Redox State Research Articles

Dulaglutide reduces oxidative DNA damage and hypermethylation in the somatic cells of mice fed a high-energy diet by restoring redox balance, inflammatory responses, and DNA repair gene expressions.

Obesity is an established risk factor for numerous malignancies, although it remains uncertain whether the disease itself or weight-loss drugs are responsible for a greater predisposition to cancer. The objective of the current study was to determine the impact of dulaglutide on genetic and epigenetic DNA damage caused by obesity, which is a crucial factor in the development of cancer. Mice were administered a low-fat or high-fat diet for 12 weeks, followed by a 5-week treatment with dulaglutide. Following that, modifications of the DNA bases were examined using the comet assay. To clarify the underlying molecular mechanisms, oxidized and methylated DNA bases, changes in the redox status, levels of inflammatory cytokines, and the expression levels of some DNA repair genes were evaluated. Animals fed a high-fat diet exhibited increased body weights, elevated DNA damage, oxidation of DNA bases, and DNA hypermethylation. In addition, obese mice showed altered inflammatory responses, redox imbalances, and repair gene expressions. The findings demonstrated that dulaglutide does not exhibit genotoxicity in the investigated conditions. Following dulaglutide administration, animals fed a high-fat diet demonstrated low DNA damage, less oxidation and methylation of DNA bases, restored redox balance, and improved inflammatory responses. In addition, dulaglutide treatment restored the upregulated DNMT1, Ogg1, and p53 gene expression. Overall, dulaglutide effectively maintains DNA integrity in obese animals. It reduces oxidative DNA damage and hypermethylation by restoring redox balance, modulating inflammatory responses, and recovering altered gene expressions. These findings demonstrate dulaglutide's expediency in treating obesity and its associated complications.

Impacts of Vitamin D3 and Zinc Supplementation on the Redox Status in Blood and Pancreas of Rats With Alcohol-Induced Chronic Pancreatitis

Impacts of Vitamin D3 and Zinc Supplementation on the Redox Status in Blood and Pancreas of Rats With Alcohol-Induced Chronic Pancreatitis

Primary Controlling Factors of Apatite Trace Element Composition and Implications for Exploration in Orogenic Gold Deposits

AbstractSignificant and readily accessible orogenic gold deposits have been previously recognized, exploited, and progressively depleted. Innovative approaches are required to discover new and deeply buried deposits. Recently, trace element variations in apatite have been used to distinguish fertile and barren environments as reliable mineral exploration tools. In this study, machine learning models using Random Forest and Deep Neutral Network are utilized to assess the fertility of quartz veins and altered zones in the orogenic gold systems. The two models have been trained using trace element data of apatite, and the performance of both models yield good classification accuracy (∼90% on average) with low false positive rates. Feature importance analysis (Gini decrease and hidden layer weights) suggest that Pb, As, U, Sr, Eu, Mn, and Fe are the important parameters. Arsenic, U, Eu, Mn, and Fe are redox‐sensitive elements, with their concentrations responding to changes in fluid redox conditions. Strontium primarily originates from the breakdown of plagioclase, which is more likely to occur under oxidizing fluid conditions. Therefore, we infer that the main controlling factor of the models is the redox conditions. The two distinct models consistently highlight the most significant contribution of Pb to this differentiation, even though Pb is not a redox‐sensitive element and can only substitute for Ca2+ in apatite as Pb2+. We infer that the high contribution of Pb may be attributed to the potential transportation of Au in the form of a Pb‐(Bi)‐Au melt, and the Pb content in apatite is influenced by the Pb content in the melt, fluid oxygen, and sulfur fugacity. We also propose a novel discriminant plot using Linear Discriminant Analysis (LDA) to assess the mineralization potential in quartz veins and alteration zones based on apatite trace element data. The machine learning and LDA results suggest that apatite trace elements could be used effectively in the future orogenic gold deposit exploration.

Stimulus-Responsive Hydrogels for Targeted Cancer Therapy.

Cancer is a highly heterogeneous disease and remains a global health challenge affecting millions of human lives worldwide. Despite advancements in conventional treatments like surgery, chemotherapy, and immunotherapy, the rise of multidrug resistance, tumor recurrence, and their severe side effects and the complex nature of the tumor microenvironment (TME) necessitates innovative therapeutic approaches. Recently, stimulus-responsive nanomedicines designed to target TME characteristics (e.g., pH alterations, redox conditions, enzyme secretion) have gained attention for their potential to enhance anticancer efficacy while minimizing the adverse effects of chemotherapeutics/bioactive compounds. Among the various nanocarriers, hydrogels are intriguing due to their high-water content, adjustable mechanical characteristics, and responsiveness to external and internal stimuli, making them promising candidates for cancer therapy. These properties make hydrogels an ideal nanocarrier for controlled drug release within the TME. This review comprehensively surveys the latest advancements in the area of stimulus-responsive hydrogels for cancer therapy, exploring various stimuli-responsive mechanisms, including biological (e.g., pH, redox), chemical (e.g., enzymes, glucose), and physical (e.g., temperature, light), as well as dual- or multi-stimuli responsiveness. Furthermore, this review addresses the current developments and challenges in hydrogels in cancer treatment. Our aim is to provide readers with a comprehensive understanding of stimulus-responsive hydrogels for cancer treatment, offering novel perspectives on their development for cancer therapy and other medical applications.

Evaluation of the Possible Pathophysiological Role of Redox Status in Patients with Sickle Cell Anemia

Abstract BACKGROUND: The disease of sickle cell anemia (SCA) is an inherited blood disease that causes several complications, and oxidative stress (OS) may play a very important role in its complications and pathophysiology. OBJECTIVE: The aims of the study is to evaluate the possible pathophysiological role of some antioxidant and oxidant biomarkers within SCA patients and to evaluate the correlation of OS and atherogenic index of plasma (AIP) to predict the cardiovascular risk in SCA subjects. MATERIALS AND METHODS: A case–control research includes three study groups: SCA patients, sickle cell trait (SCT) subjects, and healthy controls (HCs). All study groups were evaluated for their serum catalase (CAT), serum superoxide dismutase (SOD), glutathione peroxidase (GPx), and malondialdehyde (MDA) as well as plasma triglycerides and high-density lipoprotein cholesterol. Data were collected, tabulated, and statistically analyzed using (SPSS) version 31 program. The frequencies, relative frequencies, and means were obtained as descriptive methods. The associations among parameters were obtained using the Chi-square statistical method. RESULTS: The results revealed significantly lower levels of serum SOD and GPx among sickle cell disease (SCD) and SCT subjects than the HCs, whereas the inverse findings were reported for CAT and AIP. However, the MDA results revealed a significantly higher level in SCD patients compared to SCT and HC. Furthermore, the levels of SOD and MDA were positively associated in all study groups, and the levels of GPx and MDA were negatively correlated in SCD and SCT groups. The AIP was positively correlated with MDA in the SCT group and negatively correlated with CAT in the SCD group. CONCLUSIONS: The conclusion of the study indicated the presence of an OS and antioxidant compensatory status in patients with SCD and the SCT subjects. The altered biomarkers in SCA patients made it clear that the impairment and generation of OS in this disease, as well as antioxidant biomarkers, are contributory factors toward cellular redox homeostasis. This addressed the aim of the study.

Involvement of Nrf2 Signaling in Lead-induced Toxicity.

Nuclear factor erythroid 2-related factor 2 (Nrf2) is used as one of the main protective factors against various pathological processes, as it regulates cells resistant to oxidation. Several studies have extensively explored the relationship between environmental exposure to heavy metals, particularly lead (Pb), and the development of various human diseases. These metals have been reported to be able to, directly and indirectly, induce the production of reactive oxygen species (ROS) and cause oxidative stress in various organs. Since Nrf2 signaling is important in maintaining redox status, it has a dual role depending on the specific biological context. On the one hand, Nrf2 provides a protective mechanism against metal-induced toxicity; on the other hand, it can induce metalinduced carcinogenesis upon prolonged exposure and activation. Therefore, the aim of this review was to summarize the latest knowledge on the functional interrelation between toxic metals, such as Pb and Nrf2 signaling.

Effect of gamma irradiation on the proteogenome of cold-acclimated Kocuria rhizophila PT10

The effects of ionizing radiation (IR) on the protein dynamics of cold-stressed cells of a radioresistant actinobacterium, Kocuria rhizophila PT10, isolated from the rhizosphere of the desert plant Panicum turgidum were investigated using a shotgun methodology based on nanoflow liquid chromatography coupled to tandem mass spectrometry. Overall, 1487 proteins were certified, and their abundances were compared between the irradiated condition and control. IR of cold-acclimated PT10 triggered the over-abundance of proteins involved in (1) a strong transcriptional regulation, (2) amidation of peptidoglycan and preservation of cell envelope integrity, (3) detoxification of reactive electrophiles and regulation of the redox status of proteins, (4) base excision repair and prevention of mutagenesis and (5) the tricarboxylic acid (TCA) cycle and production of fatty acids. Also, one of the more significant findings to emerge from this study is the SOS response of stressed PT10. Moreover, a comparison of top hits radio-modulated proteins of cold-acclimated PT10 with proteomics data from gamma-irradiated Deinococcus deserti showed that stressed PT10 has a specific response characterised by a high over-abundance of NemA, GatD, and UdgB.

A type III-Dv CRISPR-Cas system is controlled by the transcription factor RpaB and interacts with the DEAD-box RNA helicase CrhR

How CRISPR-Cas systems defend bacteria and archaea against invading genetic elements is well understood, but less is known about their regulation. In the cyanobacterium Synechocystis sp. PCC 6803, the expression of one of the three different CRISPR-Cas systems responds to changes in environmental conditions. The cas operon promoter of this system is controlled by the light- and redox-responsive transcription factor RpaB binding to an HLR1 motif, resulting in transcriptional activation at low light intensities. However, the strong promoter that drives transcription of the cognate repeat-spacer array is not controlled by RpaB. Instead, the leader transcript is bound by the redox-sensitive RNA helicase CrhR. Crosslinking coupled with mass spectrometry analysis and site-directed mutagenesis revealed six residues involved in the CrhR-RNA interaction, with C371 being critically important. Thus, the expression of a type III-Dv CRISPR-Cas system is linked to the redox status of the photosynthetic cell at the transcriptional and post-transcriptional levels.

Compound Microbial Agent Improve Soil Redox Status to Reduce Methane Emissions from Paddy Fields

Paddy fields are considered as a major source of methane (CH4) emissions. Aerobic irrigation methods have proved to be efficacious in mitigating CH4 emissions in paddy cultivation. The promising role of compound microbial agents in refining the rhizospheric ecosystem intimates their potential as novel agents in reducing CH4 emissions from paddy fields. To explore a new way of using compound microbial agents to reduce CH4 emissions, we conducted pot and field experiments over the period of 2022‒2023. We measured CH4 flux, the redox potential (Eh) of the soil, the concentration of dissolved oxygen (DO) in the floodwater, and the activity of both methanogens (mcrA) and methanotrophs (pmoA). The results showed that the application of the compound microbial agent led to a significant increase in the DO levels within the floodwater and an increase of 9.26% to 35.01% in the Eh of the tillage soil. Furthermore, the abundance of pmoA increased by 31.20%, while the mcrA/pmoA ratio decreased by 25.96% at the maximum tillering stage. Applying 45−75 kg/hm2 of the compound microbial agent before transplanting resulted in a reduction of cumulative CH4 emissions from paddy fields by 17.49% in single- cropped rice and 43.54% to 50.27% in double-cropped late rice during the tillering stage. Correlation analysis indicated that CH4 flux was significantly negatively correlated with pmoA gene abundance and soil Eh, and positively related to the mcrA/pmoA ratio. Additionally, soil Eh was significantly positively correlated with pmoA gene abundance, suggesting that paddy soil Eh indirectly affected CH4 flux by influencing the pmoA gene abundance. In conclusion, the pre-planting application of the compound microbial agent at a rate of 45‒75 kg/hm2 can enhance the Eh in the rhizosphere and increase the abundance of the pmoA gene, thereby reducing CH4 emissions from paddy fields during the tillering stage of rice growth.

Effects of a supraphysiological dose of testosterone cypionate on salivary gland function in adult male Wistar rats

The abusive use of anabolic androgenic steroids has become a serious health problem worldwide, but its effects on oral health are still poorly understood. Therefore, the objective of this study was to evaluate the effects of a supraphysiological dose of testosterone cypionate (TC) on salivary biochemical, histomorphology, immunohistochemistry, and redox state parameters of parotid and submandibular glands. Twenty male Wistar rats, 12 weeks old, were divided into two groups (n=10/group): a control group and TC group, which received a dose of 20 mg/kg, once a week, for 6 weeks. Post treatment, the saliva and glands were collected. A supraphysiological dose of TC increased plasma and salivary testosterone concentrations. Although TC did not alter salivary flow, pH, and buffering capacity, the treatment increased the salivary secretion of total protein and reduced amylase, calcium, phosphate, and potassium. TC reduced the connective tissue area in the parotid gland and acinar area of the submandibular gland, while increasing the granular convoluted tubule area in the submandibular gland. Proliferating cell nuclear antigen was higher in the acinar cells of the submandibular glands from the TC group. Moreover, TC increased concentrations of total oxidant capacity and damaged lipids in both salivary glands, while total antioxidant activity and uric acid were lower in the submandibular gland, and reduced glutathione was higher in both glands. Superoxide dismutase, catalase, and glutathione peroxidase activities were higher in the parotid gland, while only glutathione peroxidase activity was lower in the submandibular gland of the TC group. In conclusion, TC abuse may be a potential factor for dysfunction of the parotid and submandibular glands, becoming a risk factor for the oral and systemic health of users.

Impressive promiscuous biomimetic models of ascorbate, amine, and catechol oxidases

Copper metalloenzymes ascorbate oxidase (AOase), amine oxidase (AmOase), and catechol oxidase (COase) possess copper(II) sites of coordination, which are trimeric, homodimeric, and dimeric, respectively. Two newly mononuclear copper(II) complexes, namely, [Cu(L)(bpy)](ClO4) (1) and [Cu(L)(phen)](ClO4) (2) where HL = Schiff base, have been synthesized. UV–visible, EPR and single-crystal X-ray diffraction examinations were used to validate the geometry in solution and solid state. For complex 1, the metal exhibits a coordination sphere between square pyramidal and trigonal bipyramidal geometry (τ, 0.49). A positive CuII/I redox potential indicates a stable switching between CuII and CuI redox states. Despite the monomeric origin, both homogeneous catalysts (1 or 2) in MeOH were found to favor three distinct chemical transformations, namely, ascorbic acid (H2A) to dehydroascorbic acid (DA), benzylamine (Ph-CH2-NH2) to benzaldehyde (Ph-CHO), and 3,5-di-tert-butylcatechol (3,5-DTBC) to 3,5-di-tert-butylquinone (3,5-DTBQ) [kcat: AOase, 9.6 (1) or 2.0 × 106 h−1(2); AmOase, 13.4 (1) or 9.4 × 106 h−1 (2); COase, 2.0 (1) or 1.9 × 103 h−1 (2)]. They exhibit higher levels of AOase activity as indicated by their kcat values compared to the AOase enzyme. The kcat values for COase activity in buffer solution [5.93 (1) or 2.95 × 105 h−1 (2)] are one order lower than those of the enzymes. This is because of the labile nature of the coordinated donor, the flexibility of the ligand, the simplicity of the catalyst-substrate interaction, and the positive CuII/I redox potential. Interestingly, more efficient catalysis is promoted by 1 and 2 concerning that of other mono- and dicopper(II) complexes.

Expression of the alfalfa gene MsMDHAR in Arabidopsis thaliana increases water stress tolerance.

The ascorbate-glutathione pathway plays an essential role in the physiology of vascular plants, particularly in their response to environmental stresses. This pathway is responsible for regulating the cellular redox state, which is critical for maintaining cell function and survival under adverse conditions. To study the involvement of the alfalfa monodehydroascorbate reductase (MsMDHAR) in water stress processes, Arabidopsis thaliana plants constitutively expressing the sequence encoding MsMDHAR were developed. Transgenic events with low and high MsMDHAR expression and ascorbate levels were selected for further analysis of drought and waterlogging tolerance. Under water stress, Arabidopsis transgenic plants generated higher biomass, produced more seeds, and had larger roots than wild type ones. This higher tolerance was associated with increased production of waxes and chlorophyll a at the basal level, greater stomatal opening and stability in regulating the relative water content and reduced H2O2 accumulation under stress conditions in transgenic plants. Overall, these results show that MsMDHAR is involved in plant tolerance to abiotic stresses. The data presented here also emphasises the potential of the MsMDHAR enzyme as a plant breeding tool to improve water stress tolerance.

Geochemistry of cherts from the northern Jiangxi region, South China: Implication for paleoenvironment

The extensive bedded cherts deposited during the Ediacaran–Cambrian (E–C) transition period play a crucial role in understanding the geological evolution of this period, yet the origin of these cherts remains disputed. Here, we present new geochemical data for cherts of the Piyuancun (PYC) Formation deposited during the Late Ediacaran and the Hetang (HT) Formation deposited during the Early Cambrian in northern Jiangxi region, Lower Yangtze region, South China. The PYC cherts contain a small amount of monaxons sponge spicules and radiolarian fragments, while the HT cherts lack siliceous organism evidence. Major and trace element analysis, coupled with discriminant diagrams, indicate a possible shift in redox conditions of seawater during the E–C transition in the northern Jiangxi region. The shift suggests a change from weakly–moderately restricted euxinic conditions to strongly restricted euxinic conditions. Furthermore, the location of both cherts are distant from the source area of siliceous organisms. Fossil evidence, as well as the values of Fe/Ti and Fe/(Mn+Ti), Eu anomalies, Post-Archean Australian Shale (PAAS) normalized REE+Y patterns, and various discriminant diagrams, support the conclusion that the PYC and HT cherts originated primarily from direct seawater precipitation, with the PYC cherts exhibiting weak hydrothermal evidence. Upwelling contributes to the formation of HT cherts and organic matter (OM) accumulation. Ocean acidification, triggered by OM degradation and biodegradation processes during the E–C transition period, leads to the extensive silica precipitation and preservation. These results enhance our understanding of the geological processes during the E–C transition.

Seawater Redox Conditions in the Late Paleoproterozoic: Insight from the North China Craton

Seawater Redox Conditions in the Late Paleoproterozoic: Insight from the North China Craton

Variable Iron Mineralogy and Redox Conditions Recorded in Ancient Rocks Measured by In Situ Visible/Near‐Infrared Spectroscopy at Jezero Crater, Mars

AbstractUsing relative reflectance measurements from the Mastcam‐Z and SuperCam instruments on the Mars 2020 Perseverance rover, we assess the variability of Fe mineralogy in Noachian/Hesperian‐aged rocks at Jezero crater. The results reveal diverse Fe3+ and Fe2+ minerals. The igneous crater floor, where small amounts of Fe3+‐phyllosilicates and poorly crystalline Fe3+‐oxyhydroxides have been reported, is spectrally similar to most oxidized basalts observed at Gusev crater. At the base of the western Jezero sedimentary fan, new spectral type points to an Fe‐bearing mineral assemblage likely dominated by Fe2+. By contrast, most strata exposed at the fan front show signatures of Fe3+‐oxides (mostly fine‐grained crystalline hematite), Fe3+‐sulfates (potentially copiapites), strong signatures of hydration, and among the strongest signatures of red hematite observed in situ, consistent with materials having experienced vigorous water‐rock interactions and/or higher degrees of diagenesis under oxidizing conditions. The fan top strata show hydration but little to no signs of Fe oxidation likely implying that some periods of fan construction occurred either during a reduced atmosphere era or during short‐lived aqueous activity of liquid water in contact with an oxidized atmosphere. We also report the discovery of alternating cm‐scale bands of red and gray layers correlated with hydration and oxide variability, which has not yet been observed elsewhere on Mars. This could result from syn‐depositional fluid chemistry variations, possibly as seasonal processes, or diagenetic overprint of oxidized fluids percolating through strata having variable permeability.

Experimental Constraints on the Storage Conditions and Differentiation of High-Ti Basalts from the Panzhihua and Hongge Layered Intrusions, SW China

Abstract High-Ti basalts are commonly believed to represent parental magmas leading to the formation of mafic-ultramafic layered intrusions, such as Late Permian Panzhihua and Hongge in the Emeishan Large Igneous Province (SW China). Consequently, elucidation of the crystallisation and crustal differentiation of high-Ti basalts is critical for our understanding of the petrogenesis of these layered intrusions and the associated oxide ore mineralisation. Here, we present the results of crystallisation experiments carried out in internally heated pressure vessels using a primitive high-Ti basaltic composition. The experiments were conducted at 100 and 300 MPa, in the temperature interval of 950–1200 °C and with water activities (aH2O) from 0 to 1. The oxygen fugacity (fO2) was controlled and varied from FMQ −1 to FMQ +3.3 log units (FMQ corresponds to fayalite-quartz-magnetite buffer). The main mineral phases are olivine, clinopyroxene and plagioclase, accompanied by Cr-Fe-Ti-oxides, orthopyroxene, apatite and amphibole, depending on the conditions. Redox conditions primarily influence the stability fields of Cr-Fe-Ti oxides. Clinopyroxene, orthopyroxene and amphibole are pressure-dependent and have larger stability fields under high pressure conditions. The olivine→orthopyroxene and olivine→amphibole peritectic reactions are observed. Comparisons of phase equilibria between this study and experiments conducted with parental magma of Skaergaard layered intrusion demonstrate the effect of bulk system composition. For instance, ilmenite crystallisation is determined not only by intrinsic parameters such as fO2 but also by additional compositional parameters (e.g. melt Ti, Fe, Al and Mg content). Although COMAGMAT and MELTS modelling results generally reproduce the crystallisation sequence, only the stability field of clinopyroxene and its composition are perfectly modelled. The comparison of experimental results with the rocks from the lowest units of Panzhihua and Hongge layered intrusions are applied to constrain storage conditions in the magma reservoirs. Compared to Hongge, we conclude that the Panzhihua magma chamber was probably located at a shallower depth (~3–6 km), that magma crystallisation started at lower temperatures (~1125–1100 °C), higher fO2 (~FMQ + 1 to FMQ + 2) and that its initial melt H2O content was lower (~0.5–1 wt. %).

Are Redox-Active Centers Bridged by Saturated Flexible Linkers Systematically Electrochemically Independent?

The extent to which electrophores covalently bridged by a saturated linker are electrochemically independent was investigated considering the charge/spin duality of the electron and functionality of the electrophore as a spin carrier upon reduction. By combining computational modeling with electrochemical experiments, we investigated the mechanism by which tethered electrophores react together within 4,4'-oligo[n]methylene-bipyridinium assemblies (with n=2 to 5). We show that native dicationic electrophores (redox state Z=+2) are folded prior to electron injection into the system, allowing the emergence of supra-molecular orbitals (supra-MOs) likely to support the process of the reductive σ bond formation giving cyclomers. Indeed, for Z=+2, London Dispersion (LD) forces contribute to flatten the potential energy surface such that all-trans and folded conformers are approximately isoenergetic. Then, upon one-electron injection, for radical cations (Z=+1), LD forces significantly stabilize the folded conformers, except for the ethylene derivative deprived of supra-MOs. For radical cations equipped with supra-MOs, the unpaired electron is delocalized over both heterocycles through space. Cyclomer completion (Z=0) upon the second electron transfer occurs according to the inversion of redox potentials. This mechanism explains why intramolecular reactivity is favored and why pyridinium electrophores are not independent.

Are Redox‐Active Centers Bridged by Saturated Flexible Linkers Systematically Electrochemically Independent?

AbstractThe extent to which electrophores covalently bridged by a saturated linker are electrochemically independent was investigated considering the charge/spin duality of the electron and functionality of the electrophore as a spin carrier upon reduction. By combining computational modeling with electrochemical experiments, we investigated the mechanism by which tethered electrophores react together within 4,4′‐oligo[n]methylene‐bipyridinium assemblies (with n=2 to 5). We show that native dicationic electrophores (redox state Z=+2) are folded prior to electron injection into the system, allowing the emergence of supra‐molecular orbitals (supra‐MOs) likely to support the process of the reductive σ bond formation giving cyclomers. Indeed, for Z=+2, London Dispersion (LD) forces contribute to flatten the potential energy surface such that all‐trans and folded conformers are approximately isoenergetic. Then, upon one‐electron injection, for radical cations (Z=+1), LD forces significantly stabilize the folded conformers, except for the ethylene derivative deprived of supra‐MOs. For radical cations equipped with supra‐MOs, the unpaired electron is delocalized over both heterocycles through space. Cyclomer completion (Z=0) upon the second electron transfer occurs according to the inversion of redox potentials. This mechanism explains why intramolecular reactivity is favored and why pyridinium electrophores are not independent.

Redox state of plastoquinone QA and lifetime of the P680 +•Pheo ‒• pair in photosystem II reaction centers

When plastoquinone QA (the electron acceptor) presents in one- or two-electron reduced states, the energy barrier between the radical pair and the excited photoactive chlorophyll ( ) in the photosystem II (PSII) reaction centers was estimated to be ~0.06 eV and ~0.12 eV, respectively (Safarova et al., 2023). In this study, the effect of the one- and two-electron reduced states of plastoquinone on the lifetime of the pair formed in the primary photochemical reaction in the PSII reaction center was evaluated. It has been shown that the lifetime of the pair formed when plastoquinone is doubly reduced is ≥10 times greater than when plastoquinone undergoes single reduction (recombination of charges, accordingly, occurs at a ≥10 times lower rate). The obtained result was compared with the existing experimental data. Keywords: Photosystem II, plastoquinone, charge recombination, lifetime

Occurrence and fate of perfluoroalkyl and polyfluoroalkyl substances (PFAS) in an urban aquifer located at the Besòs River Delta (Spain)

Urban aquifers are at risk of contamination from persistent and mobile organic compounds (PMOCs), especially per- and polyfluoroalkyl substances (PFAS), which are artificial organic substances widely used across various industrial sectors. PFAS are considered toxic, mobile and persistent, and have therefore gained significant attention in environmental chemistry. Moreover, precursors could transform into more recalcitrant products under natural conditions. However, there is limited information about the processes which affect their behaviour in groundwater at the field-scale. In this context, the aim of this study is to assess the presence of PFAS in an urban aquifer in Barcelona, and identify processes that control their evolution along the groundwater flow. 21 groundwater and 6 river samples were collected revealing the presence of 16 PFAS products and 3 novel PFAS. Short and ultra-short chain PFAS were found to be ubiquitous, with the highest concentrations detected for perfluorobutanesulfonic acid (PFBS), trifluoroacetic acid (TFA) and trifluoromethanesulfonic acid (TFSA). Long chain PFAS and novel PFAS were found to be present in very low concentrations (<50 ng/L). It was observed that redox conditions influence the behaviour of a number of PFAS controlling their attenuation or recalcitrant behaviour. Most substances showed accumulation, possibly explained by sorption/desorption processes or transformation processes, highlighting the challenges associated with PFAS remediation. In addition, the removal processes of different intensities for three PFAS were revealed. Our results help to establish the principles of the evolution of PFAS along the groundwater flow, which are important for the development of conceptual models used to plan and adopt site specific groundwater management activities (e.g., Managed Aquifer Recharge).