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In all variants where carbon felt was present, imidacloprid degradation by the microflora of bottom sediments was many times higher than in the control, reaching 84.0 ± 1.7% under the polar connection of an external voltage source (1.2 V). When Shewanella oneidensis MR-1 was introduced, almost complete degradation of the pollutant was observed, while in the control without electrodes, it was 29.7 ± 6.0%. The relative representation of the genes of the MtrB transmembrane protein of the respiratory chain, which is associated with exoelectrogenesis, depended on the external chain and had a maximum value when the voltage source was connected polarly, correlating with the pesticide degradation by the autochthonous microflora, similar to the DyP-type peroxidase genes. The introduction of S. oneidensis MR-1 resulted in an almost tenfold increase in the relative representation of DyP-type peroxidase genes. In all experimental variants, the values of the DyP relative representation were significantly higher than in the control without carbon felt, as well as the degree of imidacloprid degradation under these experimental conditions. [ABSTRACT FROM AUTHOR]

Despite the major influence of soils on climate change, carbon sequestration, pollution remediation, and food security, soil remains a largely unexplored media with an extreme complexity of microbes, minerals, and dead organic matter, most of them being actually poorly known. In particular, soil biofilms have recently attracted attention because they strongly influence biogeochemical reactions and processes. Here we review biofilms with focus on their behavior, proliferation, distribution, characterization methods, and applications. Characterization methods include optical, electron, scanning probe, and X-ray microscopy; metagenomics, metatranscriptomics, metaproteomics, metabolomics; and tracking approaches. Applications comprise pollution remediation by metal immobilization or organics degradation; and methane oxidation, carbon dioxide reduction, and carbon sequestration. Advanced methods such as DNA-stable isotope probing and meta-omics have uncovered the multiple functions of soil biofilms and their underlying molecular mechanisms. Investigations have improved our understanding of inter- and intra-kingdom interactions, and of gene transfer. Extracellular materials such as polysaccharides enhance the transport of substances and electrons flow among microorganisms. [ABSTRACT FROM AUTHOR]

We reported herein the synthesis, characterization of hybrid conjugates composed of phthalimide (Phth) and acridine-1,8-diones (Acr) for optical and medical applications. For the synthetic procedure, a three-step synthetic strategy has been utilized. The optical properties of the examined 1,8-acridinedione–phthalimide connected molecules (AcrPhth 1–5) have been examined utilizing various spectroscopic techniques, e.g., steady-state absorption and fluorescence, and time-correlated single photon counting. The steady-state absorption studies showed that AcrPhth 1–5 absorbs the light in the UV and visible region. The fluorescence studies of AcrPhth 1–5 exhibited significant fluorescence quenching compared to the acridinedione control compounds (Acr 1–5) suggesting the occurrence of electron-transfer reactions from the electron donating acridinedione moiety (Acr) to the electron accepting phthalimide moiety (Phth). The rate and efficiency of the electron-transfer reactions were determined from the fluorescence lifetime measurements indicating the fast electron-transfer processes of the covalently connected AcrPhth 1–5 conjugates. Computational studies supported the intramolecular electron-transfer reaction of AcrPhth conjugates using ab initio B3LYP/6-311G methods. In the optimized structures, the HOMO was found to be entirely located on the Acr entity, while the LUMO was found to be entirely on the Phth entity. Further, the synthesized compounds were tested as photosensitizers for generating the singlet oxygen species, which is a key factor in the photodynamic therapy (PDT) applications. The nanosecond laser flash measurements enable us to detect the triplet-excited states of examined Acr and AcrPhth conjugates, determining the triplet quantum yields, and direct detecting the singlet oxygen in an accurate way. From this observation, the singlet quantum yields were found to be in the range of 0.12–0.27 (for Acr 1–5) and 0.07–0.19 (for AcrPhth 1–5 conjugates). The molecular docking studies revealed that compound AcrPhth 2 exhibited high binding affinity with for key genes (p53, TOP2B, p38, and EGFR) suggesting its potential as a targeted anticancer therapy. [ABSTRACT FROM AUTHOR]

Bacterial small laccases (SLAC) are promising industrial biocatalysts due to their ability to oxidize a broad range of substrates with exceptional thermostability and tolerance for alkaline pH. Electron transfer between substrate, copper centers, and O2 is one of the key steps in the catalytic turnover of SLAC. However, limited research has been conducted on the electron transfer pathway of SLAC and SLAC-catalyzed reactions, hindering further engineering of SLAC to produce tunable biocatalysts for novel applications. Herein, the combinational use of electron paramagnetic resonance (EPR) and ultravioletevisible (UV evis) spectroscopic methods coupled with redox titration were employed to monitor the electron transfer processes and obtain further insights into the electron transfer pathway in SLAC. The reduction potentials for type 1 copper (T1Cu), type 2 copper (T2Cu) and type 3 copper (T3Cu) were determined to be 367 ± 2 mV, 378 ± 5 mV and 403 ± 2 mV, respectively. Moreover, the reduction potential of a selected substrate of SLAC, hydroquinone (HQ), was determined to be 288 mV using cyclic voltammetry (CV). In this way, an electron transfer pathway was identified based on the reduction potentials. Specifically, electrons are transferred from HQ to T1Cu, then to T2Cu and T3Cu, and finally to O2. Furthermore, superhyperfine splitting observed via EPR during redox titration indicated a modification in the covalency of T2Cu upon electron uptake, suggesting a conformational alteration in the protein environment surrounding the copper sites, which could potentially influence the reduction potential of the copper sites during catalytic processes. The results presented here not only provide a comprehensive method for analyzing the electron transfer pathway in metalloenzymes through reduction potential measurements, but also offer valuable insights for further engineering and directed evolution studies of SLAC in the aim for biotechnological and industrial applications. [ABSTRACT FROM AUTHOR]

The boundary slip condition is pivotal for nanoscale fluid motion. Recent research has primarily focused on simulating the interaction mechanism between the electronic structure of two-dimensional materials and slip of water at the nanoscale, raising the possibility for ultralow friction flow of water at the nanoscale. However, experimentally elucidating electronic interactions at the dynamic solid–liquid interface to control boundary slip poses a significant challenge. In this study, the crucial role of electron structures at the dynamic solid–liquid interface in regulating slip length was revealed. Notably, the slip length of water on the molybdenum disulfide/graphene (MoS2/G) heterostructure (100.9 ± 3.6 nm) significantly exceeded that of either graphene (27.7 ± 2.2 nm) or MoS2 (5.7 ± 3.1 nm) alone. It was also analyzed how electron transfer significantly affected interface interactions. Excess electrons played a crucial role in determining the type and proportion of excitons at both MoS2–water and MoS2/G–water interfaces. Additionally, by applying voltage, distinct photoluminescence (PL) responses at static and dynamic interfaces were discovered, achieving a 5-fold modulation in PL intensity and a 2-fold modulation in the trion to exciton intensity ratio. More electrons transfer from the top graphene to the bottom MoS2 at the MoS2/G–water interface, reducing surface charge density. Thus, the reduction of electrostatic interactions between the solid and water leads to an increased slip length of water on the MoS2/G heterostructure. The process aids in comprehending the origin of frictional resistance at the subatomic scale. This work establishes a foundation for actively controlling and designing of fluid transport at the nanoscale. [ABSTRACT FROM AUTHOR]

Polyferric sulfate (PFS), an economical coagulant widely used for removing heavy metal contaminants from water, is susceptible to reduction and transformation by iron-reducing bacteria prevalent in sediments. However, the effect of heavy metal ions adsorbed in PFS flocs on this biological process remains unclear. According to our results, compared with other heavy metal cations (e.g., Cu2+, Cd2+, Zn2+, Ni2+, Pb2+, and Co2+), Cu2+ had a stronger inhibitory effect on PFS floc reduction by Shewanella putrefaciens CN32, a typical dissimilatory iron-reducing bacterium. The presence of Cu2+ remarkably influenced the global transcription of CN32, resulting in 782 upregulated genes and 713 downregulated genes that are mainly annotated in energy production, amino acid metabolism, protein biosynthesis, and oxidation‒reduction processes. The anaerobic TCA cycle for energy (electron) production was significantly activated in the presence of Cu2+, while the transcription of many genes related to the extracellular electron transfer pathway was downregulated, which is responsible for the decreased Fe3+ reduction. Moreover, the pathways of assimilatory sulfate reduction and subsequent cysteine biosynthesis were significantly enriched, which is hypothesized to result in the consumption of abundant energy produced from the enhanced anaerobic TCA cycle, revealing a strategy to address the oxidative stress caused by Cu2+. This work elucidates the unusual suppressive effects of Cu2+ on the microbial reduction of PFS flocs, which reveals the high resistance of PFS flocs to microbial destruction when used to treat Cu2+ pollution in water, thus demonstrating their tremendous practical prospects. [ABSTRACT FROM AUTHOR]

Diaryliodonium salts (Ar2I+X−) are used as a photosensitive initiator that generates acid or radical species by ultraviolet light irradiation. Recently, sensitization of Ar2I+X− has gained importance owing to the escalating demand for high‐sensitive initiators with longer wavelength absorption such as 365 and 436 nm. However, the mechanism of photolysis of Ar2I+X− has not been strictly elucidated. This paper shows discussions of the details of its mechanism. Herein, we analyzed the photosensitization of Ar2I+X− with 2–isopropylthioxanthone (ITX) based on transient absorption techniques. As a result, it was revealed that electron transfer occurred from a triplet excited state of ITX to Ar2I+X− with an electron transfer rate constant of 4.2 × 109 s−1. Furthermore, high performance liquid chromatography measurements found the quantum yield of the photolysis was determined to be 0.48. [ABSTRACT FROM AUTHOR]

In the green alga Chlamydomonas reinhardtii, hydrogen production is catalyzed via the [FeFe]-hydrogenases HydA1 and HydA2. The electrons required for the catalysis are transferred from ferredoxin (FDX) towards the hydrogenases. In the light, ferredoxin receives its electrons from photosystem I (PSI) so that H2 production becomes a fully light-driven process. HydA1 and HydA2 are highly O2 sensitive; consequently, the formation of H2 occurs mainly under anoxic conditions. Yet, photo-H2 production is tightly coupled to the efficiency of photosynthetic electron transport and linked to the photosynthetic control via the Cyt b6f complex, the control of electron transfer at the level of photosystem II (PSII) and the structural remodeling of photosystem I (PSI). These processes also determine the efficiency of linear (LEF) and cyclic electron flow (CEF). The latter is competitive with H2 photoproduction. Additionally, the CBB cycle competes with H2 photoproduction. Consequently, an in-depth understanding of light-driven H2 production via photosynthetic electron transfer and its competition with CO2 fixation is essential for improving photo-H2 production. At the same time, the smart design of photo-H2 production schemes and photo-H2 bioreactors are challenges for efficient up-scaling of light-driven photo-H2 production. [ABSTRACT FROM AUTHOR]

A long‐standing question in electron transfer research concerns the number and identity of collective nuclear motions that drive electron transfer or localisation. It is well established that these nuclear motions are commonly gathered into a so‐called electron transfer coordinate. In this theoretical study, we demonstrate that both anti‐symmetric and symmetric vibrational motions are intrinsic to bridged systems, and that both are required to explain the characteristic shape of their intervalence charge transfer bands. Using the properties of a two‐state Marcus–Hush model, we identify and quantify these two coordinates as linear combinations of normal modes from ab initio calculations. This quantification gives access to the potential coupling, reorganization energy and curvature of the potential energy surfaces involved in electron transfer, independent of any prior assumptions about the system of interest. We showcase these claims with the Creutz–Taube ion, a prototypical Class III mixed valence complex. We find that the symmetric dimension is responsible for the asymmetric band shape, and trace this back to the offset of the ground and excited state potentials in this dimension. The significance of the symmetric dimension originates from geometry dependent coupling, which in turn is a natural consequence of the well‐established superexchange mechanism. The conceptual connection between the symmetric and anti‐symmetric motions and the superexchange mechanism appears as a general result for bridged systems. [ABSTRACT FROM AUTHOR]

MIL-125-(Ti) is an attractive material in photocatalysis due to its notable characteristics, including its expansive specific surface area, porous structure, high thermal stability, and chemical resistance. Unfortunately, the high electron-hole recombination rate and weak utilization of visible light restrict its practical application. Here, a CuS nanoparticle/MIL-125-(Ti) heterojunction with a compact interface contact was prepared by a facile hydrothermal method for photocatalytic tetracycline degradation. The aligned internal electric field and interface structure of the CuS nanoparticles/MIL-125-(Ti) heterojunction show promise in effectively addressing the aforementioned challenges. Detailed characterization showed that CuS nanoparticles/MIL-125-(Ti) generated a redshift in light absorption, and the photogenerated electron-hole recombination rate was reduced by about 67.5% compared with MIL-125-(Ti), greatly improving the photocatalytic performance. Photogenerated electrons between the conductive band of CuS nanoparticles and MIL-125-(Ti) with Ti4+ to Ti3+ reduction contributed to the enhanced photocatalytic performance, and the generated active species (h+, ·OH, ·O2-) degraded tetracycline rapidly. The kinetic parameters of tetracycline degradation by the CuS/MIL-125-(Ti) composite with an optimal doping amount are 12.7 and 7.9 times higher than those of a single component. [ABSTRACT FROM AUTHOR]

Direct interspecies electron transfer (DIET) is essential for maintaining the function and stability of anaerobic microbial consortia. However, only limited natural DIET modes have been identified and DIET engineering remains highly challenging. In this study, an unnatural DIET between Shewanella oneidensis MR‐1 (SO, electron donating partner) and Rhodopseudomonas palustris (RP, electron accepting partner) was artificially established by a facile living cell‐cell click chemistry strategy. By introducing alkyne‐ or azide‐modified monosaccharides onto the cell outer surface of the target species, precise covalent connections between different species in high proximity were realized through a fast click chemistry reaction. Remarkably, upon covalent connection, outer cell surface C‐type cytochromes mediated DIET between SO and RP was achieved and identified, although this was never realized naturally. Moreover, this connection directly shifted the natural H2 mediated interspecies electron transfer (MIET) to DIET between SO and RP, which delivered superior interspecies electron exchange efficiency. Therefore, this work demonstrated a naturally unachievable DIET and an unprecedented MIET shift to DIET accomplished by cell‐cell distance engineering, offering an efficient and versatile solution for DIET engineering, which extends our understanding of DIET and opens up new avenues for DIET exploration and applications. [ABSTRACT FROM AUTHOR]

Weak doping can broaden, shift, and quench plasmon peaks in nanoparticles, but the mechanistic intricacies of the diverse responses to doping remain unclear. In this study, we used the time-dependent density functional theory (TD-DFT) to compute the excitation properties of transition-metal Pd- or Pt-doped gold and silver atomic arrays and investigate the evolution characteristics and response mechanisms of their plasmon peaks. The results demonstrated that the Pd or Pt doping of the off-centered 10 × 2 atomic arrays broadened or shifted the plasmon peaks to varying degrees. In particular, for Pd-doped 10 × 2 Au atomic arrays, the broadened plasmon peak significantly blueshifted, whereas a slight red shift was observed for Pt-doped arrays. For the 10 × 2 Ag atomic arrays, Pd doping caused almost no shift in the plasmon peak, whereas Pt doping caused a substantial red shift in the broadened plasmon peak. The analysis revealed that the diversity in these doping responses was related to the energy positions of the d electrons in the gold and silver atomic clusters and the positions of the doping atomic orbitals in the energy bands. The introduction of doping atoms altered the symmetry and gap size of the occupied and unoccupied orbitals, so multiple modes of single-particle transitions were involved in the excitation. An electron transfer analysis indicated a close correlation between excitation energy and the electron transfer of doping atoms. Finally, the differences in the symmetrically centered 11 × 2 doped atomic array were discussed using electron transfer analysis to validate the reliability of this analytical method. These findings elucidate the microscopic mechanisms of the evolution of plasmon peaks in doped atomic clusters and provide new insights into the rational control and application of plasmons in low-dimensional nanostructures. [ABSTRACT FROM AUTHOR]

Cupriavidus necator, despite lacking direct electron transfer capabilities, demonstrates efficient reduction of various redox mediators in oxygen‐free cultivation within bioelectrochemical systems. This study investigates the reduction site of ferricyanide through inhibition and expression rate analysis of oxygen and nitrate respiration chain complexes, comparing aerobic cultivation conditions with fructose as carbon and electron donor to autotrophic (CO2/H2/O2) and anodic cultivation conditions (fructose/anode). Azide inhibition identified cytochrome c oxidase as the primary complex facilitating electron transfer to ferricyanide, with a secondary role proposed for nitrite reductase NirS, demonstrating a 3.9±1.1‐fold higher expression when exposed to anodic conditions. The 2.9±0.6‐fold increase in the expression of the natural porin OmpA under anodic conditions implies its potential involvement in ferricyanide uptake. Additionally, chemically permeabilizing cell membranes with cetyltrimethylammonium bromide doubles ferricyanide reduction rates without an anode present, offering insights for optimizing redox mediation in C. necator based bioelectrochemical systems. This study opens up new possibilities for the targeted optimization of mediated electron transfer in C. necator and other organisms. [ABSTRACT FROM AUTHOR]

Direct‐current triboelectric nanogenerators (DC‐TENGs), which are used in smart electronics and energy storage, have attracted tremendous scientific interest owing to their rectification‐free and high energy utilization efficiency. In this study, the authors propose a new type of DC‐TENG that operates in the contact–separation mode with a unique adhesive–conductive interface for the first time. The results demonstrate that the TENG output increases with increasing interfacial adhesion strength; both the adhesive polymer and conductive tribomaterial are essential factors for the DC output. The proposed mechanism is based on mechanoion generation via covalent bond cleavage during material transfer and the charge leakage effect. Specifically, the DC‐TENG exhibits unique frequency‐decreasing and force‐enhancing output characteristics. It can directly drive LEDs or charge commercial capacitors. By integrating a stretchable electrode, an adhesive‐based single‐electrode TENG can be used as a strain sensor or material detector. This work presents a new type of DC‐TENG with a conventional two‐electrode configuration and provides new perspectives on the fundamental research and applications of DC‐TENGs. [ABSTRACT FROM AUTHOR]

Ammonia is recognized as the best carrier for hydrogen storage and transportation. Nanomaterial catalysts have eminent catalytic activity for ammonia decomposition. However, the preparation of low-loading, high-activity noble metal atomically dispersed nanometer ammonia decomposition catalysts and their reaction mechanisms remain obscure. In this work, we report the synthesis of a stable ruthenium (Ru) atomically dispersed catalyst with oxygen-rich defects achieved through hydrogen etching of the support CeO2NR nanorods. The oxygen defects result in the catalyst exhibiting a favorable low-temperature catalytic activity and an exceedingly high atom utilization rate for ammonia decomposition. The hydrogen production rate from ammonia decomposition per unit mass of Ru is as high as 2446 mmol H2 gRu–1 min–1 at 1 bar, 450 °C, and gas hour space velocity = 12,000 mL gcat–1 h–1. In this case, the highly dispersed Ru provided enough active sites, while the oxygen defects of the catalyst enhanced the electron transfer tunnel between Ru and the nanorod support under a Schottky contact model. The detailed mechanism of oxygen defects for improving the catalytic performance of ammonia decomposition was studied by DFT modeling. Thus, this work provides a promising strategy to improve the catalytic efficiency of an atomically dispersed Ru nanocatalyst. [ABSTRACT FROM AUTHOR]

As excellent functional materials, the composite materials based on graphene and its derivatives (GNDs) have lots of important application values in the emerging fields such as solar energy conversion, and the exploration of electron (or energy) transfer properties of those composites is the key for revealing their further applications. In this review, femtosecond transient absorption spectroscopy (TAS) has been introduced as an essential technique to understand the carrier behaviors in GNDs composites, as well as the advancements of TAS. The specific examples of electron transport in various composite materials characterized by TAS are summarized and discussed, which consist of GNDs with semiconductor quantum dots (QDs), organic dyes, organic polymers, perovskites and other materials, respectively. This review provides a deep insight into the electron transfer (ET) kinetics of various GNDs composites from the perspective of TAS. [ABSTRACT FROM AUTHOR]

Multiheme cytochromes located in different compartments are crucial for extracellular electron transfer in the bacterium Geobacter sulfurreducens to drive important environmental processes and biotechnological applications. Recent studies have unveiled that for particular sets of electron terminal acceptors, discrete respiratory pathways selectively recruit specific cytochromes from both the inner and outer membranes. However, such specificity was not observed for the abundant periplasmic cytochromes, namely the triheme cytochrome family PpcA‐E. In this work, the distinctive NMR spectroscopic signatures of these proteins in different redox states were explored to monitor pairwise interactions and electron transfer reactions between each pair of cytochromes. The results showed that the five proteins interact transiently and can exchange electrons between each other revealing intra‐promiscuity within the members of this family. This discovery is discussed in the light of the establishment of an effective electron transfer network by this pool of cytochromes. This network is advantageous to the bacteria as it enables the maintenance of the functional working potential redox range within the cells. [ABSTRACT FROM AUTHOR]

Photocatalytic hydrogen generation from hydrogen storage media is an effective and promising approach for the green hydrogen industry as well as for achieving carbon neutrality goals. However, the lower photocatalytic efficiency due to the limited light trapping capacity, low electron transfer rate, and severe aggregation of nanoparticles caused by high surface energy seriously restricts their practical application. Herein, we constructed a series of donor–acceptor (D–A) type covalent organic frameworks to confine ultrafine bimetallic Pt-based nanoclusters for photocatalytic hydrogen generation from ammonia borane (AB) hydrolysis. Under visible light irradiation at 20 °C, PtCo2@covalent organic framework (COF) showed the highest photocatalytic activity with a turnover frequency (TOF) of 486 min−1. Experiments and density functional theory (DFT) calculations reveal that the high catalytic activity is mainly attributed to the strong electronic interactions between D–A type COF and ultrafine PtCo2 nanoclusters. Specifically, the D–A type COF can significantly enhance the light-trapping ability by fine-tuning the electron-acceptor type in the framework, and accelerate the photogenerated electron transfer from D–A type COF to PtCo2 nanocluster, which promotes the adsorption and activation of H2O and AB molecules and accelerates hydrogen release. Furthermore, PtCo2@COF also exhibited ultra-high durability due to the significantly enhanced resistance to nanocluster aggregation caused by the nanopore confinement effect of D–A type COF. We believe that this work will provide a theoretical guide for the rational design of efficient D–A COF-based catalysts for photocatalysis. [ABSTRACT FROM AUTHOR]

The strict requirement of cytochrome P450cam for its native ferredoxin redox partner, putidaredoxin (Pdx), is not exhibited by any other known cytochrome P450 (CYP) system and the molecular details of redox partner selectivity are still not completely understood. We therefore examined the selectivity of a related Pseudomonas cytochrome P450, P450lin, by testing its activity with non-native redox partners. We found that P450lin could utilize Arx, the native redox partner of CYP101D1, to enable turnover of its substrate, linalool, while Pdx showed limited activity. Arx exhibited a higher sequence similarity to P450lins native redox partner, linredoxin (Ldx) than Pdx, including several residues that are believed to be at the interface of the two proteins, based on the P450cam-Pdx complex structure. We therefore mutated Pdx to resemble Ldx and Arx and found that a double mutant, D38L/∆106, displayed higher activity than Arx. In addition, Pdx D38L/∆106 does not induce a low-spin shift in linalool bound P450lin but does destabilize the P450lin-oxycomplex. Together our results suggest that P450lin and its redox partners may form a similar interface to P450cam-Pdx, but the interactions that allow for productive turnover are different.

We have investigated the equilibrium properties and rapid-reaction kinetics of the isolated butyryl-CoA dehydrogenase (bcd) component of the electron-bifurcating crotonyl-CoA-dependent NADH:ferredoxin oxidoreductase (EtfAB-bcd) from Megasphaera elsdenii. We find that a neutral FADH• semiquinone accumulates transiently during both reduction with sodium dithionite and with NADH in the presence of catalytic concentrations of EtfAB. In both cases full reduction of bcd to the hydroquinone is eventually observed, but the accumulation of FADH• indicates that a substantial portion of reduction occurs in sequential one-electron processes rather than a single two-electron event. In rapid-reaction experiments following the reaction of reduced bcd with crotonyl-CoA and oxidized bcd with butyryl-CoA, long-wavelength-absorbing intermediates are observed that are assigned to bcdred:crotonyl-CoA and bcdox:butyryl-CoA charge-transfer complexes, demonstrating their kinetic competence in the course of the reaction. In the presence of crotonyl-CoA there is an accumulation of semiquinone that is unequivocally the anionic FAD•- rather than the neutral FADH• seen in the absence of substrate, indicating that binding of substrate/product results in ionization of the bcd semiquinone. In addition to fully characterizing the rapid-reaction kinetics of both the oxidative and reductive half-reactions, our results demonstrate that one-electron processes play an important role in the reduction of bcd in EtfAB-bcd.

The solid-state photo-CIDNP (photo-chemically induced dynamic nuclear polarization) effect allows for nuclear hyperpolarization, i.e., non-Boltzmann nuclear spin population. The effect relies on the light-induced formation of a spin-correlated radical pair (SCRP) and has been observed in various photosynthetic reaction center (RC) proteins and flavin-containing light, oxygen, voltage (LOV) proteins. Both systems exhibit strongly enhanced NMR signals originating from the electron transfer partners. Here, we present experimental data on the magnetic field dependence of the 15N solid-state photo-CIDNP effect in both phototropin LOV1 C57S from Chlamydomonas reinhardtii and the bacterial photosynthetic RC from Rhodobacter sphaeroides. Using a pneumatic field-cycling system, samples containing a frozen solution of the proteins are explored between 0.25 T and 9.4 T. Both systems yield hyperpolarized 15N NMR signals across the entire magnetic field range originating from the electron transfer moieties. Also, in both systems, hyperpolarized signals from unexpected positions are detected between 1.0 T and 2.0 T: position N-1 of the flavin in the LOV1 protein and the τ-N of the axial magnesium-coordinating histidine of the donor. A first attempt to explain the occurrence of these unexpected signals based on quantum chemical calculations is presented.

Carbon nanomaterials (CNMs) are a heterogeneous class of advanced materials. Their widespread use is associated with human safety concerns, which can be addressed by safe-by design strategies. This implies a deep knowledge of how physico-chemical properties drive biological effects. The ability of CNMs to interact with cytochrome c (cyt c), a heme-protein playing a key role in the respiratory chain, in apoptosis and in cellular redox homeostasis, has been reported in some studies. However, the consequences of this interaction on the cyt c functions are controversial. Here the mechanism of interaction of carbon nanoparticles (CNPs), chosen as model of redox-active CNMs, with cyt c has been studied with the aim to shed light into these discrepancies. The effect of CNPs on the redox state of cyt c was monitored by UV–vis spectroscopy and 1D 1H NMR, while the effect on the primary, secondary, and tertiary cyt c structure was investigated by FIA/LC-MS and Circular Dichroism (CD). Finally, the peroxidase activity of cyt c and the involvement of superoxide radicals was evaluated by EPR spectroscopy. We demonstrate the existence of two mechanisms, one leading to the suppression of the cyt c peroxidase activity following the NADH-independent reduction of the heme-iron, and the other resulting in the irreversible protein unfolding. Overall, the results suggest that these two processes might be independently modulated by redox and surface properties respectively.

Study’s Excerpt • The use of activated and non-activated carbon additives to enhance biogas production from municipal organic wastes is assessed. • The research highlighted the role of activated carbon in improving anaerobic digestion through mechanisms like direct interspecies electron transfer (DIET). • Optimization of biogas production in waste management systems could hence be achieved using activated carbon. Full Abstract Because carbon-based additives are very adaptable to large-scale deployment and have minimal running costs, they are a suitable strategy to increase biogas yield. These Carbonaceous additives have been shown to have a positive effect on biogas generation with beneficial effects in the anaerobic digestion (AD) process as explained by the mechanism of direct interspecies electron transfer (DIET), the utilization of which is linked to a variety of additional mechanisms. This study investigated the effect of activated and non-activated carbons on biogas production from municipal organic wastes. In this study, a set of three (3) bio-digesters was used to process organic municipal wastes (food wastes) supplemented with activated carbon (AC) and non-activated carbon. In comparison to the control set-up without the carbonaceous additive, the results demonstrated a direct link between the activated carbon and the non-activated carbon. The biogas yield and rate of anaerobic digestion (measured based on the biogas yield per gram of the substrate per day; results not shown) are significantly increased when 5 – 10 gL-1 of activated or non-activated carbon is used. During biogas production, the bio-digester with activated carbon displayed more encouraging outcomes. During the 14-day retention period, the total Biogas produced by the set-up with activated carbon was the highest (12 870 mL) and most flammable (+++), followed by the non-activated carbon set-up, which produced 11, 250 mL of moderately flammable (++) Biogas. The lowest (9, 755 mL) and least flammable (+) biogas yield were, however obtained from the control set-up having no carbon additive. The activated carbon was shown to significantly improve biogas yield and its quality (flammability) due to its high surface area and porosity, high chemical stability, electrical conductivity, effective biofilm formation as well as its ability to remove harmful substances (micro-pollutants), which collectively improved the performance of the methanogens, thereby accelerating microbial methanogenesis. This study, therefore, revealed that carbonaceous additives supplementation enhances biogas production and, ultimately the overall biogas quality.

The strong metal-support interaction (SMSI) in supported catalysts plays a dominant role in catalytic degradation, upgrading, and remanufacturing of environmental pollutants. Previous studies have shown that SMSI is crucial in supported catalysts' activity and stability. However, for redox reactions catalyzed in environmental catalysis, the enhancement mechanism of SMSI-induced oxygen vacancy and electron transfer needs to be clarified. Additionally, the precise control of SMSI interface sites remains to be fully understood. Here we provide a systematic review of SMSI's catalytic mechanisms and control strategies in purifying gaseous pollutants, treating organic wastewater, and valorizing biomass solid waste. We explore the adsorption and activation mechanisms of SMSI in redox reactions by examining interfacial electron transfer, interfacial oxygen vacancy, and interfacial acidic sites. Furthermore, we develop a precise regulation strategy of SMSI from systematical perspectives of interface effect, crystal facet effect, size effect, guest ion doping, and modification effect. Importantly, we point out the drawbacks and breakthrough directions for SMSI regulation in environmental catalysis, including partial encapsulation strategy, size optimization strategy, interface oxygen vacancy strategy, and multi-component strategy. This review article provides the potential applications of SMSI and offers guidance for its controlled regulation in environmental catalysis.

The efficiency of direct electron flow from electron donors to electron acceptors in redox reactions is significantly influenced by the spatial separation of these components. Geobatteries, a class of redox-active substances naturally present in soil–water systems, act as electron reservoirs, reversibly donating, storing, and accepting electrons. This capability allows the temporal and spatial decoupling of redox half-reactions, providing a flexible electron transfer mechanism. In this review, we systematically examine the critical role of geobatteries in influencing electron transfer and utilization in environmental biogeochemical processes. Typical redox-active centers within geobatteries, such as quinone-like moieties, nitrogen- and sulfur-containing groups, and variable-valent metals, possess the potential to repeatedly charge and discharge. Various characterization techniques, ranging from qualitative methods like elemental analysis, imaging, and spectroscopy, to quantitative techniques such as chemical, spectroscopic, and electrochemical methods, have been developed to evaluate this reversible electron transfer capacity. Additionally, current research on the ecological and environmental significance of geobatteries extends beyond natural soil–water systems (e.g., soil carbon cycle) to engineered systems such as water treatment (e.g., nitrogen removal) and waste management (e.g., anaerobic digestion). Despite these advancements, challenges such as the complexity of environmental systems, difficulties in accurately quantifying electron exchange capacity, and scaling-up issues must be addressed to fully unlock their potential. This review underscores both the promise and challenges associated with geobatteries in responding to environmental issues, such as climate change and pollutant transformation.

In recent years, there has been significant interest in photocatalytic technologies utilizing semiconductors and photosensitizers responsive to solar light, owing to their potential for energy and environmental applications. Current efforts are focused on enhancing existing photocatalysts and developing new ones tailored for environmental uses. Anthraquinones (AQs) serve as redox-active electron transfer mediators and photochemically active organic photosensitizers, effectively addressing common issues such as low light utilization and carrier separation efficiency found in conventional semiconductors. AQs offer advantages such as abundant raw materials, controlled preparation, excellent electron transfer capabilities, and photosensitivity, with applications spanning the energy, medical, and environmental sectors. Despite their utility, comprehensive reviews on AQs-based photocatalytic systems in environmental contexts are lacking. In this review, we thoroughly describe the photochemical properties of AQs and their potential applications in photocatalysis, particularly in addressing key environmental challenges like clean energy production, antibacterial action, and pollutant degradation. However, AQs face limitations in practical photocatalytic applications due to their low electrical conductivity and solubility-related secondary contamination. To mitigate these issues, the design and synthesis of graphene-immobilized AQs are highlighted as a solution to enhance practical photocatalytic applications. Additionally, future research directions are proposed to deepen the understanding of AQs' theoretical mechanisms and to provide practical applications for wastewater treatment. This review aims to facilitate mechanistic studies and practical applications of AQs-based photocatalytic technologies and to improve understanding of these technologies.

It is shown that data presented in a paper by Chao and co‐workers do not support the formation of active "Carbon Radicals" as claimed according to the title. The assignments of observed ESR spectra and the mechanistic interpretation are severely flawed. Hence, other reactive intermediates must be responsible for the observed tumor‐damaging effects. [ABSTRACT FROM AUTHOR]

We present a new implementation of real-time time-dependent density functional theory (RT-TDDFT) for calculating excited-state dynamics of periodic systems in the open-source Python-based PySCF software package. Our implementation uses Gaussian basis functions in a velocity gauge formalism and can be applied to periodic surfaces, condensed-phase, and molecular systems. As representative benchmark applications, we present optical absorption calculations of various molecular and bulk systems and a real-time simulation of field-induced dynamics of a (ZnO)4 molecular cluster on a periodic graphene sheet. We present representative calculations on optical response of solids to infinitesimal external fields as well as real-time charge-transfer dynamics induced by strong pulsed laser fields. Due to the widespread use of the Python language, our RT-TDDFT implementation can be easily modified and provides a new capability in the PySCF code for real-time excited-state calculations of chemical and material systems.

Abstract Sulfate‐reducing microorganisms extensively contribute to the corrosion of ferrous metal infrastructure. There is substantial debate over their corrosion mechanisms. We investigated Fe0 corrosion with Desulfovibrio vulgaris, the sulfate reducer most often employed in corrosion studies. Cultures were grown with both lactate and Fe0 as potential electron donors to replicate the common environmental condition in which organic substrates help fuel the growth of corrosive microbes. Fe0 was corroded in cultures of a D. vulgaris hydrogenase‐deficient mutant with the 1:1 correspondence between Fe0 loss and H2 accumulation expected for Fe0 oxidation coupled to H+ reduction to H2. This result and the extent of sulfate reduction indicated that D. vulgaris was not capable of direct Fe0‐to‐microbe electron transfer even though it was provided with a supplementary energy source in the presence of abundant ferrous sulfide. Corrosion in the hydrogenase‐deficient mutant cultures was greater than in sterile controls, demonstrating that H2 removal was not necessary for the enhanced corrosion observed in the presence of microbes. The parental H2‐consuming strain corroded more Fe0 than the mutant strain, which could be attributed to H2 oxidation coupled to sulfate reduction, producing sulfide that further stimulated Fe0 oxidation. The results suggest that H2 consumption is not necessary for microbially enhanced corrosion, but H2 oxidation can indirectly promote corrosion by increasing sulfide generation from sulfate reduction. The finding that D. vulgaris was incapable of direct electron uptake from Fe0 reaffirms that direct metal‐to‐microbe electron transfer has yet to be rigorously described in sulfate‐reducing microbes.

Creatively integrating synthetic materials (semiconductors and electrodes) and microorganisms, the semi-artificial photosynthetic system (SAPS) couples the advantages of natural photosystems (high catalytic reaction selectivity) and artificial photosystems (excellent light-harvesting performance). This combination effectively overcomes the shortcomings of poor selectivity in artificial photosystems, bringing new opportunities for developing photosynthetic systems. It also provides a promising strategy for addressing the current energy crisis and environmental pollution. The design and selection of synthetic materials play a crucial role in this system, aiming to achieve efficient photon capture and electron transfer. This review begins by exploring the fundamental principles of SAPS, emphasizing the integration of materials and microorganisms and the factors that influence their interactions. It provides a critical analysis of the diverse compositional arrangements and systematically elucidates the foundational research methodologies employed in the investigation of SAPS. Grounded in their distinctive redox characteristics, it comprehensively surveys their recent applications in environmental remediation and sustainable energy production over the past years. Finally, reflections on future research are proposed, beginning with the challenges that limit the application of SAPS. Building on previous studies, the present review identifies the factors that limit SAPS and suggests potential avenues for future research. Additionally, this review delves into the environmental and economic policies and practical implications. In conclusion, by critically assessing the existing research landscape, delineating challenges, and charting future research directions, the present review aims to provide valuable insights for researchers and practitioners, guiding efforts toward advancing SAPS for enhanced environmental sustainability and economic feasibility.

RuO2 has been considered a potential alternative to commercial IrO2 for the oxygen evolution reaction (OER) due to its superior intrinsic activity. However, its inherent structure dissolution in acidic environments restricts its commercial applications. In this study, we report a novel Pd-doped ruthenium oxide (Pd–RuO2) nanosheet catalyst that exhibits improved activity and stability through a synergistic effect of Pd modulation of Ru electronic structure and the two-dimensional structure. The catalyst exhibits excellent performance, achieving an overpotential of only 204 mV at a current density of 10 mA cm−2. Impressively, after undergoing 8000 cycles of cyclic voltammetry testing, the overpotential merely decreased by 5 mV. The PEM electrolyzer with Pd0.08Ru0.92O2 as an anode catalyst survived an almost 130 h operation at 200 mA cm−2. To elucidate the underlying mechanisms responsible for the enhanced stability, we conducted an X-ray photoelectron spectroscopy (XPS) analysis, which reveals that the electron transfer from Pd to Ru effectively circumvents the over-oxidation of Ru, thus playing a crucial role in enhancing the catalyst's stability. Furthermore, density functional theory (DFT) calculations provide compelling evidence that the introduction of Pd into RuO2 effectively modulates electron correlations and facilitates the electron transfer from Pd to Ru, thereby preventing the over-oxidation of Ru. Additionally, the application of the two-dimensional structure effectively inhibited the aggregation and growth of nanoparticles, further bolstering the structural integrity of the catalyst.

Time-resolved step-scan Fourier transform infrared difference spectroscopy has been used to study cyanobacterial photosystem I photosynthetic reaction centers from Synechocystis sp. PCC 6803 (S6803) with four high-potential, 1,4-naphthoquinones incorporated into the A1 binding site. The high-potential naphthoquinones are 2-chloro-, 2-bromo-, 2,3-dichloro- and 2,3-dibromo-1,4-naphthoquinone. "Foreign minus native" double difference spectra (DDS) were constructed by subtracting difference spectra for native photosystem I (with phylloquinone in the A1 binding site) from corresponding spectra obtained using photosystem I with the different quinones incorporated. To help assess and assign bands in the difference and double difference spectra, density functional theory based vibrational frequency calculations for the different quinones in solvent, or in the presence of a single asymmetric H- bond to either a water molecule or a peptide backbone NH group, were undertaken. Calculated and experimental spectra agree best for the peptide backbone asymmetrically H- bonded system. By comparing multiple sets of double difference spectra, several new bands for the native quinone (phylloquinone) are identified. By comparing calculated and experimental spectra we conclude that the mono-substituted halogenated NQs can occupy the binding site in either of two different orientations, with the chlorine or bromine atom being either ortho or meta to the H- bonded CO group.

A personal perspective is provided regarding the work in several laboratories, including the author's, that has established the reaction mechanism of xanthine oxidase and related enzymes.

A close mimic of P680 and the TyrosineZ‐Histidine190 pair in photosystem II (PS II) has been synthesized using a ruthenium chromophore and imidazole‐phenol ligands. The intramolecular oxidation of the ligands by the photoproduced Ru(III) species is characterized by a small driving force, very similar to PS II where the complexity of kinetics was attributed to the reversibility of electron transfer steps. Laser flash photolysis revealed biphasic kinetics for ligand oxidation. The fast phase (τ<50 ns) corresponds to partial oxidation of the imidazole‐phenol ligand, proton transfer within the hydrogen bond, and formation of a neutral phenoxyl radical. The slow phase (5–9 μs) corresponds to full oxidation of the ligand which is kinetically controlled by deprotonation of the distant 1‐nitrogen of the imidazolium. These results show that imidazole with its two protonatable sites plays a special role as a proton relay in a 'proton domino' reaction. [ABSTRACT FROM AUTHOR]

The presence of alkene moieties in fatty acids of (phospho)lipids and cholesterol derivatives makes them highly susceptible to damage by nitrate radicals (NO3⋅), potentially formed through simultaneous exposure to the environmental air pollutants nitrogen dioxide (NO2⋅) and ozone (O3). Absolute rate coefficients derived from reactions with simplified model systems range from 4 to 8×109 M−1 s−1 in acetonitrile, ranking among the highest determined for NO3⋅ reactions with biomolecules in solution to date. Alkenes featuring an electron‐withdrawing carbonyl substituent also display notable reactivity with k values of (2.5±1.0)×108 M−1 s−1. Calculations suggest that these reactions are initiated by oxidative electron transfer (ET) involving the C=C bond, followed by recombination of the resulting alkene radical cation with nitrate anion (NO3−) to form the nitrate adduct radical as the kinetically controlled product. Conversely, saturated fatty acid derivatives and cholestanol react with NO3⋅ through hydrogen atom transfer (HAT) with rate coefficients of 106–107 M−1 s−1, indicating that biomolecules with a considerable number of non‐ or moderately activated sp3 C−H bonds are also highly susceptible to NO3⋅ attack. These findings underscore the potential health hazards associated with exposure to combined NO2⋅ and O3 gases. [ABSTRACT FROM AUTHOR]