Conformational changes of the HsDHODH N-terminal microdomain via DEER spectroscopy

The human enzyme dihydroorotate dehydrogenase (HsDHODH) has been studied for being a target for development of new antineoplasic and antiproliferative drugs. The synthetic peptide N-t(DH) represents the N-terminal microdomain of this enzyme, responsible for anchoring it to the inner mitochondrial membrane. Also, it is known to harbor quinones that are essential for enzyme catalysis. Here we report structural features of the peptide/membrane interactions obtained by using CD and DEER spectroscopic techniques, both in micelles and in lipid vesicles. The data revealed different peptide conformational states in micelles and liposomes, which could suggest that this microdomain acts in specific regions or areas of the mitochondria, which can be related with the control of the quinone access to the HsDHODH active site. This is the first study to report on conformational changes of the HsDHODH N-terminal microdomain through a combination of CD and DEER spectroscopic techniques.

Adesivo tecidual de fibrina e sua aplicação na implantodontia

The purpose of this literature review was to evaluate the use of fibrin tissue adhesive in implant dentistry. Materials and Methods: A literature search of Medline-PubMed for articles published, describing the use of fibrin tissue adhesive in implant dentistry was performed and articles were critically reviewed. Results: The literature review reveals clinical trials and experimental studies with regard to the use of fibrin tissue adhesive in implant dentistry. This material consists of 2 components: highly purified, freeze-dried human fibrinogen with factor XIII and a starter solution containing human thrombin. Clotting factor XIII is admitted for reinforcement of the fibrin network. The components are reconstituted before use and when mixed form a clot by mimicking the terminal phase of the physiological clotting cascade. Several studies showed that fibrin tissue adhesive is fully absorbed by macrophages within 2 weeks of application. Adhesive fibrin tissue may be used for to prevent bone loss, to create contour in the periimplant soft tissue and osseous tissue, to sculpt emergence profile for prosthetic components and to mimic tissue architecture. In the last years fibrin tissue adhesive also find use as material for the controlled delivery of drugs and biologics. Conclusions: The fibrin tissue adhesive presents good properties such as biocompatibility, hemostatic properties and ability to break down like the physiologic clot. This material, alone or associated with other materials, can be used with the implants immediately after extraction. In this condition it brings the necessary anchoring and efficient maintenance of osseous/mucosal contour, which it is important for the clinical success.

Osseointegração de implantes instalados sem estabilidade primária: o papel dos materiais à base de fibrina e fosfato de cálcio

When implants are installed immediately after tooth extraction may occur anchoring primary decreased, delay or failure of osseointegration process. This occurs because of the large interface between the surrounding walls of the socket and the surface of the implant. For reconstruction, replacement or filling of bone defects the solution can be obtained with the use of autogenous, heterogenous or allogeneic bone grafts. However, these grafts suffer certain drawbacks, particularly a high rate of donor site morbidity, limited amounts of available bone, and the additional operative time required for harvest. For these reasons, intensive efforts have been directed toward developing alternative substances for to either augment or substitute. In this paper, we will examine some of the commonly used materials : fibrin and calcium phosphate.

Characterization of biomodified dentin matrices for potential preventive and reparative therapies

Biomodification of existing hard tissue structures, specifically tooth dentin, is an innovative approach proposed to improve the biomechanical and biochemical properties of tissue for potential preventive or reparative therapies. The objectives of the study were to systematically characterize dentin matrices biomodified by proanthocyanidin-rich grape seed extract (GSE) and glutaraldehyde (GD). Changes to the biochemistry and biomechanical properties were assessed by several assays to investigate the degree of interaction, biodegradation rates, proteoglycan interaction, and effect of collagen fibril orientation and environmental conditions on the tensile properties. The highest degree of agent–dentin interaction was observed with GSE, which exhibited the highest denaturation temperature, regardless of the agent concentration. Biodegradation rates decreased remarkably following biomodification of dentin matrices after 24 h collagenase digestion. A significant decrease in the proteoglycan content of GSE-treated samples was observed using a micro-assay for glycosaminoglycans and histological electron microscopy, while no changes were observed for GD and the control. The tensile strength properties of GD-biomodified dentin matrices were affected by dentin tubule orientation, most likely due to the orientation of the collagen fibrils. Higher and/or increased stability of the tensile properties of GD- and GSE-treated samples were observed following exposure to collagenase and 8 months water storage. Biomodification of dentin matrices using chemical agents not only affects the collagen biochemistry, but also involves interaction with proteoglycans. Tissue biomodifiers interact differently with dentin matrices and may provide the tissue with enhanced preventive and restorative/reparative abilities.

Resistência de união e estabilidade de um sistema adesivo universal à dentina erodida/abrasionada após desproteinização

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Sílica mesoporosa como suporte sólido para o ancoramento da molécula 4-amino-3-hidrazino-5-mercapto-1,2,4-triazole e aplicação na adsorção de Cu(II), Cd(II), Ni(II), Pb(II) e Co(II) em amostras aquosas

Pós-graduação em Química - IQ

Biocompatibility of experimental Ti-30Ta implants with compromised primary stability: effect of TEA

Purpose: Ti-Ta alloys have high potential for dental application due to a good balance between high strength and low modulus. Absence of primary anchoring may occur when dental implants are installed immediately after tooth extraction. Tranexamic acid (TEA) is used to reduce fibrin degradation and can prevent early blood clot breakdown. The aim of this study was to evaluate the biocompatibility of Ti-30Ta implants associated or not with tranexamic acid and installed with compromised primary stability. Methods and materials: Fabricated were 20 implants of titanium ASTM F67 (Grade 4) and 20 implants of Ti-30Ta alloy with dimensions of 2.1 mm × 2.8 mm Ø. They were divided (n = 10) into Group I (Ti machined), Group II (Ti machined/tranexamic acid), Group III (Ti-30Ta alloy) and Group IV (Ti-30Ta/tranexamic acid) and were implanted in tibia (defects with 2.5 mm × 3.2 mm Ø) of 40 male rats (250 g). The surgical sites were rinsed with 5% tranexamic acid solution in Groups II and IV. The animals were euthanized at 45 days postoperative. The pieces were processed in methyl methacrylate (Stevenel's blue/Alizarin red). The percentage of peri-implant tissue repair was analyzed via images obtained by an optical microscope coupled to a digital camera using Leica software and Adobe Photoshop QWin. Data were analyzed statistically with a significance level of 5%. Results: Histomorphometric results showed 97.16% of bone-implant contact for group IV, 89.78% of bone contact for group III, 70.89% for group II and 61.59% of bone contact for group I. The statistical analyses demonstrated significant differences (P < 0.05) among group I and other groups. Conclusion: The results suggest that (a) Ti-30Ta promoted an increase of bone healing and apposition around implant; (b) tranexamic acid favored the stabilization of blood clot and bone formation.

Videoaulas de escrita/redação científica na internet: um estudo bakhtiniano

Pós-graduação em Linguística e Língua Portuguesa - FCLAR