Synthesis, DNA binding and topoisomerase I inhibition activity of thiazacridine and imidazacridine derivatives.

Thiazacridine and imidazacridine derivatives have shown promising results as tumors suppressors in some cancer cell lines. For a better understanding of the mechanism of action of these compounds, binding studies of 5-acridin-9-ylmethylidene-3-amino-2-thioxo-thiazolidin-4-one, 5-acridin-9-ylmethylidene-2-thioxo-thiazolidin-4-one, 5-acridin-9-ylmethylidene-2-thioxo-imidazolidin-4-one and 3-acridin-9-ylmethyl-thiazolidin-2,4-dione with calf thymus DNA (ctDNA) by electronic absorption and fluorescence spectroscopy and circular dichroism spectroscopy were performed. The binding constants ranged from 1.46 × 10(4) to 6.01 × 10(4) M(-1). UV-Vis, fluorescence and circular dichroism measurements indicated that the compounds interact effectively with ctDNA, both by intercalation or external binding. They demonstrated inhibitory activities to human topoisomerase I, except for 5-acridin-9-ylmethylidene-2-thioxo-1,3-thiazolidin-4-one. These results provide insight into the DNA binding mechanism of imidazacridines and thiazacridines.

Immobilization of Aspergillus ficuum tannase in calcium alginate beads and its application in the treatment of boldo (Peumus boldus) tea.

Tannase (tannin acyl hydrolase, E.C. 3.1.1.20) is an enzyme that catalyzes the hydrolysis of ester and depside linkages in hydrolysable tannins such as tannic acid, releasing gallic acid and glucose. It has several commercial applications in food industry, among which are gallic acid production, reduction of tannin content in fruit juices, and preparation of instantaneous tea. In this study we immobilized Aspergillus ficuum tannase in calcium alginate beads and then used it to treat boldo (Peumus boldus) tea. Such a technique allowed entrapping tannase with a 75% efficiency and appreciably increasing its thermal and pH stability compared with the free enzyme. Storage stability and reuse of the immobilized enzyme were very promising, in that about 60% of starting enzyme activity was retained after bead storage for 90 days at 4 °C or after six cycles of use. Boldo tea treatment with immobilized tannase for 120 min at 40 °C led to 31 and 60% removals of tannins and epigallocatechin gallate, an increase of about two orders of magnitude in gallic acid content, 56 and 109% increases in total flavonoids and epigallocatechin contents, a 42.8% increase in antioxidant activity and significant enhancements of tea color, clarity and pH.

Characterisation of bare and tannase-loaded calcium alginate beads by microscopic, thermogravimetric, FTIR and XRD analyses.

Incorporating enzymes into calcium alginate beads is an effective method to immobilise them and to preserve, at the same time, their catalytic activity. Sodium alginate was mixed with Aspergillus ficuum tannase in aqueous solution, and tannase-loaded calcium alginate beads were prepared using a simple droplet-based microfluidic system. Extensive experimental analysis was carried out to characterise the samples. Microscopic imaging revealed morphological differences between the surfaces of bare alginate matrix and tannase-loaded alginate beads. Thermal analysis allowed assessing the hydration contents of alginate and revealed the presence of tannase entrapped in the loaded beads, which was confirmed by vibrational spectroscopy. X-ray diffraction allowed us to conclude that alginate of tannase-loaded beads is not crystalline, which would make them suitable as carriers for possible controlled release. Moreover, they could be used in food applications to improve tea quality or clarify juices.

Acetylcholinesterase of mangrove oyster Crassostrea rhizophorae: A highly thermostable enzyme with promising features for estuarine biomonitoring.

Enzyme biomarkers from several aquatic organisms have been used for assessing the exposure to contaminants at sublethal levels. Amongst them, the cholinesterases are commonly extracted from several organisms to evaluate/measure organophosphate and carbamate neurotoxic effects. Acetylcholinesterase (AChE; EC 3.1.1.7) is an enzyme of the group of serine esterases that acts on the hydrolysis of the neurotransmitter acetylcholine allowing the intermittence of the nerve impulses responsible for the neuronal communication. This enzyme is the main target for the action of some pesticides and the inhibition of its activity in bivalve mollusks may be used as biomarker due to their filter-feeding habit. In this context, the present study aimed to characterize physicochemical and kinetic parameters of the AChE extracted from gills and viscera of the oyster Crassostrea rhizophorae and investigate the in vitro effect of pesticides (dichlorvos, diazinon, chlorpyrifos, methyl-parathion, temephos, carbaryl, carbofuran, aldicarb, diflubenzuron and novaluron) in search for assessing its potential as biomarker. Specific substrates and inhibitors evidenced the predominance of AChE in both tissues. The optimum pH found for gills and viscera AChE were 8.0 and 8.5, respectively. The maximum peak of activity occurred at 70 °C for gill AChE and 75 °C for viscera AChE. The enzymes of both tissues presented remarkable thermostability. The Michaelis-Menten constant for both enzymes were 1.32 ±â€¯0.20 mM for gills and 0.43 ±â€¯0.12 mM for viscera. The Vmax values for gills and viscera were 53.57 ±â€¯1.72 and 27.71 ±â€¯1.15 mU/mg, respectively. The enzymes were able to reduce the activation energy to 9.75 kcal mol-1 (gills) and 11.87 kcal mol-1 (viscera) obtaining rate enhancements of 3.57 × 105 and 1.01 × 104, respectively, in relation to non-catalyzed reactions. Among the pesticides under study, the carbamates carbaryl and carbofuran exerted the strongest inhibitory effects on the enzyme activity achieving important degrees of inhibition at concentrations below national and international current regulations. The first observation of the effects of benzoylurea pesticides (diflubenzuron and novaluron) on AChE from mollusks is reported here. The gills AChE of C. rhizophorae showed potential to be specific biomarker for the carbamate carbaryl while the viscera AChE showed it for carbofuran. According to their features, these enzymes may be proposed as promising tools for estuarine monitoring as well as biocomponent of biosensor devices.

Trypsin purification using magnetic particles of azocasein-iron composite.

This work presents an inexpensive, simple and fast procedure to purify trypsin based on affinity binding with ferromagnetic particles of azocasein composite (mAzo). Crude extract was obtained from intestines of fish Nile tilapia (Oreochromis niloticus) homogenized in buffer (01g tissue/ml). This extract was exposed to 100mg of mAzo and washed to remove unbound proteins by magnetic field. Trypsin was leached off under high ionic strength (3M NaCl). Preparation was achieved containing specific activity about 60 times higher than that of the crude extract. SDS-PAGE showed that the purified protein had molecular weight (24kDa) in concordance with the literature for the Nile tilapia trypsin. The mAzo composite can be reused and applied to purify trypsin from other sources.

DNA binding and Topoisomerase inhibition: How can these mechanisms be explored to design more specific anticancer agents?

DNA is considered one of the most promising targets of molecules with anticancer activity potential. Its key role in various cell division mechanisms, which commands the intense multiplication of tumor cells, is considered in studies with compounds whose mechanisms of action suggest likeliness of interaction. In addition, inhibition of enzymes that actively participate in biological functions of cells such as Topoisomerase, is seen as a primary factor for conducting several events that result in cell death. Discovery of new anticancer chemotherapeutical capable of interacting with DNA and inhibiting Topoisomerase enzymes is highlighted in anticancer research. The present review aims at showing through distinct biological tests the performance of different candidates to anticancer drugs and their respective chemical modifications, which are crucial and/or determinant for DNA affinity and inhibition of important enzymes in cells' vital processe to either separately or synergistically optimize anticancer activity.

Prevalence of toxocariasis in northeastern Brazil based on serology using recombinant Toxocara canis antigen.

To evaluate the prevalence of toxocariasis in children in Jaboatão dos Guararapes, Pernambuco in northeastern Brazil, 215 serum samples were examined by an enzyme-linked immunosorbent assay (ELISA) using a recombinant Toxocara canis antigen. In the ELISA, 26 (12.1%) of 215 subjects were positive. In a dot-blot assay using 53 of 215 serum samples, the diagnostic results correlated with those obtained by the ELISA. Moreover, it has been confirmed that the recombinant T. canis antigen was highly specific for toxocariasis by ELISA using serum samples positive for antibody to Ascaris lumbricoides. Considering the specificity of the recombinant antigen to toxocariasis, the ELISA or dot-blot assay using the recombinant T. canis antigen is recommended in tropical and sub-tropical regions where various parasitic infections are commonly endemic.

Immunochemiluminescent detection of galectin-3 in tumoral tissue from prostate.

This work proposes a chemiluminescent quantitative method for galectin-3 (Gal3) detection in prostate tissues. Monoclonal antibody anti-Gal3 was conjugated to acridinium ester (AE) and the complex formed with Gal3 in the prostate tissue was chemiluminescently detected. The light emission (expressed in Relative Light Unit-RLU) showed mean values higher for benign prostatic hyperplasia than normal tissues and adenocarcinoma. These differences showed to be statistically significant (p < 0.001). There was a linear relationship between RLU and tissue area. Furthermore, these values were dramatically reduced when the tissue samples were previously incubated with non labeled anti-Gal3. Finally, the anti-Gal3-AE solution in buffer stored at 4°C and the treated samples showed to be stable during a year and at least 72 h, respectively. Gal3 content in prostate tissue was higher in benign prostatic hyperplasia than normal tissues and much lower in adenocarcinoma. This quantitative, specific and sensitive method based on labeling antibody to acridinium ester can be applied to detect antigen in tissue.

Comparative effect of pesticides on brain acetylcholinesterase in tropical fish.

Monitoring of pesticides based on acetylcholinesterase (AChE; EC 3.1.1.7) inhibition in vitro avoids interference of detoxification defenses and bioactivation of some of those compounds in non-target tissues. Moreover, environmental temperature, age and stress are able to affect specific enzyme activities when performing in vivo studies. Few comparative studies have investigated the inter-specific differences in AChE activity in fish. Screening studies allow choosing the suitable species as source of AChE to detect pesticides in a given situation. Brain AChE from the tropical fish: pirarucu (Arapaima gigas), cobia (Rachycentron canadum) and Nile tilapia (Oreochromis niloticus) were characterized and their activities were assayed in the presence of pesticides (the organophosphates: dichlorvos, diazinon, chlorpyrifos, temephos, tetraethyl pyrophosphate- TEPP and the carbamates: carbaryl and carbofuran). Inhibition parameters (IC50 and Ki) for each species were found and compared with commercial AChE from electric eel (Electrophorus electricus). Optimal pH and temperature were found to be 8.0 and 35-45 °C, respectively. A. gigas AChE retained 81% of the activity after incubation at 50 °C for 30 min. The electric eel enzyme was more sensitive to the compounds (mainly carbofuran, IC50 of 5 nM), excepting the one from A. gigas (IC50 of 9 nM) under TEPP inhibition. These results show comparable sensitivity between purified and non-purified enzymes suggesting them as biomarkers for organophosphorus and carbamate detection in routine environmental and food monitoring programs for pesticides.

Immobilization of anti-galectin-3 onto polysiloxane-polyvinyl alcohol disks for tumor prostatic diseases diagnosis.

This work aimed to immobilize the antibody anti-galectin-3 onto polysiloxane-polyvinyl alcohol (POS-PVA) support, to evaluate its capacity to capture the serum antigen galectin-3 and to quantify by ELISA the antigen levels in sera from patients with prostatic adenocarcinoma (PA) and benign prostatic hyperplasia (BPH) and healthy individuals. Also, for comparative effect, the galectin-3 expression in the prostate tissue through immunohistochemistry was evaluated. The optical density (galectin-3 level) values established for the sera from PA and BPH patients were lower compared with those found for the healthy individuals. Galectin-3 immunohistochemically showed a significant increase and reduction of the cytoplasmatic protein expression in BPH and PA, respectively, compared with the normal prostate. These results showed that POS-PVA disks could be used as solid phase to immobilize serum galectins and in immunoassays procedures for the correspondent IgG anti-galectins detection in human sera.

The use of polysiloxane/polyvinyl alcohol beads as solid phase in IgG anti-Toxocara canis detection using a recombinant antigen.

Immunodetection of human IgG anti-Toxocara canis was developed based on ELISA and on the use of polysiloxane/polyvinyl alcohol (POS/PVA) beads. A recombinant antigen was covalently immobilized, via glutaraldehyde, onto this hybrid inorganic-organic composite, which was prepared by the sol-gel technique. Using only 31.2 ng antigen per bead, a peroxidase conjugate dilution of 1:10,000 and a serum dilution of 1:200 were adequate for the establishment of the procedure. This procedure is comparable to that which utilizes the adsorption of the antigen to conventional PVC plates. However, the difference between positive and negative sera mean absorbances was larger for this new glass based assay. In addition to the performance of the POS/PVA bead as a matrix for immunodetection, its easy synthesis and low cost are additional advantages for commercial application.