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Doctoral Thesis
DOI
10.11606/T.43.2013.tde-03092014-160258
Document
Author
Full name
Priscila Ribeiro dos Santos
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 2013
Supervisor
Committee
Figueiredo Neto, Antonio Martins (President)
Juliano Neto, Luiz
Mesquita, Oscar Nassif de
Nussenzveig, Paulo Alberto
Torriani, Iris Concepción Linares de
Title in Portuguese
Caracterização estrutural e óptica de lipoproteínas humanas nativa e oxidadas
Keywords in Portuguese
colesterol
HDL
LDL
lente térmica
lipoproteínas
oxidação
SAXS
Varredura-Z
Abstract in Portuguese
A aterosclerose, doença sistêmica caracterizada pelo acúmulo de lipídios e elementos fibrosos nas artérias, é uma das principais causas de morte em diversos países. Partículas de lipoproteínas de baixa densidade (LDL) oxidadas estão presentes nas lesões aterogênicas, evidenciando a correlação entre estas partículas e a doença aterosclerótica. Este trabalho apresenta estudos de caracterização óptica e estrutural de lipoproteínas humanas nativas e oxidadas in vitro. As caracterizações foram realizadas por meio de diversas técnicas, sendo as principais a Varredura-Z e o espalhamento de raios X a baixos ângulos (SAXS) . Nos estudos de caracterização óptica verificou-se que a resposta não-linear das amostras de LDL está relacionada tanto com o seu conteúdo de antioxidantes, quanto com sua concentração de hidroperóxidos. Com relação à caracterização estrutural, foi proposto um novo método de análise para os dados de SAXS. Neste método, que mostrou-se mais adequando frente àqueles existentes na literatura, a curva de contraste de densidade eletrônica é obtida diretamente da curva de intensidade de espalhamento. Por meio das análises realizadas concluímos que as partículas de LDL apresentam pequenas alterações estruturais apenas quando comparamos a amostra nativa com aquela oxidada por 18 horas. São apresentados ainda alguns resultados exploratórios obtidos, tanto na caracterização óptica quanto na estrutural, para as lipoproteínas de alta densidade (HDL), que apontam para uma maior resistência deste tipo de lipoproteína ao processo oxidação. Por fim, é possível afirmar que a técnica de Varredura-Z é sensível a mudanças que ocorrem no início do processo oxidativo das lipoproteínas, enquanto a técnica de SAXS é sensível a mudanças em estágios mais avançados do mesmo processo.
Title in English
Structural and optical characterization of native and oxidized human lipoproteins
Keywords in English
HDL
LDL
lipoprotein
oxidation
SAXS
thermal lens
Z-scan
Abstract in English
Atherosclerosis, which is a systemic disease characterized by the accumulation of lipids and fibrous elements in the arteries, is a major cause of death in many countries. Particles of oxidized low density lipoproteins (LDL) are present in atherogenic lesions, showing the correlation between these particles and atherosclerosis. This thesis presents studies of structural and optical characterization of native and in vitro oxidized human lipoproteins. Characterizations were carried out by means of various techniques, the main ones being Z-scan (ZS) and small angle X-ray scattering (SAXS). In the optical characterization studies it was found that the non-linear response of LDL samples is associated with their antioxidant contents and with their concentration of hydroperoxides. With respect to the structural characterization, we propose a new method of analysis for the SAXS data. In this method, which is more suitable than those existing in the literature, the electron density curve is obtained directly from the scattering intensity curve. Through these analyses we conclude that LDL particles exhibit only small structural changes when native LDL sample is compared to the $18$ hours oxidized one. We also present preliminary results, both in structure and in optical characterization, for the high density lipoprotein (HDL), which presents a greater resistance (comparing to LDL) to the oxidation process. Finally, it is possible to say that the ZS technique is sensitive to changes that occur in early stages of the lipoprotein's oxidative process, while the SAXS technique is sensitive to changes in the later stages of the same process.
 
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Publishing Date
2014-09-05
 
WARNING: The material described below relates to works resulting from this thesis or dissertation. The contents of these works are the author's responsibility.
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  • SANTOS, M. B. L., OLIVEIRA, E. A. DE, and Neto, A.M.F. Rayleigh scattering of a new lyotropic nematic liquid crystal system: crossover of propagative and diffusive behaviour [doi:10.1080/026782900750018654]. Liquid Crystals [online], 2000, vol. 27, p. 1485-1495.
  • SANTOS, M. P., et al. Thermodiffusion in a multicomponent lyotropic mixture in the vicinity of the critical micellar concentration by using the Z-Scan technique [doi:10.1103/PhysRevE.77.011403]. Physical Review E. (Cessou em 2000. Cont. 1539-3755 Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics) [online], 2008, vol. 77, p. 011403.
  • SANTOS, P. R., et al. Behavior of the thermal diffusivity of native and oxidized human low-density lipoprotein solutions studied by the Z-scan technique [doi:10.1117/1.JBO.17.10.105003]. Journal of Biomedical Optics [online], 2012, vol. 17, p. 105003-105003.
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