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Hydrophobicity classification of polymeric materials based on fractal dimension

THOMAZINI, Daniel; GELFUSO, Maria Virginia; ALTAFIM, Ruy Alberto Corrêa
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.76%
This study proposes a new method to obtain hydrophobicity classification (HC) in high voltage polymer insulators. In the method mentioned, the HC was analyzed by fractal dimension (fd) and its processing time was evaluated having as a goal the application in mobile devices. Texture images were created from spraying solutions produced of mixtures of isopropyl alcohol and distilled water in proportions, which ranged from 0 to 100% volume of alcohol (%AIA). Based on these solutions, the contact angles of the drops were measured and the textures were used as patterns for fractal dimension calculations.

Yeast flotation viewed as the result of the interplay of supernatant composition and cell-wall hydrophobicity

deSousa, SR; Oliveira, K. F.; Souza, C. S.; Kilikian, B. V.; Laluce, C.
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 309-319
ENG
Relevância na Pesquisa
37.27%
Flotation is a process of cell separation based on the affinity of cells to air bubbles. In the present work, flotability and hydrophobicity were determined using cells from different yeasts (Hansenulla polymorpha, Saccharomyces cerevisiae, Candida albicans), which were propagated in different media and at different temperatures. Alterations to the supernatant of the cells were also carried out before the flotation assays. The results described here indicate that supernatants of the yeast cells can play a more important role on flotation than cell-wall hydrophobicity. For example, wall-hydrophobicity of strain FLT-01 of S. cerevisiae was high but flotation did not occur when their washed cells were resuspended in water. Additions of neopeptone to cultures of S. cerevisiae and H. polymorpha repressed flotation and increased the volume of foam. An additional task of the present work was to show that the relationship between cell-wall hydrophobicity and flotation performance was dependent on the method used for the measurement of hydrophobicity. Based on the assay procedure, two types of hydrophobicity were distinguished: (a) the apparent hydrophobicity for cells suspended in the medium and expressed by the degree of cell affinity to the organic solvent in the two-phase system supernatant/hexane; (b) the standard hydrophobicity...

Effect of surface roughness on the hydrophobicity of a denture-base acrylic resin and Candida albicans colonization

De Foggi, Camila C.; Machado, Ana Lucia; Zamperini, Camila A.; Fernandes, Darcy; Wady, Amanda F.; Vergani, Carlos E.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.89%
Aim The aim of the present study was to evaluate the effect of surface roughness (roughness average [Ra] μm) on the hydrophobicity of a denture-base acrylic resin and the initial adherence and biofilm formation of Candida albicans (C. albicans). Methods Disk-shaped specimens were divided into six groups: Ra 0.05, Ra 0.2, Ra 0.4, Ra 0.8, Ra 1.5, and Ra 3.0. Water contact angles (WCA) were measured, and the specimens incubated with C. albicans for 90 min (initial adherence, n = 108) or 48 h (biofilm formation, n = 108). Adhered and biofilm cells were evaluated by c.f.u./mL and 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT), and the correlation between the two methods was evaluated. The surface of the specimens and cells (adhered and biofilm) were also analyzed by scanning electron microscopy (SEM). Results Groups Ra 0.05 and 3.0 exhibited the lowest (~75°) and the highest (~100°) WCA mean values, respectively. For both initial adherence and biofilm formation, no statistically-significant differences were observed among all groups, as determined by c.f.u./mL and XTT. A positive correlation between these two methods was found. SEM analysis showed the presence of scratches and valleys on the acrylic specimens and densely-packed yeast cells covering the entire surface. Conclusions Roughness significantly increased hydrophobicity (WCA)...

The importance of the morphology and hydrophobicity of different carriers on the immobilization and sugar refinery effluent degradation activity of phanerochaete chrysosporium

Guimarães, Carla; Matos, Cláudio; Azeredo, Joana; Mota, M.; Oliveira, Rosário
Fonte: Kluwer Academic Publishers Publicador: Kluwer Academic Publishers
Tipo: Artigo de Revista Científica
Publicado em //2002 ENG
Relevância na Pesquisa
36.76%
There was no direct correlation between the surface hydrophobicity or hydrophilicity of four solid carriers and the amount of immobilized Phanerochaete chrysosporium. The immobilized biomass was 1.5–1.8 times higher and the fungal degradation activity was 5–8 and 3 times greater in terms of decolorization and phenolics reduction, respectively, with porous carriers than with non-porous carriers.. Morphology of the carriers was important and governed the amount of immobilized mycelium and specially the fungal biodegradation activity.; PEDIP - RESINAS ; Junta Nacional de Investigação Científica e Tecnológica (JNICT).

Experimental methodology to quantify candida albicans cell surface hydrophobicity

Henriques, Mariana; Gasparetto, Kelly; Azeredo, Joana; Oliveira, Rosário
Fonte: Kluwer Academic Publishers Publicador: Kluwer Academic Publishers
Tipo: Artigo de Revista Científica
Publicado em //2002 ENG
Relevância na Pesquisa
36.89%
A new method of formation of yeast cell lawns for contact angle measurement (with water, formamide and 1-bromonaphthalene) is described. The cell lawns were formed on agar layers avoiding liquid penetration. The method was validated by comparing the hydrophobicity of Candida albicans grown at different temperatures and the hydrophobicity of bacterial cell lawns built on agar layers and obtained by the usual filtration method.; Fundação para a Ciência e Tecnologia. CAPES/Brasil.

Gibbs free energy of transfer of a methylene group on {UCON + (sodium or potassium) phosphate salts} aqueous two-phase systems: Hydrophobicity effects

Silvério, Sara C.; Rodríguez, Oscar; Teixeira, J. A.; Macedo, Eugénia
Fonte: Elsevier Ltd. Publicador: Elsevier Ltd.
Tipo: Artigo de Revista Científica
Publicado em /08/2010 ENG
Relevância na Pesquisa
37.05%
The Gibbs free energy of transfer of a suitable hydrophobic probe can be regarded as a measure of the relative hydrophobicity of the different phases. The methylene group (CH2) can be considered hydrophobic, and thus be a suitable probe for hydrophobicity. In this work, the partition coefficients of a series of five dinitrophenylated-amino acids were experimentally determined, at 23 °C, in three different tie-lines of the biphasic systems: (UCON + K2HPO4), (UCON + potassium phosphate buffer, pH 7), (UCON + KH2PO4), (UCON + Na2HPO4), (UCON + sodium phosphate buffer, pH 7), and (UCON + NaH2PO4). The Gibbs free energy of transfer of CH2 units were calculated from the partition coefficients and used to compare the relative hydrophobicity of the equilibrium phases. The largest relative hydrophobicity was found for the ATPS formed by dihydrogen phosphate salts.; Fundação para a Ciência e a Tecnologia (FCT) - Programa "Ciência 2007", SFRH/BD/43439/2008; LSRE; FEDER/POCI/2010

Salt effect on the (polyethylene glycol 8000 + sodium sulfate) aqueoustwo-phase system : relative hydrophobicity of the equilibrium phases

Ferreira, Luísa A.; Teixeira, J. A.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em /07/2011 ENG
Relevância na Pesquisa
36.99%
The relative hydrophobicity of the phases of several {polyethylene glycol (PEG) 8000 + sodium sulfate (Na2SO4)} aqueous two-phase systems (ATPSs), all containing 0.01 mol.L-1 sodium phosphate buffer (NaPB, pH 7.4) and increasing concentration of a salt additive, NaCl or KCl, up to 1.0 mol.L-1, was measured by the free energy of transfer of a methylene group between the phases, DG(CH2). The DG(CH2) of the systems was determined by partitioning of a homologous series of five sodium salts of dinitrophenylated (DNP) – amino acids with aliphatic side chains in three different tie-lines of each biphasic system. The relative hydrophobicity of the phases ranged from -0.125 to -0.183 kcal.mol.L-1, being the NaCl salt the one to provide the more effective changes. The results show that, within each system, there is a linear relationship between the DG(CH2) and the tie-line length (TLL), and biphasic systems with high salt additive concentration present the most negative DG(CH2) values. Therefore, the feasibility of establishing a relationship between the relative hydrophobicity of the phases in a given TLL and the ionic strength of the salt additive was investigated and a satisfactory correlation was found for each salt.

Cell surface hydrophobicity and adherence of a strain of group B streptococci during the post-antibiotic effect of penicillin

Araújo,Ângela Maria Mendes; Oliveira,Ivi Cristina Menezes de; Mattos,Marcos Corrêa de; Benchetrit,Leslie C.
Fonte: Instituto de Medicina Tropical Publicador: Instituto de Medicina Tropical
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/08/2008 EN
Relevância na Pesquisa
36.89%
The minimum inhibitory concentration and post-antibiotic effects of an antimicrobial agent are parameters to be taken into consideration when determining its dosage schedules. The in vitro post-antibiotic effects on cell surface hydrophobicity and bacterial adherence were examined in one strain of group B streptococci. Exposure of the microorganism for 2 h at 37 °C to 1 x MIC of penicillin induced a PAE of 1.1 h. The cell surface charge of the Streptococcus was altered significantly during the post-antibiotic phase as shown by its ability to bind to xylene: hydrophobicity was decreased. Bacterial adherence to human buccal epithelial cells was also reduced. The results of the present investigation indicate that studies designed to determine therapeutic regimens should evaluate the clinical significance of aspects of bacterial physiology during the post-antibiotic period.

Hydrophobicity classification of polymeric materials based on fractal dimension

Thomazini,Daniel; Gelfuso,Maria Virginia; Altafim,Ruy Alberto Corrêa
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2008 EN
Relevância na Pesquisa
36.76%
This study proposes a new method to obtain hydrophobicity classification (HC) in high voltage polymer insulators. In the method mentioned, the HC was analyzed by fractal dimension (fd) and its processing time was evaluated having as a goal the application in mobile devices. Texture images were created from spraying solutions produced of mixtures of isopropyl alcohol and distilled water in proportions, which ranged from 0 to 100% volume of alcohol (%AIA). Based on these solutions, the contact angles of the drops were measured and the textures were used as patterns for fractal dimension calculations.

Influence of subinhibitory concentrations of antimicrobials on hydrophobicity, adherence and ultra-structure of Fusobacterium nucleatum

Okamoto,Ana C.; Gaetti-Jardim Jr.,Elerson; Arana-Chavez,Victor E.; Avila-Campos,Mario J.
Fonte: Sociedade Brasileira de Microbiologia Publicador: Sociedade Brasileira de Microbiologia
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2002 EN
Relevância na Pesquisa
36.76%
Fusobacterium nucleatum is considered a bridge organism between earlier and later colonizers in dental biofilms and a putative periodontopathogen. In Dentistry, antimicrobial agents are used for treatment and control of infectious diseases associated with dental plaque. Antiseptics have been used in association with antibiotics to reduce infections after oral surgeries. In this study, the influence of subinhibitory concentrations (SC) of chlorhexidine, triclosan, penicillin G and metronidazole, on hydrophobicity, adherence to oral epithelial cells, and ultra-structure of F. nucleatum was examined. All isolates were susceptible to chlorhexidine, triclosan, and metronidazole; however, most of the isolates were susceptible to penicillin G, and all of them were hydrophilic when grown with or without antimicrobials. Adherence was decreased by all antimicrobials. Results suggest that adherence of F. nucleatum was influenced by adhesins because structures such as fimbries or capsule were not observed by transmission electronic microscope.

Partial biochemical characterization of cell surface hydrophobicity and hydrophilicity of Candida albicans.

Hazen, K C; Lay, J G; Hazen, B W; Fu, R C; Murthy, S
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /11/1990 EN
Relevância na Pesquisa
27.2%
Hydrophobic yeast cells of Candida albicans are more virulent than hydrophilic yeast cells in mice. Results of experiments performed in vitro suggest that surface hydrophobicity contributes to virulence in multiple ways. Before definitive studies in vivo concerning the contribution of fungal surface hydrophobicity to pathogenesis can be performed, biochemical, physiological, and immunochemical characterization of the macromolecules responsible for surface hydrophobicity must be accomplished. This report describes our initial progress toward this goal. When hydrophobic and hydrophilic yeast cells of C. albicans were exposed to various enzymes, only proteases caused any change in surface hydrophobicity. Hydrophobic cell surfaces were sensitive to trypsin, chymotrypsin, pronase E, and pepsin. This indicates that surface hydrophobicity is due to protein. Papain, however, had no significant effect. The hydrophobicity of hydrophilic cells was altered only by papain. The proteins responsible for surface hydrophobicity could be removed by exposure to lyticase, a beta 1-3 glucanase, for 30 to 60 min. When 60-min lyticase digests of hydrophobic and hydrophilic cell walls were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) with a 12.5% resolving gel...

Cell Wall Mannan and Cell Surface Hydrophobicity in Candida albicans Serotype A and B Strains

Masuoka, James; Hazen, Kevin C.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /11/2004 EN
Relevância na Pesquisa
27.2%
Cell surface hydrophobicity contributes to the pathogenesis of the opportunistic fungal pathogen Candida albicans. Previous work demonstrated a correlation between hydrophobicity status and changes in the acid-labile, phosphodiester-linked β-1,2-oligomannoside components of the N-linked glycans of cell wall mannoprotein. Glycan composition also defines the two major serotypes, A and B, of C. albicans strains. Here, we show that the cell surface hydrophobicity of the two serotypes is qualitatively different, suggesting that the serotypes may differ in how they modulate cell surface hydrophobicity status. The cell wall mannoproteins from hydrophilic and hydrophobic cells of both serotypes were compared to determine whether the glycan differences due to serotype affect the glycan differences due to hydrophobicity status. Composition analysis showed that the protein, hexose, and phosphate contents of the mannoprotein fraction did not differ significantly among the strains tested. Electrophoretic profiles of the acid-labile mannan differed only with hydrophobicity status, not serotype, though some strain-specific differences were observed. Furthermore, a newly available β-1,2-oligomannoside ladder allowed unambiguous identification of acid-labile mannan components. Finally...

Surface hydrophobicity of the rat colonic mucosa is a defensive barrier against macromolecules and toxins

Lugea, A; Salas, A; Casalot, J; Guarner, F; Malagelada, J
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /04/2000 EN
Relevância na Pesquisa
27.2%
BACKGROUND—Mucosal surface hydrophobicity is a key factor of the gastric acid defence barrier. In the colon, surface hydrophobicity is high but its biological function remains unexplored.
AIMS—To investigate the functional changes of the barrier due to removal of the surface active phospholipid layer by a detergent, or to reinforcement of the surface active phospholipid by local application of a suspension of lipids.
METHODS—Surface hydrophobicity (contact angle measurement), colonic permeability (lumen to blood clearance of mannitol and dextran), and mucosal resistance against luminal aggression (distal colitis induced by dextran sodium sulphate, DSS) were investigated in three study groups: (a) rats pretreated with a detergent (Brij 35) known to remove surfactant lipids; (b) rats pretreated with a suspension of surface active lipids (tripalmitin and dipalmitoyl-phosphatidylcholine); and (c) control rats pretreated with the corresponding vehicles.
RESULTS—In controls, surface hydrophobicity was low on the caecal mucosa and high in colon and rectum. Detergent treatment reduced surface hydrophobicity, and increased colonic permeability to mannitol and dextran. Conversely, treatment with lipids increased surface hydrophobicity...

A Unified Hydrophobicity Scale for Multi-Span Membrane Proteins

Koehler, Julia; Woetzel, Nils; Staritzbichler, René; Sanders, Charles R.; Meiler, Jens
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /07/2009 EN
Relevância na Pesquisa
27.22%
The concept of hydrophobicity is critical to our understanding of the principles of membrane protein folding, structure, and function. In the last decades several groups have derived hydrophobicity scales using both experimental and statistical methods that are optimized to mimic certain natural phenomena as closely as possible. The present work adds to this toolset the first knowledge-based scale that unifies the characteristics of both, α-helical and β-barrel multi-span membrane proteins. This Unified Hydrophobicity Scale (UHS) distinguishes between amino acid preference for solution, transition, and trans-membrane states. The scale represents average hydrophobicity values of amino acids in folded proteins, irrespective of their secondary structure type. We furthermore present the first knowledge-based hydrophobicity scale for mammalian α-helical MPs (Mammalian Hydrophobicity Scale - MHS). Both scales are particularly useful for computational protein structure elucidation, for example as input for machine learning techniques, such as secondary structure or trans-membrane span prediction, or as reference energies for protein structure prediction or protein design. The knowledge-based UHS shows a striking similarity to a recent experimental hydrophobicity scale introduced by Hessa and co-workers. Convergence of two very different approaches onto similar hydrophobicity values consolidates the major differences between experimental and knowledge-based scales observed in earlier studies. Moreover...

Charge and Hydrophobicity Effects of NIR Fluorophores on Bone-Specific Imaging

Bao, Kai; Nasr, Khaled A.; Hyun, Hoon; Lee, Jeong Heon; Gravier, Julien; Gibbs, Summer L.; Choi, Hak Soo
Fonte: Ivyspring International Publisher Publicador: Ivyspring International Publisher
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
36.76%
Recent advances in near-infrared (NIR) fluorescence imaging enabled real-time intraoperative detection of bone metastases, bone growth, and tissue microcalcification. Pamidronate (PAM) has been widely used for this purpose because of its high binding affinity toward bone and remarkable therapeutic effects. Herein we describe the development of a series of PAM-conjugated NIR fluorophores that varied in net charges and hydrophobicity, and compared their bone targeting efficiency, biodistribution, and blood clearance. Since the targeting moiety, PAM, is highly negatively charged but small, the overall in vivo bone targeting and biodistribution were mediated by the physicochemical properties of conjugated fluorophores.

The hydrophobicity and roughness of a nasoenteral tube surface influences the adhesion of a multi-drug resistant strain of Staphylococcus Aureus

Lima,J.C.; Andrade,N.J.; Soares,N.F.F.; Ferreira,S.O.; Fernandes,P.E.; Carvalho,C.C.P.; Lopes,J.P.; Martins,J.F.L
Fonte: Sociedade Brasileira de Microbiologia Publicador: Sociedade Brasileira de Microbiologia
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2011 EN
Relevância na Pesquisa
36.76%
In this study, we examined the physiochemical properties of nasoenteral feeding tubes made from two different types of polymer: silicone materials and polyurethane. The internal surfaces of the nasoenteral feeding tubes were analyzed for their hydrophobicity, roughness, microtopography, rupture-tension and ability to stretch. We also studied the adhesion of an isolated, multi-drug resistant strain of S. aureus to these polymers. The polyurethane nasoenteral tube, which was classified as hydrophilic, was more resistant to rupture-tension and stretching tests than the silicone tube, which was classified as hydrophobic. Additionally, the polyurethane tube had a rougher surface than the silicone tube. Approximately 1.0 log CFU.cm-2 of S. aureus cells adhered to the tubes and this number was not statistically different between the two types of surfaces (p > 0.05). In future studies, new polymers for nasoenteral feeding tubes should be tested for their ability to support bacterial growth. Bacterial adhesion to these polymers can easily be reduced through modification of the polymer's physicochemical surface characteristics.

Hydrophobicity Classification of Polymeric Insulators Based on Embedded Methods

Dong,Zhengcheng; Fang,Yanjun; Wang,Xianpei; Zhao,Yu; Wang,Quande
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/02/2015 EN
Relevância na Pesquisa
36.89%
Hydrophobicity is an important parameter to characterize electrical properties of insulated materials. Therefore, it is an urgent task to develop on-line instruments to identify the hydrophobicity of insulated material's surface conveniently, quickly and accurately. For this purpose, a novel evaluation system with image processing and decision tree is proposed which is based on embedded platform. For obtaining satisfactory results, we first propose a mixed image segmentation method to overcome the complex conditions outside, concerning non-controlled illumination, nonstandard surfaces and unfixed shooting angle. Then we adopt four new characteristic parameters to describe the image of each sample. Finally, a classification method based on MultiBoost decision tree is conducted which synthesizes the merits of both AdaBoost and Wagging algorithm. Results indicate the procedures can be applied in the DSP (Digital Signal Processor) platform perfectly and better results can be obtained than those did in our previous study or that of some other research.

Polyethylene glycol 8000+ citrate salts aqueous two-phase systems: Relative hydrophobicity of the equilibrium phases

Silvério, Sara Isabel Cruz; Gracia, Jesús; Teixeira, J. A.; Macedo, Eugénia A.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em 15/01/2016 ENG
Relevância na Pesquisa
36.99%
The Gibbs free energy of transfer of a methylene group, G*(CH2), is reported as a measure of the relative hydrophobicity of the equilibrium phases. Furthermore, G*(CH2) is a characteristic parameter of each tie-line, and for that reason can be used for comparing different tie-lines of a given aqueous two-phase system (ATPS) or even to establish comparisons among different ATPSs. In this work, the partition coefficients of a series of four dinitrophenylated-amino acids were experimentally determined, at 23 °C, in five different tie-lines of PEG8000(sodium or potassium) citrate ATPSs. G*(CH2) values were calculated from the partition coefficients and used to evaluate the relative hydrophobicity of the equilibrium phases. PEG8000potassium citrate ATPSs presented larger relative hydrophobicity than PEG8000sodium citrate ATPSs. Furthermore, the results obtained indicated that the PEG-rich phase (top phase) has higher affinity to participate in hydrophobic hydration interactions than the salt-rich phase (bottom phase).; This work was partially supported by FCT/MEC and FEDER under Programe PT2020 (Project UID/EQU/50020/2013), and co-financed by QREN, ON2 and FEDER (Projects NORTE-07-0162FEDER-000050 and NORTE-07-0124-FEDER-0000011), for which the authors are thankful. SCS alsoa cknowledges her post-doc grant (SFRH/BPD/88584/2012) from FCT.

Characterization and Implications of Surface Hydrophobicity in Nanoparticle Fate and Transport

Xiao, Yao
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Dissertação
Publicado em //2012
Relevância na Pesquisa
27.22%

Surface chemistry plays an essential role in determining the reactivity, bioaccessibility, bioavailability and toxicity of nanoparticles (NPs) in the environment. Processes such as aggregation, deposition and biouptake are controlled in part by the attachment efficiency, α, between particles and the surfaces they encounter. One premise of this research is that surface hydrophobicity is a pivotal property of NP surfaces that can affect the behavior of NPs in aquatic environment and potentially decide the fate and transport of NPs. However, there are multiple challenges in the characterization of hydrophobicity for NPs. Methods developed for macroscopic surfaces or organic compounds may not be readily applied or interpreted for the case of nano-scale surfaces. This dissertation addresses theoretical basis for applying methods to determining hydrophobicity of NPs. The use of an octanol-water partitioning method analogous to that used for organic compounds was evaluated on the basis of trends anticipated by thermodynamics, and by experimental observations. This work shows that partitioning of NPs in two phases systems, such as water and octanol, is not uniquely determined by hydrophobicity, but also influenced by surface charge and particle size. The water-oil interface rather than the bulk phases becomes the thermodynamically favored location for NP accumulation once NPs are larger than 1-10 nm and/or the surface is amphiphilic.

Nonetheless...

Hidrofobicidade de superfície celular e aderência de uma estirpe de estreptococos do grupo B durante o efeito pós-antibiótico da penicilina; Cell surface hydrophobicity and adherence of a strain of group B streptococci during the post-antibiotic effect of penicillin

Araújo, Ângela Maria Mendes; Oliveira, Ivi Cristina Menezes de; Mattos, Marcos Corrêa de; Benchetrit, Leslie C.
Fonte: Universidade de São Paulo. Instituto de Medicina Tropical de São Paulo Publicador: Universidade de São Paulo. Instituto de Medicina Tropical de São Paulo
Tipo: info:eu-repo/semantics/article; info:eu-repo/semantics/publishedVersion; ; ; ; ; Formato: application/pdf
Publicado em 01/08/2008 ENG
Relevância na Pesquisa
36.89%
A concentração mínima inibitória e os efeitos pós-antibióticos (EPA) de um agente antimicrobiano são parâmetros que devem ser levados em consideração quando da determinação do esquema de dosagem. Os efeitos pós-antibióticos in vitro na hidrofobicidade de superfície celular e na aderência foram pesquisados em uma amostra de estreptococos do grupo B. A exposição do microrganismo por 2 h a 37 °C a 1 x CMI de penicilina induziu um EPA de 1,1 h. A carga da superfície celular da bactéria foi alterada significativamente durante a fase pós-antibiótica revelada através da capacidade de ligação ao xileno, indicada pela diminuição da hidrofobicidade. A aderência bacteriana às células epiteliais bucais humanas também foi reduzida. Os resultados da investigação demonstram que estudos clínicos destinados a determinar regimes terapêuticos deveriam incluir o conhecimento da fisiologia bacteriana durante o período pós-antibiótico.; The minimum inhibitory concentration and post-antibiotic effects of an antimicrobial agent are parameters to be taken into consideration when determining its dosage schedules. The in vitro post-antibiotic effects on cell surface hydrophobicity and bacterial adherence were examined in one strain of group B streptococci. Exposure of the microorganism for 2 h at 37 °C to 1 x MIC of penicillin induced a PAE of 1.1 h. The cell surface charge of the Streptococcus was altered significantly during the post-antibiotic phase as shown by its ability to bind to xylene: hydrophobicity was decreased. Bacterial adherence to human buccal epithelial cells was also reduced. The results of the present investigation indicate that studies designed to determine therapeutic regimens should evaluate the clinical significance of aspects of bacterial physiology during the post-antibiotic period.