Publications

Abstract Nanotechnology has led to the development of new nanomaterials with unique properties and a wide variety of applications. In the present study, we focused on the cellular uptake of a group of nanoparticles with a single metal core by pancreatic cancer cells, which has been studied by Yap et al. (Rsc Advances, 2012, 2 (2):8489-8496) using classification models. In this work, the development of a further Quantitative Nanostructure Activity Relationship (QNAR) model was performed by linear multiple linear regression (MLR) and nonlinear artificial neural network (ANN) techniques to accurately predict the cellular uptake values of these compounds by dividing them into three groups. Judging from the attained statistical results, our derived QNAR models have an acceptable overall accuracy and robustness, as well as good predictivity on the external data sets. Moreover, the results of this study provide some insights on how engineered nanomaterial features influence cellular responses and thereby outline possible approaches for developing and applying predictive computational models for biological responses caused by exposure to nanomaterials.

Abstract The authors have synthesized water-dispersible NaYF4: Er3+/Yb3+ upconversion particles via a thermal decomposition route and optimized the green upconversion emission through a concentration variation of the Yb3+ sensitizer. The prepared particles were found to be ellipsoid in shape having an average particle dimension of 600 x 150 nm. It is observed that the sample with 18 mmol% Yb3+ ion concentration and 2 mmol% Er3+ ion gives optimum upconversion intensity in the green region under 980 nm excitation. Colloidal dispersibility of the sample in different solvents was checked and hexane was found to be the best medium for the prepared particles. The particle size of the sample was found to be suitable for the preparation of colloidal ink and security writing on a plain sheet of paper. This was demonstrated successfully using ink prepared in polyvinyl chloride gold medium.

Abstract Experimental and computational studies were performed in this work with the aim of evaluating and understanding the energetic effect inherent to the substitution of the hydrogen of the morpholine amino group by aminoalkyl substituents: N-(2-aminoethyl)morpholine and N-(3-aminopropyl)morpholine. The standard enthalpies of vaporization and the standard energies of combustion of the two morpholine derivatives obtained, respectively, from Calvet microcalorimetry and combustion calorimetry measurements, are reported. These data were used to derive the standard enthalpies of formation of the morpholine derivatives, in the liquid and gaseous phases, at T=298.15 K. The computational study involved the energetic analysis of the most stable conformers on the potential energy surfaces and the determination of their gas-phase standard enthalpies of formation at the reference temperature of 298.15 K. All the computational calculations were performed using the G3(MP2)//B3LYP composite method. The combination of experimental and computational data determined in this work for morpholine derivatives, together with other available in the literature for related molecules, enabled the analyses of the energetic effects associated with the substitution of the hydrogen of the morpholine amino group by substituents aminoalkyl and alkyl, as well as the establishment of incremental schemes for the determination of the gas-phase enthalpies of formation. (C) 2018 Elsevier Ltd.

Abstract An ecological framework, named activities with parents on the computer (APC), was proposed in order to promote the collaboration between school and home as well as new literacies. In this study, we address teachers' views on APC. Seven teachers who have attended training courses (pre- or in-service) were inquired via email. Their statements were submitted to a content analysis. Results revealed a plethora of reasons why APC was not being used, including technological, socio-economic, and educational policy reasons. The findings urge us to think of activities with parents on the Internet, in order to favour the usage of mobile devices, especially in disadvantaged milieus. Besides training, teachers' mindsets should open so as to accept the amplification of their field of action and an interaction and collaboration with other community partners

Abstract The energetic study of 6-methyl-1-indanone, 6-methoxy-1-indanone and 5,6-dimethoxy-1-indanone has been developed using calorimetric techniques and a computational methodology. The enthalpies of combustion and of sublimation of these compounds were determined from, respectively, static-bomb combustion calorimetry and high-temperature Calvet microcalorimetry. From these experimental data, the gas-phase standard molar enthalpies of formation were derived. Also, the temperature and the enthalpy of fusion of each compound were obtained by differential scanning calorimetry. Additionally, the gas-phase standard molar enthalpies of formation of these compounds were obtained from high-level ab initio calculations, at the G3(MP2)//B3LYP level of theory. The computational approach of these three indanone derivatives allowed us to establish their molecular structures, the co-existence of two and four stable conformations for 6-methoxy-1-indanone and 5,6-dimethoxy-1-indanone, respectively. Furthermore, the energetic effects associated with the presence of one methyl group and one or two methoxy groups in the indanone structure were evaluated. These enthalpic increments were compared with the homologous substitutions in the benzene and naphthalene molecules.

Abstract Coelenterazine is a common substrate used by marine species in enzyme-catalyzed bioluminescent reactions, in which thermal energy is converted into excitation energy. Coelenterazine is also known to emit chemiluminescence, in the absence of enzymes. Moreover, the scaffold of this molecule is present in organisms of eight phyla, making it a prototypical system for marine chemi-/bioluminescence. The characterization of the chemiexcitation step responsible for light emission is essential for future applications in bioimaging, bioanalysis and biomedicine. We have found evidence to support the identification of a neutral dioxetanone intermediate as the responsible for efficient chemiexcitation. This is explained by attractive electrostatic interactions between the CO2 and Coelenteramide moieties, which allow the reacting dioxetanone to spend time in a PES region of degeneracy between singlet ground and excited states. Contrary to expected, there is no relationship between electron (ET)/charge (CT) transfer, from an electron-rich moiety to the peroxide, and efficient chemiexcitation. Thus, neither Chemically Induced Electron-Exchange Luminescence (CIEEL) nor Charge Transfer-Initiated Luminescence (CTIL) can be used to explain imidazopyrazinone-based chemi-/bioluminescence. We have also found a concentration-dependent quenching effect, more prevalent at acidic pH.

Abstract Coelenterazine is a common substrate used by marine species in enzyme-catalyzed bioluminescent reactions, in which thermal energy is converted into light-emission. Besides bioluminescence, Coelenterazine is also known to emit chemiluminescence in aprotic solvents. We report here the study of Coelenterazine chemiluminescence in aqueous solution. Water inhibits light-emission even in mixtures with water content as low as 20%. Moreover, we provide convincing spectroscopic evidence that the presence of water affects the ground state (S-0) chemical reaction, and not the excited state processes (as chemiexcitation and the fluorescent quantum yield). However, the energetics of the S-0 chemical reaction is not affect by addition of water, which points to the inhibition being caused by the reduced lifetime of superoxide anion in water, which is an intermediate in the luminescent reactions of Coelenterazine. This finding indicates that one of the catalytic roles of bioluminescent enzymes is to extend the lifetime of this radical.

Abstract The energetic study of 2-phenylbenzoxazole (PBO), 2-phenylbenzothiazole (PBT), 2-(2-hydroxyphenyl) benzoxazole (HBO) and 2-(2-hydroxyphenyl) benzothiazole (HBT) has been developed either using experimental techniques or computational calculations. The enthalpies of combustion and of sublimation of these compounds were determined and the gas-phase standard molar enthalpies of formation were derived. The experimental techniques used were static or rotating bomb combustion calorimetry, high temperature Calvet microcalorimetry and/or the Knudsen-effusion method. Additionally, we have obtained the gas-phase standard molar enthalpies of formation of these compounds, as well of 2-(2-hydroxyphenyl) benzimidazole (HBI), through high level ab initio calculations, at the G3(MP2)//B3LYP level. The computational study of the molecular structures of all these compounds has been carried out and four possible conformers were observed for the molecules of each compound, where the keto tautomers have always higher energy than the enol forms. Furthermore, the energetic effects associated to the presence of the hydroxyl group on the core of the 2-phenylbenzazole rings, in particular the hydrogen bond network, were also evaluated. (C) 2017 Elsevier Ltd.

Abstract Adenosine receptor (AR) subtypes are involved in several physiological and pharmacological processes. Ligands that are able to selectively modulate one receptor subtype can delay or slow down the progression of diverse diseases. In this context, our research group focused its investigation into the discovery and development of novel, potent and selective AR ligands based on coumarin scaffold. Therefore, a series of 3-phenylcarboxamidocoumarins were synthesized and their affinity for the human AR subtypes was screened by radioligand binding assays for A(1), A(2A) and A(3) receptors and for A(2B) by adenylyl cyclase assay. Compound 26 was found to be the most remarkable, with a hA(1)/hA(3) and hA(2A)/hA(3) selectivity of 42, for the A(3) AR (K-i=2.4m). Receptor-driven molecular modelling studies have provided valuable information on the binding/selectivity data of compound 26 and for the following optimization process. Moreover, compound 26 presents drug-like properties according to the general guidelines linked to the concept.