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- EPR-detectable redox centers of the periplasmic hydrogenase from Desulfovibrio vulgaris.Publication . Patil, Daulat S.; Moura, José J.; He, S. H.; Teixeira, Miguel S.; Prickril, Ben C.; DerVartanian, Daniel V.; Peck, Harry D.; LeGall, J.; Huynh, Boi Hanh; DQ - Departamento de Química; CQFB-REQUIMTE - Centro de Química Fina e Biotecnologia (Lab. Associado REQUIMTE); ASBMB - American Society for Biochemistry and Molecular BiologyThe periplasmic hydrogenase of Desulfovibrio vulgaris (Hildenbourough NCIB 8303) belongs to the category of [Fe] hydrogenase which contains only iron-sulfur clusters as its prosthetic groups. Amino acid analyses were performed on the purified D. vulgaris hydrogenase. The amino acid composition obtained compared very well with the result derived from the nucleotide sequence of the structural gene (Voordouw, G., Brenner, S. (1985) Eur. J. Biochem. 148, 515-520). Detailed EPR reductive titration studies on the D. vulgaris hydrogenase were performed to characterize the metal centers in this hydrogenase. In addition to the three previously observed EPR signals (namely, the "isotropic" 2.02 signal, the rhombic 2.10 signal, and the complex signal of the reduced enzyme), a rhombic signal with resonances at the g-values of 2.06, 1.96, and 1.89 (the rhombic 2.06 signal) was detected when the samples were poised at potentials between 0 and -250 mV (with respect to normal hydrogen electrode). The midpoint redox potentials for each of the four EPR-active species were determined, and the characteristics of each EPR signal are described. Both the rhombic 2.10 and 2.06 signals exhibit spectral properties that are distinct from a ferredoxin-type [4Fe-4S] cluster and are proposed to originate from the same H2-binding center but in two different conformations. The complex signal of the reduced hydrogenase has been shown to represent two spin-spin interacting ferredoxin-type [4Fe-4S]1+ clusters (Grande, H. J., Dunham, W. R., Averill, B., Van Dijk, C., and Sands, R. H. (1983) Eur. J. Biochem. 136, 201-207). The titration data indicated a strong cooperative effect between these two clusters during their reduction. In an effort to accurately estimate the number of iron atoms/molecule of hydrogenase, plasma emission and chemical methods were used to determine the iron contents in the samples; and four different methods, including amino acid analysis, were used for protein determination. The resulting iron stoichiometries were found to be method-dependent and vary over a wide range (+/- 20%). The uncertainties involved in the determination of iron stoichiometry are discussed.
- Harnessing Lignocellulosic Crops for Phytomanagement of Contaminated SoilsPublication . Testa, Giorgio; Ciaramella, Barbara Rachele; Fernando, Ana Luísa; Kotoula, Danai; Scordia, Danilo; Gomes, Leandro Augusto; Cosentino, Salvatore Luciano; Alexopoulou, Efthymia; Papazoglou, Eleni G.; DQ - Departamento de Química; MEtRICS - Centro de Engenharia Mecânica e Sustentabilidade de Recursos; MDPI - Multidisciplinary Digital Publishing InstituteThe dwindling availability of agricultural land, caused by factors such as rapid population growth, urban expansion, and soil contamination, has significantly increased the pressure on food production. To address this challenge, cultivating non-food crops on contaminated land has emerged as a promising solution. This approach not only frees up fertile soil for food production but also mitigates human exposure to contaminants. This work aimed to examine the impact of soil contamination with Cd, Pb, Ni, and Zn on the growth, productivity, metal accumulation, and the tolerance of five lignocellulosic non-food crops: switchgrass (Panicum virgatum L.), biomass sorghum (Sorghum bicolor L. Moench), giant reed (Arundo donax L.), African fodder cane (Saccharum spontaneum L. spp. aegyptiacum Willd. Hackel), and miscanthus (Miscanthus × giganteus Greef et Deu.). A two-year pot experiment was conducted in Greece, Italy, and Portugal, following the same protocols and applying various levels of metals: Cd (0, 4, 8 mg kg−1), Pb and Zn (0, 450, 900 mg kg−1), and Ni (0, 110, 220 mg kg−1). The experimental design was completely randomized, with three replicates for each treatment. The results showed that switchgrass and sorghum generally maintained their height and productivity under Cd and Pb stress but were adversely affected by high Zn and Ni concentrations. Giant reed and African fodder cane showed reduced height and productivity at higher Ni and Zn levels. Miscanthus exhibited resilience in height but experienced productivity reductions only at the highest Zn concentration. Heavy metal uptake varied among crops, with switchgrass and sorghum showing high Cd and Pb uptake, while giant reed accumulated the most Cd and Zn. Miscanthus had the highest Ni accumulation. The tolerance indices indicated that switchgrass and sorghum were more tolerant to Cd and Zn at lower concentrations, whereas miscanthus had lower tolerance to Cd but a higher tolerance to Zn at higher concentrations. Giant reed and African fodder cane demonstrated stable tolerance across most heavy metals. Accumulation indices highlighted the effectiveness of switchgrass and sorghum in Cd and Pb uptake, while miscanthus excelled in Ni and Zn accumulation. The cluster analysis revealed similar responses to heavy metal stress between African fodder cane and giant reed, as well as between sorghum and miscanthus, with switchgrass displaying distinct behavior. Overall, the study highlights the differential tolerance and accumulation capacities of these crops, indicating the potential for phytoremediation applications and biomass production in heavy metal-contaminated soils.
- Boosting CO2 selectivity by mono- and dicarboxylate-based ionic liquids impregnation into ZIF-8 for post-combustion separationPublication . Ferreira, Tiago J.; Carvalho, Thiago O.; Pais, Joana; Esteves, Laura M.; Silva, Ludmila P. C.; Reis, Patrícia M.; Esperança, José M. S. S.; Esteves, Isabel A. A. C.; LAQV@REQUIMTE; DQ - Departamento de Química; ElsevierPost-combustion carbon dioxide (CO2) capture/separation is considered one of the main ways to minimize the impact of global warming caused by this greenhouse gas. This work used eight mono- and dicarboxylate-based ionic liquids (ILs) to impregnate metal-organic framework (MOF) ZIF-8. This anionic effect was studied for these mostly unreported IL@MOF composites to determine its impact on gas sorption and selectivity performance. Characterization results confirmed IL impregnation into the structure of ZIF-8, along with the conservation of microporosity and crystallinity in composites. Sorption-desorption equilibrium measurements were performed, and CO2 and nitrogen (N2) isotherms were obtained at 303 K for ZIF-8 and IL@ZIF-8 composites. At 0.15 bar, the dicarboxylate-based composite [C2MIM]2[Glu]@ZIF-8 showed the highest CO2 gas sorption, showing 50 % more sorption capacity than the best monocarboxylate-base composites at this pressure. Dicarboxylate-based composites also showed remarkable N2 sorption in the low-pressure range. The ideal CO2/N2 selectivity for a typical post-combustion composition was calculated, and a trend regarding the anionic carbon chain size was observed. The composite [C2MIM][Cap]@ZIF-8 showed nearly five times more selectivity than the pristine ZIF-8 at 1 bar of total pressure. Dicarboxylate-based composites, given their low-pressure high N2 sorption capacity, were not as selective as their respective monocarboxylate-based IL@ZIF-8 materials with the same carbon chain size.
- Printable ionic liquid modified cellulose acetate for sustainable chromic and resistive temperature sensingPublication . Cruz, B. D. D.; Castro, A. S.; Fernandes, L. C.; Pereira, N.; Mendes-Felipe, C.; Tariq, M.; Esperança, J. M. S. S.; Martins, P. M.; Lanceros-Méndez, S.; Correia, D. M.; LAQV@REQUIMTE; DQ - Departamento de Química; ElsevierSustainable technologies and the circular economy paradigms require a reduction of waste, and therefore, research is focusing on the development of sustainable materials and devices capable of being reused, refurbished or recycled. In the present work, printable ionic liquid (IL)-based polymer composites with thermochromic properties have been developed through a more sustainable approach to mitigate the negative impact of advanced functional materials and processes. For this purpose, composite films based on a natural polymer, cellulose acetate (CA), and different contents of the thermochromic IL, bis(1-butyl-3-methylimidazolium) tetrachloronickelate ([Bmim]2[NiCl4]), have been processed by a solvent casting method for the development of sustainable temperature sensors. The composites are transparent at room temperature, but when exposed to a temperature of 50 °C, the colour changes to blue. Incorporating the thermochromic IL led to the appearance of pores in the material's structure, which increased with increasing IL concentration. Additionally, the Young Modulus decreases with increasing IL concentration, reaching a value of 840 ± 158 MPa) for the sample with 40 % wt. Contrarily, the electrical conductivity strongly increases with the highest DC electrical conductivity, with a maximum conductivity of 1.1 × 10–5 ± 1.5 × 10–6 S.cm-1 obtained for the sample with 40 % wt. of [Bmim]2[NiCl4]. As a proof of concept, the potential applicability of the developed natural-based nanoparticle-free materials was demonstrated with a CA/40[Bmim]2[NiCl4] sample by the development of printable thermochromic temperature sensors for thermotherapy applications in the temperature range from 33 °C to 50 °C.
- Cationic effect study in acetate-based ionic liquids/ZIF-8 composites for CO2 sorptionPublication . Ferreira, Tiago J.; Cabral, Catarina; Carvalho, Thiago O.; Pais, Joana; Esteves, Laura M.; Silva, Ludmila P. C.; Reis, Patrícia M.; Esperança, José M. S. S.; Esteves, Isabel A. A. C.; LAQV@REQUIMTE; DQ - Departamento de Química; ElsevierSeveral strategies can be considered for the mitigation of carbon dioxide (CO2) emissions to the atmosphere, and among them is its post-combustion capture/separation from flue gas emitted from coal-fired power plants. In this work, six imidazolium, ammonium- and DABCO-based ionic liquids (ILs) containing the acetate anion were used to impregnate the metal-organic framework (MOF) ZIF-8. The cationic effect was studied to determine how the different cationic families and side alkyl chain size influence the gas sorption performance of the produced IL@MOF composites. The combination of different characterization techniques confirmed IL impregnation, and that the composite materials were microporous and crystalline. Single-component CO2 and nitrogen (N2) sorption-desorption equilibrium measurements were performed at 303 K for ZIF-8 and the IL@ZIF-8 materials. At the low-pressure regime (0–1 bar), synergy was observed for the imidazolium-based composites, especially for the one with the long-side alkyl chain. The ideal CO2/N2 selectivity was calculated for post-combustion composition, and, at 1 bar, [C10MIM][Ac]@ZIF-8 was over four times more selective than ZIF-8, while the selectivity of [C2MIM][Ac]@ZIF-8 at this pressure almost tripled when compared to the MOF. A chemical reaction between CO2 and the imidazolium ILs explained the results.
- Impact of PEG Content on Doxorubicin Release from PLGA-co-PEG NanoparticlesPublication . Cardoso, Maria Margarida; Peça, Inês N.; Bicho, Ana; LAQV@REQUIMTE; DQ - Departamento de Química; Molecular Diversity Preservation International (MDPI)Nanoparticles (NPs) have become attractive vehicles for drug delivery in cancer therapy due to their ability to accumulate in tumours and mitigate side effects. This study focuses on the production of doxorubicin (DOX)-loaded NPs comprising Poly (lactic-co-glycolic acid)-Polyethylene glycol with varying PEG proportions and the examination of their impact on drug release kinetics. DOX-loaded NPs, composed of PLGA-co-PEG with PEG contents of 0%, 5%, 10%, and 15%, were synthesized by the solvent evaporation technique, exhibited spherical morphology, and had sizes ranging from 420 nm to 690 nm. In vitro drug release studies revealed biphasic profiles, with higher PEG contents leading to faster and more extensive drug release. The Baker–Lonsdale model demonstrated the best fit to the drug release data, indicating that the release process is diffusion-controlled. The diffusion coefficients for DOX determined ranged from 6.3 × 10−18 to 7.55 × 10−17 cm2s−1 and exhibited an upward trend with increasing PEG content in the polymer. In vitro cytotoxicity tests with CHO cells showed that unloaded NPs are non-toxic, while DOX-loaded PLGA-PEG 15% NPs induced a greater decrease in cellular viability compared to their PLGA counterparts. A mathematical relationship between the diffusion coefficient and PEG percentage was derived, providing a practical tool for optimizing DOX release profiles.
- Supramolecular engineering of micellar systemsPublication . Gómez-González, Borja; Basílio, Nuno; Vaz, Belén; Góñez, Karen V.; Pérez-Lorenzo, Moisés; García-Río, Luis; LAQV@REQUIMTE; DQ - Departamento de Química; ElsevierIn the quest for enhanced drug delivery systems, the combination of supramolecular receptors and surfactants represents a promising step toward developing innovative and highly efficient nanocarriers. This research highlights the paramount advantages of synergizing these elements, focusing on the manipulation of the self-assembly, charge, and polarity of the hybrid nanostructures resulting from merging these building blocks. In this vein, this work reveals that the integration of hexamethylated p-sulfonatocalix[6]arene (SC6A) and dodecyltrimethylammonium bromide (DTAB) offers significant advantages over those colloidal nanostructures stemming from the use of surfactant alone. These include the ability to stimulate early self-assembly, thereby facilitating the formation of stable nanocarriers, even in high-dilution scenarios. Additionally, the electrostatic balance established within the macrocycle-surfactant host–guest complexes can be harnessed to finely adjust the charge of the hydrophilic micellar corona. This holds great promise for modulating the bio-interaction capabilities of nanocarriers. Furthermore, the inclusion of the macrocycle in the colloidal structure induces significant alterations in the arrangement of low-molecular-weight surfactants. This leads to a significant transformation in the hydrophobic properties of the micellar core, which can be exploited to tailor this microenvironment to match the lipophilicity of specific drugs. In this regard, our findings reveal that while conventional DTAB micelles generally replicate the polarity of a solvent with a dielectric constant of 37.7, engineered SC6A-DTAB aggregates demonstrate a capability to reach a polarity akin to a solvent with dielectric constant of 17.5. This spectrum of hydrophobicities within the micellar core represents a significant advancement and opens up new possibilities for drug delivery applications.
- Facile Synthesis of Sodium Alginate (SA)-Based Quaternary Bio-Nanocomposite (SA@Co-Zn-Ce) for Antioxidant Activity and Photocatalytic Degradation of Reactive Red 24Publication . Fatima, Sidra; Javaid, Sana; Ahmad, Hira; Almasoudi, Afaf; Baamer, Doaa F.; Ali, Omar Makram; Carabineiro, Sónia A. C.; Taj, Muhammad Babar; LAQV@REQUIMTE; DQ - Departamento de Química; MDPI - Multidisciplinary Digital Publishing InstituteThis study introduces a new strategy for the environmentally friendly catalytic degradation of Reactive Red 24 (RR24) dye using sunlight. We developed a cost-effective quaternary nanocomposite by immobilizing a sodium alginate biopolymer over bioengineered Co-Zn-Ce nanoparticles, forming an SA@Co–Zn–Ce nanocomposite (where SA means sodium alginate). This composite also demonstrated an exceptional antioxidant potential of approximately 89%, attributed to the synergistic effect of sodium alginate and green-synthesized Co–Zn–Ce nanoparticles (biosynthesized using Ocimum sanctum leaf extract as a reducing agent). Scanning electron microscopy revealed grain sizes of 28.6 nm for Co–Zn–Ce NPs and 25.59 nm for SA@Co–Zn–Ce nanocomposites (NCs). X-ray diffraction showed particle sizes of 16.87 nm and 15.43 nm, respectively. Co–Zn–Ce NPs exhibited a zeta potential of 1.99 mV, whereas the sodium alginate-anchored Co–Zn–Ce showed −7.99 mV. This indicated the entrapment of negatively charged ions from sodium alginate, altering the surface charge characteristics and enhancing the photocatalytic degradation of RR24. Dynamic light scattering revealed an average particle size of approximately 81 nm for SA@Co–Zn–Ce NCs, with the larger size due to the influence of water molecules in the colloidal solution affecting hydrodynamic diameter measurement. The SA@Co–Zn–Ce NCs exhibited a CO2 adsorption capacity of 3.29 mmol/g at 25 °C and 4.76 mmol/g at 40 °C, indicating temperature-dependent variations in adsorption capabilities. The specific surface area of Co–Zn–Ce oxide NPs, measured using Brunauer–Emmett–Teller (BET) analysis, was found to be 167.346 m2/g, whereas the SA@Co–Zn–Ce oxide nanocomposite showed a surface area of 24.14 m2/g. BJH analysis revealed average pore diameters of 34.60 Å for Co–Zn–Ce oxide NPs and 9.26 Å for SA@Co–Zn–Ce oxide NCs. Although the immobilization of sodium alginate on Co–Zn–Ce oxide NPs did not increase the adsorption sites and porosity of the composite, as evidenced by the N2 adsorption–desorption isotherms, the SA@Co–Zn–Ce oxide NCs still demonstrated a high photocatalytic degradation efficiency of RR24.
- Adsorption of Carbon Dioxide and Nitrogen in Co3(ndc)3(dabco) Metal–Organic FrameworkPublication . Ribeiro, Rui Pedro Pinto Lopes; Mota, José Paulo Barbosa; LAQV@REQUIMTE; DQ - Departamento de Química; MDPI - Multidisciplinary Digital Publishing InstituteMetal–organic frameworks (MOFs) are promising materials for processes such as carbon dioxide (CO2) capture or its storage. In this work, the adsorption of CO2 and nitrogen (N2) in Co3(ndc)3(dabco) MOF (ndc: 2,6-naphthalenedicarboxylate; dabco: 1,4-diazabicyclo[2.2.2]octane) is reported for the first time over the temperature range of 273–323 K and up to 35 bar. The adsorption isotherms are successfully described using the Langmuir isotherm model. The heats of adsorption for CO2 and N2, determined through the Clausius–Clapeyron equation, are 20–27 kJ/mol and 10–11 kJ/mol, respectively. The impact of using pressure and/or temperature swings on the CO2 working capacity is evaluated. If a flue gas with 15% CO2 is fed at 6 bar and 303 K and regenerated at 1 bar and 373 K, 1.58 moles of CO2 can be captured per kg of MOF. The analysis of the multicomponent adsorption of typical flue gas streams (15% CO2 balanced with N2), using the ideal adsorbed solution theory (IAST), shows that at 1 bar and 303 K, the CO2/N2 selectivity is 11.5. In summary, this work reports essential data for the design of adsorption-based processes for CO2 capture using a Co3(ndc)3(dabco) MOF, such as pressure swing adsorption (PSA).
- Exploring Cynara cardunculus L. by-products potentialPublication . Barbosa, Cássia H.; Duarte, Maria Paula; Andrade, Mariana A.; Mateus, Ana Rita; Vilarinho, Fernanda; Fernando, Ana Luísa; Silva, Ana Sanches; DQ - Departamento de Química; MEtRICS - Centro de Engenharia Mecânica e Sustentabilidade de Recursos; ElsevierCynara cardunculus L. (cardoon), a perennial crop indigenous to the Mediterranean region, has gained recognition for its remarkable resilience to diverse weather conditions and its multifaceted applications across various industries, which includes the use of the flower as a vegetable rennet to produce some cheeses, as a source of biomass for energy, or its seed oil for human consumption, biodiesel, and animal feed. In some applications (e.g. biomass or seed production), when crop is harvested at the end of the growth cycle, the leaves remain as the main by-products, along with the flowers. In the context of a circular economy, the aim of this work was to undergone studies to determinate their biological properties (antioxidant and antimicrobial). Methanolic and ethanolic extracts of C. cardunculus L. (globe artichoke var. scolymus (L.) Fiori) and cultivated cardoon (var. altilis DC.)) leaves and flowers were characterised in terms of their polyphenol profile (total phenolic content (TPC), total flavonoid compounds (TFC), and ultra-high performance liquid chromatography coupled with time-of-flight mass spectrometry (UHPLC-ToF-MS)), antioxidant capacity (free radical DPPH inhibition system, β-carotene bleaching assay), and antimicrobial capacity (minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), antifungal). In addition, the cultivated cardoon leaves extracts were assessed before and after they were dried in an oven with forced air circulation to evaluate if this treatment affected their bioactive profile. Chlorogenic acid, apigenin, and luteolin were the most quantified of a total of sixteen compounds identified by UHPLC-ToF-MS. Cultivated cardoon dry leaf extract presented the best antioxidant capacity for both methanolic (EC50 = 0.8 mg/mL, antioxidant activity coefficient (AAC) = 279.67) and ethanolic (EC50 = 2.1 mg/mL, AAC = 448.06) extracts, compared to the cardoon flower extracts and the globe artichoke leaf extracts. Dried cultivated cardoon leaf extracts presented higher antioxidant capacity than fresh cultivated cardoon leaf extracts, but a greater number of polyphenolic compounds were identified in fresh cultivated cardoon leaf extract. The Gram-positive bacteria were more sensitive to the activity of both ethanolic and methanolic extracts than the Gram-negative and cultivated cardoon dry leaf ethanolic extract presented lower MIC and MBC values (125–2000 µg/mL) for most of the tested microorganisms, thus showing higher antimicrobial activity. As for the cultivated cardoon leaf extracts, the dried leaf extracts exhibited better antimicrobial activity, with lower MIC values, than the fresh leaf extracts. The extracts only demonstrated a slight inhibition against the fungi Aspergillus fumigatus. In conclusion, studies performed indicate that dried leaves maintain their biological activities compared to fresh leaves, and that flowers present significant biological activity which suggests the great potential of the by-products of this crop as a source of active compounds in different industrial applications (e.g. food industry).