Publications

Abstract Oxygen reduction on platinum single crystals has been studied in perchloric and sulfuric acid media using a hanging meniscus rotating disk electrode configuration. The surfaces studied belong to the [01 (1) over bar] zone and can be classified in two different series, i.e., surfaces with terraces with (111) symmetry and (100) steps and surfaces with (100) terraces and (111) steps. In sulfuric acid media, the highest catalytic activity is found for the Pt(211) electrode whereas the Pt(111) electrode exhibits an anomalously low j(0) value. Conversely, the extrapolated value for the catalytic activity of Pt(111) obtained from the series of stepped surfaces having (111) terraces is much higher than that obtained experimentally. The comparison with the results obtained in perchloric acid solutions indicates that the anomalously low catalytic activity of the Pt(111) electrode in sulfuric acid solutions is related to the formation of an ordered adlayer of specifically adsorbed (bi)sulfate anions. For practical purposes, the effect of the step density and the (bi)sulfate specific adsorption is small, except for the Pt(111) electrode.

Abstract The main objective of the work was the setup of the Caco-2 human intestinal cell-line model for the study of the intestinal permeation of monobutyltin (MBT), dibutyltin (DBT) and tributyltin (TBT). The study was focused in gathering information on (a) the relative permeability of butyltins, (b) their possible permeation routes (paracellular/transcellular) and (c) the eventual interactions between the different butyltins when occurring as a mixture. The presence of basolateral serum protein greatly influenced the permeability, causing a large net clearance, but the apparent permeability (Papp) values were comparable to that of phenolred, suggesting a low in vivo permeability of the butyltins. The found permeability pattern correlates well with the general in vivo toxicity pattern (trialkyltin>dialkyltin>monoalkyltin). The accumulation pattern (DBT>TBT>MBT) was different from that of permeability and may be an important element regarding the elucidation of some specific strong toxic effects caused by the dialkyltins in several species. The transport of MBT and DBT was found to be dependent on the paracellular route status. An interaction between the butyltin compounds in a mixture was found for the accumulation results (the accumulation was significantly higher for the three compounds when in a mixture). A set of useful information about the butyltin accumulation and transport by the epithelial Caco-2 cell line was, thus, achieved, constituting a starting point for future research on the permeability of butyltins from contaminated food and beverages.

Abstract The scope of this review encompasses the importance of furocoumarins and the most important developments in this field that have been made in recent years, with particular emphasis placed on the aspects related to medicinal chemistry. A concise and exhaustive overview is given regarding the methods used for the synthesis of these compounds, new furocoumarins isolated from natural sources, and the most significant biological properties associated with these molecules. The section describing the synthetic methods is organized on the basis of the key step used for the formation of the two different oxygenated rings. In this respect there are three possibilities: (i) formation of the furan ring onto the coumarin, (ii) formation of the pyrone ring onto the benzofuran and (iii) the simultaneous formation of both oxygenated rings onto a benzene unit. The most recent preparative approaches are discussed along with modifications or improvements to methods that, though not particularly new, are still commonly used. The recently discovered natural furocoumarins are focused and presented in tables that provide information about its structure and source. The discussion of the biological importance of furocoumarins mainly focuses on their more relevant applications in photochemotherapy, but also provides examples of their versatility in a range of applications in the fields of biology and pharmacology.

Abstract The enantioselectivity of the gold chiral surfaces towards the electrocatalvtic oxidation of D- and L-glucose in neutral phosphate-buffered media is reported. Two enantiomorphic surfaces were used, Au{32}(R) and Au{321}(S), and results obtained by cyclic voltammetry were compared with two non-chiral surfaces having the same terrace and step orientations, Au(111) and Au(211). All enantioselective effect is observed, Au {321}(R) exhibits a higher activity for D-glucose while Au{3 2 1}(S) exhibits a higher activity for L-glucose. The corresponding en anti oselectivity factor was estimated to 10% for the process occurring at lower potential values and to 50% for the process at higher potential values. These results represent the first evidence that gold chiral surfaces are capable of enantiomeric discrimination.