As Li-ion battery optimization approaches theoretical limits, interest has grown in designing next-generation batteries from low-cost earth-abundant materials. Mg–S batteries are promising candidates, exhibiting widespread abundance of elemental precursors and a relatively large theoretical energy density albeit at lower cell voltage. However, Mg–S batteries exhibit poor reversibility, in part due to interactions between dissolved polysulfides and the Mg anode. Herein, we employ electrochemical experiments using Ag2S quasi-reference electrodes to probe the interactions between Mg anodes and dissolved polysulfides. We show that Mg2+ reduction (charging) is impeded in the presence of polysulfides, while Mg metal oxidation (discharging) remains facile. Large reduction overpotentials arise due to the formation of a passivation layer on the anode surface, likely composed primarily of MgS. The passivation layer is removed under oxidative conditions but quickly reforms during reduction. We discover that dissolved S8 influences the rate of MgS formation by shifting the polysulfide disproportionation equilibria. Shorter-chain polysulfides react more readily than longer-chain polysulfides at the Mg electrode, and thus, film formation is mediated by the electrochemical generation of shorter-chain polysulfide species.

Heterologous expression of many G‐protein coupled receptors (GPCRs) is a major bottleneck in drug discovery efforts for therapeutic development of the receptor. The goal of this study was to utilize domains from a well‐trafficked GPCR to aid in improving the trafficking of a related receptor. The adenosine A2a receptor (A2aR) shows exceptional expression and trafficking to the plasma membrane in yeast; however, this is not the case for other adenosine receptors. A2aR has a longer C‐terminus than the other adenosine receptors, which may contribute to its exceptional trafficking to the plasma membrane. To test the possibility to improve trafficking of the adenosine A1 receptor (A1R), chimeric receptors containing the seven transmembrane domains of A1R and the full‐length or truncated A2aR C‐terminus were constructed. The chimeric receptor showed improved localization to the plasma membrane and was capable of binding radioligand with native A1R affinity. Functionally active A1R receptor variants were produced at a theoretical yield of 95 pmol/mg total membrane protein, estimated using radioligand binding data, which are greater than three‐fold higher than previously reported yields from other heterologous expression systems, and should facilitate biophysical characterization and drug discovery efforts. © 2018 American Institute of Chemical Engineers AIChE J, 64: 4297–4307, 2018

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