Publications

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.

Abstract Microalgae and cyanobacteria have received ample attention in the last few decades due to their environmental and biotechnological applications. Co-cultures of these microorganisms may present benefits particularly on wastewater bioremediation and biomass production. However, the understanding on the interactions between photosynthetic microorganisms is still in an early stage of knowledge. In this line, the aim of the present study was the evaluation of the growth dynamics of co-cultures of a cyanobacterium, Synechocystis salina, and a microalga, Pseudokirchneriella subcapitata, under low phosphate-phosphorus concentrations. Kinetic growth parameters were determined through the Monod and modified Gompertz models and evidence of allelochemical production was confirmed through metabolomic analysis of the supernatant obtained from the co-cultures using GC-MS and 1D-NMR. Kinetic growth parameters have shown that P. subcapitata was better adapted to grow under low phosphorus concentrations. Co-cultivation of these microorganisms did not influence P. subcapitata growth; however, S. salina growth was strongly inhibited. The modified Gompertz model has shown that growth inhibition of S. salina in co-cultures may be related to the activity of allelochemicals produced by P. subcapitata. This assumption was corroborated by the assessment of the antimicrobial potential of lactic acid (2-hydroxypropanoic acid), an organic acid identified in the supernatant from the co-cultures with growth inhibitory effects against S. salina.

Abstract The development of new chemical entities represents an important challenge in pharmaceutical industry, being the use of privileged scaffolds for library design and drug discovery a valuable approach. Among the panoply of privileged structures, our research group has focused its attention on the chromone (4H-benzopyran-4-one) scaffold due to its chemical versatility and ability to bind to multiple targets. With this endeavour we report an expedite two-step procedure for the synthesis of novel 6-aryl/heteroaryl-4-oxo-4H-chromene-2-carboxylic ethyl ester. The new chromones were synthesized by a C-C Suzuki cross-coupling microwave-assisted reaction, using Pd(OAc)(2) as a catalyst, and a classic Claisen condensation followed by an intramolecular cyclization process.

Abstract The development of fast and reliable methods for protein determination are of great relevance to a diversity of areas from industry to diagnostics. Molecular Imprinted Materials (MIM) has proved to be an interesting methodology for protein analysis however further studies of the effect of the experimental parameters and starting materials in the performance of the MIM are still required. Caffeic acid (CAF) is employed for the first time as a monomer to tailor a synthetic receptor for a protein target. This was done by bulk-electropolymerization, applying a constant potential of +2.0 V, for 30 s, on a carbon screen printed electrode, immersed in a solution of protein and CAF prepared in phosphate buffer. Annexin A3 (ANXA3) was selected as protein target due to the fact that this is an emerging biomarker in prostate cancer. The assembly of the protein imprinted material (PIM) was followed by Electrochemical Impedance Spectroscopy (EIS) and Raman Spectroscopy. A non-imprinted material (NIM) was prepared in parallel as control. Square wave voltammetry (SWV) was used to monitor the electrochemical signal of the [Fe(CN)(6)](3-)/[Fe(CN)(6)](4-) redox for the quantification of ANXA3. The optimized PIM-based device showed average detection limits (LOD) of 0.095 ng/mL, a linear behavior against log (concentration) between 0.10, and 200 ng/mL and good selectivity. The NIM-based device showed random behavior against protein concentration. Finally, the PIM-sensor was successfully applied to the analysis of ANXA3 in spiked urine samples.

Abstract Nanotechnology offers substantial prospects for the development of innovative products and it is expected that the number of nanotechnology-based products will increase in the future. A number of promising applications are emerging, such as, smart packaging, nanosensors for pathogen detection, agrochemical nanoformulations, and nanoencapsulation of food ingredients for chemical preservation and shelf life extension. In this chapter, a special attention is given on how nanotechnology can mitigate the chemical changes of bioactive compounds, mainly those with nutritional value, occurring in food industry chain. Within this framework, an overview of the main external (oxygen, temperature, and light) factors that cause chemical degradation of some bioactive compounds present in food and affect food quality, and consequently contribute to food spoilage, and safety is also presented. © 2017 Elsevier Inc. All rights reserved.