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Wong, Sze Ki. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 87-106). / Abstracts in English and Chinese. / Acknowledgements --- p.i / Abstract --- p.ii / Abstract in Chinese --- p.iv / Table of contents --- p.V / List of figures --- p.ix / List of abbreviations --- p.X / Chapter Chapter 1. --- General introduction --- p.1 / Chapter Chapter 2. --- Literature review --- p.6 / Chapter 2.1. --- Pathogenic mechanisms of Vibrio species in fish --- p.7 / Chapter 2.1.1. --- Introduction --- p.7 / Chapter 2.1.2. --- Adhesion --- p.7 / Chapter 2.1.3. --- Invasion --- p.8 / Chapter 2.1.4. --- Proliferation --- p.9 / Chapter 2.2. --- Vibrio virulence factors --- p.12 / Chapter 2.2.1. --- Introduction --- p.12 / Chapter 2.2.2. --- Hemolysin --- p.12 / Chapter 2.2.3. --- Protease --- p.14 / Chapter 2.2.4. --- Siderophore --- p.15 / Chapter 2.2.5. --- Lipopolysaccharide --- p.15 / Chapter 2.3. --- General apoptotic pathways --- p.17 / Chapter 2.3.1. --- Introduction --- p.17 / Chapter 2.3.2. --- Extrinsic apoptotic pathway --- p.17 / Chapter 2.3.2.1. --- Death receptor signaling apoptosis --- p.17 / Chapter 2.3.2.1.1. --- Fas signaling pathway --- p.18 / Chapter 2.3.2.1.2. --- TNF-R1 signaling pathway --- p.19 / Chapter 2.3.2.1.3. --- TRAIL receptors signaling pathway --- p.20 / Chapter 2.3.2.2. --- Growth factor receptor signaling apoptosis --- p.21 / Chapter 2.3.3. --- Intrinsic apoptotic pathway --- p.21 / Chapter 2.3.3.1. --- Mitochondrial apoptotic pathway --- p.21 / Chapter 2.3.3.1.1. --- Cyto c --- p.22 / Chapter 2.3.3.1.2. --- Smac/DIABLO --- p.22 / Chapter 2.3.3.1.3. --- Omi/HtrA2 --- p.22 / Chapter 2.3.3.1.4. --- AIF and endo G --- p.23 / Chapter 2.3.3.1.5. --- Bcl-2 family --- p.23 / Chapter 2.3.3.1.6. --- Mitochondrial membrane permeabilization (MMP) --- p.23 / Chapter 2.3.3.2. --- p53-regulated apoptotic pathway --- p.24 / Chapter 2.3.3.3. --- Endoplasmic reticulum (ER) stress-induced apoptotic pathway --- p.25 / Chapter 2.4. --- Membrane vesiculation in erythrocytes --- p.26 / Chapter 2.4.1. --- Introduction --- p.26 / Chapter 2.4.2. --- Induction of vesiculation --- p.26 / Chapter 2.4.3. --- Contents of vesicles --- p.28 / Chapter 2.4.4. --- Mechanisms involved during vesiculation --- p.29 / Chapter 2.4.5. --- Correlation between apoptosis and membrane vesiculation in erythrocytes --- p.31 / Chapter 2.4.6. --- Reasons for vesiculation --- p.31 / Chapter Chapter 3. --- "Induction of apoptosis by Vibrio alginolyticus thermolabile hemolysin (TLH) in blood cells of silver sea bream, Sparus sarba" --- p.33 / Chapter 3.1. --- Abstract --- p.34 / Chapter 3.2. --- Introduction --- p.34 / Chapter 3.3. --- Materials and methods --- p.36 / Chapter 3.3.1. --- Experimental fish --- p.36 / Chapter 3.3.2. --- Whole blood preparation --- p.37 / Chapter 3.3.3. --- Preparation of V. alginolyticus TLH --- p.37 / Chapter 3.3.4. --- "Caspase-3, -8, -9/6 fluorescent assay" --- p.38 / Chapter 3.3.5. --- TUNEL assay --- p.39 / Chapter 3.3.6. --- Apoptotic DNA ladder assay --- p.40 / Chapter 3.3.7. --- Statistical analysis --- p.41 / Chapter 3.4. --- Results --- p.42 / Chapter 3.4.1. --- "Increase of caspase-3, -8, -9/6 activities" --- p.42 / Chapter 3.4.2. --- Detection of DNA fragmentation by TUNEL assay --- p.44 / Chapter 3.4.3. --- Detection of DNA fragmentation by apoptotic DNA ladder assay --- p.44 / Chapter 3.5. --- Discussion --- p.46 / Chapter Chapter 4. --- "Occurrence of membrane vesiculation, apoptosis and post-apoptotic necrosis after exposure to Vibrio alginolyticus thermolabile hemolysin (TLH) in erythrocytes of silver sea bream, Sparus sarba" --- p.51 / Chapter 4.1. --- Abstract --- p.52 / Chapter 4.2. --- Introduction --- p.52 / Chapter 4.3. --- Materials and methods --- p.54 / Chapter 4.3.1. --- Experimental fish --- p.54 / Chapter 4.3.2. --- Whole blood preparation --- p.54 / Chapter 4.3.3. --- Preparation of V. alginolyticus TLH --- p.55 / Chapter 4.3.4. --- Light microscopy --- p.55 / Chapter 4.3.5. --- Transmission electron microscopy (TEM) --- p.56 / Chapter 4.3.6. --- Measurement of membrane vesiculation - acetylcholinesterase (AChE) assay --- p.56 / Chapter 4.3.7. --- Measurement of necrosis - hemoglobin colorimetric assay --- p.57 / Chapter 4.3.8. --- Apoptotic DNA ladder assay --- p.58 / Chapter 4.3.9. --- Flow cytometry --- p.59 / Chapter 4.3.10. --- Statistical analysis --- p.59 / Chapter 4.4. --- Results --- p.60 / Chapter 4.4.1. --- Ultrastructural changes in red blood cells after exposure to TLH --- p.60 / Chapter 4.4.2. --- Changes of cell population in size and granularity after exposure of TLH --- p.67 / Chapter 4.4.3. --- Effect of TLH dosage on necrosis and DNA fragmentation --- p.72 / Chapter 4.4.4. --- "Occurrence of membrane vesiculation, necrosis and DNA fragmentation in cells exposed to TLH" --- p.72 / Chapter 4.5. --- Discussion --- p.76 / Chapter Chapter 5. --- General conclusions --- p.82 / References --- p.87

Leung, Ho Wai. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 136-146). / Abstracts in English and Chinese. / THESIS COMMITTEE --- p.II / ACKNOWLEDGEMENT --- p.III / ABSTRACT --- p.IV / CHINESE ABSTRACT --- p.VI / TABLE OF CONTENT --- p.VII / OVERVIEW OF THIS PROJECT --- p.1 / Chapter SECTION 1: --- Purification and Characterization of hemagglutinins from French bean and mottled kidney bean / Chapter Chapter 1 --- INTRODUCTION / Chapter 1.1 --- General Introduction --- p.2 / Chapter 1.2 --- Physiological functions of plant lectins --- p.6 / Chapter 1.3 --- Physiological functions of animal lectins --- p.9 / Chapter 1.4 --- Biological functions of lectins --- p.12 / Chapter 1.5 --- Clinical and research applications of lectins --- p.16 / Chapter 1.6 --- Legume lectins --- p.17 / Chapter 1.7 --- Isolation and purification of lectins --- p.19 / Chapter 1.8 --- Objectives of the present study --- p.21 / Chapter Chapter 2 --- MATERIALS AND METHODS / Chapter 2.1 --- Chemicals --- p.22 / Chapter 2.2 --- Assay of hemagglutinating activity --- p.24 / Chapter 2.3 --- Purification protocol --- p.26 / Chapter 2.4 --- Assay of saccharide inhibition of hemagglutination --- p.28 / Chapter 2.5 --- Assay of pH stability --- p.28 / Chapter 2.6 --- Molecular mass determination and N-terminal sequence determination --- p.28 / Chapter 2.7 --- Assay of mitogenic activity --- p.29 / Chapter 2.8 --- Assay of antiproliferative activity --- p.30 / Chapter 2.9 --- Assay for antifungal activity --- p.30 / Chapter 2.10 --- Assay of HIV-1 reverse transcriptase inhibitory activity --- p.31 / Chapter 2.11 --- Assay of stability towards trypsin and chymotrypsin --- p.31 / Chapter 2.12 --- Assay of nitric oxide production --- p.32 / Chapter 2.13 --- Assay ofHIV-1 integrase --- p.32 / Chapter Chapter 3 --- EXPERIMENTAL RESULTS / Chapter 3.1 --- Purification scheme --- p.35 / Chapter 3.2 --- Size determination and N-terminal sequencing --- p.36 / Chapter 3.3 --- Temperature stability assay --- p.37 / Chapter 3.4 --- pH stability assay --- p.37 / Chapter 3.5 --- Saccharides inhibition of hemagglutination --- p.37 / Chapter 3.6 --- Stability towards Trypsin and Chymotrypsin --- p.38 / Chapter 3.7 --- Anti-proliferative activity --- p.38 / Chapter 3.8 --- HTV-1 reverse transcriptase inhibition --- p.39 / Chapter 3.9 --- Mitogenic activity --- p.39 / Chapter 3.10 --- Nitric oxide production --- p.39 / Chapter 3.11 --- HIV-1 integrase --- p.39 / Chapter 3.12 --- Defensin --- p.40 / Chapter Chapter 4 --- DISCUSSION / Chapter 4.1 --- Purification scheme --- p.68 / Chapter 4.2 --- Sequence comparison --- p.69 / Chapter 4.3 --- Physical Stability of the hemagglutinins --- p.70 / Chapter 4.4 --- Protease Stability --- p.71 / Chapter 4.5 --- Sugar Specificity Assay --- p.72 / Chapter 4.6 --- Anti-proliferative Aactivity toward Cancer Cells --- p.73 / Chapter 4.7 --- HTV-1 reverse trancriptase and H̐ơþV integrase inhibition --- p.74 / Chapter 4.8 --- Mitogenic activity --- p.75 / Chapter 4.9 --- Antifungal protein --- p.76 / Chapter Chapter 5 --- CONCLUSION --- p.78 / Chapter SECTION 2: --- Purification and Characterization of flammulolysin from mushroom Flαmmulinα velutipes / Chapter Chapter 1 --- INTRODUCTION / Chapter 1.1 --- General Introduction --- p.79 / Chapter 1.2 --- Mechanisms of hemolysis --- p.80 / Chapter 1.3 --- Biological role of hemolysins --- p.80 / Chapter 1.4 --- Mushroom hemolysin --- p.82 / Chapter 1.5 --- Applications of hemolysins --- p.83 / Chapter 1.6 --- Objectives of the present study --- p.83 / Chapter Chapter 2 --- MATERIALS AND METHODS --- p.84 / Chapter Chapter 3 --- EXPERIMENTAL RESULTS / Chapter 3.1 --- Purification and sequence determination --- p.90 / Chapter 3.2 --- Effect of sugars and salts on hemolysin --- p.90 / Chapter 3.3 --- Effect of Temperature and pH on hemolysin --- p.91 / Chapter 3.4 --- Effect of Proteases on hemolysin --- p.91 / Chapter 3.5 --- Effect of osmotic protection on hemolysin --- p.91 / Chapter 3.6 --- Effect of hemolysin on tumor cells --- p.91 / Chapter 3.7 --- Effect of hemolysin on spleen cells --- p.92 / Chapter 3.8 --- Effect of hemolysin on bacterial growth --- p.92 / Chapter 3.9 --- Effect of hemolysin on fungal growth --- p.92 / Chapter Chapter 4 --- DISCUSSION / Chapter 4.1 --- Purification and sequence comparison of hemolysin --- p.103 / Chapter 4.2 --- Sugar and Salts inhibition --- p.104 / Chapter 4.3 --- Temperature stability --- p.105 / Chapter 4.4 --- pH stability --- p.106 / Chapter 4.5 --- Protease stability --- p.106 / Chapter 4.6 --- Osmotic Protection --- p.106 / Chapter 4.7 --- Anti-tumour activity of the hemolysin --- p.107 / Chapter 4.8 --- Anti-fungal activity --- p.108 / Chapter Chapter 5 --- CONCLUSION --- p.109 / Chapter SECTION 3: --- Purification and Characterization of antifungal peptide from buckwheat seeds Fagopyrum esculentum / Chapter Chapter 1 --- INTRODUCTION / Chapter 1.1 --- Plant antiftmgal proteins --- p.110 / Chapter 1.2 --- Classification of antifungal proteins --- p.110 / Chapter 1.3 --- Distribution of antifungal proteins in plants --- p.111 / Chapter 1.4 --- Mechanisms of antifungal activity --- p.111 / Chapter 1.5 --- Future Perspectives of Antifungal proteins --- p.112 / Chapter 1.6 --- Antifungal peptide from Buckwheat --- p.112 / Chapter 1 .7 --- Objectives of the present study --- p.113 / Chapter Chapter 2 --- MATERIALS AND METHODS --- p.114 / Chapter Chapter 3 --- EXPERIMENTAL RESULTS / Chapter 3.1 --- Purification and sequence determination --- p.118 / Chapter 3.2 --- Effect on anti-fungal activity --- p.118 / Chapter 3.3 --- Effect of temperature and pH on antifungal activity --- p.118 / Chapter 3.4 --- Effect of the antifungal peptide on tumor cells --- p.119 / Chapter 3.5 --- Effect of antifungal peptide on HIV-1 Reverse transcriptase Activity --- p.119 / Chapter 3.6 --- Effect of antifungal peptide on spleen cells and NO Production --- p.119 / Chapter Chapter 4 --- DISCUSSION / Chapter 4.1 --- Purification scheme and N-terminal sequence --- p.130 / Chapter 4.2 --- Antifungal Activity --- p.131 / Chapter 4.3 --- Physical stability --- p.131 / Chapter 4.4 --- Anti-proliferative activity toward cancer cells --- p.131 / Chapter 4.5 --- HTV-1 Reverse Transcriptase Inhibitory activity --- p.132 / Chapter 4.6 --- Mitogenic activity and nitric oxide production --- p.132 / Chapter Chapter 5 --- CONCLUSION --- p.133 / OVERALL CONCLUSION --- p.134 / REFERENCES --- p.136

Orientador: Joelcio Francisco Abbade / Banca: José Carlos Peraçoli / Banca: Francisco Lázaro Pereira de Souza / Resumo: INTRODUÇÃO: A síndrome HELLP é uma complicação severa da pré-eclâmpsia, caracterizada por hemólise, elevação das enzimas hepáticas e trombocitopenia. Apesar de haver padronização dos valores laboratoriais que definem a síndrome HELLP, ainda existe dificuldade para a caracterização da hemólise. OBJETIVO: Avaliar o valor de haptoglobina que determina a hemólise nas pacientes com síndrome HELLP. MÉTODOS: estudo transversal e prospectivo de gestantes e puérperas com de pré-eclâmpsia. Exame laboratorial avaliado: dosagem sérica de haptoglobina. Construção da curva ROC para determinar o valor de corte da haptoglobina para diagnóstico de hemólise na síndrome HELLP. RESULTADOS: O valor da haptoglobina para diagnóstico de hemólise em pacientes com síndrome HELLP foi de 0,26g/L. DISCUSSÃO: A melhor correlação observada foi a haptoglobina com a DHL, indicando que este é o melhor marcador de hemólise intravascular para o diagnóstico da síndrome HELLP. CONCLUSÃO: A dosagem sérica da haptoglobina nos casos de pré-eclâmpsia deve fazer parte dos exames de rotina para diagnóstico de hemólise intravascular da síndrome HELLP / Abstract: CONTEXT: HELLP syndrome is a severe complication of pre-eclampsia, caracterized by hemolysis, elevated liver enzymes and low platelet count. Although there are standardized laboratory values that define the HELLP syndrome, the difficulty still exists for the characterization of hemolysis. PURPOSE: to evaluate the haptoglobin value to diagnose the hemolysis in HELLP syndrome. METHODS: transversal and prospective study of pregnant and postdelivery women with pre-eclampsia. Laboratory tests evaluated: serum haptoglobin. ROC curve to determine the cutoff value of haptoglobin in the diagnosis of hemolysis in HELLP syndrome. RESULTS: The haptoglobin value for hemolysis diagnosis in HELLP syndrome was 0.26 g / L. DISCUSSION: The best correlation was with haptoglobin and DHL, indicating that this is the best marker of intravascular hemolysis for the diagnosis of HELLP syndrome. CONCLUSION: Serum haptoglobin in cases of pre-eclampsia should be part of routine tests for diagnosis of intravascular hemolysis in HELLP syndrome / Mestre

Includes an appendix of author's previously published papers. / Bibliography: leaves 123-160. / 160, [105] leaves, [30] leaves of plates : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Microbiology and Immunology, 1990

Made available in DSpace on 2015-01-26T13:21:21Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-08-08Bitstream added on 2015-01-26T13:30:38Z : No. of bitstreams: 1 000797817.pdf: 449554 bytes, checksum: 7adc756b2ac04e5d1cbc6be34fa7a04e (MD5) / Introdução: A síndrome HELLP é uma complicação severa da pré-eclâmpsia, caracterizada por hemólise, elevação das enzimas hepáticas e trombocitopenia. Apesar de haver padronização dos valores laboratoriais que definem a síndrome HELLP, ainda existe dificuldade para a caracterização da hemólise. OBJETIVO: Avaliar o valor de haptoglobina que determina a hemólise nas pacientes com síndrome HELLP. MÉTODOS: estudo transversal e prospectivo de gestantes e puérperas com de pré-eclâmpsia. Exame laboratorial avaliado: dosagem sérica de haptoglobina. Construção da curva ROC para determinar o valor de corte da haptoglobina para diagnóstico de hemólise na síndrome HELLP. RESULTADOS: O valor da haptoglobina para diagnóstico de hemólise em pacientes com síndrome HELLP foi de 0,26g/L. DISCUSSÃO: A melhor correlação observada foi a haptoglobina com a DHL, indicando que este é o melhor marcador de hemólise intravascular para o diagnóstico da síndrome HELLP. CONCLUSÃO: A dosagem sérica da haptoglobina nos casos de pré-eclâmpsia deve fazer parte dos exames de rotina para diagnóstico de hemólise intravascular da síndrome HELLP / Context: HELLP syndrome is a severe complication of pre-eclampsia, caracterized by hemolysis, elevated liver enzymes and low platelet count. Although there are standardized laboratory values that define the HELLP syndrome, the difficulty still exists for the characterization of hemolysis. PURPOSE: to evaluate the haptoglobin value to diagnose the hemolysis in HELLP syndrome. METHODS: transversal and prospective study of pregnant and postdelivery women with pre-eclampsia. Laboratory tests evaluated: serum haptoglobin. ROC curve to determine the cutoff value of haptoglobin in the diagnosis of hemolysis in HELLP syndrome. RESULTS: The haptoglobin value for hemolysis diagnosis in HELLP syndrome was 0.26 g / L. DISCUSSION: The best correlation was with haptoglobin and DHL, indicating that this is the best marker of intravascular hemolysis for the diagnosis of HELLP syndrome. CONCLUSION: Serum haptoglobin in cases of pre-eclampsia should be part of routine tests for diagnosis of intravascular hemolysis in HELLP syndrome

Orientador: Tomomassa Yano / Dissertação (mestrado) - Universidade Estadual de Campinas,. Instituto de Biologia / Made available in DSpace on 2018-08-14T11:00:37Z (GMT). No. of bitstreams: 1 Thome_JacquelineDarcSilva_M.pdf: 1223668 bytes, checksum: 17699f260f82fb8a09136004fcc1e28a (MD5) Previous issue date: 2006 / Mestrado / Microbiologia / Mestre em Genética e Biologia Molecular

<i>Actinobacillus pleuropneumoniae</i> is the etiological agent of contagious swine pleuropneumonia, an economically important disease of the swine industry worldwide. Improved control of this disease requires enhanced understanding of the factors contributing to pathogenesis. The objectives of this study were to investigate the immune response and virulence properties of the 110-kilodalton (110-KDa) hemolysins [hemolysin I (HlyI) and hemolysin II (HlyII)] of <i>A. pleuropneumoniae</i>. Several monoclonal antibodies (MAb) to the hemolysins were developed. An IgGl. MAb (8C2) specific for HlyII, as determined by immunoblotting, was cross-linked to Protein A-Sepharose, and HlyII was purified from serotypes 1 and 5 by immunoaffinity chromatography. An indirect enzyme-linked immunosorbent assay (ELISA) using MAb 8C2, or affinitypurified rabbit IgG to both hemolysins, was developed for detection of swine antibody to one or both hemolysins, respectively. In comparison with the complement fixation test, the ELISA was highly sensitive and specific, and was able to identify animals infected with or exposed to most, if not all, serotypes of <i>A. pleuropneumoniae</i>. Several nonhemolytic mutants of <i>A. pleuropneumoniae</i> serotype 5 were isolated following electroporation of the parent with an hemolysin gene whose open-reading-frame was disrupted with a kanamycin resistance gene. One mutant was characterized for phenotypic and pathogenic properties. Biochemical profiles, growth rate, capsule content, and lipopolysaccharide and whole cell protein electrophoretic profiles of the parent and one of the mutants were similar. The nonhemolytic mutant lacked both HlyI and HlyII proteins in culture supernatant and in whole cell lysates as determined by immunoblot analysis; extracellular and intracellular hemolytic and cytotoxic activity was also absent. The mutant was avirulent in mice and pigs at doses greater than 10 times the lethal dose of the parent. Unlike the parent, the nonhemolytic mutant failed to confer protection against lethal challenge in mice following immunization. Thus, one or both hemolysins are essential for virulence and immunoprotection in <i>A. pleuropneumoniae</i> serotype 5. / Ph. D.

Orientador: Eneida de Paula / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-07T20:44:09Z (GMT). No. of bitstreams: 1 Prete_PauloSergioCastilho_D.pdf: 3376950 bytes, checksum: fd06e65f64531668e35cf4a9cb817913 (MD5) Previous issue date: 2006 / Resumo: Surfatantes ou detergentes são compostos anfifílicos que, na presença de água, têm a característica de formar agregados micelares. Surfatantes induzem a desestruturação de outros agregados como bicamadas sendo, por isso, usados para ruptura celular ou solubilização de lipídios e proteínas de membrana. A capacidade lítica dos surfatantes resulta de sua estrutura química, que determina o modo de interação dos mesmos com as membranas. Em concentrações mais altas (acima da concentração micelar crítica), os surfatantes desestabilizam as bicamadas lipídicas, levando à formação de micelas-mistas. Ensaios hemolíticos são bons modelos para estudo do efeito lítico de surfatantes em biomembranas. Aplicando em eritrócitos humanos o tratamento quantitativo proposto por Lichtenberg (1985) para estudo da solubilização de bicamadas lipídicas mensurou-se, neste trabalho, as concentrações para início (Csat) e 100% de hemólise (Csol), induzidas por 25 surfatantes clássicos, pertencentes a cinco diferentes famílias. A variação dos valores de Csat, Csol determinada com diferentes hematócritos permitiu o cálculo da constante de ligação surfatante/membrana e da razão surfatante/lipídio de membrana (Re) para início e 100% de hemólise. O parâmetro Re foi usado para classificar os detergentes como fortes, médios ou fracos agentes solubilizantes, com boa correlação com dados da literatura o que nos permitiu propor seu uso para descrever o efeito lítico de surfatantes, como uma alternativa simples e aplicável as membranas biológicas. As transições durante o processo hemolítico foram acompanhadas pela técnica de Ressonância Paramagnética Eletrônica, com uso marcador de spin 5 doxil-estearato (incorporado a 1 mol% nas membranas de eritrócito) e lise induzida pelo surfatante não iônico Triton X100. Concomitante ao aparecimento de hemoglobina e fosfato livres no sobrenadante - indicadores da ruptura da membrana, medidas do parâmetro de ordem daquele marcador de spin permitiram estudar as transições que acontecem durante (membrana:membrana mista) e após (membrana mista:micela mista) a hemólise / Abstract: Surfactants or detergents are amphiphilic compounds that form micellar aggregates in the presence of excess water. Surfactants are able to induce disruption of lamellar aggregates, justifying their use for cell lysis or in the extraction of membrane constituents such as lipids and proteins. The lytic capacity of a given surfactant is determined by its chemical structure, that rules its interaction with the membranes. At high concentration (above the critic micelle concentration), surfactants destabilize lipid bilayer leading to mixed micelle formation. Hemolytic assays are a good model to study the lytic effect of surfactants on biomembranes. In this study we have applied to human erythrocytes the quantitative treatment proposed by Lichtenberg (1985) to describe the solubilization of model lipid membranes. The concentration for onset (Csat) and complete (Csol) hemolysis induced by 25 classic surfactants from five different families were measured. Changes in Csat and Csol values at different hematocrits allowed the determination of the surfactant/membrane lipid molar ratio (Re) for beginning and 100% lysis. The Re arameter was used to classify the surfactants as strong, medium or weak membrane solubilizers. The classification was in good correlation with data in the literature, allowing us to recommend the use of Re parameter to describe the lyric effect of surfactants on biomembranes. The transitions in the hemolytic process were accompanied by Electron Paramagnetic Resonance, using the 5-doxyl-stearate spin-probe (1 mol%, incorporated in the erythrocyte membrane) and the non-ionic surfactant Triton X100. Simultaneously to the appearance of hemoglobin and phosphate released in the supernatant, measurements of the order parameter of the spin probe were used to characterize the transitions that take place during (membrane :mixed membrane) and after (mixed: membrane: mixed micelle) hemolysis / Doutorado / Bioquimica / Doutor em Biologia Funcional e Molecular