Alexandre R. F. Carvalho

Spectral Features and Stability of Oligomeric Pyranoanthocyanin-flavanol Pigments Isolated from Red Wines

The spectral characteristics and stability of three red wine pigments (pyranoMv-catechin, pyranoMv-epicatechin, and pyranoMv-dimer B3) toward pH variation and bisulfite bleaching, as well as their color stability and degradation during storage, have been studied. Unlike the absorbance spectra of most wine pigments, the intensity of which is more increased in more acidic conditions, oligomeric pyranoMv-flavanols have maximum absorbance at wine pH around 3.6, up to 30-50% higher than that in pH 1.0. This particular hyperchromic effect shown in mildly acidic solutions suggests the presence of intramolecular copigmentation in the molecule of pyranoanthocyanin-flavanols, giving rise to higher molar extinction coefficients around wine pH and contributing to the overall wine color. The most probable conformations were determined by computer-assisted model building and molecular mechanics. Besides exceptional stability toward pH variations, pyranoanthocyanin-flavanols were also shown to be entirely resistant to bleaching by sulfur dioxide. During a 6 month storage period, pyranoanthocyanin-flavanols were much more stable against degradation than the anthocyanin with the following order: pyranoMv-catechin > pyranoMv-dimer B3 > pyranoMv-epicatechin > carboxy-pyranoMv ≫ Mv. Kinetic decomposition monitored by high-performance liquid chromatography-diode array detection-mass spectrometry revealed the formation of a new pigment (pyranone-Mv structure) and the cleavage of the interflavanic linkage of procyanidin dimer in the solutions containing carboxy-pyranoMv and pyranoMv-dimer B3, respectively. Despite some degree of decline of these oligomeric pyranoanthocyanins, their color intensity was surprisingly enhanced, and their color stability greatly improved throughout the entire storage period, thus contributing significantly as long-lived orange-red pigments to the maintenance of aged wine color.

Unusual color change of vinylpyranoanthocyanin-phenolic pigments.

Anthocyanins are responsible for an interesting variety of colors in flowers, red fruits, and plant-derived foodstuffs. Experimental evidence is presented supporting an unusual color change from red to blue during storage. It has been investigated as a function of temperature at constant pH (pH <2). The color properties of the vinylpyranoanthocyanin pigments, usually designated portisins, have been studied in this work using both experimental and theoretical techniques. The visible spectra obtained from the two approaches were in good agreement. This behavior was explained by a reversible physical-chemical change due to electronic and vibrational properties.

A Spatio-temporal Database System Based on TimeDB and Oracle Spatial

The importance of the spatial component of data items has been long recognized and gave rise to a successful line of research and development in Geographic Information Systems (GIS). In many application domains it is also essential to deal with the evolution of data along time and to integrate spatial, temporal and other aspects of the information domain in an expressive and operationally effective manner. Until recently, temporal solutions provided by spatial database systems were semi-temporal approaches lacking full temporal support. As a consequence, most spatial database systems manage snapshots of the present state of facts without fully exploiting historical temporal aspects. This paper provides preliminary results on a spatiotemporal database implementation. The proposed system builds on existing database technologies, TimeDB and Oracle Spatial, for temporal and spatial support, respectively. The justification for the choice of these technologies is given, based on the state of the art in spatial and temporal database research. The integration of the spatial and temporal components is achieved with the extension of the TimeDB implementation layer. A set of goals has been established in order to cover both the integration of the spatial support and the enforcement of the temporal requirements in the extended system. Issues and solutions are presented and illustrative examples show the use of the implemented functionalities.

A spatiotemporal extension for dealing with moving objects with extent in Oracle 11g

This paper deals with the design and implementation of a data model and operations for dealing with continuously changing spatial data in Oracle 11g object-relational DBMS. The data model relies on abstract data types but we introduce modifications to the internal structure of the spatiotemporal data representations proposed in the literature, to reduce storage requirements and to enable the reuse of data during the execution of queries. We show how to implement spatiotemporal operations relying on the spatial functions released by the underlying DBMS and how to use the alternative data representations to reduce the volume of temporary data created in the evaluation of spatiotemporal operations. We also demonstrate how to use the proposed data types and operations for storage and manipulation of moving objects data using SQL. Finally, we discuss on the advantages and disadvantages of the proposed solutions.

A Novel Nonparametric Distance Estimator for Densities with Error Bounds

The use of a metric to assess distance between probability densities is an important practical problem. In this work, a particular metric induced by an α-divergence is studied. The Hellinger metric can be interpreted as a particular case within the framework of generalized Tsallis divergences and entropies. The nonparametric Parzen’s density estimator emerges as a natural candidate to estimate the underlying probability density function, since it may account for data from different groups, or experiments with distinct instrumental precisions, i.e., non-independent and identically distributed (non-i.i.d.) data. However, the information theoretic derived metric of the nonparametric Parzen’s density estimator displays infinite variance, limiting the direct use of resampling estimators. Based on measure theory, we present a change of measure to build a finite variance density allowing the use of resampling estimators. In order to counteract the poor scaling with dimension, we propose a new nonparametric two-stage robust resampling estimator of Hellinger’s metric error bounds for heterocedastic data. The approach presents very promising results allowing the use of different covariances for different clusters with impact on the distance evaluation.

Representation and management of spatiotemporal data in object-relational databases

This paper deals with the design and implementation of a data model and operations for dealing with continuously changing spatial data in object-relational DBMS. The data model relies on abstract data types but we introduce modifications to the internal structure of the spatiotemporal data representations proposed in the literature, to reduce storage requirements and to enable the reutilization of data during the execution of the queries. We show how to implement spatiotemporal operations relying on the spatial functions released by the underlying DBMS and how to use the alternative data representations to reduce the volume of temporary data created in the evaluation of spatiotemporal operations. We also discuss on the advantages and disadvantages of the proposed solutions.

Quantum Semiempirical Energy Based (SEEB) Descriptors Performance with Benzamidine Inhibitors of Trypsin

MLR is a classical approach to regression problems in QSARs. In this study, the behaviour of SEEB descriptors was analysed with a MLR model. For this purpose a SEEB/MLR 3D‐QSAR model was developed to evaluate the efficiency of benzamide trypsin inhibitors. The development of inhibitors of trypsin‐like serine proteases has been an active area of research. They are involved in many biological processes like protein digestion and blood coagulation and also serve as a useful model system to study protein‐ligand interaction. The regression coefficients, obtained by this procedure, have an intuitively simple and therefore appealing meaning for the relative influence of each amino acid residue to the predictive model. The predictive capability of SEEB is shown to be comparable to those of other QSAR methods.

Exact and Effective Pair-Wise Potential for Protein-Ligand Interactions Obtained from a Semiempirical Energy Partition

In this work, the partition method introduced by Carvalho and Melo was used to study the complex between Cucurbita maxima trypsin inhibitor (CMTI-I) and glycerol at the AM1 level. An effective potential, combining non-bonding and polarization plus charge transfer (PLCT) terms, was introduced to evaluate the magnitude of the interaction between each amino acid and the ligand. In this case study, the nonbonding–PLCT non-compensation characterizes the stabilization energy of the association process in study. The main residues (Gly29, Cys3 and Arg5) with net attractive effects and Arg1 (with a net repulsive effect), responsible by the stability of protein-ligand complex, are associated with large nonbonding energies non-compensated by PLCT effects. The results obtained enable us to conclude that the present decomposition scheme can be used for understanding the cohesive phenomena in proteins.