Fluorescent photoionic devices with two receptors and two switching mechanisms: applications to pH sensors and implications for metal ion detection

Two leading designs of fluorescent sensors are combined to yield the novel hybrid system of the ‘Fluorophore-Receptor₁-Spacer-Receptor₂’ format. We use 4-(dialkylaminoalkylamino)-7-nitrobenzo-2-oxa-1,3-diazoles as examples. The emission from internal charge transfer excited states in the present instances are highly responsive to N-H deprotonation as well as being quenched by intramolecular tertiary amine groups via photoinduced electron transfer (PET). When applied to pH sensing, this leads in favourable cases to two steps in the fluorescence-pH profile which can be viewed as a multi-stable photoionic device, even though single steps are more usual. The former situation is favoured when the two proton-associated equilibria are sufficiently separated on the pH scale and when the PET process is of moderate efficiency. These systems have the added feature of excitation/emission wavelengths in the visible region. As a secondary theme, we point out that caution is required when designing sensors for transition metal ions from systems with intrinsically proton-sensitive fluorescence due to receptors either integrated with or spaced from the fluorophore.     

A versatile and stereocontrolled route to pyranose and furanose C-glycosides

[reaction: see text] The alpha,beta-unsaturated-gamma,delta-epoxyester 1 is a novel and versatile precursor to a wide variety of C-glycosides. For instance, treatment of Z-1 or E-1 with palladium(0) affords, stereospecifically, beta- or alpha-C-furanosides, respectively. In contrast, reaction of Z-1 or E-1 with base gives, stereoselectively, the beta- or alpha-C-pyranosides, respectively.     

Preparation and coordination chemistry of N-diallylaminodiphenylphosphine and N-allylaminobis(diphenyl)phosphine

N-diallylaminodiphenylphosphine and N-allylaminobis(diphenyl)phosphine have been prepared by reaction of the appropriate amine with Ph₂PCl. The coordination chemistry of these phosphines has been studied with a range of metals [Pd, Pt, Rh, Ir, Au, Ru, Mo]. Whilst the majority of the complexes are simple bidentate P,P donors, in the case of N-diallylaminodiphenylphosphinecoordination can involve the CC group or the nitrogen centre.     

Comparison and validation of calibration methods for in vivo SPME determinations using an artificial vein system

The success of in vivo solid phase microextraction (SPME) depends significantly on the selection of calibration method. Three kinetic in vivo SPME calibration methods are evaluated in this paper: (1) on-fibre standardization (OFS), (2) dominant pre-equilibrium desorption (DPED), and (3) the diffusion-based interface (DBI) model. These are compared in terms of precision, accuracy, and ease of experimental use by employing a flow device simulating an animal circulatory system. In addition, the kinetic calibration methods were validated against established SPME equilibrium extraction (EE) external calibration and a conventional sample preparation method involving protein precipitation. The comparison was performed using a hydrophilic drug fenoterol as the analyte of interest. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used for the determinations. All three kinetic methods compared well with both EE extraction and the conventional method in terms of accuracy (93-119%). In terms of precision, the DBI model had the best precision in whole blood and buffered phosphate saline solution with %RSD similar to the standard techniques (9-15%). DPED had the poorest precision of %RSD (20-30%) possibly due to errors associated with uncertainty in the amount of standard loaded on-fibre and remaining on the fibre after desorption. In addition, incurred errors could result due to the greater number of fibres used in comparison to the other two calibration methods. The precision of the OFS procedure was better than for DPED primarily because the use of multiple fibres is eliminated. In terms of the ease of use for calibration, the DBI model was the simplest and most convenient as it did not require standards once it had been calibrated or the uptake constant was calculated. This research suggests the potential use of DBI model as the best kinetic calibration method for future in-vein blood SPME investigations.     

Total Synthesis of Rapamycin

Rapamycin (1) is a macrocyclic natural product, established as a potent immunosuppressant and currently of interest to the scientific community as the framework for a series of novel anticancer drugs. Extensive studies have culminated in a new convergent total synthesis of 1 , which features a number of group‐derived methodologies and an unusual catechol‐templating strategy for the construction of the challenging macrocyclic core.

     

Direct and simultaneous determination of 5-aminolaevulinic acid and porphobilinogen in urine by hydrophilic interaction liquid chromatography-electrospray ionisation/tandem mass spectrometry

Urinary concentrations of 5-aminolaevulinic acid (ALA) and porphobilinogen (PBG) are elevated in patients with acute hepatic porphyrias, especially during acute attacks. Current assays require lengthy sample pre-treatment and derivatisation steps. We report here a rapid, sensitive and specific hydrophilic interaction liquid chromatography-tandem mass spectrometry (LC-MS/MS) method, for the direct and simultaneous quantitation of ALA and PBG in urine following simple dilution with acetonitrile and centrifugation prior to injection. ALA and PBG were detected using selected reaction monitoring mode, following positive electrospray ionisation. Urine samples (N?=?46) from active and latent mutation-confirmed acute hepatic porphyria patients and normal subjects (N?=?45) were analysed and the results compared with those of a commercially available spectrophotometric method. The validated calibration range was 3-3000?μmol/L for ALA and 2-2000?μmol/L for PBG. For both analytes, imprecision (relative standard deviation) was less than 5% and accuracy (percentage nominal concentrations) was between 88 and 109%. The lower limit of quantitation was 0.1 μmol/L for both analytes. The calculated LC-MS/MS and spectrophotometric results from patient samples compared well [Pearson correlation (r2) of 0.99 and 0.95, for ALA and PBG, respectively]. The method was successfully applied to the measurement of ALA and PBG in urine samples for the screening, biochemical diagnosis and treatment monitoring of patients with acute hepatic porphyrias.     

Graphene nucleation on transition metal surface: structure transformation and role of the metal step edge

The nucleation of graphene on a transition metal surface, either on a terrace or near a step edge, is systematically explored using density functional theory calculations and applying the two-dimensional (2D) crystal nucleation theory. Careful optimization of the supported carbon clusters, C(N) (with size N ranging from 1 to 24), on the Ni(111) surface indicates a ground state structure transformation from a one-dimensional C chain to a 2D sp(2) C network at N ≈ 10-12. Furthermore, the crucial parameters controlling graphene growth on the metal surface, nucleation barrier, nucleus size, and nucleation rate on a terrace or near a step edge are calculated. In agreement with numerous experimental observations, our analysis shows that graphene nucleation near a metal step edge is superior to that on a terrace. On the basis of our analysis, we propose the use of graphene seeds to synthesize high-quality graphene in large area.     

On the Approximation of the SABR with Mean Reversion Model: A Probabilistic Approach

Abstract

In this paper, we study the stochastic alpha beta rho with mean reversion model (SABR-MR). We first compare the SABR model with the SABR-MR model in terms of future volatility to point out the fundamental difference in the models’ dynamics. We then derive an efficient probabilistic approximation for the SABR-MR model to price European options. Similar to the method derived in Kennedy, J. E., Mitra, S., & Pham, D. (2012). On the approximation of the SABR model: A probabilistic approach. Applied Mathematical Finance, 19(6), 553–586., we focus on capturing the terminal distribution of the underlying asset (conditional on the terminal volatility) to arrive at the implied volatilities of the corresponding European options for all strikes and maturities. Our resulting method allows us to work with a wide range of parameters that cover the long-dated option and different market conditions.     

Hedgehog frames and a cardinal extension of normality

The hedgehog metric topology is presented here in a pointfree form, by specifying its generators and relations. This allows us to deal with the pointfree version of continuous (metric) hedgehog-valued functions that arises from it. We prove that the countable coproduct of the metric hedgehog frame with κ spines is universal in the class of metric frames of weight $\kappa ?{\mathrm{?}}_0$. We then study κ-collectionwise normality, a cardinal extension of normality, in frames. We prove that this is the necessary and sufficient condition under which Urysohn separation and Tietze extension-type results hold for continuous hedgehog-valued functions. We show furthermore that κ-collectionwise normality is hereditary with respect to $F_{\sigma }$-sublocales and invariant under closed maps.     

The “Historical Materials BAG”: A New Facilitated Access to Synchrotron X-ray Diffraction Analyses for Cultural Heritage Materials at the European Synchrotron Radiation Facility

The European Synchrotron Radiation Facility (ESRF) has recently commissioned the new Extremely Brilliant Source (EBS). The gain in brightness as well as the continuous development of beamline instruments boosts the beamline performances, in particular in terms of accelerated data acquisition. This has motivated the development of new access modes as an alternative to standard proposals for access to beamtime, in particular via the “block allocation group” (BAG) mode. Here, we present the recently implemented “historical materials BAG”: a community proposal giving to 10 European institutes the opportunity for guaranteed beamtime at two X-ray powder diffraction (XRPD) beamlines—ID13, for 2D high lateral resolution XRPD mapping, and ID22 for high angular resolution XRPD bulk analyses—with a particular focus on applications to cultural heritage. The capabilities offered by these instruments, the specific hardware and software developments to facilitate and speed-up data acquisition and data processing are detailed, and the first results from this new access are illustrated with recent applications to pigments, paintings, ceramics and wood.