RESUMO
Reliable control of the conductivity and its polarity in semiconductors is at the heart of modern electronics1-7, and has led to key inventions including diodes, transistors, solar cells, photodetectors, light-emitting diodes and semiconductor lasers. For archetypal semiconductors such as Si and GaN, positive (p)- and negative (n)-type conductivities are achieved through the doping of electron-accepting and electron-donating elements into the crystal lattices, respectively1-6. For halide perovskites, which are an emerging class of semiconductors, mechanisms for reliably controlling charge conduction behaviours while maintaining high optoelectronic qualities are yet to be discovered. Here we report that the p- and n-type characteristics in a wide-bandgap perovskite semiconductor can be adjusted by incorporating a phosphonic acid molecular dopant with strong electron-withdrawing abilities. The resultant carrier concentrations were more than 1013 cm-3 for the p- and n-type samples, with Hall coefficients ranging from -0.5 m3 C-1 (n-type) to 0.6 m3 C-1 (p-type). A shift of the Fermi level across the bandgap was observed. Importantly, the transition from n- to p-type conductivity was achieved while retaining high photoluminescence quantum yields of 70-85%. The controllable doping in the emissive perovskite semiconductor enabled the demonstration of ultrahigh brightness (more than 1.1 × 106 cd m-2) and exceptional external quantum efficiency (28.4%) in perovskite light-emitting diodes with a simple architecture.
Assuntos
Compostos de Cálcio , Óxidos , Semicondutores , Titânio , Compostos de Cálcio/química , Titânio/química , Óxidos/química , Condutividade Elétrica , Elétrons , Eletrônica/instrumentaçãoRESUMO
Femtosecond transient absorption spectroscopy was used to study the dynamics of the excited primary electron donor in the reaction centers of the purple bacterium Rhodobacter sphaeroides. Using global analysis and the interval method, we found a correlation between the vibrational coherence damping of the excited primary electron donor and the lifetime of the charge-separated state P+BA-, indicating the reversibility of electron transfer to the primary electron acceptor, the BA molecule. In the reaction centers, the signs of superposition of two electronic states of P were found for a delay time of less than 200 fs. It is suggested that the admixture value of the charge transfer state PA+PB- with the excited primary electron donor P* is about 24%. The results obtained are discussed in terms of the two-step electron transfer mechanism.
Assuntos
Complexo de Proteínas do Centro de Reação Fotossintética , Rhodobacter sphaeroides , Rhodobacter sphaeroides/metabolismo , Complexo de Proteínas do Centro de Reação Fotossintética/metabolismo , Complexo de Proteínas do Centro de Reação Fotossintética/química , Transporte de Elétrons , Elétrons , Proteínas de Bactérias/química , Proteínas de Bactérias/metabolismoRESUMO
Nitrous oxide (N2O) is a greenhouse gas that could accumulate during the heterotrophic denitrification process. In this study, the effects of different chemical oxygen demand to nitrogen ratio (COD/N) on N2O production and electron competition was investigated. The electron competition was intensified with the decrease of electron supply, and Nos had the best electron competition ability. The model simulation results indicated that the degradation of NOx-Ns was a combination of diffusion and biological degradation. As reaction proceeding, N2O could accumulate inside biofilm. A thinner biofilm and a longer hydraulic retention time (HRT) might be an effective way to control N2O emission. The application of mathematical model is an opportunity to gain deep understanding of substrate degradation and electron competition inside biofilm.
Assuntos
Biofilmes , Análise da Demanda Biológica de Oxigênio , Nitrogênio , Óxido Nitroso , Óxido Nitroso/metabolismo , Nitrogênio/metabolismo , Desnitrificação , Reatores Biológicos , Elétrons , Eliminação de Resíduos Líquidos/métodos , Poluentes Atmosféricos , Modelos TeóricosRESUMO
BACKGROUND: The large-scale biocatalytic application of oxidoreductases requires systems for a cost-effective and efficient regeneration of redox cofactors. These represent the major bottleneck for industrial bioproduction and an important cost factor. In this work, co-expression of the genes of invertase and a Baeyer-Villiger monooxygenase from Burkholderia xenovorans to E. coli W ΔcscR and E. coli BL21 (DE3) enabled efficient biotransformation of cyclohexanone to the polymer precursor, ε-caprolactone using sucrose as electron source for regeneration of redox cofactors, at rates comparable to glucose. E. coli W ΔcscR has a native csc regulon enabling sucrose utilization and is deregulated via deletion of the repressor gene (cscR), thus enabling sucrose uptake even at concentrations below 6 mM (2 g L-1). On the other hand, E. coli BL21 (DE3), which is widely used as an expression host does not contain a csc regulon. RESULTS: Herein, we show a proof of concept where the co-expression of invertase for both E. coli hosts was sufficient for efficient sucrose utilization to sustain cofactor regeneration in the Baeyer-Villiger oxidation of cyclohexanone. Using E. coli W ΔcscR, a specific activity of 37 U gDCW-1 was obtained, demonstrating the suitability of the strain for recombinant gene co-expression and subsequent whole-cell biotransformation. In addition, the same co-expression cassette was transferred and investigated with E. coli BL21 (DE3), which showed a specific activity of 17 U gDCW- 1. Finally, biotransformation using photosynthetically-derived sucrose from Synechocystis S02 with E. coli W ΔcscR expressing BVMO showed complete conversion of cyclohexanone after 3 h, especially with the strain expressing the invertase gene in the periplasm. CONCLUSIONS: Results show that sucrose can be an alternative electron source to drive whole-cell biotransformations in recombinant E. coli strains opening novel strategies for sustainable chemical production.
Assuntos
Escherichia coli , Sacarose , beta-Frutofuranosidase , Escherichia coli/genética , Escherichia coli/metabolismo , beta-Frutofuranosidase/metabolismo , beta-Frutofuranosidase/genética , Sacarose/metabolismo , Oxigenases de Função Mista/metabolismo , Oxigenases de Função Mista/genética , Cicloexanonas/metabolismo , Oxirredução , Proteínas Recombinantes/metabolismo , Proteínas Recombinantes/genética , Elétrons , Biotransformação , Caproatos , LactonasRESUMO
Two-dimensional material hexagonal boron nitride (h-BN), and its one-dimensional thin strips, boron nitride nanoribbons (BNNRs) are electrically insulating with high thermal stability, making them excellent thermal conductors suitable for high-temperature application. BNNRs are wide bandgap semiconductors with bandgaps ranging from 4 to 6 eV. This study investigates the electronic properties of BNNRs with single vacancy defects in armchair and zigzag configurations. The nearest-neighbour tight-binding model and numerical method were used to simulate the electronic properties of BNNRs with a single vacancy, including band structure and local density of states. The alpha and beta matrices were adjusted to account for missing boron or nitrogen atoms. Furthermore, a small perturbations were introduced to model the effects of impurities and edge imperfections. The simulation result from this work was compared with pristine BNNRs to examine the impact of a single vacancy on their electronic properties. The findings reveal that both armchair and zigzag BNNRs with single vacancy defects exhibit distorted band structures and local density of states due to the delocalization of pz orbitals. The valence bands show a higher concentration of nitrogen, while the conduction bands are richer in boron. These findings provide insights into how vacancy defects and edge perturbations can influence the electronic properties of BNNRs, which can guide the design and optimization of BNNR-based electronic devices in future research.
Assuntos
Compostos de Boro , Nanotubos de Carbono , Compostos de Boro/química , Nanotubos de Carbono/química , Elétrons , SemicondutoresRESUMO
The chromogenic reaction between 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) and ferrate [Fe(VI)] has long been utilized for Fe(VI) content measurement. However, the presence of electron-rich organic compounds has been found to significantly impact Fe(VI) detection using the ABTS method, leading to relative errors ranging from â¼88 to 100%. Reducing substances consumed ABTSâ¢+ and resulted in underestimated Fe(VI) levels. Moreover, the oxidation of electron-rich organics containing hydroxyl groups by Fe(VI) could generate a phenoxyl radical (Phâ¢), promoting the transformation of Fe(VI) â Fe(V) â Fe(IV). The in situ formation of Fe(IV) can then contribute to ABTS oxidation, altering the ABTSâ¢+:Fe(VI) stoichiometry from 1:1 to 2:1. To overcome these challenges, we introduced Mn(II) as an activator and 3,3',5,5'-tetramethylbenzidine (TMB) as a chromogenic agent for Fe(VI) detection. This Mn(II)/TMB method enables rapid completion of the chromogenic reaction within 2 s, with a low detection limit of approximately 4 nM and a wide detection range (0.01-10 µM). Importantly, the Mn(II)/TMB method exhibits superior resistance to reductive interference and effectively eliminates the impact of phenoxyl-radical-mediated intermediate valence iron transfer processes associated with electron-rich organic compounds. Furthermore, this method is resilient to particle interference and demonstrates practical applicability in authentic waters.
Assuntos
Elétrons , Oxirredução , Ferro/química , Compostos Orgânicos/química , Benzotiazóis/química , Ácidos SulfônicosRESUMO
The polymer-based denitrification system is an effective nitrate removal process for treating low carbon/nitrogen wastewater. However, in polymer denitrification systems, carbon used for the denitrification reaction is weakly targeted. Improving the efficiency of carbon utilization in denitrification is important to reduce carbon wastage. In this study, a symbiotic biofilm-sludge denitrification system was constructed using polycaprolactone as electron donors. Results show that the carbon release amount in 120 days was 85.32±0.46 g, and the unit mass of polycaprolactone could remove 1.55±0.01 g NO3--N. Meaningfully, the targeted carbon utilization efficiency for denitrification could achieve 79%-85%. The quantitative results showed that the release of electron donors can be well matched to the demand for electron acceptors in the biofilm-sludge denitrification system. Overall, the symbiotic system can improve the nitrate removal efficiency and reduce the waste of carbon source.
Assuntos
Biofilmes , Carbono , Desnitrificação , Esgotos , Esgotos/microbiologia , Nitratos/metabolismo , Elétrons , Poliésteres/química , Poliésteres/metabolismo , Polímeros/química , Simbiose/fisiologia , Purificação da Água/métodos , Reatores BiológicosRESUMO
PURPOSE AND OBJECTIVE: Squamous cell carcinoma of the anal margin (SCCAM) is an uncommon lesion that comprises one-third to a quarter of all anal squamous cell carcinoma. Treatment involves surgery or exclusive radiotherapy for small tumours, whereas the preferred treatment for larger tumours is chemoradiotherapy. In our department, selected patients with SCCAM are treated with electron beam radiotherapy using one perineal field. The present study evaluates this strategy. MATERIAL AND METHODS: All consecutive patients with SCCAM and treated with electron beam radiotherapy from 2012 to 2022 were included. Data were retrospectively extracted from the medical records and analysed descriptively. Local control (LC) and overall survival (OS) were analysed using Kaplan-Meier statistics. RESULTS: Forty patients were evaluated. Primary radiotherapy was delivered in 35 (87.5%) patients. Five (12.5%) patients had postoperative radiotherapy. Median prescription dose was 60.0 (range 45.0-60.2) Gy in 28 (range 10-30) fractions delivered with 8 (range 4-18) MeV using a standard circular aperture and bolus. At a median follow-up of 73 (range 9-135) months, 7 (17.5%) patients were diagnosed with local recurrences. The 5-year LC rate was 84.3% (95% CI: 71.4%-97.2%). Analysis of LC according to T-stage revealed a 5-year LC of 100% (95% CI: 100%-100%) in T1 tumours compared to 57.0% (95% CI: 27.4%-86.6%) in T2 tumours (p < 0.001). 5-year OS was 91.6% (95% CI: 83.0%-100%). Late grade 3 toxicity included ulceration in the skin and subcutis in 2 (5.0%) patients. INTEPRETATION: Electron beam radiotherapy enables the delivery of 'eye-guided' radiotherapy directly to the tumour. LC is good in patients with T1 tumours. Patients with T2 tumours have less satisfactory LC and should be treated with chemoradiotherapy. Electron beam radiotherapy enables the delivery of "eye-guided" RT directly to the tumour. LC is excellent in patients with T1 tumours. Patients with T2 tumours have less satisfactory LC and should be treated with chemoradiotherapy.
Assuntos
Neoplasias do Ânus , Carcinoma de Células Escamosas , Humanos , Neoplasias do Ânus/patologia , Neoplasias do Ânus/radioterapia , Neoplasias do Ânus/mortalidade , Masculino , Feminino , Idoso , Pessoa de Meia-Idade , Carcinoma de Células Escamosas/radioterapia , Carcinoma de Células Escamosas/patologia , Carcinoma de Células Escamosas/mortalidade , Estudos Retrospectivos , Idoso de 80 Anos ou mais , Adulto , Elétrons/uso terapêutico , Recidiva Local de Neoplasia/patologia , Recidiva Local de Neoplasia/radioterapia , Margens de Excisão , Dosagem RadioterapêuticaRESUMO
Cellular redox homeostasis is essential for maintaining cellular activities, such as DNA synthesis and gene expression. Inspired by this, new therapeutic interventions have been rapidly developed to modulate the intracellular redox state using artificial transmembrane electron transport. However, current approaches that rely on external electric field polarization can disrupt cellular functions, limiting their in vivo application. Therefore, it is crucial to develop novel electric-field-free modulation methods. In this work, we for the first time found that graphene could spontaneously insert into living cell membranes and serve as an electron tunnel to regulate intracellular reactive oxygen species and NADH based on the spontaneous bipolar electrochemical reaction mechanism. This work provides a wireless and electric-field-free approach to regulating cellular redox states directly and offers possibilities for biological applications such as cell process intervention and treatment for neurodegenerative diseases.
Assuntos
Membrana Celular , Grafite , Oxirredução , Espécies Reativas de Oxigênio , Grafite/química , Humanos , Espécies Reativas de Oxigênio/metabolismo , Espécies Reativas de Oxigênio/química , Transporte de Elétrons , Membrana Celular/metabolismo , Membrana Celular/química , NAD/química , NAD/metabolismo , ElétronsRESUMO
Objective.We demonstrate detection of high energy particle current (HEC) for MeV therapeutic electron beams. Detection of HEC comprises of remote sensing or acquiring information about HEC inside radiation transport medium from a distance outside of the medium.Approach.HEC is self-propelled motion of charged particles through a radiation transport medium. Remote sensing of HEC is embodied in an experimental setup, which includes homogeneous and heterogeneous phantoms irradiated with 4-15 MeV electron beams and two large area parallel-plane electrodes extraneous to the phantoms providing two-parameter detection. We also introduce a new type of scanning method (depth-scan) for probing object properties along the beamline axis.Main Results.Deterministic radiation transport simulations and measurements agree, considering differences in simulation vs experimental geometry and experimental uncertainties.Significance.This method may be suitable for range detection of charged particle beams, or for probing of radiation opaque objects in non-destructive testing.
Assuntos
Elétrons , Imagens de Fantasmas , Tecnologia de Sensoriamento Remoto/instrumentação , Tecnologia de Sensoriamento Remoto/métodos , Radioterapia de Alta EnergiaRESUMO
Exploring antioxidant potential of flavonoid derivatives after ESIPT process provides a theoretical basis for discovering compounds with higher antioxidant capacity. In this work, employing the density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods, the antioxidant potential of two citrus-derived naringenin flavonoids after ESIPT process is explored. Based on studies of ESIPT process including IMHB intensity variations, potential energy curves, and transition state, these molecules exist only in enol and ketoâ forms due to ultra-fast ESIPT. The HOMOs are utilized to explore electron-donating capacity, demonstrating that the molecules in ketoâ form is stronger than that in enol form. Furthermore, the atomic dipole moment corrected Hirshfeld population (ADCH) and Fukui functions indicate that the sites attacked by the electrophilic free radical of the two molecules in the ketoâ form are O3 and O5' respectively, and both are more active than in the enol form. Overall, a comprehensive consideration of the ESIPT process and antioxidant potential of flavonoid derivatives will facilitate the exploration and design of substances with higher antioxidant capacity.
Assuntos
Antioxidantes , Flavanonas , Flavonoides , Ligação de Hidrogênio , Flavanonas/química , Antioxidantes/química , Antioxidantes/farmacologia , Flavonoides/química , Teoria da Densidade Funcional , Termodinâmica , ElétronsRESUMO
Breaking the activity-selectivity trade-off has been a long-standing challenge in catalysis. Here, we proposed a nanoheterostructure engineering strategy to overcome the trade-off in metal phosphide catalysts for the oxidative desulfurization (ODS) of fuels. Experimental and theoretical results demonstrated that electron delocalization was the key driver to simultaneously achieve high activity and high selectivity for the molybdenum phosphide (MoP)/tungsten phosphide (WP) nanoheterostructure catalyst. The electron delocalization not only promoted the catalytic pathway transition from predominant radicals to singlet oxygens in H2O2 activation but also simultaneously optimized the adsorption of reactants and intermediates on Mo and W sites. The presence of such dual-enhanced active sites ideally compensated for the loss of activity due to the nonradical catalytic pathway, consequently disentangling the activity-selectivity trade-off. The resulting catalyst (MoWP2/C) unprecedentedly achieved 100% removal of thiophenic compounds from real diesel at an initial concentration of 2676 ppm of sulfur with a high turnover frequency (TOF) of 105.4 h-1 and a minimal O/S ratio of 4. This work provides fundamental insight into the structure-activity-selectivity relationships of heterogeneous catalysts and may inspire the development of high-performance catalysts for ODS and other catalytic fields.
Assuntos
Oxirredução , Catálise , Enxofre/química , Elétrons , Elementos de Transição/químicaRESUMO
The use of artificial enzymes and light energy in photocatalytic therapy, a developing drug-free therapeutic approach, can treat malignant tumors in vivo. However, the relatively deficient oxygen concentration in the tumor microenvironment (TME) restrains their further tumor treatment capability. Herein, a novel nanoplatform with Cu7S4@Au nanocatalyst coated by MnO2 was successfully designed. After 1064 nm light irradiation, the designed nanocatalyst can promote the separation of light generated electron-hole pairs, resulting in ROS generation and tumor cell apoptosis. The MnO2 shelled nanoplatform can function as a TME-responsive oxygen self-supplied producer to improve photocatalyst treatment and GSH depletion. In summary, the designed novel nanoplatform shows efficient inhibition of tumor growth via GSH depletion and synergistic photocatalytic therapy, which is of great significance for improving the clinical tumor treatment effect.
Assuntos
Glutationa , Compostos de Manganês , Oxigênio , Glutationa/metabolismo , Glutationa/química , Oxigênio/química , Oxigênio/metabolismo , Compostos de Manganês/química , Humanos , Catálise , Óxidos/química , Animais , Camundongos , Apoptose/efeitos dos fármacos , Antineoplásicos/química , Antineoplásicos/farmacologia , Espécies Reativas de Oxigênio/metabolismo , Microambiente Tumoral/efeitos dos fármacos , Linhagem Celular Tumoral , Elétrons , Raios Infravermelhos , Fotoquimioterapia , Neoplasias/tratamento farmacológico , Neoplasias/metabolismo , Neoplasias/patologia , Ouro/química , Cobre/química , Sulfetos/químicaRESUMO
BACKGROUND: Carbon monoxide (CO), hypothetically linked to prebiotic biosynthesis and possibly the origin of the life, emerges as a substantive growth substrate for numerous microorganisms. In anoxic environments, the coupling of CO oxidation with hydrogen (H2) production is an essential source of electrons, which can subsequently be utilized by hydrogenotrophic bacteria (e.g., organohalide-respring bacteria). While Dehalococcoides strains assume pivotal roles in the natural turnover of halogenated organics and the bioremediation of chlorinated ethenes, relying on external H2 as their electron donor and acetate as their carbon source, the synergistic dynamics within the anaerobic microbiome have received comparatively less scrutiny. This study delves into the intriguing prospect of CO serving as both the exclusive carbon source and electron donor, thereby supporting the reductive dechlorination of trichloroethene (TCE). RESULTS: The metabolic pathway involved anaerobic CO oxidation, specifically the Wood-Ljungdahl pathway, which produced H2 and acetate as primary metabolic products. In an intricate microbial interplay, these H2 and acetate were subsequently utilized by Dehalococcoides, facilitating the dechlorination of TCE. Notably, Acetobacterium emerged as one of the pivotal collaborators for Dehalococcoides, furnishing not only a crucial carbon source essential for its growth and proliferation but also providing a defense against CO inhibition. CONCLUSIONS: This research expands our understanding of CO's versatility as a microbial energy and carbon source and unveils the intricate syntrophic dynamics underlying reductive dechlorination.
Assuntos
Acetatos , Biodegradação Ambiental , Monóxido de Carbono , Carbono , Chloroflexi , Elétrons , Halogenação , Hidrogênio , Oxirredução , Tricloroetileno , Tricloroetileno/metabolismo , Chloroflexi/metabolismo , Hidrogênio/metabolismo , Monóxido de Carbono/metabolismo , Acetatos/metabolismo , Carbono/metabolismo , Microbiota , Redes e Vias Metabólicas , Anaerobiose , Bactérias/metabolismo , Bactérias/classificaçãoRESUMO
DNA is continuously exposed to a variety of harmful factors, which, on the one hand, can force undesirable processes such as ageing, carcinogenesis and mutagenesis, while on the other hand, can accelerate evolutionary changes. Of all the canonical nucleosides, 2'-deoxyguanosine (dG) exhibits the lowest ionization potential, making it particularly prone to the one-electron oxidizing process. The most abundant type of nucleobase damage is constituted by 7,8-dihydro-8-oxo-2'-deoxyguanosine (OXOdG), with an oxidation potential that is 0.56 V lower than that of canonical dG. All this has led to OXOdG, as an isolated lesion, being perceived as a sink for radical cations in the genome. In this paper, a comparative analysis of the electronic properties of an OXOGC base pair within the context of a clustered DNA lesion (CDL) has been conducted. It is based on previous DFT studies that were carried out at the M06-2x/6-31++G** level of theory in non-equilibrated and equilibrated condensed phases. The results of the comparative analysis presented here reveal the following: (A) The ionization potentials of OXOG4C2 were largely unaffected by a second lesion. (B) The positive charge and spin were found predominantly on the OXOG4C2 moiety. (C) The electron-hole transfers A3T3âG4C2 and G4C2âA5T1 were found in the Marcus inverted region and were resistant to the presence of a second DNA lesion in close proximity. It can therefore be reasonably postulated that OXOGC becomes the sink for a radical cation migrating through the double helix, irrespective of the presence of other 2'-deoxyguanosine lesions in the CDL structure.
Assuntos
8-Hidroxi-2'-Desoxiguanosina , Pareamento de Bases , DNA , Desoxiguanosina , Desoxiguanosina/química , Desoxiguanosina/análogos & derivados , DNA/química , 8-Hidroxi-2'-Desoxiguanosina/química , Dano ao DNA , Elétrons , Modelos Moleculares , OxirreduçãoRESUMO
DNA glycosidic bond cleavage may induce cancer under the ultraviolet (UV) effect. Yet, the mechanism of glycosidic bond cleavage remains unclear and requires more detailed clarification. Herein, quantum chemical studies on its photoinduced mechanism are performed using a 5'-thymidine monophosphate (5'-dTMPH) model. In this study, four possible paths were examined to study the glycosidic bond cleavage. The results showed that, upon excitation, the electronic transition from the π bonding to π antibonding orbitals of the thymine ring leads to the damage of the thymine ring. Afterwards, the glycosidic bond is cleaved. At first, the doublet ground state (GS) path of glycosidic bond cleavage widely studied by other groups is caused by free electron generated by photoirradiation, with a kinetically feasible energy barrier of ~23 kcal/mol. Additionally, then, the other three paths were proposed that also might cause the glycosidic bond cleavage. The first one is the doublet excited state (ES) path, triggered by free electron along with UV excitation, which can result in a very-high-energy barrier ~49 kcal/mol that is kinetically unfavorable. The second one is the singlet ES path, induced by direct UV excitation, which assumes DNA is directly excited by UV light, which features a very low-energy barrier ~16 kcal/mol that is favored in kinetics. The third one is the triplet ES path, from the singlet state via intersystem crossing (ISC), which refers to a feasible ~27 kcal/mol energy barrier. This study emphasizes the pivotal role of the DNA glycosidic bond cleavage by our proposed direct UV excitation (especially singlet ES path) in addition to the authorized indirect free-electron-induced path, which should provide essential insights to future mechanistic comprehension and novel anti-cancer drug design.
Assuntos
Timina , Raios Ultravioleta , Timina/química , Glicosídeos/química , Teoria Quântica , Nucleotídeos/química , DNA/química , Modelos Moleculares , Processos Fotoquímicos , Elétrons , TermodinâmicaRESUMO
Heavy metal pollution is a critical environmental issue that has garnered significant attention from the international community. Subcritical hydrothermal liquefaction (HTL) as an emerging green technology has demonstrated remarkable promise in environmental remediation. However, there is limited research on the remediation of highly toxic Cr(VI) using HTL. This study reveals that the HTL reaction of biomass enables the simultaneous reduction and precipitation of Cr(VI). At 280 °C, the reduction of Cr(VI) was nearly complete, with a high reduction rate of 98.9%. The reduced Cr as Cr(OH)3 and Cr2O3 was primarily enriched in hydrochar, accounting for over 99.9% of the total amount. This effective enrichment resulted in the removal of Cr(VI) from the aqueous phase while simultaneously yielding clean liquid compounds like organic acids and furfural. Furthermore, the elevated temperature facilitated the formation of Cr(III) and enhanced its accumulation within hydrochar. Notably, the resulting hydrochar and small oxygenated compounds, especially aldehyde, served as electron donors for Cr(VI) reduction. Additionally, the dissolved Cr facilitated the depolymerization and deoxygenation processes of macromolecular compounds with lignin-like structures, leading to more small oxygenated compounds and subsequently influencing Cr(VI) reduction. These findings have substantial implications for green and sustainable development.
Assuntos
Biomassa , Cromo , Cromo/química , Elétrons , Recuperação e Remediação Ambiental , OxirreduçãoRESUMO
Catalysis and translocation of multisubunit DNA-directed RNA polymerases underlie all cellular mRNA synthesis. RNA polymerase II (Pol II) synthesizes eukaryotic pre-mRNAs from a DNA template strand buried in its active site. Structural details of catalysis at near-atomic resolution and precise arrangement of key active site components have been elusive. Here, we present the free-electron laser (FEL) structures of a matched ATP-bound Pol II and the hyperactive Rpb1 T834P bridge helix (BH) mutant at the highest resolution to date. The radiation-damage-free FEL structures reveal the full active site interaction network, including the trigger loop (TL) in the closed conformation, bonafide occupancy of both site A and B Mg2+, and, more importantly, a putative third (site C) Mg2+ analogous to that described for some DNA polymerases but not observed previously for cellular RNA polymerases. Molecular dynamics (MD) simulations of the structures indicate that the third Mg2+ is coordinated and stabilized at its observed position. TL residues provide half of the substrate binding pocket while multiple TL/BH interactions induce conformational changes that could allow translocation upon substrate hydrolysis. Consistent with TL/BH communication, a FEL structure and MD simulations of the T834P mutant reveal rearrangement of some active site interactions supporting potential plasticity in active site function and long-distance effects on both the width of the central channel and TL conformation, likely underlying its increased elongation rate at the expense of fidelity.
Assuntos
Domínio Catalítico , Magnésio , Simulação de Dinâmica Molecular , RNA Polimerase II , Transcrição Gênica , RNA Polimerase II/metabolismo , RNA Polimerase II/química , RNA Polimerase II/genética , Magnésio/metabolismo , Magnésio/química , Lasers , Conformação Proteica , Elétrons , Ligação Proteica , Trifosfato de Adenosina/metabolismo , Trifosfato de Adenosina/química , Sítios de LigaçãoRESUMO
Caproate production by microbial fermentation gained the advantages of sustainability and eco-friendliness, but challenged by sterile fermentation environment, necessity of organic electron donors. Here, a single-step electro-fermentation (EF) process of mixed culture was proposed for caprate production from rice straw. At the optimal potential of -0.8 V, caproate concentration, yield and selectivity in the neutral red (NR)-mediated EF system were 2.4 g/L, 0.2 g/g and 26.6%. Long-term operation accumulated 5.3 g/L caproate with the yield and selectivity of 0.2 g/g and 34.2% in the EF+NR system. Bioaugmentation by dosing chain-elongation microbial consortium further improved the caproate production, yield and selectivity to 9.1 g/L, 0.3 g/g and 41.5%, respectively. The improved caproate production in the bioaugmented EF+NR system was likely due to the enhanced interspecies electron transfer, reconstructed microbial community, multiple electron donors and suitable pH environment. Present study offers a feasible strategy for cost-effective caprate production directly from waste biomass.
Assuntos
Fermentação , Lignina , Lignina/metabolismo , Elétrons , Oryza/metabolismo , Consórcios Microbianos/fisiologiaRESUMO
The programmed cell death (PCD) pathway removes functionally insignificant, infection-prone, or potentially tumorigenic cells, underscoring its important role in maintaining the stability of the internal environment and warding off cancer and a host of other diseases. PCD includes various forms, such as apoptosis, copper death, iron death, and cellular pyroptosis. However, emerging solid-state electron-mediated Z-scheme heterostructured semiconductor nanomaterials with high electron-hole (e-h+) separation as a new method for inducing PCD have not been well studied. We synthesize the Bi2S3-Bi2O3-Au-PEG nanorods (BB-A-P NRs) Z-scheme heterostructured semiconductor has a higher redox capacity and biocompatibility. Firstly, the BB-A-P NRs are excited by near-infrared (NIR) light, which mimics the action of catalase by supplying oxygen (O2) and converting it to a single-linear state of oxygen (1O2) via e-h+ transfer. Secondly, they react with hydrogen peroxide (H2O2) and water (H2O) in tumor to produce hydroxyl radicals (â¢OH), inducing apoptosis. Intriguingly, the Caspase-1/Gasdermin D (GSDMD)-dependent conventional pyroptosis pathway induced cellular pyroptosis activated by apoptosis and reactive oxygen species (ROS) which causes the intense release of damage associated molecular patterns (DAMPs), leading to the inflammatory death of tumor cells. This, in turn, activates the immunological environment to achieve immunogenic cell death (ICD). BB-A-P enables computed tomography imaging, which allows for visualization of the treatment. BB-A-P activated dual PCD can be viewed as an effective mode of cell death that coordinates the intracellular environment, and the various pathways are interrelated and mutually reinforcing which shows promising therapeutic effects and provides a new strategy for eliminating anoxic tumors.