Publications

Abstract In the laboratory, data acquisition systems are important, as they allow us to easily and precisely collect data. In this sense, Arduino emerges as an automatic data acquisition device with great potential, due to its low cost and high versatility. In this work, we describe the development of an experimental apparatus, with automatic data acquisition using Arduino, to determine the variation of the solubility of potassium nitrate in water as a function of temperature. Ten chemistry teachers in initial training were involved in developing and validating that alternative experimental procedure for secondary school. Pre-service chemistry teachers determined the solubility of the aforementioned salt at different temperatures, using both a method for the study of the solubility of salts that does not resort to automatic data acquisition as well as the alternative method proposed in this work. The experimental solubility curves of potassium nitrate were plotted for both situations. The experimental results obtained by both methods are similar and very close to the values reported in the literature. Moreover, chemistry teachers in initial training recognize that the proposed method can promote the development of secondary students' skills such as greater mastery in assembling electrical circuits and in the use of technological devices or software for automatic data acquisition and processing. Thus, the results suggest the feasibility of the developed experimental method for its implementation in an educational context with secondary students and prove it to be an asset for the education of students, when compared to the traditionally used method.

Abstract Society needs transdisciplinary citizens with good scientific literacy. One way to achieve this could be through the use of areas or subjects for which students have more affinity and expertise. This study seeks to maximize the chemistry learning of students who want to be musicians, through the use of analogies. Analogies are a powerful tool to explain abstract, unfamiliar, or complex scientific concepts (such as the quantum atomic model) in familiar terms and to promote positive attitudes toward learning science. A case study is presented regarding the use of musical analogies developed to teach the atom concept, subatomic particles, and the atomic structure, according to the quantum mechanical model of the atom. A cohort of 50 Portuguese 12 to 13 year old students, enrolled in the seventh grade of a middle school music course, was selected by convenience sampling from four schools. A questionnaire and interviews were used for data gathering. The results show that the musical analogies used helped to overcome students' difficulties regarding the topics taught, improved chemistry learning, and stimulated attentiveness and interest. The use of analogies between music and chemistry with students of similar characteristics to those of this study, or the use of different areas and subjects for other student backgrounds and tastes, can be fruitful for teaching chemical content.

Abstract The thermochemical study of the 1,3-bis(N-carbazolyl)benzene (NCB) and 1,4-bis(diphenylamino)benzene (DAB) involved the combination of combustion calorimetric (CC) and thermogravimetric techniques. The molar heat capacities over the temperature range of (274.15 to 332.15) K, as well as the melting temperatures and enthalpies of fusion were measured for both compounds by differential scanning calorimetry (DSC). The standard molar enthalpies of formation in the crystalline phase were calculated from the values of combustion energy, which in turn were measured using a semi-micro combustion calorimeter. From the thermogravimetric analysis (TGA), the rate of mass loss as a function of the temperature was measured, which was then correlated with Langmuir's equation to derive the vaporization enthalpies for both compounds. From the combination of experimental thermodynamic parameters, it was possible to derive the enthalpy of formation in the gaseous state of each of the title compounds. This parameter was also estimated from computational studies using the G3MP2B3 composite method. To prove the identity of the compounds, the H-1 and C-13 spectra were determined by nuclear magnetic resonance (NMR), and the Raman spectra of the study compounds of this work were obtained.

Abstract Combined experimental and computational studies were performed aiming the analysis of energetic properties vs structural characteristics of three methyl nitrobenzoate isomers (methyl 2-nitrobenzoate, M2NB, methyl 3-nitro benzoate, M3NB, methyl 4-nitrobenzoate, M4NB). The experimental studies include the determination of the enthalpy of formation in the condensed state (crystal and liquid) of the compounds by static combustion, and the determination of enthalpies of phase transition, using Differential Scanning Calorimetry, high temperature Calvet microcalorimetry and the Knudsen effusion method. These data were combined to derive the enthalpy of formation of the methyl nitrobenzoate isomers in the gaseous phase, at T = 298.15 K. At the computational level, the gas-phase enthalpy of formation of the methyl nitrobenzoate isomers were estimated using theoretical approaches, resorting to the G3(MP2)//B3LYP composite method and to appropriate hypothetical gas-phase reactions. The enthalpies of formation obtained experimental and computationally will be discussed and the energetic structural synergies for the three methyl nitrobenzoate, along with other analogous isomers, will be also analyzed.

Abstract Simple Summary Most cases of differentiated thyroid carcinoma (DTC) are associated with a good prognosis. However, a significant number progress to advanced disease exhibiting aggressive clinical characteristics. These cases have a poorer prognosis because they become resistant to radioactive iodine (RAI) treatment. One of the causes for this resistance is the reduction of the channel responsible for iodide uptake (NIS-the sodium iodide symporter) at the plasma membrane (PM) of metastatic thyroid cancer cells. Here we describe that cell-cell adhesion is a key determinant for NIS residency at the PM, suggesting that loss of cell-cell adhesion during metastization contributes to RAI treatment resistance in advanced TC. Our findings indicate that successful resensitization therapies might require the use of agents that improve epithelial cell-cell adhesion in refractory TC cells. While most cases of differentiated thyroid carcinoma (DTC) are associated with a good prognosis, a significant number progress to advanced disease exhibiting aggressive clinical characteristics and often becoming refractory to radioactive iodine (RAI) treatment, the current gold-standard therapeutic option for metastatic disease. RAI-refractoriness is caused by defective functional expression of the sodium-iodide symporter (NIS), which is responsible for the active transport of iodide across the plasma membrane (PM) into thyroid follicles. NIS deficiency in these tumors often reflects a transcriptional impairment, but also its defective targeting and retention at the cells' PM. Using proteomics, we previously characterized an intracellular signaling pathway derived from SRC kinase that acts through the small GTPase RAC1 to recruit and bind the actin-anchoring adaptor EZRIN to NIS, regulating its retention at the PM of both non-transformed and cancer thyroid cells. Here, we describe how by reanalyzing the proteomics data, we identified cell-cell adhesion as the molecular event upstream the pathway involved in the anchoring and retention at the PM. We show that by interacting with NIS at the PM, adherens junction (AJ)-associated P120-catenin recruits and is phosphorylated by SRC, allowing it to recruit RAC1 to the complex. This enables SRC-phosphorylated VAV2 exchange factor to activate RAC1 GTPase, inducing NIS retention at the PM, thus increasing its abundance and function at the surface of thyroid cells. Our findings indicate that the loss of epithelial cell-cell adhesion may contribute to RAI refractoriness, indicating that in addition to stimulating NIS expression, successful resensitization therapies might require the employment of agents that improve cell-cell adhesion and NIS PM retention in refractory TC cells.

Abstract <jats:p>Fullerenes are reactive as dienophiles in Diels–Alder reactions. Their distinctive molecular shape and properties result in interesting and sometimes elusive reaction patterns. Herein, to contribute to the understanding of fullerene reactivity, we evaluate the energies of reactions for Diels–Alder cycloadditions of C60, C70, and IC60MA with anthracene (Ant), by means of DFT computational analysis in vacuum and solution. The methods used showed little differentiation between the reactivity of the different fullerenes. The C70-Ant adducts where addition takes place near the edge of the fullerene were found to be the most stable regioisomers. For the IC60MA-Ant adducts, the calculated energies of reaction increase in the order: equatorial &gt; trans-3 &gt; trans-2 ≈ trans-4 ≈ trans-1 &gt; cis-3 &gt; cis-2. The change in the functional suggests the existence of stabilizing dispersive interactions between the surface of the fullerene and the addends. HOMA (harmonic oscillator model of aromaticity) analysis indicated an increase in aromaticity in the fullerene hexagons adjacent to the bonded addend. This increase is bigger in the rings of bisadduct isomers that are simultaneously adjacent to both addends, which helps explain the extra stability of the equatorial isomers. Solvation by m-xylene decreases the exothermicity of the reactions studied but has little distinguishing effect on the possible isomers. Thermal corrections reduce the exothermicity of the reactions by ~10 kJ∙mol−1.</jats:p>

Abstract This work reports a comprehensive experimental evaluation of the solid-liquid-gas phase equilibria for five representative phenylene-thiophene co-oligomers (3-ring aromatic compounds having both phenyl and thienyl units). The melting temperatures and corresponding standard molar enthalpies and entropies of fusion were measured by differential scanning calorimetry. The equilibrium vapor pressures of the crystalline solids as a function of temperature were measured by a combined Knudsen/quartz-crystal effusion method, with the consequent derivation of the standard molar enthalpies, entropies, and Gibbs energies of sublimation. The thermodynamic properties of vaporization were estimated from the fusion and sublimation data. The results were analyzed together with the literature data for the corresponding phenylene and thiophene homo-oligomers. The thermodynamic properties of fusion and sublimation exhibited a dependence on ring identity and position that cannot be adequately described by a simple group additivity reasoning. The plot of the Gibbs energy of sublimation as a function of the number of thienyl rings in the co-oligomer showed the existence of two series. Terminal 3-thienyl rings and a linear molecular shape were found to be consistent factors contributing to the stabilization of the crystal phase. The higher melting temperatures and lower volatilities of crystalline 3-thienyl compounds were tentatively explained by the ability of these rings to maximize intermolecular C-H & BULL;& BULL;& BULL;pi interactions independently of the sulfur position. The optical energy gaps, as measured by UV-vis in solution, were found to lie within the values for typical organic semiconductors (< 4 eV) and to decrease for co-oligomers containing more 2-thienyl units, following the increased ring-ring planarity of the molecules. The surface morphology of vapor-deposited thin films suggests a stronger tendency of the co-oligomers, if compared to their corresponding homo-oligomers p-terphenyl and terthiophene, to form less amorphous films.

Abstract Hypothesis: The injection of air into the sample cell of an isothermal titration calorimeter containing a liquid provides a rich-in-information signal, with a periodic contribution arising from the creation, growing and release of bubbles. The identification and analysis of such contributions allow the accurate determination of the surface tension of the target liquid. Experiments: Air is introduced at a constant rate into the sample cell of the calorimeter containing either a pure liquid or a solution. The resulting calorimetric signal is analyzed by a new algorithm, which is implemented into a computational code. Findings: The thermal power generated by our experiments is often noisy, thus hiding the periodic signal arising from the bubbles' formation and release. The new algorithm was tested with a range of different types of calorimetric raw data, some of them apparently being just noise. In all cases, the contribution of the bubbles to the signal was isolated and the corresponding period was successfully determined in an automated way. It is also shown that two reference measurements suffice to calibrate the instrument at a given temperature, regardless the injection rate, allowing the direct determination of surface tension values for the liquid contained in the sample cell. (c) 2021 The Author(s). Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Abstract Fluorescence spectroscopy is used to characterize the partition of three second-generation D,L-alpha-cyclic peptides to two lipid model membranes. The peptides have proven antimicrobial activity, particularly against Gram positive bacteria, and the model membranes are formed of either with 1,2-dimyristoyl-sn-glycero-3-phospho- (1'- rac-glycerol) (DMPG) or its mixture with 1,2-dimyristoyl-sn-glycero-3-phosphoethanolamine (DMPE), at a molar ratio of (1:1). The peptide's intrinsic fluorescence was used in the Steady State and/or Time Resolved Fluorescence Spectroscopy experiments, showing that the peptides bind to the membranes, and the extent of their partition is thereof quantified. The peptide-induced membrane leakage was followed using an encapsulated fluorescent dye. Overall, the partition is mainly driven by electrostatics, but also involves hydrophobic interactions. The introduction of a hydrocarbon tail in one of the residues of the parent peptide, CPR, adjacent to the tryptophan (Trp) residue, significantly improves the partition of the modified peptides, CPRT10 and CPRT14, to both membrane systems. Further, we show that the length of the tail is the main distinguishing factor for the extension of the partition process. The parent peptide induces very limited leakage, at odds with the peptides with tail, that promote fast leakage, increasing in most cases with peptide concentration, and being almost complete for the highest peptide concentration and negatively charged membranes. Overall, the results help the unravelling of the antimicrobial action of these peptides and are well in line with their proven high antimicrobial activity.

Abstract A novel formulation of cationic liposomes was studied by mixing dipalmitoylphosphatidylcholine (DPPC) with tetradecyltrimethylammonium bromide gemini surfactants with different alkane spacer groups lengths attached to their ammonium head-groups. The physicochemical characterization of the cationic liposomes was obtained by combining experimental results from differential scanning microcalorimetry (DSC) with molecular dynamic simulations, in order to understand their structural configuration. An adapted Ising model was used to interpret the results in terms of cooperativity of the phase transitions. The gemini surfactants partition into the lipid bilayer of DPPC liposomes, and the induced changes in colloidal stability and phase transition were analyzed in detail.The DPPC liposomes became positively charged upon gemini surfactant partition, showing increased colloidal stability. Our results show signif-icant differences in structural configuration between gemini surfactants with short and long spacer lengths. While gemini with shorter spacers allocate within the lipid bilayer with both headgroups in the same layer, geminis with longer spacers unexpectedly intercalate in the lipid membrane in a partic-ular zig-zag configuration, with each headgroup located at a different side of the bilayer, altering the cou-pling degree parameters of the membrane's phase transition.The extraordinary increase of colloidal stability of DPPC liposomes with gemini surfactants at very low molar ratio and the possibility to tune the physicochemical properties of the membrane by control de spacer length of the geminis opens new possibilities for cationic liposomal formulations with potential applications in vaccines, drug/gene delivery or biosensing.(c) 2022 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/).