Proton Activation Research Articles

Electrodeposition of rhenium with suppressed hydrogen evolution from water-in-salt electrolyte

The electrodeposition of rhenium was studied using a “water-in-salt” type of electrolyte with a superhigh concentration of lithium chloride to suppress the proton activity. Cyclic voltammetry and DC plating were carried out on rotating disc electrodes to characterize the electrolyte and to prepare thin films. Electrolytes without metal cations were also studied, where the cathodic reduction of proton was significantly suppressed when the concentration of supporting salt approached the solubility limit. Film cracks were eliminated for rhenium films deposited from this superhigh ionic strength electrolyte.

Leaching of Chalcopyrite in Acidified Nitrate Using Seawater-Based Media

The leaching of copper from industrial copper ore with 4.8 wt % chalcopyrite by acidified nitrate with seawater based media was investigated. Water quality (pure water and seawater), temperature (25–70 °C), reagent concentration, and nitrate type (sodium and potassium) were studied variables. Leaching conditions were: 100 g ore/1 L solution; P80 of 62.5 µm; 400 rpm and leaching time, varying between 3 and 7 days. Nitrates in sulfuric acid are known to be good oxidants for sulfide ores. This study showed that up to 80 wt % copper could be extracted at 45 °C in 7 days. In the absence of nitrate, under the same leaching conditions, only a 28 wt % copper extraction was achievable. The extraction rate increased to 97.2 wt % when leach temperature was increased to 70 °C in nitrate-chloride-acid media. The presence of chloride ions also increased the copper extraction rate. The copper extraction achieved in seawater systems were higher than in water systems under the same leaching conditions (increased by an average of 18 wt %). This effect can be attributable to the contribution of chloride that increases proton (H+) activity.

Local spatial charge separation and proton activation induced by surface hydroxylation promoting photocatalytic hydrogen evolution of polymeric carbon nitride

Polymeric carbon nitride as an intriguing earth-abundant visible light photocatalyst for H2 evolution has projected huge potentials. A high-performance polymeric carbon nitride photocatalyst system always requires fabrication of nanostructure or assistance of other semiconductors for ample reactive sites or rapid carrier migration/charge separation. Here, we disclose that hydroxylation as an efficient surface polarization decoration tactic without involving nanostructure or other semiconductors can substantially promote local spatial charge separation and proton activation of polymeric carbon nitride, thus achieving high photocatalytic H2 evolution. The post-hydrothermal treatment allows polymeric carbon nitride surface controllable grafting of abundant hydroxyls (-OH) on the -C≡N sites, which not only extends the 2D conjugate electron system of polymeric carbon nitride to 3D space to realize local spatial charge separation, but also polarizes the neighboring N atoms (C-N=C) to promote the proton adsorption and activation on them, further contributing to the high H2 evolution performance. The deep hydroxylation offered by introduction of basic ammonium salts discloses a pH-dependent hydroxylation-level mechanism and renders a ~ 11-fold enhancement in H2 generation rate with an AQY of 9.1% at 420 ± 15 nm. The finding may bring a new opportunity for developing highly-efficient HER materials base on surface polarization of functional groups.

Stabilization of Electrodeposit in Soluble Lead Flow Batteries with Acetate Additive

The emerging of renewable energy demands energy storage. Redox flow batteries are inherently suited for large-scale applications, but their market penetration is thwarted by the high materials cost. In contrast, membrane-less and single-flow soluble lead flow batteries (SLFBs) are more economical to scale up and free of expensive noble metals. However, lifespan of SLFBs reported so far is limited to approximately 200 cycles under normal flow conditions, which is insufficient for long-term operation in utility applications. Failures of SLFBs are believed to be associated with PbO2 deposition/dissolution at the positive electrode. Although failure mechanisms are not well understood, passivation and shedding of PbO2 are suggested to decrease efficiency of SLFBs. Formation of a passivation layer of non-stoichiometric PbOx is found to be correlated to proton activities. PbO2 deposits of poor adherence and low quality are also observed to occur when the electrolyte is high in acidity. We therefore employ sodium acetate (NaOAc) as electrolyte additive, and successfully extend the cycle life of SLFBs by over 50%. In this study, effects of acetate additive on electroplating of PbO2 are investigated. Surface morphology and mechanical strength of electroplated PbO2 via electrolyte with and without NaOAc are examined by scanning electron microscopy (SEM) and nano-indentation, respectively. Acetate-assisted electrolyte is found to substantially enhance deposited film strength and leads to a more integrated and smoother surface. Crystal structures, grain sizes, and grain orientations of plated PbO2 are analyzed via x-ray diffraction (XRD) and electron back scatter diffraction (EBSD), and very different phase distributions and grain orientations are observed for electrolyte with and without NaOAc. Electroplating and oxygen evolution kinetics are further investigated by rotating disk electrode (RDE) experiments. Our findings elucidate acetate additive effects on electroplating of PbO2 in SLFB systems and shed lights on battery life extension.

Dissolution kinetics of monazite LnPO4 (Ln = La to Gd): A multiparametric study

The chemical durability of monazites LnPO4 (Ln = La → Gd) was investigated. The influence of several parameters on the normalized dissolution rates, including acidity and temperature, was investigated under dynamic conditions. The impact of the saturation processes of the solution was also examined through static experiments. Under the investigated conditions, the normalized dissolution rates were found to be very low for all the lanthanide elements considered (La → Gd). The partial order of the dissolution reaction related to the proton activity varied from 0.7 ± 0.2 to 1.5 ± 0.3 for LnPO4 (Ln = La, Ce, Nd and Gd). The apparent range of activation energies associated with the dissolution of monazites Eapp shifted from 54 to 103 kJ mol−1 below 313 K (characteristic values for dissolution process controlled by surface reactions) to 6–17 kJ mol−1 between 313 K and 363 K. These values are usually associated with mass transport as the rate-limiting step in the dissolution mechanism. This modification suggested an impact of the f(ΔRG) term included in the multiparametric expression for the normalized dissolution rate. Indeed, the Gibbs energy of the dissolution reaction, ΔRG, increased from 298 K to 363 K with a significant break at 313 K. This result indicated that the solutions approached thermodynamic equilibrium with respect to rhabdophane in experiments performed above 313 K. This could impact the normalized dissolution rates, and thus, the parameters associated with kinetics. The study on the long-term behavior of NdPO4 under static conditions (298 K, 0.1 M HNO3) confirmed this point. After 10 days of leaching, the normalized dissolution rate decreased by more than one decade, whereas the saturation index with respect to rhabdophane increased significantly. This strong decrease in the normalized dissolution rate suggests that the saturation index in the solution impacts the normalized dissolution rates, even for solutions that were macroscopically under-saturated with respect to the rhabdophane.

The kinetics of the dissolution of malachite in acid solutions

The dissolution of screened samples of pure malachite in dilute (0.033 to 0.15 M) sulfuric acid solutions has been shown to be rapid and the kinetics of dissolution are consistent with rate-determining chemical reaction on the surface of the shrinking particles. There is no evidence of mass transport controlled dissolution even at the highest rates. The rate is inversely proportional to the particle size and increases with increasing acidity. However, the relationship between the rate and the acid concentration is not linear but is directly proportional to the proton activity as obtained from pH measurements. The effect of the addition of chloride ions on the rate is relatively small and it appears to involve a specific effect of chloride at low concentrations and the effect of chloride on the proton activity at high concentrations. The rate increases with increasing temperature and the activation energy of 53.6 kJ mol−1 is in the range expected for a rate-determining chemical reaction.A simple fundamental rate equation has been developed that will allow prediction of the dissolution curves for any particle size at any acid concentration and temperature within the range studied.From a practical perspective, these results suggest that heap leaching of malachite in dilute acid should present no chemical problems and that there is little advantage to be gained from the addition of chloride ions to increase the rate of leaching.

Thermodynamics and proton activities of protic ionic liquids with quantum cluster equilibrium theory.

We applied the binary Quantum Cluster Equilibrium (bQCE) method to a number of alkylammonium-based protic ionic liquids in order to predict boiling points, vaporization enthalpies, and proton activities. The theory combines statistical thermodynamics of van-der-Waals-type clusters with ab initio quantum chemistry and yields the partition functions (and associated thermodynamic potentials) of binary mixtures over a wide range of thermodynamic phase points. Unlike conventional cluster approaches that are limited to the prediction of thermodynamic properties, dissociation reactions can be effortlessly included into the bQCE formalism, giving access to ionicities, as well. The method is open to quantum chemical methods at any level of theory, but combination with low-cost composite density functional theory methods and the proposed systematic approach to generate cluster sets provides a computationally inexpensive and mostly parameter-free way to predict such properties at good-to-excellent accuracy. Boiling points can be predicted within an accuracy of 50 K, reaching excellent accuracy for ethylammonium nitrate. Vaporization enthalpies are predicted within an accuracy of 20 kJ mol-1 and can be systematically interpreted on a molecular level. We present the first theoretical approach to predict proton activities in protic ionic liquids, with results fitting well into the experimentally observed correlation. Furthermore, enthalpies of vaporization were measured experimentally for some alkylammonium nitrates and an excellent linear correlation with vaporization enthalpies of their respective parent amines is observed.

Stabilizing the electrodeposit-electrolyte interphase in soluble lead flow batteries with ethanoate additive

The soluble lead flow battery (SLFB) is a promising energy storage system. In comparison to conventional flow batteries, the membrane-less and single-flow design of SLFBs is potentially much more economical to scale up for utility-scale applications. However, SLFB lifespan reported so far is less than 200 cycles under normal flow conditions. This study reports a method for significantly extending the cycle life and expanding capacity of SLFBs. By adding an adequate amount of sodium ethanoate to the electrolyte, lead dioxide (PbO2) deposition stability is materially improved and shed PbO2 particles are substantially reduced. Lifespan of ethanoate-added SLFBs is shown to extend by over 50%, and under optimal condition exceeds 500 cycles at over 65% energy efficiency. This improvement in SLFB performance is primarily attributed to the stabilization of both the electroplated PbO2 layers and proton activity at the electrodeposit-electrolyte interphase. We demonstrate a novel and economical approach for advancing performance of membrane-less flow batteries that involve redox reactions associated with acidity variation and operate through electrodeposition.

Proton-Coupled Electron Transfer in Artificial Photosynthetic Systems.

Artificial photosynthetic constructs can in principle operate more efficiently than natural photosynthesis because they can be rationally designed to optimize solar energy conversion for meeting human demands rather than the multiple needs of an organism competing for growth and reproduction in a complex ecosystem. The artificial photosynthetic constructs described in this Account consist primarily of covalently linked synthetic chromophores, electron donors and acceptors, and proton donors and acceptors that carry out the light absorption, electron transfer, and proton-coupled electron transfer (PCET) processes characteristic of photosynthetic cells. PCET is the movement of an electron from one site to another accompanied by proton transfer. PCET and the transport of protons over tens of angstroms are important in all living cells because they are a fundamental link between redox processes and the establishment of transmembrane gradients of proton electrochemical potential, known as proton-motive force (PMF), which is the unifying concept in bioenergetics. We have chosen a benzimidazole phenol (BIP) system as a platform for the study of PCET because with appropriate substitutions it is possible to design assemblies in which one or multiple proton transfers can accompany oxidation of the phenol. In BIP, oxidation of the phenol increases its acidity by more than ten pKa units; thus, electrochemical oxidation of the phenol is associated with a proton transfer to the imidazole. This is an example of a PCET process involving transfer of one electron and one proton, known as electron-proton transfer (EPT). When the benzimidazole moiety of BIP is substituted at the 4-position with good proton acceptor groups such as aliphatic amines, experimental and theoretical results indicate that two proton transfers occur upon one-electron oxidation of the phenol. This phenomenon is described as a one-electron-two-proton transfer (E2PT) process and results in translocation of protons over ∼7 Å via a Grotthuss-type mechanism, where the protons traverse a network of internally H-bonded sites. In the case of the E2TP process involving BIP analogues with amino group substituents, the thermodynamic price paid in redox potential to move a proton to the final proton acceptor is ∼300 mV. In this example, the decrease in redox potential limits the oxidizing power of the resulting phenoxyl radical. Thus, unlike the biological counterpart, the artificial construct is thermodynamically incapable of effectively advancing the redox state of a water oxidation catalyst. The design of systems where multiple proton transfer events are coupled to an oxidation reaction while a relatively high redox potential is maintained remains an outstanding challenge. The ability to control proton transfer and activity at defined distances and times is key to achieving proton management in the vicinity of catalysts operating at low overpotential in myriad biochemically important processes. Artificial photosynthetic constructs with well-defined structures, such as the ones described in this Account, can provide the means for discovering design principles upon which efficient redox catalysts for electrolysis and fuel cells can be based.

Improved Endurance Gain in BALB / C Mice by a Nanotechnology Medical Device

The main finding of the present study was the improved gain in BALB / C mice, following the application of a patch (T-NES®-HIT Tech.), enriched with an active central pad, based on micronized silver. In order to transfer very thin Extremely Low Frequency (ELF) magnetoelectric signals, the pad contains a nanotechnological material (silver micronized by plasma vaporization) that is appropriately activated with optical, magnetic, electrical, and acoustic signals. It has been reported previously that the ELF magnetic field, induces an action on cellular glycocalics, fundamental for cellular communication and recognition, and a direct activation of protons and ionic fluxes. The treated animals underwent exercises with Rotarod and several parameters were evaluated and compared with untreated control mice. The following parameters were measured: steady state generic training, long slow distance, high intensity endurance and steady state split session training. The ELF magnetic field of T-NES®-HIT Tech. micronized silver patch device, applied to BALB / C mice, markedly improved their gain performance as evidenced by the increase of their aerobic capacity, maximum heart rate and maximum aerobic speed.

Full mutational mapping of titratable residues helps to identify proton-sensors involved in the control of channel gating in the Gloeobacter violaceus pentameric ligand-gated ion channel.

The Gloeobacter violaceus ligand-gated ion channel (GLIC) has been extensively studied by X-ray crystallography and other biophysical techniques. This provided key insights into the general gating mechanism of pentameric ligand-gated ion channel (pLGIC) signal transduction. However, the GLIC is activated by lowering the pH and the location of its putative proton activation site(s) still remain(s) unknown. To this end, every Asp, Glu, and His residue was mutated individually or in combination and investigated by electrophysiology. In addition to the mutational analysis, key mutations were structurally resolved to address whether particular residues contribute to proton sensing, or alternatively to GLIC-gating, independently of the side chain protonation. The data show that multiple residues located below the orthosteric site, notably E26, D32, E35, and D122 in the lower part of the extracellular domain (ECD), along with E222, H235, E243, and H277 in the transmembrane domain (TMD), alter GLIC activation. D122 and H235 were found to also alter GLIC expression. E35 is identified as a key proton-sensing residue, whereby neutralization of its side chain carboxylate stabilizes the active state. Thus, proton activation occurs allosterically to the orthosteric site, at the level of multiple loci with a key contribution of the coupling interface between the ECD and TMD.

Electronic effect on the optical properties and sensing ability of AIEgens with ESIPT process based on salicylaldehyde azine

Two novel AIE-active salicylaldehyde azine (SAA) derivatives with a typical excited-state intramolecular proton transfer (ESIPT) process are prepared by introducing electron-withdrawing and donating groups at para-position of phenolic hydroxyl group (CN-SAA and TPA-SAA). The effect of the proton activity in SAA framework on their optical behaviors is investigated spectroscopically. The results from NMR and solvation measurements show that the proton of phenolic hydroxyl group has higher activity when there are electron-withdrawing groups, and the absorption and fluorescence spectra in buffers with different pH also provide the same results. After inviting F− as a nucleophilic probe, this proton activity difference in CN-SAA and TPA-SAA becomes more obvious. The potential application of both molecules is investigated. TPA-SAA exhibits good quantitative sensing ability towards F− with a fluorescence “turn-on” mode, whereas the aggregates of TPA-SAA can selectively and sensitively detect Cu2+ in aqueous solution. From these results, a structure-property relationship is established: the occurrence of ESIPT process will become much easier when linking electron-withdrawing groups at the para-position of phenolic hydroxyl group (e.g., CN-SAA), and it is better to introduce electron-donating groups to enhance the sensing ability towards ions (e.g., TPA-SAA). This work will provide guidance for further design and preparation of AIE-active luminogens with ESIPT process for sensing applications.

Divergent Reactivity of 2-Vinylpyridine and 1-Vinylpyrazole in Rhodium-Phosphine Systems: C-H Activation and Dinuclear Chemistry

The RhI-RhIII mixed valence dinuclear complex Rh2-Cl2(μ-H)(μ-η2,κ2-C,N-NC5H4-2-(Z)CH=CH)(PPhMe2)3 has been prepared by reaction of [Rh(μ-Cl)(η2-coe)2]2 with 2-vinylpyridine in the presence of dimethylphenylphosphine as a result of C-H activation of the terminal olefinic proton. The X-ray structure presents anagostic Rh···HC and π-π interactions between aromatic rings. In contrast, 1-vinylpyrazole does not undergo a C-H activation process, resulting in the formation of dinuclear species supported by 1-vinylpyrazole bridges. Anagostic Rh···HC interactions and CH···Cl hydrogen bonds are responsible for the 3D packing of the complex.

Inflight proton activation and damage on a CdTe detection plane

Future high-energy space telescope missions require further analysis of orbital environment induced activation and radiation damage on main instruments. A scientific satellite is exposed to the charged particles harsh environment, mainly geomagnetically trapped protons (up to ∼300 MeV) that interact with the payload materials, generating nuclear activation background noise within instruments’ operational energy range and causing radiation damage in detector material. As a consequence, instruments’ performances deteriorate during the mission time-frame. In order to optimize inflight operational performances of future CdTe high-energy telescope detection planes under orbital radiation environment, we measured and analyzed the effects generated by protons on CdTe ACRORAD detectors with 2.56 cm2 sensitive area and 2 mm thickness. To carry-out this study, several sets of measurements were performed under a ∼14 MeV cyclotron proton beam. Nuclear activation radionuclides’ identification was performed. Estimation of activation background generated by short-lived radioisotopes during one day was less than ∼1.3×10−5 counts cm−2 s−1 keV−1 up to 800 keV. A noticeable gamma-rays energy resolution degradation was registered (∼60% @ 122 keV, ∼14% @ 511 and ∼2.2% @ 1275 keV) after an accumulated proton fluence of 4.5×1010 protons cm−2, equivalent to ∼22 years in-orbit fluence. One year later, the energy resolution of the irradiated prototype showed a good level of performancerecovery.

Charging Lithium-Oxygen Battery Via Protic Solvent-Enhanced Redox Shuttle Mechanism

Lithium-oxygen battery has the highest theoretic energy density among all rechargeable batteries. But its discharge product Li2O2 is difficult to be oxidized back in the charge process, which causes high charge overpotential, serious electrolyte decomposition and poor cyclability. An effective way to solve this problem is adding redox mediator (RM) in the electrolyte to catalyze the charge reaction via a solution phase process. However, the reaction kinetics between the oxidized RM and Li2O2 is seldom investigated. Here, taking iodine species as the model RM, we find that the efficiency of the solution phase catalysis is limited by the reaction rate between the oxidized RM and Li2O2, which is largely dependent on the electrolyte solvent. Protic solvents, such as water and alcohols lead to high reaction rate because of the hydrogen bond induced solvation of Li2O2. However, too high proton activity may also bring unwanted peroxide disproportionation. Among a series of alcohols, n-butanol is found to show proper proton activity and significantly improves the solution phase catalytic efficiency. Some issues on objectively evaluating the cathode performance of lithium-oxygen battery will also be discussed in this talk. Because of the complexity of the multi-phase electrochemical reaction, conventional half-cell testing methods and parameters to evaluate the performance of lithium-ion cathodes are not suitable for lithium-oxygen cathodes. It is common to use unlimited lithium and unlimited oxygen in half-cell tests. But such tests are just testing the “reusability of the catalyst” instead of the “reversibility of the electrochemical reaction”. The result cannot objectively reflect the parasitic reactions. To objectively evaluate the electrochemical reversibility, we propose a Li2O2-graphite cell with limited amount of lithium-ion. Such configuration can eliminate the “fake reversible capacity” caused by parasitic cathodic reactions, and thus is more reliable. We found that the real reversible ratio of the cathode reaction is much improved with the presence of redox mediator and butanol, but still far from satisfactory. ref: 1. Shen, Y.; Zhang, W.; Chou, S.-L.; Dou, S.-X. Science 2016, 352, 667. 2. Sun, D.; Shen, Y.; Zhang, W.; Yu, L.; Yi, Z.; Yin, W.; Wang, D.; Huang, Y.; Wang, J.; Wang, D.; Goodenough, J. B. J. Am. Chem. Soc. 2014, 136, 8941. 3. Zhang, W.; Shen, Y.; Sun, D.; Huang, Z.; Zhou, J.; Yan, H.; Huang, Y. Nano Energy 2016, 30, 43. 4. Zhang, W; Shen, Y. ; Sun, D.;Huang, Z.; Huang, Y. Adv. Energy Mater. 2017, DOI:aenm201602938.

Luminescent Three- and Four-Coordinate Dinuclear Copper(I) Complexes Triply Bridged by Bis(diphenylphosphino)methane and Functionalized 3-(2'-Pyridyl)-1,2,4-triazole Ligands.

A new series of bimetallic Cu(I) complexes 1-5 triply bridged by a monoanionic or charge-neutral functionalized 3-(2'-pyridyl)-1,2,4-triazole in a μ-η1(N),η2(N,N) tridentate binding mode and two bis(diphenylphosphino)methane (dppm) ligands have been synthesized. Complexes 1-5 are singly or doubly charged dinuclear Cu(I) species with an eight-membered Cu2C2P4 ring of {Cu(μ-dppm)2Cu} unit, in which 3 and 4 adopt the boat-boat conformation, while 1, 2, and 5 display the chair-boat form. In these dimeric copper(I) complex cations, one of the two Cu(I) ions is four-coordinated, in a highly distorted N2P2 tetrahedral environment and the other is three-coordinated, in a distorted NP2 trigonal planar arrangement. All these Cu(I) complexes exhibit a comparatively weak low-energy absorption in CH2Cl2 solution, ascribed to the charge-transfer transitions with appreciable 1MLCT contribution, as suggested by time-dependent density functional theory (TDDFT) analyses. Complexes 1-5 display good emission properties in both solution and solid states at ambient temperature, which are well-modulated via structural modification of 3-(2'-pyridyl)-1,2,4-triazole, including the alteration of the substituent type (-CF3, -H, -CH3, and -C(CH3)3) and position (ortho-, meta-, and para-position). Furthermore, the variation of the substituent (-CF3 and -C(CH3)3) on the 5-site of the 1,2,4-triazolyl ring markedly influences the proton activity of the 1,2,4-triazolyl-NH, thus leading to the formation of both singly and doubly charged bimetallic Cu(I) species regulated by the NH ↔ N- conversion, resulting from NH deprotonation of the 1,2,4-triazolyl ring.

Measurement and adjustment of proton activity in solid polymer electrolytes

Technological progress in electrochemical energy conversion devices requires new solid polymer electrolyte membrane (PEM) materials with particular properties. The strongly acidic nature of Nafion® is not always desirable; for instance, CO2 electroreduction requires a low proton activity to avoid excess hydrogen evolution. This communication presents a novel measurement technique for determining the acidity of a PEM, using a pH-sensitive electrode half-cell attached to the membrane sample, connected to a reference electrode via a salt bridge. A dynamic hydrogen electrode on platinized‑platinum surface (DHE) was found to give repeatable results within 5% uncertainty. Several membranes based on Nafion® impregnated with various basic species were tested, as well as an anion-exchange membrane and a poly-phosphonic acid membrane. The technique is expected to have wider reaching applications in PEM fuel cell and redox flow battery development, as well as in the electrolysis and electrodialysis industries.

Abstract 5429: The Warburg Effect: protons suck

Abstract Aerobic glycolysis (the Warburg Effect) is a hallmark of cancer and is associated with local invasion and metastasis. This metabolic phenotype results in acidification of the microenvironment in solid tumors, which is responsible for many of the known sequelae. For example, systemic buffer therapy directly and specifically increases extracellular tumor pH and reduces spontaneous and experimental metastasis in vivo. Further, extracellular acidosis can be a potent inhibitor of anti-tumor immunity. Removal of glycolytically-derived acids requires the activity of proton transporting mechanisms, such as NHE, V-ATPase and CA-IX. While it is commonly believed that these transporters are responding to the demands imposed by increased glycolytic flux, an alternative hypothesis states that glycolytic flux is increased to satisfy the demand driven by these transporters. Hence, expression of transporters that drive extracellular acidosis would induce a more glycolytic phenotype. To test this, we have transfected lowly glycolytic and non-metastatic MCF-7 breast adenocarcinoma cells with two different proton transporters. In the first model, we used the yeast plasma membrane proton ATPase 1 (PMA1); a Type 1 P-type ATPase. PMA1 was stably over-expressed in MCF7 cell line and over-expression of PMA1 transformed the cells into a more aggressive phenotype with increased glucose consumption, lactate production, and proton production. Phenotypically, the transfected clones had elevated rates of migration and invasion in vitro and increased metastasis in vivo. This experimental evidence supports the hypothesis that proton export alone could drive the Warburg phenotype. Hence, in this system, glucose is metabolized to replenish either the ATP expended or the exported hydrogen-ions. In the second model we used CA-IX; an exofacial carbonic anhydrase that is highly expressed in invasive cancers and materially participates in acidifying the microenvironment. CA-IX is upregulated in multiple cancer types with minimal expression in normal tissue, and is therefore an attractive and biologically relevant therapeutic target. In vitro, we have observed that many cells expressing a glycolytic phenotype have elevated CA-IX expression, leading us to postulate that these phenotypes are coupled. To test this, we stably overexpressed CA-IX in MCF7 cells and again this resulted in a stable, glycolytic phenotype with increased glucose consumption, lactate production, and proton production observed using assay kits and live cell metabolic phenotyping with the Seahorse Extracellular Flux Analyzer. Through this study we have shown that acidosis leads to a more aggressive behavior and that CA-IX expression alone can induce a glycolytic phenotype. Hence, we hypothesise this is due to the enzymatic activity of CA-IX “sucking in” glucose to replenish intracellular H+ that are exported by this mechanism. Citation Format: Shonagh Russell, Liping Xu, Rober J. Gillies. The Warburg Effect: protons suck [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5429. doi:10.1158/1538-7445.AM2017-5429

New Cobalt‐Bisterpyridyl Catalysts for Hydrogen Evolution Reaction

AbstractPreparation of a series of terpyridyl ligands bearing different substituents recently led to the synthesis of new cobalt‐bisterpyridyl complexes spanning over a wide range of redox potentials. In this work, we describe the catalytic properties of these complexes for the electroreduction of protons into hydrogen (hydrogen evolution reaction (HER)) in acetonitrile. The substituents of the ligands were found to greatly affect the catalytic performances of the systems, in terms of stability and overpotential. Interestingly, systems based on dimethylamino‐terpyridine derivatives perform HER with high efficiency, low overpotential and excellent stability. Density functional theory calculations were used to provide insights into the reaction mechanism of HER catalyzed by these systems, highlighting the role of the ligand for proton activation.

Concerted One-Electron Two-Proton Transfer Processes in Models Inspired by the Tyr-His Couple of Photosystem II.

Nature employs a TyrZ-His pair as a redox relay that couples proton transfer to the redox process between P680 and the water oxidizing catalyst in photosystem II. Artificial redox relays composed of different benzimidazole–phenol dyads (benzimidazole models His and phenol models Tyr) with substituents designed to simulate the hydrogen bond network surrounding the TyrZ-His pair have been prepared. When the benzimidazole substituents are strong proton acceptors such as primary or tertiary amines, theory predicts that a concerted two proton transfer process associated with the electrochemical oxidation of the phenol will take place. Also, theory predicts a decrease in the redox potential of the phenol by ∼300 mV and a small kinetic isotope effect (KIE). Indeed, electrochemical, spectroelectrochemical, and KIE experimental data are consistent with these predictions. Notably, these results were obtained by using theory to guide the rational design of artificial systems and have implications for managing proton activity to optimize efficiency at energy conversion sites involving water oxidation and reduction.