The Measurement of Mixed Potentials Using Platinum Decorated Nanoporous Gold Electrodes

Potentiometric redox sensing in solutions containing multiple redox molecules was evaluated using in-house constructed nanoporous gold (NPG)-platinum (Pt) and unmodified NPG electrodes. The NPG-Pt electrode was fabricated by electrodepositing Pt into the nanoporous framework of a chemically dealloyed NPG electrode. By varying the concentration of the Pt salt and the electrodeposition time, different amounts of Pt were introduced. Characterization by SEM shows the pore morphology doesn’t change with the addition of Pt and XPS indicates the electrodes contain ∼2.5–24 wt% Pt. Open-circuit potential (OCP) measurements in buffer and solutions containing ascorbic acid, cysteine, and/or uric acid show that the OCP shifts positive with the addition of Pt. These results are explained by an increase in the rate of the oxygen reduction reaction with the addition of Pt. The overall shape of the potentiometric titration curves generated from solutions containing one or more bioreagents is also highly dependent on the amount of Pt in the nanoporous electrode. Furthermore, the generation of OCP vs Log [bioreagent] from the results of the potentiometric experiments shows an ∼2-fold increase in sensitivity can result with the addition of Pt. These results indicate the promise that these electrodes have in potentiometric redox sensing.

Role of Plasma Membrane Redox Activities in Immune Response Mechanisms

The plasma membrane redox system (PMRS) is an important component of the cell's ability to defend itself against oxidative stress. Many immune signaling pathways are regulated through redox reactions. Biological systems utilize oxidationreduction reactions to modulate their responses to environmental cues. The role of redox molecules such as NO and ROS as key mediators of immunity has recently gathered a lot of interest and attention. Beyond the chemical interactions of NO and ROS that combine to eradicate pathogens, these redox small molecules are effective immune-modulators that regulate cellular metabolism as well as multiple pro-inflammatory and repair/tissue-restoration pathways. Redox molecules such as peroxide, superoxide, NO, and RNS, once thought to be only toxic, are essential in tissue repair. These species are generated, converted and metabolized during host microbe interaction involving the innate immune system. Cytochrome b558 is the flavin binding component of the NADPH oxidase. NADPH oxidases are key producers of ROS. A variety of RNS and ROS is produced in the acidic mileu of phagosomes, which provide an environment conducive to the redox chemistry, which is the first line in fighting infection. Bacterial cell immune response also involves NO. Thus understanding the plasma membrane redox activities can help unravel the mechanisms of immune response. Keywords: Plasma membrane, Redox activities, oxidative stress, NO, ROS, RNS. Nitrous Oxide, Reactive Oxygen Species, Reactive Nitrogen species.

Electrochemical and Molecular Assessment of Quinones as CO2-Binding Redox Molecules for Carbon Capture

The complexation and decomplexation of CO2 with a series of quinones of different basicity during electrochemical cycling in dimethylformamide solutions were studied systematically by cyclic voltammetry. In the absence of CO2, all quinones exhibited two well-separated reduction waves. For weakly complexing quinones, a positive shift in the second reduction wave was observed in the presence of CO2, corresponding to the dianion quinone-CO2 complex formation. The peak position and peak height of the first re-duction wave were unchanged, indicating no formation of complexes between the semiquinones and CO2. The relative heights of both reduction waves remained constant. In the case of strongly complexing quinones, the second reduction wave disappeared while the peak height of the first reduction wave approximately doubled, indicating that the two electrons transferred simultaneously at this potential. The observed voltammograms were rationalized through several equilibrium arguments. Both weakly and strongly complexing quinones underwent either stepwise or concerted mechanisms of oxidation and CO2 dissociation depending on the sweep rate in the cyclic voltammetric experiments. Relative to stepwise oxidation, the concerted process requires a more positive electrode potential to remove the electron from the carbonate complexes to release CO2 and regenerate the quinone. For weakly complexing quinones, the stepwise process corresponds to oxidation of the uncomplexed dianion and accompanying equilibrium shift, while for strongly complexing quinones the stepwise process would correspond to the oxidation of mono(carbonate) dianion to the complexed semiquinone and accompanying equilibrium shift. This study provides a mechanistic interpretation of the interactions that lead to the formation of quinone-CO2 complexes required for the potential development of an energy efficient electrochemical separation process and discusses important considerations for practical implementation of CO2 capture in the presence of oxygen with lower vapor pressure solvents.

Long-lifetime, potentially low-cost anthraquinone flow battery chemistry developed from study of effects of water-solubilizing group and connection to core

Water-soluble anthraquinones (AQs) hold great promise serving as redox-active species in aqueous organic redox flow batteries. Systematic investigations into how the properties of redox molecules depend on the water-solubilizing groups and the way in which they are bound to the redox core are, however, still lacking. We introduce water-solubilizing groups linked to anthraquinone by C=C bonds via Heck cross-coupling reactions and convert C=C bonds to CC bonds through hydrogenation. The anthraquinone and the ending groups are connected via branched or straight chains with either unsaturated or saturated bonds. We investigate the influence of water-solubilizing chains and ionic ending groups on redox potentials of molecules and identify three important trends. (1): The electron-withdrawing ending groups can affect redox potentials of AQs with two unsaturated hydrocarbons on the chains through π-conjugation. (2): For chains with two saturated or unsaturated straight hydrocarbons, water-solubilizing ending groups increase redox potentials of the AQs in the order of PO32 <CO2<SO3. (3): AQs with saturated and unbranched chains at high pH possess desirably low redox potentials, high solubilities, and high stability. Disproportionation leads to the formation of anthrone, which can be regenerated to anthraquinone. Tautomerization results in the saturation of alkene chains, stabilizing the structure. We utilize these observations to identify a potentially low-cost and long-lifetime negolyte that demonstrates a temporal fade rate as low as 0.0128%/day when paired with a potassium ferrocyanide posolyte.

A modular toolset for electrogenetics

Synthetic biology research and its industrial applications rely on the deterministic spatiotemporal control of gene expression. Recently, electrochemical control of gene expression has been demonstrated in electrogenetic systems (redox-responsive promoters used alongside redox inducers and an electrode), allowing for the direct integration of electronics with complex biological processes for a variety of new applications. However, the use of electrogenetic systems is limited by poor activity, tunability and standardisation. Here, we have developed a variety of genetic and electrochemical tools that facilitate the design and vastly improve the performance of electrogenetic systems. We developed a strong, unidirectional, redox-responsive promoter before deriving a mutant promoter library with a spectrum of strengths. We then constructed genetic circuits with these parts and demonstrated their activation by multiple classes of redox molecules. Finally, we demonstrated electrochemical activation of gene expression in aerobic conditions utilising a novel, modular bioelectrochemical device. This toolset provides researchers with all the elements needed to design and build optimised electrogenetic systems for specific applications.