from the marine sponge Clathria (Thalysias) araiosa

Four new tris-bromoindole cyclic guanidine alkaloids, araiosamines A-D, were isolated from the methanol extract of a marine sponge, Clathria (Thalysias) araiosa, collected from Vanuatu. Their carbon skeletons delineate a new class of indole alkaloids apparently derived from a linear polymerization process involving a carbon-carbon bond formation. Comparison of the structures including the relative configurations suggests a common intermediate containing a dihydroaminopyrimidine moiety capable of undergoing various modalities of conjugate addition to yield unprecedented ring systems.     

Specific detection of DNA through coupling of a TaqMan assay with surface enhanced Raman scattering (SERS)

We have combined the benefits of a TaqMan assay with surface enhanced Raman scattering (SERS), to generate a novel DNA detection method which provides increased sensitivity, with clear applications for disease identification through clinical testing. Target DNA detection limits by SERS were shown to be lower than conventional fluorescence detection and clinically relevant samples of methicillin-resistant Staphylococcus aureus were detected with high specificity.     

'One-pot' Hammett plots: a general method for the rapid acquisition of relative rate data

A general 'one-pot' method for determining relative rates of reaction in complex mixtures has been established using free energy relationships to demonstrate its utility. Competition experiments involving as many as seven species gave relative rate constants that are in good agreement to those obtained from individual kinetic analyses.