Publications

Abstract In this work we developed a new force field model (FFM) for propylene glycol (PG) based on the OPLS all-atom potential. The OPLS potential was refined using quantum chemical calculations, taking into account the densities and self-diffusion coefficients. The validation of this new FFM was carried out based on a wide range of physicochemical properties, such as density, enthalpy of vaporization, self-diffusion coefficients, isothermal compressibility, surface tension, and shear viscosity. The molecular dynamics (MD) simulations were performed over a large range of temperatures (293.15-373.15 K). The comparison with other force field models, such as OPLS, CHARMM27, and GAFF, revealed a large improvement of the results, allowing a better agreement with experimental data. Specific structural properties (radial distribution functions, hydrogen bonding and spatial distribution functions) were then analyzed in order to support the adequacy of the proposed FFM. Pure propylene glycol forms a continuous phase, displaying no microstructures. It is shown that the developed FFM gives rise to suitable results not only for pure propylene glycol but also for mixtures by testing its behavior for a 50 mol % aqueous propylene glycol solution. Furthermore, it is demonstrated that the addition of water to the PG phase produces a homogeneous solution and that the hydration interactions prevail over the propylene glycol self-association interactions.

Abstract Photodynamic therapy (PDT) is a minimally invasive therapeutic modality for cancer therapy. The main advantage of PDT is its selectivity as it is only activated upon photo-excitation of a photosensitizer by light of selected wavelengths, thereby reducing the number of side effects when compared with other therapies. However, typical photosensitizers absorb strongly UV or visible light, which is generally unsuitable for biological penetration due to light absorption and scattering by tissue. Moreover, the depth of light penetration into the tissues is less than 1 cm. Thus, PDT is usually only used on tumors on or just under the skin or on the outer lining of internal organs/cavities. Moreover, PDT is also ineffective against metastatic tumors, given its localized nature. Therefore, developing ways in which the photosensitizer can be activated inside the cell without an external light source is a challenging and hot research topic, as achieving this goal will increase immensely the role of PDT in routine cancer therapy. In this chapter will be discussed the benefits and pitfalls of using chemi-and bioluminescent systems as intracellular excitation sources in PDT. Bioluminescence is a widespread natural phenomenon, which consists on light emission that results from an oxidation reaction, catalyzed by an enzyme in a biological system. Bioluminescence can be found in fireflies, bacteria, fishes, dinoflagellates and fungi, among others. Bioluminescence can be considered as a sub-type of chemiluminescence, which consists on the chemical production of light as the result of chemical reactions. Given this, these systems can be coupled to the photosensitizer inside tumor cells, thereby creating self-illuminating PDT systems without the problems associated with the use of external light sources. © Nova Science Publishers, Inc.

Abstract Background: Virtual methodologies have become essential components of the drug discovery pipeline. Specifically, structure-based drug design methodologies exploit the 3D structure of molecular targets to discover new drug candidates through molecular docking. Recently, dual target ligands of the Adenosine A2A Receptor and Monoamine Oxidase B enzyme have been proposed as effective therapies for the treatment of Parkinson’s disease. Methods: In this paper we propose a structure-based methodology, which is extensively validated, for the discovery of dual Adenosine A2A Receptor/Monoamine Oxidase B ligands. This methodology involves molecular docking studies against both receptors and the evaluation of different scoring functions fusion strategies for maximizing the initial virtual screening enrichment of known dual ligands. Results: The developed methodology provides high values of enrichment of known ligands, which outperform that of the individual scoring functions. At the same time, the obtained ensemble can be translated in a sequence of steps that should be followed to maximize the enrichment of dual target Adenosine A2A Receptor antagonists and Monoamine Oxidase B inhibitors. Conclusion: Information relative to docking scores to both targets have to be combined for achieving high dual ligands enrichment. Combining the rankings derived from different scoring functions proved to be a valuable strategy for improving the enrichment relative to single scoring function in virtual screening experiments. © 2017 Bentham Science Publishers.

Abstract The detection of dissolved carbon dioxide (dCO(2)) is made possible through a colorimetric effect that occurs in a sensitive membrane. The reaction with dCO(2) changes the pH of the membrane causing a small difference in its colour which results in a characteristic absorbance spectrum band near 435 nm. A sensing platform based on this effect was developed and tested in gaseous and in aqueous environments. It is a combination of a bundle of large core fibre optics (with diameters above 200 mu m) with light emission diodes (LEDs) in the visible range of the spectrum, a silicon photodetector and a polymer membrane sensitive to CO2. A variation in the absorption of 3 / %VV was obtained in the range from 0 to 1.6 % of gaseous CO2 with an estimated response time below 60 seconds.

Abstract The present work aimed to evaluate the effects of exogenous application of 24-epibrassinolide (24-EBL) in the physiological and biochemical responses of Solanum nigrum L exposed to nickel (Ni). After the seedling stage, 24-EBL treated and untreated plants were grown hydroponically for 28 days in the presence of 100 mu M NiSO4 center dot 6H(2)O. The exposure of S. nigrum to high levels of Ni resulted in a decrease of biometric parameters in both shoots and roots, with a partial recovery of both fresh weight and length in the 24-EBL pre-treated plants. Higher levels of Ni were found in roots, regardless of the pre-treatment with the brassinolide. Older leaves of Ni-exposed plants exhibited cell death symptoms, manifested in the form of chlorotic and necrotic spots. A decrease in photosynthetic pigments, soluble protein and relative RuBisCO contents were also observed in Ni-treated plants, however Ni-mediated toxicity was partially reverted by 24-EBL pre-treatment. Lipid peroxidation was chosen as a stress biomarker and malondialdehyde (MDA) levels did not change neither in roots nor in shoots. Soluble proline levels increased in response to Ni in both organs, but the pre-treatment with the phytohormone seems to mitigate the differences observed from the control shoots and roots. When ROS accumulation is concerned, generally Ni-exposed plants exhibited decreases in O-2(center dot)- and H2O2 levels regardless of being or not treated with 24-EBL. The Ni treatment led to a positive response of the plant's enzymatic antioxidant system. In shoots of Ni-stressed plants, an enhanced activity of superoxide dismutase (SOD) and ascorbate peroxidase (APX), accompanied by a decline of catalase (CAT) activity were observed. In roots, increases in SOD and CAT activities were detected in response to Ni, whilst APX was not. 24-EBL pre-treatment caused a decline in APX and CAT activities, while SOD activity was positively affected. Reverse transcriptase-PCR analysis revealed that mRNA transcript levels do not correlate with total enzymatic activity for SOD, CAT and APX, suggesting that these enzymes are regulated posttranscriptionally. Overall, the results suggested that Ni did not induce a severe oxidative stress in S. nigrum, yet the exogenous application of the brassinolide enhanced the plant tolerance to Ni.

Abstract We report the application of two poly[Ni(salen)]-type electroactive polymer films as new electrochromic materials. The two films, poly[Ni(3-Mesalen)] (poly[1]) and poly[Ni(3-MesaltMe)] (poly[2]), were successfully electrodeposited onto ITO/PET flexible substrates, and their voltammetric characterization revealed that poly[1] showed similar redox profiles in LiClO4/CH3CN and LiClO4/propylene carbonate (PC), while poly[2] showed solvent-dependent electrochemical responses. Both films showed multielectrochromic behavior, exhibiting yellow, green, and russet colors according to their oxidation state, and promising electrochromic properties with high electrochemical stability in LiClO4/PC supporting electrolyte. In particular, poly[1] exhibited a very good electrochemical stability, changing color between yellow and green (lambda = 750 nm) during 9000 redox cycles, with a charge loss of 34.3%, an optical contrast of Delta T = 26.2%, and an optical density of Delta OD = 0.49, with a coloration efficiency of ? = 75.55 cm(2) C-1. On the other hand, poly[2] showed good optical contrast for the color change from green to russet (Delta T = 58.5%), although with moderate electrochemical stability. Finally, poly[1] was used to fabricate a solid-state electrochromic device using lateral configuration with two figures of merit: a simple shape (typology 1) and a butterfly shape (typology 2); typology 1 showed the best performance with optical contrast Delta T = 88.7% (at lambda = 750 nm), coloration efficiency eta = 130.4 cm(2) C-1, and charge loss of 37.0% upon 3000 redox cycles.

Abstract The crystal structures of two chromone derivatives, viz. ethyl 6-(4-methylphenyl)-4-oxo-4H-chromene-2-carboxylate, C19H16O4, (1), and ethyl 6-(4-fluorophenyl)-4-oxo-4H-chromene-2-carboxylate C18H13FO4, (2), have been determined: (1) crystallizes with two molecules in the asymmetric unit. A comparison of the dihedral angles beween the mean planes of the central chromone core with those of the substituents, an ethyl ester moiety at the 2-position and a para-substituted phenyl ring at the 6-position shows that each molecule differs significantly from the others, even the two independent molecules (a and b) of (1). In all three molecules, the carbonyl groups of the chromone and the carboxylate are trans-related. The supramolecular structure of (1) involves only weak C-H center dot center dot center dot pi interactions between H atoms of the substituent phenyl group and the phenyl group, which link molecules into a chain of alternating molecules a and b, and weak pi-pi stacking interactions between the chromone units. The packing in (2) involves C-H center dot center dot center dot O interactions, which form a network of two intersecting ladders involving the carbonyl atom of the carboxylate group as the acceptor for H atoms at the 7-position of the chromone ring and from an ortho-H atom of the exocyclic benzene ring. The carbonyl atom of the chromone acts as an acceptor from a meta-H atom of the exocyclic benzene ring. pi-pi interactions stack the molecules by unit translation along the a axis.

Abstract This work reports the experimental determination of relevant thermophysical properties of five halogenated fluorenes. The vapor pressures of the compounds studied were measured at different temperatures using two different experimental techniques. The static method was used for studying 2-fluorofluorene (liquid and crystal vapor pressures between 321.04 K and 411.88 K), 2-iodofluorene (liquid and crystal vapor pressures between 362.63 K and 413.86 K), and 2,7-dichlorofluorene (crystal vapor pressures between 364.64 K and 394.22 K). The Knudsen effusion method was employed to determine the vapor pressures of 2,7-difluorofluorene (crystal vapor pressures between 299.17 K and 321.19 K), 2,7-diiodofluorene (crystal vapor pressures between 393.19 K and 415.14 K), and (again) 2-iodofluorene (crystal vapor pressures between 341.16 K and 361.12 K). The temperatures and the molar enthalpies of fusion of the five compounds were determined using differential scanning calorimetry. The application to halogenated fluorenes of recently developed methods for predicting vapor pressures and enthalpies of sublimation and vaporization of substituted benzenes is also discussed.

Abstract The first potent and selective hA(1)AR ligand based on the chromone scaffold is reported in this work. Receptor-driven molecular modeling studies provide valuable information about the molecular interactions responsible for the high affinity of N-(2-nitrophenyl)-4-oxo-4H-chromene-2-carboxamide to the hA(1)AR (K-i = 0.219 mu M) and reinforce the crucial role of AR affinity of the amide linker located at C-2 of the pyrone ring.