Use of Dithiasuccinoyl-Caged Amines Enables COS/H2S Release Lacking Electrophilic Byproducts

The enzymatic conversion of carbonyl sulfide (COS) to hydrogen sulfide (H₂S) by carbonic anhydrase has been used to develop self-immolating thiocarbamates as COS-based H₂S donors to further elucidate the impact of reactive sulfur species in biology. The high modularity of this approach has provided a library of COS-based H₂S donors that can be activated by specific stimuli. A common limitation, however, is that many such donors result in the formation of an electrophilic quinone methide byproduct during donor activation. As a mild alternative, we demonstrate here that dithiasuccinoyl groups can function as COS/H₂S donor motifs, and that these groups release two equivalents of COS/H₂S and uncage an amine payload under physiologically relevant conditions. Additionally, we demonstrate that COS/H₂S release from this donor motif can be altered by electronic modulation and alkyl substitution. These insights are further supported by DFT investigations, which reveal that aryl and alkyl thiocarbamates release COS with significantly different activation energies.     

Vibrational Circular Dichroism Unravels Supramolecular Chirality and Hydration Polymorphism of Nucleoside Crystals

Vibrational circular dichroism (VCD) spectroscopy has been widely used to study (bio)molecules in solution. However, its solid-state applications have been restricted due to experimental limitations and artifacts. Having overcome some of them, the first VCD study of nucleoside crystals is now presented. A two-orders-of-magnitude enhancement of VCD signal was observed due to high molecular order in the crystals and resulting supramolecular chirality. This allowed to obtain high-quality VCD spectra within minutes using minute amounts of samples. The VCD technique is extremely sensitive in detecting changes in a crystal order and is able to distinguish different hydration states of crystals. This elevates it to a new level, as a fast and efficient tool to study chiral crystalline samples. This study demonstrates that VCD is capable of near-instantaneous detection of hydration polymorphs and crystal degradation, which is of substantial interest in pharmaceutical industry (quality and stability control).     

Redox-Active Hybrid Polyoxometalate-Stabilised Gold Nanoparticles

We report the design and preparation of multifunctional hybrid nanomaterials through the stabilization of gold nanoparticles with thiol-functionalised hybrid organic–inorganic polyoxometalates (POMs). The covalent attachment of the hybrid POM forms new nanocomposites that are stable at temperatures and pH values which destroy analogous electrostatically functionalised nanocomposites. Photoelectrochemical analysis revealed the unique photochemical and redox properties of these systems.     

Remote Oxidative Activation of a [Cp*Rh] Monohydride**

Half-sandwich rhodium monohydrides are often proposed as intermediates in catalysis, but little is known regarding the redox-induced reactivity accessible to these species. Herein, the bis(diphenylphosphino)ferrocene (dppf) ligand has been used to explore the reactivity that can be induced when a [Cp*Rh] monohydride undergoes remote (dppf-centered) oxidation by 1e⁻. Chemical and electrochemical studies show that one-electron redox chemistry is accessible to Cp*Rh(dppf), including a unique quasi-reversible Rh^II/I process at −0.96 V vs. ferrocenium/ferrocene (Fc^+/0). This redox manifold was confirmed by isolation of an uncommon Rh^II species, [Cp*Rh(dppf)]⁺, that was characterized by electron paramagnetic resonance (EPR) spectroscopy. Protonation of Cp*Rh(dppf) with anilinium triflate yielded an isolable and inert monohydride, [Cp*Rh(dppf)H]⁺, and this species was found to undergo a quasireversible electrochemical oxidation at +0.41 V vs. Fc^+/0 that corresponds to iron-centered oxidation in the dppf backbone. Thermochemical analysis predicts that this dppf-centered oxidation drives a dramatic increase in acidity of the Rh−H moiety by 23 pK_a units, a reactivity pattern confirmed by in situ ¹H NMR studies. Taken together, these results show that remote oxidation can effectively induce M−H activation and suggest that ligand-centered redox activity could be an attractive feature for the design of new systems relying on hydride intermediates.     

Towards synthetic diatoms: The Phaeodactylum tricornutum Pt-syn 1.0 project

Synthetic genomics is an emerging field where large-scale DNA engineering is used to study and produce organisms of interest. Here we propose the marine diatom, Phaeodactylum tricornutum, as a candidate for a synthetic genome project and describe some of the strategies to bring this design, termed Pt-syn1.0, to life. This project is fueled by the emergence of a completed genome assembly, powerful methods for manipulating large-scale DNA, and effective DNA delivery methods. We propose that a recombination-deficient strain be created as a prerequisite to downstream genome manipulation to preserve any genetic modifications. In addition, the synthetic genome will be split between 50 chromosomes of approximately 500 kbp each to allow for easy construction and delivery. The establishment of a Pt-syn1.0 strain will lay the foundation for a streamlined engineering platform for P. tricornutum, alleviating many of the current constraints, and would drive diatom research and biotechnology into the next era.     

Colourimetric Carboxylate Anion Sensors Derived from Viologen‐Based Receptors

A series of tri‐ and tetrapodal viologen‐based anion receptors showing a colourimetric response to carboxylates, such as acetate, have been synthesised. Alteration of the anion binding sites allows for binding site competition within a receptor. This results in a delayed colourimetric response for urea derivatives compared with pyridinium systems because the anions are initially bound to the periphery of the receptor, away from the viologen unit. DFT calculations and experimental measurements allow the colour change to be assigned to an anion–receptor charge‐transfer process, facilitated by the exceptionally low reduction potential of the cationic host compounds. Evidence for electron transfer to give the viologen radical cation is also seen in some cases.     

Effect of Nb alloying additions on the characteristics of anodic oxide films on zirconium and their stability in NaOH solution

The characteristics of oxide films on Zr and Zr–Nb alloys (with Nb content of 2.5, 5, and 10 at.%) galvanostatically formed (at a current density of 100 μA cm^?2) in 0.5 M H₂SO₄ solution were investigated by means of electrochemical impedance spectroscopy. Electrochemical impedance spectroscopy spectra were interpreted in terms of an “equivalent circuit” with the circuit elements representing the electrochemical properties of a single layer oxide. The resistance of the oxide films was found to increase with increased Nb content in the alloy while the capacitance showed an opposite trend. The stability of the anodic oxide films grown in the sulfuric acid solution on Zr and Zr–Nb alloys was investigated by simultaneously measuring the electrode capacitance and resistance at a working frequency of 1 kHz as a function of exposure time to naturally aerated 3 M NaOH solution. Analyses of the electrode capacitance and resistance values indicated a decrease in chemical dissolution rate of the oxide films with the increase of Nb content in the alloy.     

Simultaneous determination of acidic,neutral and basic pharmaceuticals in urban wastewater by ultra high-pressure liquid chromatography-tandem mass spectrometry

In this work, an ultra high-pressure liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method has been developed for the simultaneous quantification and confirmation of the 20 most consumed pharmaceuticals in Spain in urban wastewater and surface water samples. The scope of the method included acidic, neutral and basic compounds belonging to different therapeutic classes and allows their simultaneous determination in just a single injection, giving realistic information of the most widely consumed pharmaceuticals in only one analysis. An enrichment step based on solid-phase extraction using Oasis HLB cartridges was carried out, followed by UHPLC-MS/MS measurement with a fast-acquisition triple quadrupole mass analyzer. It allowed working with short dwell times and made possible to acquire three simultaneous SRM transitions per compound to assure a reliable identification. Several isotope-labelled internal standards were used as surrogates to correct SPE losses, as well as matrix effects that notably affect quantification of analytes. The method was validated in surface water and effluent and influent urban wastewater at different concentrations from 0.005 μg/L (surface water) to 1.25 μg/L (influent wastewater). The optimized method was applied to the analysis of 84 urban wastewater samples (influent and effluent), with the result that 17 out of 20 compounds monitored were detected in the samples. Analgesics and anti-inflamatories, cholesterol lowering statin drugs and lipid regulators were the major groups found, with diclofenac, ketoprofen, naproxen, 4-aminoantipyrine, bezafibrate, gemfibrozil and venlafaxine being the most frequently detected. The highest concentration level reached was 277 μg/L for salicylic acid in influent wastewater.     

Sources of contamination and remedial strategies in the multi-elemental trace analysis laboratory

In theory, state of the art inductively coupled plasma mass spectrometry (ICP–MS) instrumentation has the prerequisite sensitivity to carry out multi-elemental trace analyses at sub-ng L⁻¹ to sub-pg L⁻¹ levels in solution. In practice, constraints mainly imposed by various sources of contamination in the laboratory and the instrument itself, and the need to dilute sample solutions prior to analysis ultimately limit detection capabilities. Here we review these sources of contamination and, wherever possible, propose remedial strategies that we have found efficacious for ameliorating their impact on the results of multi-elemental trace analyses by ICP–MS. We conclude by providing a list of key points to consider when developing methods and preparing the laboratory to routinely meet the demands of multi-elemental analyses at trace analytical levels by ICP–MS.