Understanding how protons influence heterogeneous electrocatalytic CO2 reduction on electrode surfaces is critical for advancing energy-efficient carbon conversion technologies. Here, we show that on Ag, Au, and Zn surfaces, a concerted proton-electron transfer (CPET) pathway enables CO2-to-CO conversion at up to ∼400mV lower overpotential than commonly proposed cation-stabilized mechanisms, which dominate reactivity at higher overpotentials. Using both positively charged and neutral proton donors, we show that CPET operates at low overpotentials but is limited by the rate of proton supply. Kinetic isotope effect measurements and infrared adsorption spectroscopy support the involvement of protons in the rate-determining step. Furthermore, our data shed light on the complex competition for proton donors between CO2 reduction, carbonate acidification, and hydrogen evolution, explaining commonly reported product trends. Our findings suggest that enhancing proton flux and suppressing the hydrogen evolution reaction can further promote CPET-based CO2 reduction, offering a pathway to more efficient electrocatalytic processes.

ABSTRACT Understanding how protons influence heterogeneous electrocatalytic CO 2 reduction on electrode surfaces is critical for advancing energy‐efficient carbon conversion technologies. Here, we show that on Ag, Au, and Zn surfaces, a concerted proton‐electron transfer (CPET) pathway enables CO 2 ‐to‐CO conversion at up to ∼400 mV lower overpotential than commonly proposed cation‐stabilized mechanisms, which dominate reactivity at higher overpotentials. Using both positively charged and neutral proton donors, we show that CPET operates at low overpotentials but is limited by the rate of proton supply. Kinetic isotope effect measurements and infrared adsorption spectroscopy support the involvement of protons in the rate‐determining step. Furthermore, our data shed light on the complex competition for proton donors between CO 2 reduction, carbonate acidification, and hydrogen evolution, explaining commonly reported product trends. Our findings suggest that enhancing proton flux and suppressing the hydrogen evolution reaction can further promote CPET‐based CO 2 reduction, offering a pathway to more efficient electrocatalytic processes.

Plants primarily acquire inorganic nitrogen (N) as nitrate (NO3-) and ammonium (NH4+). The uptake of these forms is strongly modulated by external pH, which influences both their availability and the activity of their specific root transporters (NRTs for NO3- and AMTs for NH4+). Moreover, NO3- and NH4+ uptake exerts opposite effects on net proton (H+) fluxes, raising the question of how external H+ availability shapes the balance between both N forms and their reciprocal regulation. Using Arabidopsis knockout mutants deficient in key NO3- and NH4+ transporters, in combination with N and H+ flux assays and gene expression analyses, this study shows that low external pH strongly promotes NO3- uptake but severely constrains plant growth under NH4+ nutrition. The stimulatory effect of external H+ over-rides the H+ efflux typically induced by NH4+. Conversely, at higher external pH, an alternative, AMT-independent transport mechanism probably related to K+ transport appears to facilitate NH4+ uptake and mitigate its toxicity. Furthermore, mutants lacking AMTs exhibited enhanced high-affinity NO3- uptake at low pH, while the NRT1.1 mutant (chl1-5) showed increased high-affinity NH4+ acquisition at higher pH. These findings highlight a new and complex interplay between pH and reciprocal N uptake dynamics and point to AMT- and NRT1.1-independent pathways contributing to the acquisition of alternative N forms under contrasting pH conditions.

Direct electrolysis of carbon dioxide (CO2)-captured bicarbonate solutions offers a promising route for CO2 valorization, as it avoids the energy-intensive regeneration and compression steps required to supply purified gaseous CO2. However, most bicarbonate electrolyzers rely on proton-driven in situ CO2 release at the cathode, which promotes hydrogen evolution, increases the cell voltage, and limits energy efficiency. Here, we demonstrate a bicarbonate electrolyzer based on a forward-bias bipolar membrane (fBPM) that decouples local CO2 release from direct proton flux. The fBPM cell delivers a carbon monoxide (CO) partial current density of 167.1 (±2.6) mA cm-2 at 4.44 (±0.03) V, with CO Faradaic efficiencies of up to 71% at 100 mA cm-2, surpassing the reverse-bias BPM and cation-exchange membrane configurations and comparing favorably with state-of-the-art bicarbonate systems. Operando Raman spectroscopy revealed that the fBPM maintains a more alkaline cathode-membrane microenvironment, increasing the availability of locally released CO2. A system-level energy analysis indicates an energy cost of 36.7 GJ per tonne of CO, highlighting fBPM-enabled bicarbonate electrolysis as a viable approach for integrated CO2 capture and electrochemical conversion.

The mycobacterial membrane exporter MmpL3 transports trehalose monomycolates (TMM) from the cytosol to the outer membrane of Mycobacterium tuberculosis, making it a potential drug target. Proton influx is believed to drive TMM efflux, suggesting that disrupting proton transfer (PT) could be therapeutic. However, the PT mechanism and its relation to function remain unclear. Recent MmpL3 structures reveal a potential proton channel in its hydrophobic core, which also binds potential antituberculosis compounds. We investigated the PT process using hybrid quantum-mechanical/molecular-mechanical and classical molecular dynamics simulations. We show that transient water chains form in two connected transmembrane cavities that act as proton conduits. Four consecutive PT events are necessary to alter the protonation states of acidic residues in the protein core, triggering conformational changes that affect the TMM binding site. The process begins with the tandem movement of two protons through an upper cavity, protonating two aspartate residues via a classical hydronium migration. After conformational shifts, PT proceeds through a lower cavity, protonating two glutamate residues near the cytosolic opening and inducing further conformational shifts; here, PT occurs sequentially via hydronium and proton-hole migration. The cycle ends with the release of protons into the cytosol. Based on the observed conformational changes, we propose a mechanism for TMM efflux.

The exceptionally strong geomagnetic storm of 10–11 May 2024 injected new energetic protons and electrons into the terrestrial radiation belts, creating extraordinary conditions to study the loss mechanisms scattering these particles into the atmosphere after the storm. For the first time, four electron belts were observed during several weeks. We show that this structure was due to electron loss, highly dependent on specific positions. Using the proton and electron fluxes measured by the Energetic Particle Telescope, EPT, on board PROBA-V, we determine the lifetimes of these populations depending on their energy ranges and positions. We show that the lifetimes are much longer for protons than for electrons, which enables us to determine their time variations independently. For electrons, the wave–particle loss mechanisms depend on the background ionosphere–plasmasphere density. The lifetimes determined after the May 2024 and 10 October 2024 big events are compared with average ones to understand their unusual specificity for the formation of four and three belts, respectively. For the injected protons of 9.5 to 13 MeV, the lifetime is minimum at L~1.9, where the fluxes are maximum, showing a lifetime depending on the flux intensity. Loss is due to pitch angle diffusion and collisions with electrons and nuclei in the ambient plasma and neutral atmosphere. At the outer edge of the proton belt, the flux is depleted at all energies after the geomagnetic perturbation, and we determine that the progressive time of refilling after the storm generally reaches more than 40 days. There is an excellent discrimination between the different populations of energetic electrons (0.5–8 MeV) and the injected protons (9.5–13 MeV) that are still observed several months after the event. Such results contribute to advancing understanding of the interactions between the terrestrial atmosphere and space radiation.

The RADiation-hard Electron Monitor (RADEM) aboard the JUpiter ICy moons Explorer (JUICE) mission, launched on April 14, 2023, measures high-energy protons and electrons during the cruise phase and will continue to do so during the nominal mission phase. However, ground calibration results were unable to explain the initial flight observations, which prompted an in-flight calibration campaign. Our main goal was to calibrate RADEM and develop a procedure to compute particle fluxes from the count rates obtained by the RADEM detector heads. We used galactic cosmic rays (GCRs) to calibrate RADEM's sensors by increasing the respective thresholds and therefore modifying their response to high-energy particles. We then compared the count rates obtained in flight for each threshold to theoretical count rates calculated using the Badhwar-O'Neill 2020 (BON2020) GCR model and threshold-dependent response functions. We used these results to develop a flux-reconstruction algorithm based on the bow-tie method. We derived a new set of in-flight calibration coefficients for all sensors. In several cases, the in-flight calibration slopes differ by up to an order of magnitude from pre-flight ground calibration values. Proton fluxes from solar energetic particle (SEP) events, reconstructed using the bow-tie method, show good agreement (within a factor of two) with measurements from the SOlar and Heliospheric Observatory (SOHO). The RADEM provides accurate measurements of proton fluxes in interplanetary space and is well suited for both single-spacecraft analyses and coordinated multi-mission studies of SEPs. While electrons have been clearly identified during the JUICE Lunar-Earth gravity assist (LEGA), reconstructing their fluxes needs a more detailed analysis.

The essential oil (EO) of Tanacetum argyrophyllum harvested from Armenian flora (2080m above sea level), characterized by a eucalyptol-camphor chemotype, and was investigated for its antibacterial activity, particularly against antibiotic-resistant bacterial strains. Chemical profiling revealed eucalyptol (35.0%), camphor (24.0%), and camphene (17.0%) as major constituents, alongside several minor terpenoids. The EO exhibited notable inhibitory effects against both wild-type Escherichia coli K-12 and kanamycin-resistant E. coli pARG-25 strains, with minimal inhibitory concentrations (MICs) reaching 100 µL/mL. . The combined influence of the EO with kanamycin could be described as synergistic, as Fractional Inhibitory Concentration Index (FICI) is 0.54. In this case the 62.5 µL/mL concentration of EO reduces the antibiotic MIC value fourfold. The investigation of colony-forming ability of bacteria under the influence of T. argyrophyllum EO revealed a reduction in bacterial viability by 30%. The changes in growth kinetics were also observed for both strains, which was indicated by a prolonged lag phase, suggesting impairment of early adaptation mechanisms. Further studies revealed that EO treatment significantly suppressed proton fluxes and ATPase activity in both strains. Particularly, total and DCCD-sensitive ATPase activities decreased by 1.5-fold, indicating a deviation in proton motive force maintenance and energy metabolism. The antibiotic-resistant E. coli pARG-25 strain exhibited higher ATPase activity compared to the wild-type, suggesting an elevated energy demand linked to resistance plasmid carriage, which was also targeted by the EO. These findings highlight that T. argyrophyllum EO disrupts bacterial energy homeostasis, representing a promising strategy for combating antibiotic-resistant pathogens. Overall, the results support the potential use of T. argyrophyllum EO as a natural antimicrobial agent.

The potato production in semi-arid regions is often hampered by extreme temperatures, high solar radiation, and low soil fertility, which reduce photosynthetic performance and nutrient absorption. Therefore, it is crucial to identify cultivars that can tolerate such conditions without compromising their yield for sustainable production. To address this challenge, a two-year field trial (2023-2025) was conducted at the Horticulture Experimental Area of the Islamia University of Bahawalpur, Pakistan. Six commercial potato cultivars, including Sante, Musica, Sadaf, Lady Rosetta, Berna, and Kuroda, were evaluated in a randomized complete block design with four replications. The experimental site was characterized by sandy loam soil and moderate salinity in irrigation water. Measurements were taken on morphological, chlorophyll fluorescence, and nutrient uptake attributes and subjected to ANOVA to determine significant genotypic differences (p ≤ 0.05). Results revealed that cultivar Sadaf produced 25-80% higher tuber yield, and 5-30% greater nitrogen, while 20-60% greater phosphorus-uptake efficiency compared to the rest of cultivars. Musica also demonstrated a stable performance; however, Sante and Berna were constrained in physiological adaptability and nutrient-uptake efficiency. Principal component and cluster analyses confirmed these patterns, grouping Sadaf and Musica with favorable traits and placing Sante and Berna with stress-linked parameters. The improved performance in Sadaf might be linked with enhanced PSII quantum yield, proton flux, and chlorophyll content, indicating improved light energy utilization and nutrient assimilation. The study highlights developing climate-resilient and input-efficient cultivars for sustainable cultivation in semi-arid ecosystems.

Abstract The Io footprint tail (FPT) region is crucial for studying the interactions between Io and Jupiter's magnetosphere. In this region, Juno spacecraft observed significant acceleration of energetic protons, concurrently with electromagnetic ion cyclotron (EMIC) waves below the proton gyro‐frequency. Utilizing data from Juno's 12th perijove, we calculate proton scattering rates induced by EMIC waves, and simulate the proton evolution by solving the two‐dimensional Fokker‐Planck equation. Results show that EMIC waves can efficiently accelerate protons from tens of keV to MeV. For ∼50–500 keV protons, the modeled energy spectrum is highly consistent with observations. EMIC waves can largely increase 100 keV proton fluxes by approximately two orders of magnitude within 1 day, a timescale that depends strongly on the wave amplitude. Our results confirm the vital role of EMIC waves in driving proton acceleration in Io FPT, providing essential insights into the global picture of Io‐Jupiter interactions.

The acidic environment within the lysosome lumen is essential for its digestive function. However, the source of protons responsible for acidification has remained elusive. Here, using a molecular probe to monitor lysosomal digestion, we discovered enhanced lysosome content degradation at mitochondria-lysosome contact (MLC) sites, which was caused by lysosomal acidification. Using a mitochondrial probe, we observed a proton flux from mitochondria to lysosomes at these MLC sites. Furthermore, we found that physically bringing mitochondria and lysosomes into close proximity can increase lysosome acidification to enhance content digestion under disease conditions. These findings unveil a crucial physiological role of MLCs in cellular functions.

Abstract Nowcasting and forecasting of the radiation environment in the Earth's lower atmosphere are critical for the safety of aircraft and spacecraft crews and passengers. Currently, this problem is addressed by employing statistical and physics‐based models that take into account particle transport and precipitation. However, given the increased number of radiation measurements available to the community, it is possible to start developing data‐driven approaches. We prepared Machine Learning‐ready (ML‐ready) data sets to nowcast the effective dose rates at aviation altitudes. The presented data sets contain 92,476 individual measurements from 589 flights obtained by the Automated Radiation Measurements for Aerospace Safety (ARMAS) experiment from 2013 to 2023. The ARMAS measurements are augmented with the properties of the Geospace environment, such as solar soft X‐ray and proton fluxes, solar wind properties, secondary cosmic ray neutrons, space weather indexes, and global solar activity indicators (such as daily sunspot number). ARMAS data are separated into three partitions, ensuring that (a) the data points from a single flight remain within the same partition, and (b) each partition samples the flight locations and Geospace environment conditions equally. Several versions of the data sets allow predictions based on point‐in‐time measurements and use up to 24 hr of Geospace parameter history. The test of the use case demonstrates a possibility of nowcasting ARMAS measurements with accuracies slightly better than the considered physics‐based models. The publicly available ML‐ready data sets could serve as the first step in data preparation for ML‐driven nowcasting and forecasting of the radiation environment.

Lactic acid bacteria (LAB) have dominated food fermentation globally and are ingrained in many food cultures. Obesity is a global health concern, and LAB ingestion is known to exert anti-obesity effects in animals. However, the characteristics of individual bacterial strains and their underlying mechanisms require elucidation since the anti-obesity effects can differ with variations in the strain, host, and living environment. In this study, we aimed to evaluate the safety and anti-obesity effects of Lactiplantibacillus plantarum TO-A (LPTOA), isolated from silage, using Caenorhabditis elegans as the model organism. The study findings revealed that LPTOA was non-toxic to mice, as established via subacute toxicity tests, and extended the lifespan of C. elegans. Furthermore, both LPTOA and heat-killed LPTOA reduced fat accumulation in C. elegans by 60% and 58%, respectively. However, in vitro experiments suggested that LPTOA does not decompose cholesterol and triglycerides, nor does it inhibit lipase activity. We identified that pept-1 (a dipeptide transporter) in C. elegans is involved in the anti-obesity effects of LPTOA. PEPT-1 is a protein that controls proton influx into the intestinal tract and is involved in not only peptide uptake but also free fatty acid absorption. These results demonstrate the anti-obesity effects and probiotic potential of LPTOA for application in products, including foods and supplements.

Abstract The 11-yr variation of galactic cosmic-ray flux lags behind the variation of the sunspot number. An average ~1-yr time-lag is expected from the outward propagating solar wind with the frozen-in photospheric magnetic field varying in the solar cycle, and from the inward diffusive transport of cosmic-ray particles. The long-term neutron monitor data, however, show that the time-lag is significantly longer (shorter) in the odd (even) solar cycle. In this paper, we analyze the time-lag in proton and electron fluxes observed by the CALET. It is found that the time-lag is similar in proton and electron fluxes during an A > 0 polarity epoch of the solar dipole magnetic field. In an even solar cycle 24 including a polarity reversal from A < 0 to A > 0, on the other hand, it is found that the time-lag of proton (electron) flux variation is significantly shorter (longer) than the average ~1-yr lag by analyzing the combined data with CALET and AMS-02. This is the first observation of the charge-sign dependent time-lag. We demonstrate that these observations can be qualitatively interpreted in terms of different 11-yr time profiles of proton and electron fluxes in A > 0 and A < 0 epochs expected from the drift effect.

ABSTRACT Galactic cosmic rays (GCRs) entering the heliosphere are modulated by the magnetized solar wind plasma, resulting in temporal intensity variations that closely follow the 11-yr solar activity cycle. In this work, we present a generalized force-field approximation for modelling the solar cycle modulation of GCRs, in which the diffusion coefficient is expressed as $\kappa \propto \beta \, \kappa _2(P)$, with $\beta = v/c$ and P the particle rigidity in GV (gigavolts). Unlike the conventional assumption of a linear rigidity dependence, we parametrize $\kappa _2(P)$ as a triple power law in rigidity. Our analysis suggests that while the overall rigidity dependence of $\kappa _2(P)$ is fundamentally shaped by diffusion, particle drifts introduce a significant modification at rigidities below ${\sim} 4 \, \mathrm{GV}$. Using PAMELA (Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics) and AMS-02 (Alpha Magnetic Spectrometer-02) proton flux data, we determine three key model parameters. These parameters are time dependent and capture variations in the modulation strength throughout the solar cycle. Applying the same parameter set accurately reproduces the temporal evolution of helium fluxes and the He/p ratio, providing a unified and compact framework for describing GCR modulation across different nuclear species.

Abstract The 11-yr variation of galactic cosmic-ray flux lags behind the variation of the sunspot number. An average ~1-yr time-lag is expected from the outward propagating solar wind with the frozen-in photospheric magnetic field varying in the solar cycle, and from the inward diffusive transport of cosmic-ray particles. The long-term neutron monitor data, however, show that the time-lag is significantly longer (shorter) in the odd (even) solar cycle. In this paper, we analyze the time-lag in proton and electron fluxes observed by the CALET. It is found that the time-lag is similar in proton and electron fluxes during an A > 0 polarity epoch of the solar dipole magnetic field. In an even solar cycle 24 including a polarity reversal from A < 0 to A > 0, on the other hand, it is found that the time-lag of proton (electron) flux variation is significantly shorter (longer) than the average ~1-yr lag by analyzing the combined data with CALET and AMS-02. This is the first observation of the charge-sign dependent time-lag. We demonstrate that these observations can be qualitatively interpreted in terms of different 11-yr time profiles of proton and electron fluxes in A > 0 and A < 0 epochs expected from the drift effect.

HEliospheric pioNeer for sOlar and interplanetary threats defeNce (HENON) is a 12U CubeSat that will explore for the first time ever the Distant Retrograde Orbit in the Sun-Earth system, bringing a payload suited for Space Weather observations and science. Initially designed for the Foresail-2 nanosatellite mission, the Relativistic Electron and Proton Experiment (REPE) instrument has since evolved for deployment in a variety of future missions, including the HENON mission. REPE is a particle telescope developed to measure fluxes of high-energy electrons and protons over broad ranges of energies, relevant to the space radiation environment. The instrument is designed to measure electron energy spectrum from 0.1 to 10.4 MeV and proton energy spectrum from 2 to hundreds of MeV. We present Monte Carlo simulations of REPE performance using Geant4. We evaluate the performance in terms of sensitivity (geometric factor), energy resolution, and cross-contamination between measured species. We show that the instrument meets the scientific requirements of the mission.

The inner membrane of mitochondria presents folds, the cristae, which are the production place of ATP. This synthesis is catalized by transmembrane proteins and relies on a flow of protons confined to the surface of the membrane. We posit that, in turn, the proton flux shapes the crista membrane in a way that suits these proteins. To study this hypothesis, we model a crista as a spherical vesicle submitted to a diffusive proton gradient flowing from the poles to the equator. Using Helfrich model, we introduce a pH-dependent spontaneous curvature for the membrane and determine the shape of the vesicle, in the regime of small deformations. We show that the pH gradient can produce shapes featuring flat zones at the poles and curved zones at the equator. These correspond to the geometry of the proteins involved in the process. Based on biophysical arguments, we define a functionality score for the vesicle and construct a phase diagram identifying the zones of "well-functioning" cristae, which we compare to experimental measurements.

Escherichia coli swimming motility is powered by the flagellar motor, a rotary nanomachine driven by inward proton flux through its torque-generating stators. How these proton currents arise from proton motive force is often described using a simple circuit model, in which the membrane acts as a capacitor discharging through the flagellar motors and other resistive proton channels. By monitoring the swimming activity of E. coli expressing a light-driven outward proton pump, we probe the dynamical response of the system under tunable optical driving and test the limits of simplified circuit-based description. Our results show that the flagellar motors are not the main sink for proton motive force discharge. Instead, other membrane channels carry a larger proton current and exhibit a nonlinear resistive behavior. Using the same experimental approach, we directly quantify proteorhodopsin pumping activity as a function of illumination wavelength and compare it with previously reported absorption spectra.

During a period of intense solar activity and highly disturbed geomagnetic conditions, a large Forbush decrease began on 10 May 2024 accompanied by a historic geomagnetic storm that lasted for four days. This extreme geomagnetic disturbance classified as G5 according to “NOAA Space Weather Scale for Geomagnetic Storms” is referred to in the literature as the Mother’s Day Storm. This resulted from multiple, at least seven, Coronal Mass Ejections (CMEs) that had been occurring since 7 May. In addition, on 11 May, a powerful X5.8 class solar flare, reaching its maximum at 01:32 UT, was followed by an abrupt increase in proton flux with energies > 100 MeV (with onset on 11 May at 01:45 UT and peaking at 02:45 UT), as recorded by GOES satellites. This resulted in a Ground Level Enhancement (GLE), identified as GLE74, occurring on 11 May 2024 during the recovery phase of the deep Forbush decrease (~15%). This Solar Energetic Particle (SEP) event consisted of both impulsive and gradual components, where the high-energy tail of the gradual component was recorded by several stations of the worldwide ground-based neutron monitor network. Approximately 15 minutes after the onset of the SEP event and 40 minutes prior to its peak, an alert was issued by the GLE Alert++ system of the Athens Neutron Monitor Station of the National and Kapodistrian University of Athens (NKUA), available as a federated product on the ESA SWE Portal under the Space Radiation Expert Service Centre. In this paper, a description of the solar activity, i.e., solar flares and CMEs, occurring during this time period is given. Moreover, recordings of cosmic ray data obtained by ground-based neutron monitors are used to perform a detailed analysis of GLE74. Finally, the response of the NKUA GLE Alert++ system to GLE74 is thoroughly presented.