Three-way chemometric method study and UV-Vis absorbance for the study of simultaneous degradation of anthocyanins in flowers of the Hibiscus rosa-sinensys species

Ultraviolet-visible spectra of flower extracts of the Hibiscus rosa-sinensys L. var. regius maximus species have been measured between 240.02 and 747.97 nm at pH values ranging from 1.1 to 13.0. Deconvolution of these spectra using the Parallel Factor Analysis (PARAFAC) model permitted the study of anthocyanin systems without isolation and purification of the individual species. Seven species were identified: flavilium cation, carbinol, quinoidal base, and E and Z-chacone and their ionized forms. The concentration changes of flavilium cation, quinoidal basen, and E and Z ionized chalcones were determined as function of pH at the different wavelengths. The flavilium cation, quinoidal base, and ionized E-clacone are involved in tho stage kinetic processes, a fast one followed by a slower one. Ionized Z-chalcone obeys a simple first-order processes. The spectral profiles recovered by PARAFAC model are in excellent agreement with bands of experimental spectra reported in the literature for the individual species measured at specific pH values. These results complement those obtained using chemical and simple mathematical techniques and demonstrate how chemometric methods can resolve problems for complex systems.     

A new application of humic substances: activation of supports for invertase immobilization

Invertase was immobilized on aminopropyl silica (APTS-SiO2) activated with humic substances (APTS-SiO2-HS) and on aminopropyl silica activated with glutaraldehyde (APTS-SiO2-GA). The resulting activity of both systems was compared. Humic substances (HS) used for the activation of the silica were extracted from soil of Cananéia, S?o Paulo State, Brazil, according to the procedure recommended by the International Humic Substances Society. Activity was determined by measuring the rate of formation of reduced sugars using the reaction with dinitrosalicylic acid (DNS). The amount of HS bound on the APTS-SiO2 was equal to 50 mg. The maximum amount of invertase immobilized on APTS-SiO2-HS was 15,200 U/g while in the system APTS-SiO2-GA it was 13,400 U/g. The experimental enzymatic activity was 3,700 and 3,300 U/g, for the systems APTS-SiO2-HS and APTS-SiO2-GA, respectively. Considering the increased amount and activity of immobilized enzyme compared with the glutaraldehyde method, it was concluded that this technique opens a new perspective in the preparation of supports for enzyme immobilization employing humic substances.     

Direct determination of ephedrine intermediate in a biotransformation reaction using infrared spectroscopy and PLS

Fourier transform mid-infrared spectroscopy (FT-MIR) coupled with a homemade attenuated total reflectance (ATR) flow-cell was used for on-line monitoring of a biotransformation reaction. The reaction was also monitored off-line by gas chromatography-mass spectrometry (GC-MS) enabling to establish a multivariate model for the infrared data based on partial least squares (PLS) regression. The method developed allowed the simultaneous determination of the substrate, two intermediates and the final product involved in the reduction reaction of 1-phenyl 1,2-propanedione at an initial concentration of 0.5% (v/v). The reaction was accomplished with a whole-cell suspension of Saccharomyces cerevisiae in a phosphate buffer of pH 3.0 at 32+/-1 degrees C. The ATR infrared monitoring was performed directly on the suspension cell without any separation process or extraction over 3h, totaling 188 spectra. The data were split into two subsets, with 158 times for calibration and 30 times for validation. The results showed that the proposed method may be used for on-line monitoring of the biotransformation reactions when the initial concentration is very low.     

New quinolizidine and diaza-adamantane alkaloids from Acosmium dasycarpum (Vog.) Yakovlev—Fabaceae

The phytochemical investigation of the methanol crude extract obtained from Acosmium dasycarpum (Vog.) Yakovlev root bark led to the isolation of the quinolizidine alkaloids lupanine, acosmine, acosminine and lupanacosmine, as well as the diaza-adamantane alkaloids panacosmine and dasycarpumine. Lupanacosmine (4) and dasycarpumine (6) have been described for the first time herein.     

Gold(III)–pyrrolidinedithiocarbamato Derivatives as Antineoplastic Agents

Transition metals offer many possibilities in developing potent chemotherapeutic agents. They are endowed with a variety of oxidation states, allowing for the selection of their coordination numbers and geometries via the choice of proper ligands, leading to the tuning of their final biological properties. We report here on the synthesis, physico-chemical characterization, and solution behavior of two gold(III) pyrrolidinedithiocarbamates (PDT), namely [Au^IIIBr₂(PDT)] and [Au^IIICl₂(PDT)]. We found that the bromide derivative was more effective than the chloride one in inducing cell death for several cancer cell lines. [Au^IIIBr₂(PDT)] elicited oxidative stress with effects on the permeability transition pore, a mitochondrial channel whose opening leads to cell death. More efficient antineoplastic strategies are required for the widespread burden that is cancer. In line with this, our results indicate that [Au^IIIBr₂(PDT)] is a promising antineoplastic agent that targets cellular components with crucial functions for the survival of tumor cells.     

A new application of humic substances: activation of supports for invertase immobilization

Invertase was immobilized on aminopropyl silica (APTS-SiO₂) activated with humic substances (APTS-SiO₂-HS) and on aminopropyl silica activated with glutaraldehyde (APTS-SiO₂-GA). The resulting activity of both systems was compared. Humic substances (HS) used for the activation of the silica were extracted from soil of Cananéia, São Paulo State, Brazil, according to the procedure recommended by the International Humic Substances Society. Activity was determined by measuring the rate of formation of reduced sugars using the reaction with dinitrosalicylic acid (DNS). The amount of HS bound on the APTS-SiO₂ was equal to 50 mg. The maximum amount of invertase immobilized on APTS-SiO₂-HS was 15200 U/g while in the system APTS-SiO₂-GA it was 13400 U/g. The experimental enzymatic activity was 3700 and 3300 U/g, for the systems APTS-SiO₂-HS and APTS-SiO₂-GA, respectively. Considering the increased amount and activity of immobilized enzyme compared with the glutaraldehyde method, it was concluded that this technique opens a new perspective in the preparation of supports for enzyme immobilization employing humic substances.     

Erythromycin-excipients compatibility studies using the thermal analysis and dynamic thermal infrared spectroscopy coupled with chemometrics

Journal of Thermal Analysis and Calorimetry - This study aims to characterize erythromycin (ERY) estolate by thermogravimetry analysis and differential scanning calorimetry. For such a purpose,...     

Robust classification of low-grade cervical cytology following analysis with ATR-FTIR spectroscopy and subsequent application of self-learning classifier eClass

Although the UK cervical screening programme has reduced mortality associated with invasive disease, advancement from a high-throughput predictive methodology that is cost-effective and robust could greatly support the current system. We combined analysis by attenuated total reflection Fourier-transform infrared spectroscopy of cervical cytology with self-learning classifier eClass. This predictive algorithm can cope with vast amounts of multidimensional data with variable characteristics. Using a characterised dataset [set A: consisting of UK cervical specimens designated as normal (n = 60), low-grade (n = 60) or high-grade (n = 60)] and one further dataset (set B) consisting of n = 30 low-grade samples, we set out to determine whether this approach could be robustly predictive. Variously extending the training set consisting of set A with set B data produced good classification rates with three two-class cascade classifiers. However, a single three-class classifier was equally efficient, producing a user-friendly, applicable methodology with improved interpretability (i.e., better classification with only one set of fuzzy rules). As data from set B were added incrementally to the training set, the model learned and evolved. Additionally, monitoring of results of the set B low-grade specimens (known to be low-grade cervical cytology specimens) provided the opportunity to explore the possibility of distinguishing patients likely to progress towards invasive disease. eClass exhibited a remarkably robust predictive power in a user-friendly fashion (i.e., high throughput, ease of use) compared to other classifiers (k-nearest neighbours, support vector machines, artificial neural networks). Development of eClass to classify such datasets for applications such as screening exhibits robustness in identifying a dichotomous marker of invasive disease progression.     

Modeling and Numerical Simulation of Breaking Waves on Structures

This work deals with the analytical and numerical simulation of the loads on cylindrical offshore structures due to breaking waves. We investigate breaking waves impact on a cylindrical structure on the surface of the water by using a multiphase flow model of immiscible fluids based on the Volume of Fluid (VOF) method. Different numerical schemes are applied to identify the sharp interface between water and gas. The results are compared as well with the already existing experimental, analytical and numerical studies by [1-3]. The agreement shows that the analytical and numerical models are suited to describe the experimental results. (© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Three theorems regarding testing graph properties

Property testing is a relaxation of decision problems in which it is required to distinguish YES ‐instances (i.e., objects having a predetermined property) from instances that are far from any YES ‐instance. We presents three theorems regarding testing graph properties in the adjacency matrix representation. More specifically, these theorems relate to the project of characterizing graph properties according to the complexity of testing them (in the adjacency matrix representation). The first theorem is that there exist monotone graph properties in ???? for which testing is very hard (i.e., requires to examine a constant fraction of the entries in the matrix). The second theorem is that every graph property that can be tested making a number of queries that is independent of the size of the graph can be so tested by uniformly selecting a set of vertices and accepting iff the induced subgraph has some fixed graph property (which is not necessarily the same as the one being tested). The third theorem refers to the framework of graph partition problems, and is a characterization of the subclass of properties that can be tested using a one‐sided error tester making a number of queries that is independent of the size of the graph. © 2003 Wiley Periodicals, Inc. Random Struct. Alg., 23: 23–57, 2003