An allosteric redox switch involved in oxygen protection in a CO2 reductase.

Metal-dependent formate dehydrogenases reduce CO2 with high efficiency and selectivity, but are usually very oxygen sensitive. An exception is Desulfovibrio vulgaris W/Sec-FdhAB, which can be handled aerobically, but the basis for this oxygen tolerance was unknown. Here we show that FdhAB activity is controlled by a redox switch based on an allosteric disulfide bond. When this bond is closed, the enzyme is in an oxygen-tolerant resting state presenting almost no catalytic activity and very low formate affinity. Opening this bond triggers large conformational changes that propagate to the active site, resulting in high activity and high formate affinity, but also higher oxygen sensitivity. We present the structure of activated FdhAB and show that activity loss is associated with partial loss of the metal sulfido ligand. The redox switch mechanism is reversible in vivo and prevents enzyme reduction by physiological formate levels, conferring a fitness advantage during O2 exposure.

Understanding the local chemical environment of bioelectrocatalysis.

Bioelectrochemistry employs an array of high-surface-area meso- and macroporous electrode architectures to increase protein loading and the electrochemical current response. While the local chemical environment has been studied in small-molecule and heterogenous electrocatalysis, conditions in enzyme electrochemistry are still commonly established based on bulk solution assays, without appropriate consideration of the nonequilibrium conditions of the confined electrode space. Here, we apply electrochemical and computational techniques to explore the local environment of fuel-producing oxidoreductases within porous electrode architectures. This improved understanding of the local environment enabled simple manipulation of the electrolyte solution by adjusting the bulk pH and buffer pKa to achieve an optimum local pH for maximal activity of the immobilized enzyme. When applied to macroporous inverse opal electrodes, the benefits of higher loading and increased mass transport were employed, and, consequently, the electrolyte adjusted to reach -8.0 mA ⋅ cm-2 for the H2 evolution reaction and -3.6 mA ⋅ cm-2 for the CO2 reduction reaction (CO2RR), demonstrating an 18-fold improvement on previously reported enzymatic CO2RR systems. This research emphasizes the critical importance of understanding the confined enzymatic chemical environment, thus expanding the known capabilities of enzyme bioelectrocatalysis. These considerations and insights can be directly applied to both bio(photo)electrochemical fuel and chemical synthesis, as well as enzymatic fuel cells, to significantly improve the fundamental understanding of the enzyme-electrode interface as well as device performance.

Effect of Polymer Hydrophobicity in the Performance of Hybrid Gel Gas Sensors for E-Noses.

Relative humidity (RH) is a common interferent in chemical gas sensors, influencing their baselines and sensitivity, which can limit the performance of e-nose systems. Tuning the composition of the sensing materials is a possible strategy to control the impact of RH in gas sensors. Hybrid gel materials used as gas sensors contain self-assembled droplets of ionic liquid and liquid crystal molecules encapsulated in a polymeric matrix. In this work, we assessed the effect of the matrix hydrophobic properties in the performance of hybrid gel materials for VOC sensing in humid conditions (50% RH). We used two different polymers, the hydrophobic PDMS and the hydrophilic bovine gelatin, as polymeric matrices in hybrid gel materials containing imidazolium-based ionic liquids, [BMIM][Cl] and [BMIM][DCA], and the thermotropic liquid crystal 5CB. Better accuracy of VOC prediction is obtained for the hybrid gels composed of a PDMS matrix combined with the [BMIM][Cl] ionic liquid, and the use of this hydrophobic matrix reduces the effect of humidity on the sensing performance when compared to the gelatin counterpart. VOCs interact with all the moieties of the hybrid gel multicomponent system; thus, VOC correct classification depends not only on the polymeric matrix used, but also on the IL selected, which seems to be key to achieve VOCs discrimination at 50% RH. Thus, hybrid gels' tunable formulation offers the potential for designing complementary sensors for e-nose systems operable under different RH conditions.

Carboxysome-Inspired Electrocatalysis using Enzymes for the Reduction of CO2 at Low Concentrations.

The electrolysis of dilute CO2 streams suffers from low concentrations of dissolved substrate and its rapid depletion at the electrolyte-electrocatalyst interface. These limitations require first energy-intensive CO2 capture and concentration, before electrolyzers can achieve acceptable performances. For direct electrocatalytic CO2 reduction from low-concentration sources, we introduce a strategy that mimics the carboxysome in cyanobacteria by utilizing microcompartments with nanoconfined enzymes in a porous electrode. A carbonic anhydrase accelerates CO2 hydration kinetics and minimizes substrate depletion by making all dissolved carbon available for utilization, while a highly efficient formate dehydrogenase reduces CO2 cleanly to formate; down to even atmospheric concentrations of CO2 . This bio-inspired concept demonstrates that the carboxysome provides a viable blueprint for the reduction of low-concentration CO2 streams to chemicals by using all forms of dissolved carbon.

Tracking W-Formate Dehydrogenase Structural Changes During Catalysis and Enzyme Reoxidation.

Metal-dependent formate dehydrogenases (Fdh) catalyze the reversible conversion of CO2 to formate, with unrivalled efficiency and selectivity. However, the key catalytic aspects of these enzymes remain unknown, preventing us from fully benefiting from their capabilities in terms of biotechnological applications. Here, we report a time-resolved characterization by X-ray crystallography of the Desulfovibrio vulgaris Hildenborough SeCys/W-Fdh during formate oxidation. The results allowed us to model five different intermediate structures and to chronologically map the changes occurring during enzyme reduction. Formate molecules were assigned for the first time to populate the catalytic pocket of a Fdh. Finally, the redox reversibility of DvFdhAB in crystals was confirmed by reduction and reoxidation structural studies.

Formate Dehydrogenases Reduce CO2 Rather than HCO3- : An Electrochemical Demonstration.

Mo/W formate dehydrogenases catalyze the reversible reduction of CO2 species to formate. It is thought that the substrate is CO2 and not a hydrated species like HCO3- , but there is still no indisputable evidence for this, in spite of the extreme importance of the nature of the substrate for mechanistic studies. We devised a simple electrochemical method to definitively demonstrate that the substrate of formate dehydrogenases is indeed CO2 .

A Semi-artificial Photoelectrochemical Tandem Leaf with a CO2 -to-Formate Efficiency Approaching 1 .

Semi-artificial photoelectrochemistry can combine state-of-the-art photovoltaic light-absorbers with enzymes evolved for selective fuel-forming reactions such as CO2 reduction, but the overall performance of such hybrid systems has been limited to date. Here, the electrolyte constituents were first tuned to establish an optimal local environment for a W-formate dehydrogenase to perform electrocatalysis. The CO2 reductase was then interfaced with a triple cation lead mixed-halide perovskite through a hierarchically structured porous TiO2 scaffold to produce an integrated photocathode achieving a photocurrent density of -5 mA cm-2 at 0.4 V vs. the reversible hydrogen electrode during simulated solar light irradiation. Finally, the combination with a water-oxidizing BiVO4 photoanode produced a bias-free integrated biophotoelectrochemical tandem device (semi-artificial leaf) with a solar CO2 -to-formate energy conversion efficiency of 0.8 %.

Interfacing Formate Dehydrogenase with Metal Oxides for the Reversible Electrocatalysis and Solar-Driven Reduction of Carbon Dioxide.

The integration of enzymes with synthetic materials allows efficient electrocatalysis and production of solar fuels. Here, we couple formate dehydrogenase (FDH) from Desulfovibrio vulgaris Hildenborough (DvH) to metal oxides for catalytic CO2 reduction and report an in-depth study of the resulting enzyme-material interface. Protein film voltammetry (PFV) demonstrates the stable binding of FDH on metal-oxide electrodes and reveals the reversible and selective reduction of CO2 to formate. Quartz crystal microbalance (QCM) and attenuated total reflection infrared (ATR-IR) spectroscopy confirm a high binding affinity for FDH to the TiO2 surface. Adsorption of FDH on dye-sensitized TiO2 allows for visible-light-driven CO2 reduction to formate in the absence of a soluble redox mediator with a turnover frequency (TOF) of 11±1 s-1 . The strong coupling of the enzyme to the semiconductor gives rise to a new benchmark in the selective photoreduction of aqueous CO2 to formate.

The moderating effect of gender on the relationship between coping and suicide risk in a Portuguese community sample of adults.

Background and aims(s): The study evaluated the contribution of coping strategies, based on the Toulousiane conceptualization of coping, to the prediction of suicide risk and tested the moderating effect of gender, controlling for depressive symptoms. METHOD: A two-time data collection design was used. A community sample of 195 adults (91 men and 104 women) ranging in age from 19 to 65 years and living in several Portuguese regions, mostly in Alentejo, participated in this research. RESULTS: Gender, depressive symptoms, control, and withdrawal and conversion significantly predicted suicide risk and gender interacted with control, withdrawal and conversion, and social distraction in the prediction of suicide risk. Coping predicted suicide risk only for women. CONCLUSIONS: Results have important implications for assessment and intervention with suicide at-risk individuals. In particular,the evaluation and development of coping skills is indicated as a goal for therapists having suicide at-risk women as clients.

Self-report depressive symptoms do not directly predict suicidality in nonclinical individuals: Contributions toward a more psychosocial approach to suicide risk.

Although suicidality is associated with mental illness in general and depression in particular, many depressed individuals do not attempt suicide and some individuals who attempt to or do die by suicide do not present depressive symptoms. This article aims to contribute to a more psychosocial approach to understanding suicide risk in nonclinical populations. In advocating a psychosocial perspective rather than a depression-focused approach, this article presents four diverse studies that demonstrate sampling and measurement invariance in findings across different populations and specific measures. Study 1 tests the mediation effects of 2 interpersonal variables, thwarted belongingness and perceived burdensomeness, in the association between depressive symptoms and recent suicidality. Studies 2 and 3 evaluate the contribution of hopelessness and psychache, beyond depressive symptoms, to suicidality. Study 4 tests the contribution of life events behind depressive symptoms, and other relevant sociodemographic and clinical variables, to the estimation of "future suicidality." Overall, results demonstrate that depressive symptoms do not directly predict suicidality in nonclinical individuals, but that other psychosocial variables mediate the association between depressive symptoms and suicidality or predict suicidality when statistically controlling for depressive symptoms. The article contributes to understanding some of the nonpsychopathological factors that potentially link depressive symptoms to suicide risk and that might themselves contribute to suicidality, even when controlling for depressive symptoms.

Assessment of IrisPlex-based multiplex for eye and skin color prediction with application to a Portuguese population.

DNA phenotyping research is one of the most emergent areas of forensic genetics. Predictions of externally visible characteristics are possible through analysis of single nucleotide polymorphisms. These tools can provide police with "intelligence" in cases where there are no obvious suspects and unknown biological samples found at the crime scene do not result in any criminal DNA database hits. IrisPlex, an eye color prediction assay, revealed high prediction rates for blue and brown eye color in European populations. However, this is less predictive in some non-European populations, probably due to admixing. When compared to other European countries, Portugal has a relatively admixed population, resulting from a genetic influx derived from its proximity to and historical relations with numerous African territories. The aim of this work was to evaluate the utility of IrisPlex in the Portuguese population. Furthermore, the possibility of supplementing this multiplex with additional markers to also achieve skin color prediction within this population was evaluated. For that, IrisPlex was augmented with additional SNP loci. Eye and skin color prediction was estimated using the multinomial logistic regression and binomial logistic regression models, respectively. The results demonstrated eye color prediction accuracies of the IrisPlex system of 90 and 60% for brown and blue eye color, respectively, and 77% for intermediate eye color, after allele frequency adjustment. With regard to skin color, it was possible to achieve a prediction accuracy of 93%. In the future, phenotypic determination multiplexes must include additional loci to permit skin color prediction as presented in this study as this can be an advantageous tool for forensic investigation.

Small bait traps as accurate predictors of dipteran early colonizers in forensic studies.

Insect carrion communities vary among habitats and over time. Concerning the dipteran early colonizers of carrion, the use of small bait traps should be accurate because the odors emitted from meat baits should contain many of the volatile organic compounds emitted from the freshly dead mammals. In addition, this kind of trap is easy to replicate and set in position in a given habitat. In the present study, small bait preferences of early Diptera carrion colonizers were examined in an urban biotope. Specifically, three baits were compared (pork muscle, pork liver, and fish flavored cat food) in respect to the number of specimens and species captured and the presence or absence of oviposition at high and low environmental temperatures. A total of 2371 specimens were trapped, primarily belonging to three insect orders, Diptera, Coleoptera, and Hymenoptera. Diptera was the predominant order, with blowflies (Calliphoridae) being the most representative family, followed by filth flies (Muscidae). The pork muscle bait was responsible for the highest number of captures and the highest diversity. The community of Diptera collected with the most efficient bait, pork muscle, was compared with the carrion communities reported in the literature from the Iberian Peninsula. Similar taxonomic species composition was found regarding Calliphoridae species. A specimen from all species morphologically identified were also identified at a molecular level using the cytochrome c oxidase I (COI) barcode region, and the sequences were submitted to online databases.

Growth after pediatric kidney transplantation: a 25-year study in a pediatric kidney transplant center.

OBJECTIVES: Growth failure is one of the major complications of pediatric chronic kidney disease. Even after a kidney transplant (KT), up to 50 % of patients fail to achieve the expected final height. This study aimed to assess longitudinal growth after KT and identify factors influencing it. METHODS: A retrospective observational study was performed. We reviewed the clinical records of all patients who underwent KT for 25 years in a single center (n=149) and performed telephone interviews. Height-for-age and body mass index (BMI)-for-age were examined at KT, 3 months, 6 months, 1 year, and 5 years post-transplant and at the transition to adult care. We evaluated target height, disease duration before KT, need and type of dialysis, recombinant human growth hormone pretransplant use, nutritional support, glomerular filtration rate (GFR), and cumulative corticosteroid dose. RESULTS: At transplant, the average height z-score was -1.38, and height z-scores showed catch-up growth at 6 months (z-score -1.26, p=0.006), 1 year (z-score -1.15, p<0.001), 5 years after KT (z-score -1.08, p<0.001), and on transition to adult care (z-score -1.22, p=0.012). Regarding BMI z-scores, a significant increase was also detected at all time points (p<0.001). After KT, GFR was significantly associated with height z-score (p=0.006) and BMI z-score (p=0.006). The height in transition to adult care was -1.28 SD compared to the target height. CONCLUSIONS: Despite the encouraging results regarding catch-up growth after KT in this cohort, results remain far from optimum, with a lower-than-expected height at the time of transition.

The Biology of Lysosomes: From Order to Disorder.

Since its discovery in 1955, the understanding of the lysosome has continuously increased. Once considered a mere waste removal system, the lysosome is now recognised as a highly crucial cellular component for signalling and energy metabolism. This notable evolution raises the need for a summarized review of the lysosome's biology. As such, throughout this article, we will be compiling the current knowledge regarding the lysosome's biogenesis and functions. The comprehension of this organelle's inner mechanisms is crucial to perceive how its impairment can give rise to lysosomal disease (LD). In this review, we highlight some examples of LD fine-tuned mechanisms that are already established, as well as others, which are still under investigation. Even though the understanding of the lysosome and its pathologies has expanded through the years, some of its intrinsic molecular aspects remain unknown. In order to illustrate the complexity of the lysosomal diseases we provide a few examples that have challenged the established single gene-single genetic disorder model. As such, we believe there is a strong need for further investigation of the exact abnormalities in the pathological pathways in lysosomal disease.

Impact of the Cationic Moiety of Ionic Liquids on Chemoselective Artificial Olfaction.

Ionogels and derived materials are assemblies of polymers and ionic liquids characterized by high stability and ionic conductivity, making them interesting choices as gas sensors. In this work, we assessed the effect of the ionic liquid moiety to generate ionogels and hybrid gels as electrical and optical gas sensors. Six ionic liquids consisting of a constant anion (chloride) and distinct cationic head groups were used to generate ionogels and hybrid gels and further tested as gas sensors in customized electronic nose devices. In general, ionogel-based sensors yielded higher classification accuracies of standard volatile organic compounds when compared to hybrid material-based sensors. In addition, the high chemical diversity of ionic liquids is further translated to a high functional diversity in analyte molecular recognition and sensing.

Psychological group intervention to support parenting: Qualitative study about needs and preferences of mothers with breast cancer.

PURPOSE: Parental worries and parenting stress can increase when a mother receives a breast cancer diagnosis. This study presents the findings of needs and preferences of mothers with breast cancer to inform the development of a group intervention program for mothers with breast cancer and other alternatives of support. METHODS: Using qualitative data from eighteen Portuguese women with at least one minor child when they received a breast cancer diagnosis, and content analysis on three focus groups transcripts, we uncover the participants' parenting needs and their perceptions of the potential benefits and the formal aspects of a group intervention. RESULTS: Mothers revealed that they need support on several parenting-related issues (e.g., communicating with the children about the mother's diagnosis, dealing with children's responses and difficult questions). They provided information about the potential benefits of group intervention and preferences regarding intervention content, sessions' structure, frequency, location, and timing. Some participants also suggested other types of support, such as online information and individual psychological support. CONCLUSIONS: The development of an intervention informed by the patients' needs and preferences can contribute to increasing its feasibility and efficacy. The findings indicated the specific parenting needs of Portuguese mothers with breast cancer, and it offered health professionals some important clues on how to support other family members.

Spectroscopic and Structural Characterization of Reduced Desulfovibrio vulgaris Hildenborough W-FdhAB Reveals Stable Metal Coordination during Catalysis.

Metal-dependent formate dehydrogenases are important enzymes due to their activity of CO2 reduction to formate. The tungsten-containing FdhAB formate dehydrogenase from Desulfovibrio vulgaris Hildenborough is a good example displaying high activity, simple composition, and a notable structural and catalytic robustness. Here, we report the first spectroscopic redox characterization of FdhAB metal centers by EPR. Titration with dithionite or formate leads to reduction of three [4Fe-4S]1+ clusters, and full reduction requires Ti(III)-citrate. The redox potentials of the four [4Fe-4S]1+ centers range between -250 and -530 mV. Two distinct WV signals were detected, WDV and WFV, which differ in only the g2-value. This difference can be explained by small variations in the twist angle of the two pyranopterins, as determined through DFT calculations of model compounds. The redox potential of WVI/V was determined to be -370 mV when reduced by dithionite and -340 mV when reduced by formate. The crystal structure of dithionite-reduced FdhAB was determined at high resolution (1.5 Å), revealing the same structural alterations as reported for the formate-reduced structure. These results corroborate a stable six-ligand W coordination in the catalytic intermediate WV state of FdhAB.

Fast CO2 hydration kinetics impair heterogeneous but improve enzymatic CO2 reduction catalysis.

The performance of heterogeneous catalysts for electrocatalytic CO2 reduction suffers from unwanted side reactions and kinetic inefficiencies at the required large overpotential. However, immobilized CO2 reduction enzymes-such as formate dehydrogenase-can operate with high turnover and selectivity at a minimal overpotential and are therefore 'ideal' model catalysts. Here, through the co-immobilization of carbonic anhydrase, we study the effect of CO2 hydration on the local environment and performance of a range of disparate CO2 reduction systems from enzymatic (formate dehydrogenase) to heterogeneous systems. We show that the co-immobilization of carbonic anhydrase increases the kinetics of CO2 hydration at the electrode. This benefits enzymatic CO2 reduction-despite the decrease in CO2 concentration-due to a reduction in local pH change, whereas it is detrimental to heterogeneous catalysis (on Au) because the system is unable to suppress the H2 evolution side reaction. Understanding the role of CO2 hydration kinetics within the local environment on the performance of electrocatalyst systems provides important insights for the development of next-generation synthetic CO2 reduction catalysts.

Elucidating Film Loss and the Role of Hydrogen Bonding of Adsorbed Redox Enzymes by Electrochemical Quartz Crystal Microbalance Analysis.

The immobilization of redox enzymes on electrodes enables the efficient and selective electrocatalysis of useful reactions such as the reversible interconversion of dihydrogen (H2) to protons (H+) and formate to carbon dioxide (CO2) with hydrogenase (H2ase) and formate dehydrogenase (FDH), respectively. However, their immobilization on electrodes to produce electroactive protein films for direct electron transfer (DET) at the protein-electrode interface is not well understood, and the reasons for their activity loss remain vague, limiting their performance often to hour timescales. Here, we report the immobilization of [NiFeSe]-H2ase and [W]-FDH from Desulfovibrio vulgaris Hildenborough on a range of charged and neutral self-assembled monolayer (SAM)-modified gold electrodes with varying hydrogen bond (H-bond) donor capabilities. The key factors dominating the activity and stability of the immobilized enzymes are determined using protein film voltammetry (PFV), chronoamperometry (CA), and electrochemical quartz crystal microbalance (E-QCM) analysis. Electrostatic and H-bonding interactions are resolved, with electrostatic interactions responsible for enzyme orientation while enzyme desorption is strongly limited when H-bonding is present at the enzyme-electrode interface. Conversely, enzyme stability is drastically reduced in the absence of H-bonding, and desorptive enzyme loss is confirmed as the main reason for activity decay by E-QCM during CA. This study provides insights into the possible reasons for the reduced activity of immobilized redox enzymes and the role of film loss, particularly H-bonding, in stabilizing bioelectrode performance, promoting avenues for future improvements in bioelectrocatalysis.

Heavy Metals Removal from Aqueous Solutions by Multiwall Carbon Nanotubes: Effect of MWCNTs Dispersion.

Carbon nanotubes (CNTs) are one of the most studied nanoparticles due to their physical, chemical and electronic properties. However, strong Van der Waals bonds, which promote CNTs aggregation are usually present, affecting their unique properties. Avoiding CNTs aggregation is one of the main difficulties when using these nanoparticles. Regarding the adsorption capacity of CNTs, the tendency of CNTs to aggregate decreases the surface area available to retain contaminants. One way to overcome this issue is by changing the surface energy of CNTs through chemical (covalent and noncovalent methods) or mechanical stabilization, but there is not yet a unique solution to solve this problem. In this work, a chemical noncovalent method (addition of surfactants) combined with mechanical energy (ultrasounds) was applied for CNTs stabilization, and the influence in heavy metal ions removal, Pb (II), Cu (II), Ni (II) and Zn (II), an area of high environmental relevance, was evaluated. It was proved that high amounts of metals could be removed from water during the first eighteen hours. Competitive adsorption between heavy metals, during adsorption tests with the simultaneous presence of all ions, was also studied and it was possible to prove that the electronegativity and atomic radius of cations influence their removal. Pb (II) and Cu (II) were the metals removed in higher percentages, and Ni (II) and Zn (II) were the metals less removed during competitive adsorption. Finally, the results obtained show that MWCNTs, if adequately dispersed, present a good solution for the treatment of water contaminated with highly toxic heavy metals, even when using very low concentrations of Multiwall Carbon Nanotubes (MWCNTs).