1,721,153 research outputs found
Probing the electrochemical behavior of tubular enzyme membrane electrodes using simulations
No full textTubular geometry can help us emulate biological systems. Applications include medical sensors and biofuel cells among others
Rheological behaviour of probiotic bacteria dispersed in maltodextrin and sucrose solutions
No full textProbiotic bacteria are live microorganisms, which manifest health benefits in humans. The goal of this work was to characterize rheological properties of probiotic bacteria (Lactobacillus reuteri) formulation in which maltodextrin and sucrose used as excipients. To fulfil the goal, first, thermal, structural and rheological properties of maltodextrin, sucrose solutions and probiotic bacteria slurry were investigated. Probiotic bacteria formulations were prepared by adding probiotic bacteria slurry to maltodextrin and sucrose solutions at different mass fractions. Finally, rheological properties of probiotic bacteria formulations were evaluated. From TGA, the water content of PB slurry including intracellular water found 81%. In DLS, three different types of aggregations of maltodextrin were observed and characteristic size of Probiotic bacteria found 1μm. The optical microscopy results indicate that at the liquid - air interface and in dehydrated state the bacteria are birefringent and arranged in an ordered fashion resembling a nematic phase. Most of the MD, SU and MD+SU solutions show Newtonian behaviour. MD and SU solutions show strong increase of viscosity with increasing concentration. This dependence can be described by using the Spurlin–Martin–Tennent’s model. The viscosities of MD+SU solutions increase with increasing proportion of maltodextrin. The oscillation data of MD and MD+SU solutions can be described by Maxwell model. The viscosities of MD, SU, MD+SU mixed solutions decrease with increasing temperature. This temperature dependency can be described by Arrhenius model of viscosity. At very high concentrations of MD, a deviation from this behaviour is observed. The probiotic bacteria slurry shows shear thinning behaviour at low shear stress and Newtonian behaviour at higher stresses. All probiotic formulations in which probiotic bacteria dispersed in maltodextrin and sucrose solutions show Newtonian behaviour. The viscosities of maltodextrin solutions and MD+SU mixed solutions decrease by addition of probiotic bacteria whereas mixed effects of probiotic bacteria addition on the viscosity of sucrose solutions were observed. The viscosity of probiotic bacteria slurry decreases with increasing temperature, although deviations from this behavior are seen at certain conditions
Direct electron transfer reactions between human ceruloplasmin and electrodes
No full textIn an effort to find conditions favoring bioelectrocatalytic redn. of oxygen by surface-immobilized human ceruloplasmin (Cp), direct electron transfer (DET) reactions between Cp and an extended range of surfaces were considered. Exploiting advances in surface nanotechnol., bare and carbon-nanotube-modified spectrog. graphite electrodes as well as bare, thiol- and gold-nanoparticle-modified gold electrodes were considered, and ellipsometry provided clues as to the amt. and form of adsorbed Cp. DET was studied under different conditions by cyclic voltammetry and chronoamperometry. Two Faradaic processes with midpoint potentials of about 400 mV and 700 mV vs. NHE, corresponding to the redox transformation of copper sites of Cp, were clearly obsd. In spite of the significant amt. of Cp adsorbed on the electrode surfaces, as well as the quite fast DET reactions between the redox enzyme and electrodes, bioelectrocatalytic redn. of oxygen by immobilized Cp was never registered. The bioelectrocatalytic inertness of this complex multi-functional redox enzyme interacting with a variety of surfaces might be assocd. with a very complex mechanism of intramol. electron transfer involving a kinetic trapping behavior
Quo Vadis, Implanted Fuel Cell?
No full textThe road to safe and effective implantable electrical power devices has been long-and the goal has not been reached yet, although a certain amount of scientific and technological progress has been made. This brief review is focused on highlighting the stages of development of implanted fuel cells capable of providing electrical power for running implanted "personal electronics". The paper starts with early efforts to implant glucose-burning fuel cells in dogs, and ends with realistic attempts at interfacing a more sophisticated enzymatic glucose/oxygen fuel cell in an actual human blood stream. However, before that, the review deals with thermodynamic aspects of fuel cells, emphasizing the general advantages of these devices. Further steps, which are needed to realize the potential of this technology and which somehow differ from generally accepted ideas, are presented. These next steps are evaluated in the context of theoretically achievable abilities of implantable chemical power sources, which are not as great as many researchers might expect
Investigating the specificity of molecularly imprinted polymers targeting sialic acid on cancer cell surfaces
No full textBiophysical differences between COPD, CF and healthy airways mucus.
No full textAn improved understanding of the mucus biophysical alteration in chronic obstructive pulmonary disease (COPD) and cystic fibrosis (CF) patients is a milestone towards a more accurate and effective treatment of these common and highly debilitating conditions. Little is known about the variations in mucus structure between ill and healthy individuals. An established fact, however, is the role of the mucus obstruction in the exacerbation of the two conditions which impairs the physiological cleaning mechanism of the airways (mucociliary clearance) and is assessed as the strongest predictor of mortality. Therefore, it appears relevant to investigate which properties and structural changes are responsible of the impaired clearance of airway mucus. This thesis presents investigations of mucus on the basis of mucin structure observed in healthy, COPD and cystic fibrosis bronchial mucus samples. AFM (atomic force microscopy) and synchrotron SAXS (small angle X-ray scattering) techniques were used to characterise the structural features of the mucin molecules and allowed to identify the dumbbell structure of airways mucin monomers. The analysis of structural and dimensional features of mucins, highlighted a greater similarity of COPD with the healthy sample rather than with cystic fibrosis. The water sorption analysis using QCM-D (quartz crystal microbalance with dissipation monitoring), established a divergent behaviour between COPD and cystic fibrosis. Compared to healthy specimen, the mucus from COPD donors, showed a greater tendency to absorb water while cystic fibrosis mucus, in contrast, displayed the lowest water absorption
Investigation of the alpha-synuclein preformed fibrils surface properties and their relation to Parkinson’s disease modelling
No full textBackground: Parkinson’s disease is the second most common neurodegenerative disease worldwide. Accumulating evidence are linking the misfolding and aggregation of the protein alpha-synuclein leading to generation of fibrils, with the disease progression. Fibrillation of alpha-synuclein in vitro can be achieved by induced aggregation of recombinant monomer and termed pre-formed fibrils. When controlling the parameters during fibrillation, different fibril strains can be generated. The strains are hypothesized to induce different diseases due to their different structures.
Aim: To obtain different strains of pre-formed fibrils presenting different surface structures and to obtain biophysical characteristics of highly active pre-formed fibrils.
Methods: Generation of the multiple forms of pre-formed fibrils were executed by varying chosen physical and chemical parameters. The fibril preparations were analyzed for a number of biophysical and surface structure properties. These includes size distribution, amount of beta-sheet structure formation, zeta potential and limited proteolysis by proteinase K. Furthermore, determination of interaction with a solid support lipid bilayer and measurement of fibril activity were conducted.
Results: Variation of physical and chemical parameters during fibrillation generates fibrils of different surfaces assessed by their structural properties. These included differences in degradation patterns in response to proteinase K and behavior in response to a lipid bilayer. Seeding activity of fibrils is dependent on the size distribution. The choice of buffer, concentration and pH value has shown to affect the size of fibrils.
Conclusions: Pre-formed fibrils of two strains with different surface structures were generated successfully. While the results indicate different strains are formed, advanced analysis is necessary to evaluate the extent of the differences that are present in the three-dimensional structures of these. We identified key parameters affecting the seeding activity when measured in vitro such as fibril size distribution. Data suggests that these are also affected by buffer composition and protein concentration
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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