Discovery of a Superconducting Cu–Bi Intermetallic Compound by High‐Pressure Synthesis

A new intermetallic compound, the first to be structurally identified in the Cu?Bi binary system, is reported. This compound is accessed by high‐pressure reaction of the elements. Its detailed characterization, physical property measurements, and ab initio calculations are described. The commensurate crystal structure of Cu₁₁Bi₇ is a unique variation of the NiAs structure type. Temperature‐dependent electrical resistivity and heat capacity measurements reveal a bulk superconducting transition at T_c=1.36 K. Density functional theory calculations further demonstrate that Cu₁₁Bi₇ can be stabilized (relative to decomposition into the elements) at high pressure and temperature. These results highlight the ability of high‐pressure syntheses to allow for inroads into heretofore‐undiscovered intermetallic systems for which no thermodynamically stable binaries are known.     

Identification of a Fluorescent Protein from Rhacostoma Atlantica

We have cloned a novel fluorescent protein from the jellyfish Rhacostoma atlantica. The closest known related fluorescent protein is the Phialidium yellow fluorescent protein, with only a 55% amino acid sequence identity. A somewhat unusual alanine–tyrosine–glycine amino acid sequence forms the presumed chromophore of the novel protein. The protein has an absorption peak at 466 nm and a fluorescence emission peak at 498 nm. The fluorescence quantum yield was measured to be 0.77 and the extinction coefficient is 58 200 M^?1 cm^?1. Several mutations were identified that shift the absorption peak to about 494 nm and the emission peak to between 512 and 514 nm.     

A semi‐quantitative approach for the rapid screening and mass profiling of naphthenic acids directly in contaminated aqueous samples

We report the use of a direct sampling, online analytical approach for the determination of acid extractable naphthenic acids in complex aqueous samples, known as condensed phase membrane introduction mass spectrometry (CP‐MIMS). The technique employs a capillary hollow fibre semi‐permeable membrane probe configured for immersion into a pH adjusted sample. A continuously flowing methanol acceptor phase transfers naphthenic acids to an electrospray ionization source, operated in negative ion mode, whereupon they are analysed by mass spectrometry as [M–H]^? ions. High‐resolution mass spectrometry is used to characterize the influence of sample pH on membrane transport of multiple components of complex naphthenic acid mixtures. We demonstrate the use of CP‐MIMS for semi‐quantitative analysis of real‐world samples using selected ion monitoring and full scan mass spectra at unit mass resolution. The technique has also been employed to continuously monitor the temporal evolution in the mass profile and concentrations of individual naphthenic acid isomer classes in heterogeneous solutions during adsorption processes. Copyright © 2015 John Wiley & Sons, Ltd.     

XAS spectroelectrochemistry: reliable measurement of X‐ray absorption spectra from redox manipulated solutions at room temperature

The design and operation of a low‐volume spectroelectrochemical cell for X‐ray absorption spectroscopy (XAS) of solutions at room temperature is described. Fluorescence XAS measurements are obtained from samples contained in the void space of a 50 µL reticulated vitreous carbon (sponge) working electrode. Both rapid electrosynthesis and control of the effects of photoreduction are achieved by control over the flow properties of the solution through the working electrode, where a good balance between the rate of consumption of sample and the minimization of decomposition was obtained by pulsing the flow of the solution by 1–2 µL with duty cycle of ～3 s while maintaining a small net flow rate (26–100 µL h^?1). The performance of the cell in terms of control of the redox state of the sample and minimization of the effects of photoreduction was demonstrated by XAS measurements of aqueous solutions of the photosensitive Fe^III species, [Fe(C₂O₄)₃]^3?, together with that of the electrogenerated [Fe(C₂O₄)₃]^4? product. The current response from the cell during the collection of XAS spectra provides an independent measure of the stability of the sample of the measurement. The suitability of the approach for the study of small volumes of mM concentrations of protein samples was demonstrated by the measurement of the oxidized and electrochemically reduced forms of cytochrome c.     

Scandium triflate and secondary amine promoted AA′B 2:1 coupling and formal inverse electron demand Diels-Alder reactions of dienals

Reaction prospecting studies resulted in the discovery of a Sc(OTf)₃ promoted novel AA′B 2:1 coupling of imidazolone or benzofuran substituted enals with morpholine. A related Sc(OTf)₃/morpholine promoted reaction was demonstrated for the coupling of a benzofuran substituted enal with dihydrofuran. The formation of these adducts is consistent with formal inverse electron demand Diels-Alder cycloadditions, most likely in a stepwise manner via a domino Michael-Mannich annulation process, involving iminium ion activation of the diene. A purely amine promoted formal inverse electron demand Diels-Alder cycloaddition approach was also demonstrated in the 2:1 coupling of 2,4-hexadienal with methanol. These reactions demonstrate the concepts of dual metal/amine catalysis and amine promoted formal inverse electron demand Diels-Alder cycloadditions. They differ from known examples of organocatalyzed Diels-Alder reactions, in which iminium ion activation of the dienophiles or enamine activation of the dienes occur.     

New tools for rapid clinical and bioagent diagnostics: microwaves and plasmonic nanostructures

In this timely review, we summarize recent work on ultra-fast and sensitive bioassays based on microwave heating, and provide our current interpretation of the role of the combined use of microwave energy and plasmonic nanostructures for applications in rapid clinical and bioagent diagnostics. The incorporation of microwave heating into plasmonic nanostructure-based bioassays brings new advancements to diagnostic tests. A temperature gradient, created by the selective heating of water in the presence of plasmonic nanostructures, results in an increased mass transfer of target biomolecules towards the biorecognition partners placed on the plasmonic nanostructures, enabling diagnostic tests to be completed in less than a minute, and in some cases only a few seconds, by further microwave heating. The diagnostic tests can also be run in complex biological samples, such as human serum and whole blood.     

Consideration of some sampling problems in the on-line analysis of batch processes by low-field NMR spectrometry

A low-field medium-resolution NMR spectrometer, with an operating frequency of 29 MHz for 1H, has been assessed for on-line process analysis. A flow cell that incorporates a pre-magnetisation region has been developed to minimise the decrease in the signal owing to incomplete polarisation effects. The homogeneous esterification reaction of crotonic acid and 2-butanol was monitored using a simple sampling loop; it was possible to monitor the progression of the reaction through changes in CH signal areas of butanol and butyl crotonate. On-line analysis of heterogeneous water-toluene mixtures proved more challenging and a fast sampling loop system was devised for use with a 5 L reactor. The fast sampling loop operated at a flow rate of 8 L min(-1) and a secondary sampling loop was used to pass a sub-sample through the NMR analyser at a slower (mL min(-1)) rate. It was shown that even with super-isokinetic sampling conditions, unrepresentative sampling could occur owing to inadequate mixing in the reactor. However, it was still possible to relate the 1H NMR signal obtained at a flow rate of 60 mL min(-1) to the composition of the reactor contents.     

Behavior of thin films of poly(oxyethylene)-poly(oxybutylene) copolymers studied by brewster angle microscopy and atomic force microscopy

Surface films of two copolymers of ethylene oxide (E) and butylene oxide (B), namely E23B8 and E87B18, have been examined by Brewster angle microscopy (BAM) and atomic force microscopy (AFM). Isotherms taken on unsupported films of these copolymers at the air-water interface showed a clear gas to liquid phase transition for E57B18 and a barely discernible phase transition for E23B8. The BAM studies showed a gradual brightening of the films as the surface pressure was increased, which was associated with a film thickening and/or a film densification. Several bright spots were also observed within the films, with the number of spots increasing gradually as the film surface pressure was increased. AFM studies of these films did not show any localized ordering, which fits in with the results from our previous X-ray study of these copolymers [Hodges, C. S.; Neville, F.; Konovalov, O.; Gidalevitz, D.; Hamley, I. W.; Langmuir 2006, 22 (21), 8821-8825], where no long-range ordering was observed. AFM imaging showed two sizes of particulates that were irregularly spaced across the film. The larger particulates were associated with silica contaminants from the copolymer synthesis, whereas the smaller particulates were assumed to be aggregated copolymer. An analysis of the semidilute region of the isotherm showed that while both copolymers had intermixed ethylene oxide and butylene oxide units, the lower molecular weight E23B8 copolymer manifested significantly more intermixing than E87B18.     

Enrichment of low molecular weight serum proteins using acetonitrile precipitation for mass spectrometry based proteomic analysis

A rapid acetonitrile (ACN)-based extraction method has been developed that reproducibly depletes high abundance and high molecular weight proteins from serum prior to mass spectrometric analysis. A nanoflow liquid chromatography/tandem mass spectrometry (nano-LC/MS/MS) multiple reaction monitoring (MRM) method for 57 high to medium abundance serum proteins was used to characterise the ACN-depleted fraction after tryptic digestion. Of the 57 targeted proteins 29 were detected and albumin, the most abundant protein in serum and plasma, was identified as the 20th most abundant protein in the extract. The combination of ACN depletion and one-dimensional nano-LC/MS/MS enabled the detection of the low abundance serum protein, insulin-like growth factor-I (IGF-I), which has a serum concentration in the region of 100 ng/mL. One-dimensional sodium dodecyl sulfate/polyacrylamide gel electrophoresis (SDS-PAGE) analysis of the depleted serum showed no bands corresponding to proteins of molecular mass over 75 kDa after extraction, demonstrating the efficiency of the method for the depletion of high molecular weight proteins. Total protein analysis of the ACN extracts showed that approximately 99.6% of all protein is removed from the serum. The ACN-depletion strategy offers a viable alternative to the immunochemistry-based protein-depletion techniques commonly used for removing high abundance proteins from serum prior to MS-based proteomic analyses.     

Limits of the plane wave approximation in the measurement of molecular properties

Rescattering electrons offer great potential as probes of molecular properties on ultrafast timescales. The most famous example is molecular tomography, in which high harmonic spectra of oriented molecules are mapped to "tomographic images" of the relevant molecular orbitals. The accuracy of such reconstructions can be greatly affected by the distortion of scattering wave functions from their asymptotic forms due to interactions with the parent ion. We investigate the validity of the commonly used plane wave approximation in molecular tomography, showing how such distortions affect the resulting orbital reconstructions.