Haemoglobin smart plastic antibody material tailored with charged binding sites on silica nanoparticles: its application as an ionophore in potentiometric transduction

This work uses surface imprinting to design a novel smart plastic antibodymaterial (SPAM) for Haemoglobin (Hb). Charged binding sites are described here for the first time to tailor plastic antibody nanostructures for a large size protein such as Hb. Its application to design small, portable and low cost potentiometric devices is presented. The SPAM material was obtained by linking Hb to silica nanoparticles and allowing its ionic interaction with charged vinyl monomers. A neutral polymeric matrix was created around these and the imprinted protein removed. Additional materials were designed in parallel acting as a control: a neutral imprinted material (NSPAM), obtained by removing the charged monomers from the procedure, and the Non-Imprinted (NI) versions of SPAM and NSPAM by removing the template. SEM analysis confirmed the surface modification of the silica nanoparticles. All materials were mixed with PVC/plasticizer and applied as selective membranes in potentiometric transduction. Electromotive force (emf) variations were detected only for selective membranes having a lipophilic anionic additive in the membrane. The presence of Hb inside these membranes was evident and confirmed by FTIR, optical microscopy and Raman spectroscopy. The best performance was found for SPAM-based selective membranes with an anionic lipophilic additive, at pH 5. The limits of detection were 43.8 mg mL 1 and linear responses were obtained down to 83.8 mg mL 1, with an average cationic slope of +40 mV per decade. Good selectivity was also observed against other coexisting biomolecules. The analytical application was conducted successfully, showing accurate and precise results.

SPR based Studies for Pentagalloyl Glucose Binding to α-Amylase

Astringency is an organoleptic property resulting mostly from the interaction of salivary proteins with dietary polyphenols. It is of great importance to consumers but being typically measured by sensorial panels it turns out subjective and expensive. The main goal of the present work is to develop a sensory system to estimate astringency relying on protein/polyphenol interactions. For this purpose, a model protein was immobilized on a sensory gold surface and its subsequent interaction with polyphenols was measured by Surface Plasma Resonance (SPR). α-amylase and pentagalloyl glucose (PGG) were selected as model protein and polyphenol, respectively. To ensure specific binding between these, various surface chemistries were tested. Carboxylic terminated thiol decreased the binding ability of PGG and allowed covalent attachment of α-amylase to the surface. The pH 5 was the optimal condition for α-amylase immobilization on the surface. Further studies focus on Localized SPR sensor and application to wine samples, providing objectivity when compared to a trained panel.

Smart Plastic Antibody Material for Hemoglobin Tailored by Silica Surface Imprinting and with Charged Binding Sites: Its use as Ionophore in Potentiometric Transduction

JORNADAS DE ELECTROQUÍMICA E INOVAÇÃO 2013

Exposure of Lycopersicon Esculentum to Microcystin-LR: Effects in the Leaf Proteome and Toxin Translocation from Water to Leaves and Fruits

Natural toxins such as those produced by freshwater cyanobacteria have been regarded as an emergent environmental threat. However, the impact of these water contaminants in agriculture is not yet fully understood. The aim of this work was to investigate microcystin-LR (MC-LR) toxicity in Lycopersicon esculentum and the toxin accumulation in this horticultural crop. Adult plants (2 month-old) grown in a greenhouse environment were exposed for 2 weeks to either pure MC-LR (100 μg/L) or Microcystis aeruginosa crude extracts containing 100 μg/L MC-LR. Chlorophyll fluorescence was measured, leaf proteome investigated with two-dimensional gel electrophoresis and Matrix Assisted Laser Desorption Ionization Time-of-Flight (MALDI-TOF)/TOF, and toxin bioaccumulation assessed by liquid chromatography-mass spectrometry (LC-MS)/MS. Variations in several protein markers (ATP synthase subunits, Cytochrome b6-f complex iron-sulfur, oxygen-evolving enhancer proteins) highlight the decrease of the capacity of plants to synthesize ATP and to perform photosynthesis, whereas variations in other proteins (ribulose-1,5-bisphosphate carboxylase/oxygenase large subunit and ribose-5-phosphate isomerase) suggest an increase of carbon fixation and decrease of carbohydrate metabolism reactions in plants exposed to pure MC-LR and cyanobacterial extracts, respectively. MC-LR was found in roots (1635.21 μg/kg fw), green tomatoes (5.15–5.41 μg/kg fw), mature tomatoes (10.52–10.83 μg/kg fw), and leaves (12,298.18 μg/kg fw). The results raise concerns relative to food safety and point to the necessity of monitoring the bioaccumulation of water toxins in agricultural systems affected by cyanotoxin contamination.

Integrated study by NMR and X-ray Crystallography on the analysis of the molecular interactions in heme-binding proteins

Dissertação para obtenção do Grau de Doutor em Bioquímica, Especialidade Bioquímica Estrutural

Molecular determinants of ligand specificity in carbohydrate-binding modules: an NMR and X-ray crystallography integrated study

Dissertação para obtenção do Grau de Doutor em Bioquímica – Ramo Bioquímica Estrutural

Peptidoglycan assembly machines: The Staphylococcus aureus Penicillin-Binding Proteins

Dissertation presented to obtain the Ph.D degree in Biology

Functional and structural studies of two enzymes: membrane bound kinase and Z-DNA/Z-RNA-binding protein

Dissertação para obtenção do Grau de Doutor em Sistemas de Bioengenharia

Electron Transfer and Ligand Binding Properties of Cytochromes

Dissertation presented to obtain the Ph.D degree in Biochemistry

Characterization of mannose-binding lectin plasma levels and genetic polymorphisms in HIV-1-infected individuals

INTRODUCTION: The present study investigated the association between mannose-binding lectin (MBL) gene polymorphism and serum levels with infection by HIV-1. METHODS: Blood samples (5mL) were collected from 97 HIV-1-infected individuals resident in Belém, State of Pará, Brazil, who attended the Special Outpatient Unit for Infections and Parasitic Diseases (URE-DIPE). CD4+ T-lymphocyte count and plasma viral load were quantified. A 349bp fragment of exon 1 of the MBL was amplified via PCR, using genomic DNA extracted from controls and HIV-1-infected individuals, following established protocols. MBL plasma levels of the patients were quantified using an enzyme immunoassay kit. RESULTS: Two alleles were observed: MBL*O, with a frequency of 26.3% in HIV-1-infected individuals; and the wild allele MBL*A (73.7%). Similar frequencies were observed in the control group (p > 0.05). Genotype frequencies were distributed according to the Hardy-Weinberg equilibrium in both groups. Mean MBL plasma levels varied by genotype, with statistically significant differences between the AA and AO (p < 0.0001), and AA and OO (p < 0.001) genotypes, but not AO and OO (p = 0.17). Additionally, CD4+ T-lymphocytes and plasma viral load levels did not differ significantly by genotype (p > 0.05). CONCLUSIONS: The results of this study do not support the hypothesis that MBL gene polymorphism or low plasma MBL concentrations might have a direct influence on HIV-1 infection, although a broader study involving a large number of patients is needed.

Aptamers binding to Bradykinin

Bradykinin is a peptide of the kinin group, involved in a number of receptor-mediated physiological actions, including inflammation and vasodilation, as well as neuromodulation, neuroprotection and promotion of neurogenesis. Bradykinin is the main ligand of the B2 receptor- the main kinin receptor- which is involved in the cardiac and renal protective effects of kinins in diseases. Antibodies have been considered for a long time as promising therapeutic agents in various fields, especially cancer-related ones. Aptamers, on the other hand, have proven to be an excellent alterative, since they have similar properties to those of monoclonal antibodies, such a high-specificity of recognition and high-affinity binding. Plus, they are developed using in vitro selection procedures and can be reproduced by enzymatic reactions. SELEX is a powerful tool for the development of both DNA and RNA aptamers. The main goal of this project was to design a method to select aptamers against bradykinin using capillary electrophoresis alongside the SELEX technique. The selection was done by comparing the aptamers’ (ssDNA-target complex) electrophoretic mobility with that of the ssDNA and the target, which allowed us to define an appropriate collection window that took into consideration the analytes’ detection time, thus enabling the collection of the desired oligonucleotides. After two selection rounds, the collected pool was sequenced, the affinity was measured and the aptamers’ secondary structure was predicted. We concluded that with only two selection cycles, the original DNA library’s bulk affinity grew around 0.4%. The structural characterization of the aptamers, performed with the aid of the Mfold software, revealed that there are many repetitive motifs amongst them, indicating that the selection process was successful. We have obtained 16 sequences of candidate aptamers as bradykinin ligands of similar sequences and secondary structures whose biological activity should be analyzed after synthesis; mainly in regard to their role as bradykinin inhibitors.

The use of botulinum toxin type A in the treatment of HTLV-1-associated overactive bladder refractory to conventional therapy

Urinary symptoms occur in 19% of human T-cell lymphotropic virus type 1 (HTLV-1)-infected patients who do not fulfill criteria for HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) and in almost 100% of HAM/TSP patients. Few studies have evaluated therapies for overactive bladder (OAB) caused by HTLV-1 infection. This case report describes the effect of onabotulinum toxin A on the urinary manifestations of three patients with HAM/TSP and OAB symptoms. The patients were intravesically administered 200 units of Botox®. Their incontinence episodes improved, and their OAB symptoms scores (OABSS) reduced significantly. These data indicate that Botox® should be a treatment option for OAB associated with HTLV-1 infection.

Frequency of the toxic shock syndrome toxin-1 gene in methicillin-susceptible and -resistant Staphylococcus aureus isolates from teaching hospitals in Shiraz, Iran

INTRODUCTION: Staphylococcus aureus produces a range of virulence factors such as toxic shock syndrome toxin-1. METHODS: In this cross-sectional study of 345 clinical S. aureus isolates, the presence of the tst gene was assessed by polymerase chain reaction (PCR). RESULTS: The study revealed 53/345 (15.4%) isolates were positive for the tst gene. The tst gene was present in 18.1% of methicillin-susceptible S. aureus (MSSA) isolates and 11.6% of methicillin-resistant S. aureus (MRSA) isolates (p = 0.136). CONCLUSIONS: These results reveal the remarkable risk of S. aureus infections in hospitals, regardless of methicillin-resistance status.

Evaluation of the cytokine mannose-binding lectin as a mediator of periportal fibrosis progression in patients with schistosomiasis

INTRODUCTION : We hypothesized higher mannose-binding lectin level and classic factors (i.e., age, sex, alcohol consumption, exposure, and specific treatment) are associated with the severity of periportal fibrosis in schistosomiasis. METHODS : This cross-sectional study involved 79 patients infected with Schistosoma mansoni with severe or mild/moderate periportal fibrosis. Serum concentrations of mannose-binding lectin were obtained by enzyme-linked immunosorbent assay (ELISA). RESULTS: Higher serum level of mannose-binding lectin was significantly associated with advanced periportal fibrosis. CONCLUSIONS: Mannose-binding lectin may contribute to liver pathology in schistosomiasis and may represent a risk factor for advanced periportal fibrosis in the Brazilian population studied.