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Abstract: Vanadium is a toxic metal present in alkaline leachates produced during the weathering of steel slags. Slag leaching can therefore have deleterious effects on local watercourses due to metal toxicity, the effects of the high pH (9–12.5) and rapid carbonation (leading to smothering of benthic communities). We studied the fate and behaviour of V in slag leachate both through field observations of a heavily affected stream (Howden Burn, Consett UK) and in controlled laboratory experiments where slag leachates were neutralised by CO2 ingassing from air. V was found to be removed from leachates downstream from the Howden Burn source contemporaneously with a fall in pH, Ca, Al and Fe concentrations. In the neutralisation experiments pH reduced from 12 → 8, and limited quantities of V were incorporated into precipitated CaCO3. The presence of kaolinite clay (i.e. SiOH and AlOH surfaces) during neutralisation experiments had no measureable effect on V uptake in the alkaline to circumneutral pH range. XANES analysis showed that V was present in precipitates recovered from experiments as adsorbed or incorporated V(V) indicating its likely presence in leachates as the vanadate oxyanion (HVO42−). Nano-scale particles of 2-line ferrihydrite also formed in the neutralised leachates potentially providing an additional sorption surface for V uptake. Indeed, removal of V from leachates was significantly enhanced by the addition of goethite (i.e. FeOOH surfaces) to experiments. EXAFS analysis of recovered goethite samples showed HVO42− was adsorbed by the formation of strong inner-sphere complexes, facilitating V removal from solution at pH < 10. Results show that carbonate formation leads to V removal from leachates during leachate neutralisation, and the presence of both naturally occurring and neoformed Fe (oxy)hydroxides provide a potent sink for V in slag leachates, preventing the spread of V in the environment.

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Abstract: This is a review that describes the golden rules and tips on how to characterise the molecular interactions of membrane sensor kinase proteins with ligands using mainly circular dichroism (CD) spectroscopy. CD spectroscopy is essential for this task as any conformational change observed in the far-UV (secondary structures (α-helix, β-strands, poly-proline of type II, β-turns, irregular and folding) and near-UV regions [local environment of the aromatic side-chains of amino acid residues (Phe, Tyr and Trp) and ligands (drugs) and prosthetic groups (porphyrins, cofactors and coenzymes (FMN, FAD, NAD))] upon ligand addition to the protein can be used to determine qualitatively and quantitatively ligand-binding interactions. Advantages of using CD versus other techniques will be discussed. The difference CD spectra of the protein–ligand mixtures calculated subtracting the spectra of the ligand at various molar ratios can be used to determine the type of conformational changes induced by the ligand in terms of the estimated content of the various elements of protein secondary structure. The highly collimated microbeam and high photon flux of Diamond Light Source B23 beamline for synchrotron radiation circular dichroism (SRCD) enable the use of minimal amount of membrane proteins (7.5 µg for a 0.5 mg/ml solution) for high-throughput screening. Several examples of CD titrations of membrane proteins with a variety of ligands are described herein including the protocol tips that would guide the choice of the appropriate parameters to conduct these titrations by CD/SRCD in the best possible way.

Open Access

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Abstract: Sustainable technologies require both renewable feedstocks and catalysts that are able to direct their conversion to specific products. We establish a structure-activity relationship for the aqueous phase reforming of glycerol over 2% Pt/Al2O3 catalysts, whereby the reaction pathway can be controlled to produce either hydrogen or 1,2-propanediol as the main product. Using the colloidal synthesis method, the reduction temperature was altered to produce Pt nanoparticle catalysts supported on Al2O3 with varying Pt particle size. The catalytic activity of the samples for the APR of glycerol resulted in a higher conversion of glycerol (34%) for the larger Pt particle size of ∼3.5 nm, producing the liquid 1,2-propanediol as the major product with a yield of 12.5%, whereas smaller particles of ∼2.2 nm gave hydrogen as the main product (5.5% yield). This work demonstrates how the APR of glycerol can be tuned to yield both valuable liquid and gas products using tailored Pt nanoparticles.

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Abstract: Ubiquitin (Ub)-conjugating enzymes and Ub ligases control protein degradation and regulate many cellular processes in eukaryotes. Cellular inhibitor of apoptosis protein-1 (cIAP1) plays a central role in apoptosis and tumor necrosis factor signaling. It harbors a C-terminal RING domain that homodimerizes to recruit E2~Ub (~ denotes a thioester bond) complex to catalyze Ub transfer. Non-covalent Ub binding to the backside of the E2 Ub-conjugating enzyme UbcH5 has previously been shown to enhance RING domain activity, but the molecular basis for this enhancement is unclear. To investigate how dimeric cIAP1 RING activates E2~Ub for Ub transfer and what role non-covalently bound Ub has in Ub transfer, here we determined the crystal structure of the cIAP1 RING dimer bound to both UbcH5B covalently-linked to Ub (UbcH5B–Ub) and a non-covalent Ub to 1.7 Å resolution. The structure along with biochemical analyses revealed that the cIAP1 RING domain interacts with UbcH5B–Ub and thereby promotes the formation of a closed UbcH5B–Ub conformation that primes the thioester bond for Ub transfer. We observed that the non-covalent Ub binds to the backside of UbcH5B and abuts UbcH5B’s α1β1-loop, which, in turn, stabilizes the closed UbcH5B–Ub conformation. Our results disclose the mechanism by which cIAP1 RING dimer activates UbcH5B~Ub and indicate that non-covalent Ub binding further stabilizes the cIAP1-UbcH5B~Ub complex in the active conformation to stimulate Ub transfer.

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Abstract: This paper investigates the possibility for suppression of the head-tail instability in an electron storage ring using a bunch-by-bunch transverse feedback system. General conditions are found whereby the Gaussian bunch profile may be modeled by a two-particle system which interacts with the vacuum chamber broadband impedance. We choose the kick factor received by a Gaussian bunch with the rms bunch length σt , from a broadband impedance with the resonance frequency ωr and quality factor Qr , as the relevant parameter and explain why the kick factor depends on ωrσt∕Qr . Finally, we demonstrate that a Gaussian bunch can be modeled by a two-particle system when the parameter ωrσt∕Qr is sufficiently small.