Active site engineering for heterogeneous catalysis using emerging nano-structured materials

The growing concern about the depletion of oil has spurred worldwide interest in finding alternative feedstocks for important petrochemical commodities and fuels. On the one hand, the enormous re-serves found (208 trillion cubic feet proven1), environmental sustainability and lower overall costs point to natural gas as the primary source for energy and chemicals in the near future.2 Nowadays the transformation of methane into useful chemicals and liquid fuels is only feasible via synthesis gas, a mixture of molecular hydrogen and carbon monoxide, that is further transformed to methanol or to hydrocarbons under moderate reaction conditions (150-350 °C and 10-100 bar).3 For a major cost reduction and in order to valorize small natural gas sources, either more efficient "syngas to products" catalysts should be produced or the manner in which methane is initially activated should be changed, ideally by developing catalysts able to directly oxidize methane to interesting products such as methanol. On the other hand, from the point of view of CO2 emissions, the use of the re-maining fossil resources will further contribute to global warming. In this scenario, the development of efficient routes for the transformation of CO2 into useful chemicals and fuels would represent a considerable step forward towards sustainability. Indeed, the environmental and economic incen-tives to develop processes for the conversion of CO2 into fuels and chemicals are great. However, for such conversions to become economically feasible, considerable research is necessary. In this lecture we will summarize our recent efforts into the design of new catalytic systems, based on MOFs and COFs, to address these challenges. Examples include the development of new Fe based FTS catalysts, electrocatalysts for the selective conversion of CO2 into syngas, the development of efficient catalysts for the utilization of formic acid as hydrogen storage vector and the development of new enzyme inspired systems for the direct transformation of methane to methanol under mild reaction conditions. References (1) http://www.clearonmoney.com/dw/doku.php?id=public:natural_gas_reserves. (2) Derouane, E. G.; Parmon, V.; Lemos, F.; Ribeiro, F. R. Sustainable Strategies for the Up-grading of Natural Gas: Fundamentals, Challenges, and Opportunities; Springer, 2005. (3) Rofer-DePoorter, C. K. Chemical Reviews. ACS Publications 1981, pp 447–474.

Poly(epsilon-caprolactone)nanocapsules as carrier systems for herbicides: Physico-chemical characterization and genotoxicity evaluation

The toxicity of herbicides used in agriculture is influenced by their chemical stability, solubility, bioavailability, photodecomposition, and soil sorption. Possible solutions designed to minimize toxicity include the development of carrier systems able to modify the properties of the compounds and allow their controlled release. Polymeric poly(epsilon-caprolactone) (PCL) nanocapsules containing three triazine herbicides (ametryn, atrazine, and simazine) were prepared and characterized in order to assess their suitability as controlled release systems that could reduce environmental impacts. The association efficiencies of the herbicides in the nanocapsules were better than 84%. Assessment of stability (considering particle diameter, zeta potential, polydispersity, and pH) was conducted over a period of 270 days, and the particles were found to be stable in solution. In vitro release kinetics experiments revealed controlled release of the herbicides from the nanocapsules, governed mainly by relaxation of the polymer chains. Microscopy analyses showed that the nanocapsules were spherical, dense, and without aggregates. In the infrared spectra of the PCL nanocapsules containing herbicides, there were no bands related to the herbicides, indicating that interactions between the compounds had occurred. Genotoxicity tests showed that formulations of nanocapsules containing the herbicides were less toxic than the free herbicides. The results indicate that the use of PCL nanocapsules is a promising technique that could improve the behavior of herbicides in environmental systems. (C) 2012 Elsevier B.V. All rights reserved.

Poly(Lactide-co-Glycolide) Nanocapsules Containing Benzocaine: Influence of the Composition of the Oily Nucleus on Physico-Chemical Properties and Anesthetic Activity

The aim of this work was to investigate the influence of the oily nucleus composition on physico-chemical properties and anesthetic activity of poly (lactide-co-glycolide) nanocapsules with benzocaine.Nanocapsules containing benzocaine were prepared with three different oily nucleus composition and characterized by mean diameter, polydispersivity, zeta potential, pH and stability were investigated as a function of time. In vitro release kinetics were performed in a system with two compartments separated by a cellulose membrane. Intensity and duration of analgesia were evaluated in rats by sciatic nerve blockade.The greatest stability, slower release profile and improvement in the local anesthetic activity of BZC were obtained with the formulation using USP mineral oil as component.Results from our study provide useful perspectives on selection of the primary materials needed to produce suspensions of polymeric nanocapsules able to act as carriers of BZC, with potential future application in the treatment of pain.

Designing Hydrogels that Transform their Shape in Response to Molecular Cues

There has been considerable interest in developing shape-changing soft materials for potential applications in drug delivery, microfluidics and biosensing. These shape- changing materials are inspired by the morphological changes exhibited by plants in nature, such as the Venus flytrap. One specific class of shape-change is that from a flat sheet to a folded structure (e.g., a tube). Such “self-folding” materials are usually composed of polymer hydrogels, and these typically fold in response to external stimuli such as pH and temperature. In order to develop these hydrogels for the previously described applications, it is necessary to expand the range of triggers. The focus of this dissertation is the advancement of shape-changing polymer hydrogels that are sensitive to uncommon cues such as specific biomolecules (enzymes), the substrates for such enzymes, or specific multivalent cations. First, we describe a hybrid gel that responds to the presence of low concentrations of a class of enzymes known as matrix metalloproteinases (MMPs). The hybrid gel was created by utilizing photolithographic techniques to combine two or more gels with distinct chemical composition into the same material. Certain portions of the hybrid gel are composed of a biopolymer derivative with crosslinkable groups. The hybrid gel is flat in water; however, in the presence of MMPs, the regions containing the biopolymer are degraded and the flat sheet folds to form a 3D structure. We demonstrate that hydrogels with different patterns can transform into different 3D structures such as tubes, helices and pancakes. Furthermore, this shape change can be made to occur at physiological concentrations of enzymes. Next, we report a gel with two layers that undergoes a shape change in the presence of glucose. The enzyme glucose oxidase (GOx) is immobilized in one of the layers. GOx catalyzes the conversion of glucose to gluconic acid. The production of gluconic acid decreases the local pH. The decrease in local pH causes one of the layers to swell. As a result, the flat sheet folds to form a tube. The tube unfolds to form a flat sheet when it is transferred to a solution with no glucose present. Therefore, this biomolecule- triggered shape transformation is reversible, meaning the glucose sensing gel is reusable. Furthermore, this shape change only occurs in the presence of glucose and it does not occur in the presence of other small sugars such as fructose. In our final study, we report the shape change of a gel with two layers in the presence of multivalent ions such as Ca2+ and Sr2+. The gel consists of a passive layer and an active layer. The passive layer is composed of dimethylyacrylamide (DMAA), which does not interact with multivalent ions. The active layer consists of DMAA and the biopolymer alginate. In the presence of Ca2+ ions, the alginate chains crosslink and the active layer shrinks. As a result, the gel converts from a flat sheet to a folded tube. What is particularly unusual is the direction of folding. In most cases, when flat rectangular gels fold, they do so about their short-side. However, our gels typically fold about their long-side. We hypothesize that non-homogeneous swelling determines the folding axis.

Diazene photoswitches in artificial molecular machines and light-effected materials

The research developed in this thesis focused on the spectroscopic and photochemical characterization of molecular diazene photoswitches, both as individual species and as functional components of mechanically interlocked molecules, molecular-based materials and artificial molecular machines and motors. Among the plethora of photochromes reported so far, azobenzene is the most versatile photoswitch due to its reproducible and well-established photochemical properties. Part I of this thesis work focuses on the characterization of light-responsive supramolecular systems based on azobenzene: a photochemically-driven rotary motor, a light-responsive supramolecular polymeric material and a supramolecular system capable of photoinduced entantiodiscrimination. Despite the wide success of azobenzene photoswitches, the tunability of their photochemical properties as a function of the diversified substitution pattern on its aryl ring presents intrinsic limitations. To overcome this issue, in the last decade heteroaryl azoswitches (i.e., azobenzene having heterocyclic rings in place of one or both phenyl groups) have attracted a great deal of attention. Hence, Part II of this thesis work treats the photochemical characterization of two different families of azoheteroarenes embedding imidazolium and thienyl functionalities in their structures. Their potential implementation in water-soluble artificial molecular machines and light-effected semiconductor materials is also assessed.

Low-molecular-weight gels: from the rational design to the application of versatile soft materials

Low-molecular-weight (LMW) gels are a versatile class of soft materials that gained increasing interest over the last few decades. They are made of a small percentage, often lower than 1.0 %, of organic molecules called gelators, dispersed in a liquid medium. Such molecules have a molecular weight usually lower than 1 kDa. The gelator molecules start to interact after the addition of a trigger, and form fibres, whose entanglement traps the solvent through capillary forces. A plethora of LMW gelators have been designed, including short peptides. Such gelators present several advantages: the synthesis is easy and can be easily scaled up; they are usually biocompatible and biodegradable; the gelation phenomenon can be rationalised by making small variation on the peptide scaffold; they find application in several fields. In this thesis, an overview of several peptide based LMW gels is presented. In each study, the gelation conditions were carefully studied, and the final materials were thoroughly investigated. First, the gelation ability of a fluorinated phenylalanine was assessed, to understand how the presence of a rigid moiety and the presence of fluorine may influence the gelation. In this context, a method for the dissolution of sensitive gelators was studied. Then, the control over the gel formation was studied both over time and space, taking advantage of either the pH-annealing of the gel or the reaction-diffusion of a hydrolysing reagent. Some gels were probed for various applications. Due to their ability of trapping water and organic solvents, we used gels for trapping pollutants dissolved in water, as well as a medium for the controlled release of either fragrances or bioactive compounds. Finally, the interaction of the gel matrix with a light-responsive molecule was assessed to understand wether the gel properties or the interaction of the additive with light were affected.

The Crosslinking Degree Controls The Mechanical, Rheological, And Swelling Properties Of Hyaluronic Acid Microparticles.

Viscosupplements, used for treating joint and cartilage diseases, restore the rheological properties of synovial fluid, regulate joint homeostasis and act as scaffolds for cell growth and tissue regeneration. Most viscosupplements are hydrogels composed of hyaluronic acid (HA) microparticles suspended in fluid HA. These microparticles are crosslinked with chemicals to assure their stability against enzyme degradation and to prolong the action of the viscosupplement. However, the crosslinking also modifies the mechanical, swelling and rheological properties of the HA microparticle hydrogels, with consequences on the effectiveness of the application. The aim of this study is to correlate the crosslinking degree (CD) with these properties to achieve modulation of HA/DVS microparticles through CD control. Because divinyl sulfone (DVS) is the usual crosslinker of HA in viscosupplements, we examined the effects of CD by preparing HA microparticles at 1:1, 2:1, 3:1, and 5:1 HA/DVS mass ratios. The CD was calculated from inductively coupled plasma spectrometry data. HA microparticles were previously sized to a mean diameter of 87.5 µm. Higher CD increased the viscoelasticity and the extrusion force and reduced the swelling of the HA microparticle hydrogels, which also showed Newtonian pseudoplastic behavior and were classified as covalent weak. The hydrogels were not cytotoxic to fibroblasts according to an MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assay. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2014.

A Putative Otu Domain-containing Protein 1 Deubiquitinating Enzyme Is Differentially Expressed In Thyroid Cancer And Identifies Less-aggressive Tumours.

This study aimed to identify novel biomarkers for thyroid carcinoma diagnosis and prognosis. We have constructed a human single-chain variable fragment (scFv) antibody library that was selected against tumour thyroid cells using the BRASIL method (biopanning and rapid analysis of selective interactive ligands) and phage display technology. One highly reactive clone, scFv-C1, with specific binding to papillary thyroid tumour proteins was confirmed by ELISA, which was further tested against a tissue microarray that comprised of 229 thyroid tissues, including: 110 carcinomas (38 papillary thyroid carcinomas (PTCs), 42 follicular carcinomas, 30 follicular variants of PTC), 18 normal thyroid tissues, 49 nodular goitres (NG) and 52 follicular adenomas. The scFv-C1 was able to distinguish carcinomas from benign lesions (P=0.0001) and reacted preferentially against T1 and T2 tumour stages (P=0.0108). We have further identified an OTU domain-containing protein 1, DUBA-7 deubiquitinating enzyme as the scFv-binding antigen using two-dimensional polyacrylamide gel electrophoresis and mass spectrometry. The strategy of screening and identifying a cell-surface-binding antibody against thyroid tissues was highly effective and resulted in a useful biomarker that recognises malignancy among thyroid nodules and may help identify lower-risk cases that can benefit from less-aggressive management.

Reduced Insulin Clearance And Lower Insulin-degrading Enzyme Expression In The Liver Might Contribute To The Thrifty Phenotype Of Protein-restricted Mice.

Nutrient restriction during the early stages of life usually leads to alterations in glucose homeostasis, mainly insulin secretion and sensitivity, increasing the risk of metabolic disorders in adulthood. Despite growing evidence regarding the importance of insulin clearance during glucose homeostasis in health and disease, no information exists about this process in malnourished animals. Thus, in the present study, we aimed to determine the effect of a nutrient-restricted diet on insulin clearance using a model in which 30-d-old C57BL/6 mice were exposed to a protein-restricted diet for 14 weeks. After this period, we evaluated many metabolic variables and extracted pancreatic islet, liver, gastrocnemius muscle (GCK) and white adipose tissue samples from the control (normal-protein diet) and restricted (low-protein diet, LP) mice. Insulin concentrations were determined using RIA and protein expression and phosphorylation by Western blot analysis. The LP mice exhibited lower body weight, glycaemia, and insulinaemia, increased glucose tolerance and altered insulin dynamics after the glucose challenge. The improved glucose tolerance could partially be explained by an increase in insulin sensitivity through the phosphorylation of the insulin receptor/protein kinase B and AMP-activated protein kinase/acetyl-CoA carboxylase in the liver, whereas the changes in insulin dynamics could be attributed to reduced insulin secretion coupled with reduced insulin clearance and lower insulin-degrading enzyme (IDE) expression in the liver and GCK. In summary, protein-restricted mice not only produce and secrete less insulin, but also remove and degrade less insulin. This phenomenon has the double benefit of sparing insulin while prolonging and potentiating its effects, probably due to the lower expression of IDE in the liver, possibly with long-term consequences.

The Characterization Of The Endoglucanase Cel12a From Gloeophyllum Trabeum Reveals An Enzyme Highly Active On β-glucan.

The basidiomycete fungus Gloeophyllum trabeum causes a typical brown rot and is known to use reactive oxygen species in the degradation of cellulose. The extracellular Cel12A is one of the few endo-1,4-β-glucanase produced by G. trabeum. Here we cloned cel12A and heterologously expressed it in Aspergillus niger. The identity of the resulting recombinant protein was confirmed by mass spectrometry. We used the purified GtCel12A to determine its substrate specificity and basic biochemical properties. The G. trabeum Cel12A showed highest activity on β-glucan, followed by lichenan, carboxymethylcellulose, phosphoric acid swollen cellulose, microcrystalline cellulose, and filter paper. The optimal pH and temperature for enzymatic activity were, respectively, 4.5 and 50 °C on β-glucan. Under these conditions specific activity was 239.2 ± 9.1 U mg(-1) and the half-life of the enzyme was 84.6 ± 3.5 hours. Thermofluor studies revealed that the enzyme was most thermal stable at pH 3. Using β-glucan as a substrate, the Km was 3.2 ± 0.5 mg mL(-1) and the Vmax was 0.41 ± 0.02 µmol min(-1). Analysis of the effects of GtCel12A on oat spelt and filter paper by scanning electron microscopy revealed the morphological changes taking place during the process.

Immobilization Of Papain On Chitin And Chitosan And Recycling Of Soluble Enzyme For Deflocculation Of Saccharomyces Cerevisiae From Bioethanol Distilleries.

Yeast flocculation (Saccharomyces cerevisiae) is one of the most important problems in fuel ethanol production. Yeast flocculation causes operational difficulties and increase in the ethanol cost. Proteolytic enzymes can solve this problem since it does not depend on these changes. The recycling of soluble papain and the immobilization of this enzyme on chitin or chitosan were studied. Some cross-linking agents were evaluated in the action of proteolytic activity of papain. The glutaraldehyde (0.1-10% w·v(-1)), polyethyleneimine (0.5% v·v(-1)), and tripolyphosphate (1-10% w·v(-1)) inactivated the enzyme in this range, respectively. Glutaraldehyde inhibited all treatments of papain immobilization. The chitosan cross-linked with TPP in 5 h of reaction showed the yield of active immobilized enzyme of 15.7% and 6.07% in chitosan treated with 0.1% PEI. Although these immobilizations have been possible, these levels have not been enough to cause deflocculation of yeast cells. Free enzyme was efficient for yeast deflocculation in dosages of 3 to 4 g·L(-1). Recycling of soluble papain by centrifugation was effective for 14 cycles with yeast suspension in time perfectly compatible to industrial conditions. The reuse of proteases applied after yeast suspension by additional yeast centrifugation could be an alternative to cost reduction of these enzymes.

Análise do perfil de humor e da enzima alfa-amilase salivar em indivíduos fisicamente ativos = : Analysis of profile of mood states and salivary alpha amylase enzyme in physically active individuals

Universidade Estadual de Campinas . Faculdade de Educação Física

Linear dimensional changes in plaster die models using different elastomeric materials

Dental impression is an important step in the preparation of prostheses since it provides the reproduction of anatomic and surface details of teeth and adjacent structures. The objective of this study was to evaluate the linear dimensional alterations in gypsum dies obtained with different elastomeric materials, using a resin coping impression technique with individual shells. A master cast made of stainless steel with fixed prosthesis characteristics with two prepared abutment teeth was used to obtain the impressions. References points (A, B, C, D, E and F) were recorded on the occlusal and buccal surfaces of abutments to register the distances. The impressions were obtained using the following materials: polyether, mercaptan-polysulfide, addition silicone, and condensation silicone. The transfer impressions were made with custom trays and an irreversible hydrocolloid material and were poured with type IV gypsum. The distances between identified points in gypsum dies were measured using an optical microscope and the results were statistically analyzed by ANOVA (p < 0.05) and Tukey's test. The mean of the distances were registered as follows: addition silicone (AB = 13.6 µm, CD=15.0 µm, EF = 14.6 µm, GH=15.2 µm), mercaptan-polysulfide (AB = 36.0 µm, CD = 36.0 µm, EF = 39.6 µm, GH = 40.6 µm), polyether (AB = 35.2 µm, CD = 35.6 µm, EF = 39.4 µm, GH = 41.4 µm) and condensation silicone (AB = 69.2 µm, CD = 71.0 µm, EF = 80.6 µm, GH = 81.2 µm). All of the measurements found in gypsum dies were compared to those of a master cast. The results demonstrated that the addition silicone provides the best stability of the compounds tested, followed by polyether, polysulfide and condensation silicone. No statistical differences were obtained between polyether and mercaptan-polysulfide materials.

Subcutaneous connective tissue response to primary root canal filling materials

This study evaluated the response of the subcutaneous connective tissue of BALB/c mice to root filling materials indicated for primary teeth: zinc oxide/eugenol cement (ZOE), Calen paste thickened with zinc oxide (Calen/ZO) and Sealapex sealer. The mice (n=102) received polyethylene tube implants with the materials, thereby forming 11 groups, as follows: I, II, III: Calen/ZO for 7, 21 and 63 days, respectively; IV, V, VI: Sealapex for 7, 21 and 63 days, respectively; VII, VIII, IX: ZOE for 7, 21 and 63 days, respectively; X and XI: empty tube for 7 and 21 days, respectively. The biopsied tissues were submitted to histological analysis (descriptive analysis and semi-quantitative analysis using a scoring system for collagen fiber formation, tissue thickness and inflammatory infiltrate). A quantitative analysis was performed by measuring the area and thickness of the granulomatous reactionary tissue (GRT). Data were analyzed by Kruskal-Wallis, ANOVA and Tukey's post-hoc tests (?=0.05). There was no significant difference (p>0.05) among the materials with respect to collagen fiber formation or GRT thickness. However, Calen/ZO produced the least severe inflammatory infiltrate (p<0.05). The area of the GRT was significantly smaller (p<0.05) for Calen/ZO and Sealapex. In conclusion, Calen/ZO presented the best tissue reaction, followed by Sealapex and ZOE.

Histopathological evaluation of root canal filling materials for primary teeth

This study aimed to assess the response of apical and periapical tissues of dogs' teeth after root canal filling with different materials. Forty roots from dogs' premolars were prepared biomechanically and assigned to 4 groups filled with: Group I: commercial calcium hydroxide and polyethylene glycol-based paste (Calen®) thickened with zinc oxide; Group II: paste composed of iodoform, Rifocort® and camphorated paramonochlorophenol; Group III: zinc oxide-eugenol cement; Group IV: sterile saline. After 30 days, the samples were subjected to histological processing. The histopathological findings revealed that in Groups I and IV the apical and periapical regions exhibited normal appearance, with large number of fibers and cells and no resorption of mineralized tissues. In Group II, mild inflammatory infiltrate and mild edema were observed, with discrete fibrogenesis and bone resorption. Group III showed altered periapical region and thickened periodontal ligament with presence of inflammatory cells and edema. It may be concluded that the Calen paste thickened with zinc oxide yielded the best tissue response, being the most indicated material for root canal filling of primary teeth with pulp vitality.