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1. Extraction anode lens effects in gas phase peptide cation-electron reactions

   https://doi.org/10.1016/j.ijms.2024.117390  

   DeFiglia, Steven A; Lee, Teresa; Mikawy, Neven N; Szot, Carson W; Håkansson, Kristina (March 2025, International Journal of Mass Spectrometry)

   Gas phase cation-electron reactions, from electron capture dissociation (ECD; <1 eV electrons) to electron ionization dissociation (>~26 eV electrons), are highly beneficial for biomolecular structural characterization. These techniques offer high sequence coverage, labile posttranslational modification retention, and sidechain loss fragments which can differentiate isomeric residues. For optimum performance, careful tuning of electron energy, flux, and irradiation time is required to reach efficiency at a particular energy regime. The cathode bias voltage (CBV) is the primary determinant of electron energy, while several parameters including CBV, extraction anode lens voltage (LV), and cathode heating current determine electron flux. We present an in-depth examination of how the interplay of these parameters at variable irradiation times results in differing peptide cation-electron reaction regimes. A particularly interesting finding was the prominent high energy fragmentation pathways observed at low (~- 1.0 V) CBV and high (>50 V) LV, as compared with conventional (~5 V) LV for peptide ECD. Specifically, high LV resulted in tandem ionization, observed for both singly- and doubly protonated peptides, alongside increased sequence coverage for both charge states from complex spectra containing a multitude of a/b/c/d/w/x/y/z•-type terminal fragments as well as internal fragments and a large number of neutral losses. Electron flux and energy measurements as well as electron irradiation at constant flux showed that an increased number of higher energy electrons are present at high vs. low LV, i.e., the observed “lens effect” is likely due to the presence of high energy electrons under such conditions. This extraction anode lens effect may explain previous observations of unexpected internal fragments from ECD. 

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2. A Biobattery Capsule for Ingestible Electronics in the Small Intestine: Biopower Production from Intestinal Fluids Activated Germination of Exoelectrogenic Bacterial Endospores

   https://doi.org/10.1002/aenm.202202581  

   Rezaie, Maryam; Rafiee, Zahra; Choi, Seokheun (November 2022, Advanced Energy Materials)

   Abstract Functioning ingestible capsules offer tremendous promise for a plethora of diagnostic and therapeutic applications. However, the absence of realistic and practical power solutions has greatly hindered the development of ingestible electronics. Microbial fuel cells (MFCs) hold great potential as power sources for such devices as the small intestinal environment maintains a steady internal temperature and a neutral pH. Those conditions and the constant supply of nutrient‐rich organics are a perfect environment to generate long‐lasting power. Although previous small‐scale MFCs have demonstrated many promising applications, little is known about the potential for generating power in the human gut environment. Here, this work reports the design and operation of a microbial biobattery capsule for ingestible applications. DormantBacillus subtilisendospores are a storable anodic biocatalyst that will provide on‐demand power when revived by nutrient‐rich intestinal fluids. A conductive, porous, poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate hydrogel anode enables superior electrical performance in what is the world's smallest MFC. Moreover, an oxygen‐rich cathode maintains its effective cathodic capability even in the oxygen‐deficit intestinal environment. As a proof‐of‐concept demonstration in stimulated intestinal fluid, the biobattery capsule produces a current density of 470 µA cm⁻²and a power density of 98 µW cm⁻², ensuring its practical efficacy as a novel and sole power source for ingestible applications in the small intestine. 

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3. The electron transport chain of Shewanella oneidensis MR-1 can operate bidirectionally to enable microbial electrosynthesis

   https://doi.org/10.1128/aem.01387-23  

   Ford, Kathryne C.; TerAvest, Michaela A. (January 2024, Applied and Environmental Microbiology)

   Buan, Nicole R. (Ed.)

   ABSTRACT Extracellular electron transfer is a process by which bacterial cells can exchange electrons with a redox-active material located outside of the cell. InShewanella oneidensis, this process is natively used to facilitate respiration using extracellular electron acceptors such as Fe(III) or an anode. Previously, it was demonstrated that this process can be used to drive the microbial electrosynthesis (MES) of 2,3-butanediol (2,3-BDO) inS. oneidensisexogenously expressing butanediol dehydrogenase (BDH). Electrons taken into the cell from a cathode are used to generate NADH, which in turn is used to reduce acetoin to 2,3-BDO via BDH. However, generating NADH via electron uptake from a cathode is energetically unfavorable, so NADH dehydrogenases couple the reaction to proton motive force. We therefore need to maintain the proton gradient across the membrane to sustain NADH production. This work explores accomplishing this task by bidirectional electron transfer, where electrons provided by the cathode go to both NADH formation and oxygen (O₂) reduction by oxidases. We show that oxidases use trace dissolved oxygen in a microaerobic bioelectrical chemical system (BES), and the translocation of protons across the membrane during O₂reduction supports 2,3-BDO generation. Interestingly, this process is inhibited by high levels of dissolved oxygen in this system. In an aerated BES, O₂molecules react with the strong reductant (cathode) to form reactive oxygen species, resulting in cell death. IMPORTANCEMicrobial electrosynthesis (MES) is increasingly employed for the generation of specialty chemicals, such as biofuels, bioplastics, and cancer therapeutics. For these systems to be viable for industrial scale-up, it is important to understand the energetic requirements of the bacteria to mitigate unnecessary costs. This work demonstrates sustained production of an industrially relevant chemical driven by a cathode. Additionally, it optimizes a previously published system by removing any requirement for phototrophic energy, thereby removing the additional cost of providing a light source. We also demonstrate the severe impact of oxygen intrusion into bioelectrochemical systems, offering insight to future researchers aiming to work in an anaerobic environment. These studies provide insight into both the thermodynamics of electrosynthesis and the importance of the bioelectrochemical systems’ design. 

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4. Electrical decoupling of microbial electrochemical reactions enables spontaneous H ₂ evolution

   https://doi.org/10.1039/C9EE02571E  

   Chen, Xi; Lobo, Fernanda Leite; Bian, Yanhong; Lu, Lu; Chen, Xiaowen; Tucker, Melvin P.; Wang, Yuxi; Ren, Zhiyong Jason (February 2020, Energy & Environmental Science)

   Hydrogen evolution is not a spontaneous reaction, so current electrochemical H 2 systems either require an external power supply or use complex photocathodes. We present in this study that by using electrical decoupling, H 2 can be produced spontaneously from wastewater. A power management system (PMS) circuit was deployed to decouple bioanode organic oxidation from abiotic cathode proton reduction in the same electrolyte. The special PMS consisted of a boost converter and an electromagnetic transformer, which harvested energy from the anode followed by voltage magnification from 0.35 V to 2.2–2.5 V, enabling in situ H 2 evolution for over 96 h without consuming any external energy. This proof-of-concept demonstrated a cathode faradaic efficiency of 91.3% and a maximum overall H 2 conversion efficiency of 28.9%. This approach allows true self-sustaining wastewater to H 2 evolution, and the system performance can be improved via the PMS and reactor optimization. 

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5. Biomimetic composite architecture achieves ultrahigh rate capability and cycling life of sodium ion battery cathodes

   https://doi.org/10.1063/5.0020805  

   Shin, Kang_Ho; Park, Sul_Ki; Nakhanivej, Puritut; Wang, Yixian; Liu, Pengcheng; Bak, Seong-Min; Choi, Min_Sung; Mitlin, David; Park, Ho_Seok (December 2020, Applied Physics Reviews)

   Sodium ion batteries are an emerging candidate to replace lithium ion batteries in large-scale electrical energy storage systems due to the abundance and widespread distribution of sodium. Despite the growing interest, the development of high-performance sodium cathode materials remains a challenge. In particular, polyanionic compounds are considered as a strong cathode candidate owing to their better cycling stability, a flatter voltage profile, and stronger thermal stability compared to other cathode materials. Here, we report the rational design of a biomimetic bone-inspired polyanionic Na3V2(PO4)3-reduced graphene oxide composite (BI-NVP) cathode that achieves ultrahigh rate charging and ultralong cycling life in a sodium ion battery. At a charging rate of 1 C, BI-NVP delivers 97% of its theoretical capacity and is able to retain a voltage plateau even at the ultra-high rate of 200 C. It also shows long cycling life with capacity retention of 91% after 10 000 cycles at 50 C. The sodium ion battery cells with a BI-NVP cathode and Na metal anode were able to deliver a maximum specific energy of 350 W h kg−1 and maximum specific power of 154 kW kg−1. In situ and postmortem analyses of cycled BI-NVP (including by Raman and XRD spectra) HRTEM, and STEM-EELS, indicate highly reversible dilation–contraction, negligible electrode pulverization, and a stable NVP-reduced graphene oxide layer interface. The results presented here provide a rational and biomimetic material design for the electrode architecture for ultrahigh power and ultralong cyclability of the sodium ion battery full cells when paired with a sodium metal anode. 

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