Publications

Abstract Hydroxycinnamic acids (HCAs) are important phytochemicals possessing significant biological properties. Several investigators have studied in vitro antioxidant activity of HCAs in detail. In this review, we have gathered the studies focused on the structure-activity relationships (SARs) of these compounds that have used medicinal chemistry to generate more potent antioxidant molecules. Most of the reports indicated that the presence of an unsaturated bond on the side chain of HCAs is vital to their activity. The structural features that were reported to be of importance to the antioxidant activity were categorized as follows: modifications of the aromatic ring, which include alterations in the number and position of hydroxy groups and insertion of electron donating or withdrawing moieties as well as modifications of the carboxylic function that include esterification and amidation process. Furthermore, reports that have addressed the influence of physicochemical properties including redox potential, lipid solubility and dissociation constant on the antioxidant activity were also summarized. Finally, the pro-oxidant effect of HCAs in some test systems was addressed. Most of the investigations concluded that the presence of ortho-dihydroxy phenyl group (catechol moiety) is of significant importance to the antioxidant activity, while, the presence of three hydroxy groups does not necessarily improve the activity. Optimization of the structure of molecular leads is an important task of modern medicinal chemistry and its accomplishment relies on the careful assessment of SARs. SAR studies on HCAs can identify the most successful antioxidants that could be useful for management of oxidative stress-related diseases.

Abstract In this paper an optimized enzymatic assay for inorganic sulfate (SO4-2) detection and quantitation in freshwater, relying on adenosine-5'-triphosphate sulfurylase catalyzed reaction coupled to bioluminescent detection by firefly luciferase, is described. Inorganic sulfate is converted, by adenosine-5'-triphosphate sulfurylase, into adenosine-5'-phosphosulfate and inorganic pyrophosphate, with consumption of adenosine-5'-triphosphate. The remaining adenosine-5'-triphosphate is used as a co-factor in the reaction catalyzed by firefly luciferase generating, as a co-product, photons of visible light. The light output is inversely proportional to the inorganic sulfate content. Using sodium sulfate as a model, the assay was optimized through a statistical experimental design methodology and validated in water samples from domestic wells from two municipalities within the Metropolitan Area of Porto plus tap water as control. The optimized method requires 20 mu L of sample in a final reaction volume of 100 mu L. It is linear in the range from 14 to 134 mg L-1 of inorganic sulfate, with limits of detection and quantitation of 10 and 34 mg L-1, respectively. Repeatability, expressed as relative standard deviation, is 7.23% at 34 mg L-1, 6.87% at 68 mg L-1 and 4.67% at 96 mg L-1. The inorganic sulfate concentration in the wells is approximately 124, 182 and 182 mg L-1, whereas it was found to be a value of about 200 mg L-1 in tap water. Samples can be quantified by calibration curves without any pre-treatment other than dilution. The optimized method is fast, simple to perform and robust.

Abstract The chemiluminescence properties of firefly luciferin were studied, in a variety of chemical systems different from those in which it is usually studied. It was found that luciferin is a multifunctional chemiluminescence molecule, as it can behave as a chemiluminescence sensitizer, an emitter and a substrate. The first two roles are here reported for the first time, while we have found a novel way of obtaining excited state oxyluciferin from luciferin. Evidence was also found that does not support the newly proposed radical-mechanism of the formation of firefly dioxetanone. With this study we hope to open the way for novel chemiluminescence applications for firefly luciferin.

Abstract This work presents a new approach for estimating sublimation enthalpies and vapor pressures of substituted benzenes. Proposed estimating equations were based on a collection of selected literature results of vapor pressures of ca. 240 benzene derivatives attached with 30 different substituents. Compared to experimental results, best estimates are obtained from the equations that include the temperature of fusion. A review of the results determined for substituted benzenes using two different calorimetric techniques shows that the results of enthalpies of sublimation derived from vapor pressures seem to be more reliable than those derived from the calorimetric techniques.

Abstract The photophysical properties of four bare firefly bioluminophores were studied in vacuo by means of a density functional theory approach. The objective of this work was to fingerprint the excited-state properties of these molecules without perturbations of the microenvironment (either solution or enzyme active site). It is known that intermolecular interactions formed between the light-emitter and active site molecules govern the bioluminescence multicolor tuning mechanism. However, it is difficult to disentangle the numerous active site-oxyluciferin interactions and understand the effect exerted by each one of these interactions on the color of light emitted. Thus, the study of these isolated bioluminophores allows us to obtain their intrinsic photophysics properties, which can serve as a reference in studies aiming to understand the role of perturbations from the microenvironment.

Abstract Phenolic compounds constitute a diverse group of secondary metabolites which are present in both grapes and wine. The phenolic content and composition of grape processed products (wine) are greatly influenced by the technological practice to which grapes are exposed. During the handling and maturation of the grapes several chemical changes may occur with the appearance of new compounds and/or disappearance of others, and consequent modification of the characteristic ratios of the total phenolic content as well as of their qualitative and quantitative profile. The non-volatile phenolic qualitative composition of grapes and wines, the biosynthetic relationships between these compounds, and the most relevant chemical changes occurring during processing and storage will be highlighted in this review. (C) 2013 Published by Elsevier Ltd.

Abstract The addition of surfactants to lipid bilayers is important for the modulation of lipid bilayer properties (e.g., in protein reconstitution and development of nonviral gene delivery vehicles) and to provide insight on the properties of natural biomembranes. In this work, the thermal behavior, organization, and nanomechanical stability of model cationic lipid-surfactant bilayers have been investigated. Two different cationic surfactants, hexadecyltrimethylammonium bromide (CTAB) and a novel derivative of the amino acid serine (Ser16TFAc), have been added (up to 50 mol %) to both liposomes and supported lipid bilayers (SLBs) composed by the zwitterionic phospholipid DPPC. The thermal phase behavior of mixed liposomes has been probed by differential scanning calorimetry (DSC), and the morphology and nanomechanical properties of mixed SLBs by atomic force microscopy based force spectroscopy (AFM-FS). Although DSC thermograms show different results for the two mixed liposomes, when both are deposited on mica substrates similar trends on the morphology and the mechanical response of the lipid-surfactant bilayers are observed. DSC thermograms indicate microdomain formation in both systems, but while CTAB decreases the degree of organization on the liposome bilayer, Ser16TFAc ultimately induces the opposite effect. Regarding the AFM-FS studies, they show that microphase segregation occurs for these systems and that the effect is dependent on the surfactant content. In both SLB systems, different microdomains characterized by their height and breakthrough force F-b are formed. The molecular organization and composition is critically discussed in the light of our experimental results and literature data on similar lipid-surfactant systems.

Abstract Betula pendula pollen, under laboratory conditions, was exposed to three atmospheric pollutants: carbon monoxide (CO), ozone (O-3) and sulphur dioxide (SO2). Two levels of each pollutant were used; the first level corresponds to a concentration on the atmospheric hour-limit value acceptable for human health protection in Europe, the second level to a higher, at least more than double of the first, concentration level. Experiments were done under artificial solar light with controlled temperature and relative humidity. Our results indicate that, in urban areas, concentrations of CO, O-3 and SO2 on the limits established for human protection, can affect pollen fertility. We verified a decrease in the viability and germination of the pollen, indicating damage to the pollen membrane system. Also, a general decreasing trend in the total protein content of the exposed samples when compared with the control samples was observed, which suggests alterations in the antigenic characteristics of pollen.

Abstract This work describes that the conventional analysis by Fourier transform infrared spectroscopy of a set of coals grouped by means of multivariate analysis (nonlinear mapping and hierarchical cluster analysis) obtained results that show this methodology is a good approach to summarize and classify coals by their structural relationships and the geochemical processes of their origin.