Estudo comparativo entre as alterações produzidas pelas biomoléculas floretina e barbaloína na estrutura e na hidratação de membranas modelo negativamente carregadas de DMPG
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Data
2010-04-29
Autores
Arima, Anderson Akira [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
A floretina (3-(4-hidroxifenil)-1-(2,4,6-trihidroxifenil)-1-propanona) é uma dihidrocalcona presente principalmente em maçãs que ultimamente vem sendo empregada para fins terapêuticos e cosméticos. Essa molécula tem demonstrado interagir com membranas modelo neutras e carregadas, alterando a hidratação, a qual é importante tanto para a estabilidade de bicamadas, como para suas permeabilidades seletivas. Neste trabalho, o efeito da floretina foi estudado em lipossomos (vesículas) negativamente carregados de DMPG (dimiristoilfosfatidilglicerol) a baixa força iônica (10 mM Hepes pH 7.4 + 2 mM NaCI). Os resultados foram comparados com os obtidos para a barbaloína [10-glicopiranosil-1,8-dihidroxi-3-(hidroximetil)-9(10H)-antracenona], - uma antraquinona glicosilada extraída de folhas de diferentes plantas do gênero Aloe -, porque essa biomolécula demonstrou ser capaz de interagir fortemente com vesículas de DMPG a baixa força iônica. As alterações dinâmicas e estruturais foram monitoradas pela técnica espectroscópica de ressonância paramagnética eletrônica (RPE) através da incorporação de marcadores de spin nas membranas lipídicas. Os dados foram analisados através de parâmetros medidos diretamente sobre os espectros e por meio de parâmetros simulados (soluções da equação estocástica de Liouville para um conjunto de spins magnéticos). Os resultados de RPE no intervalo entre 5 ºC e 10 ºC mostraram que a floretina aumenta sensivelmente a anisotropia tanto na superfície quanto no centro das bicamadas; enquanto que entre 15 ºC a 19 ºC, tanto a floretina como a barbaloína aumentam a mobilidade e a fluidez no centro da bicamada. Para altos valores de temperaturas (35 ºC a 45 ºC) a adição da floretina aparentemente não alterou a hidratação, mas mudou significantemente o empacotamento e a difusão molecular na região das cabeças polares; enquanto...
Phloretin (3-(4-Hydroxyphenyl)-1-(2,4,6-trihydroxyphenyl)-1-propanone) is a dihydrochalcone present mainly in apples, which lately has been used for medical and cosmetic purposes. It has been shown that phloretin interacts with neutral and charged model membranes, changing the hydration, which is important as for bilayer stability as for its permeability properties. In this work, the effect of phloretin was studied in negatively charged DMPG (dimyristoylphosphatidylglycerol) liposomes (vesicles) at low ionic strength (10mM Hepes pH 7.4 + 2 mM NaCI). The results were compared with the biomolecule barbaloin (10-glucopyranosyl-1,8-dihydroxy-3-(hydroxymethyl)-9(10H)-anthracenone), - a known active ingredient extracted from leaves of different Aloe plants -, because this glycosilated anthraquinone has showed to interact strongly with DMPG vesicles at low ionic strength. The dynamics and structural changes were monitored by ESR (electron spin resonance), using spin labels incorporated in the membranes. The data were analyzed by using parameters measured directly on the spectra and by simulated parameters (solutions of the stochastic Liouville equation for a set of magnetic spins). The ESR results for the interval between 5 ºC and 10 ºC showed that phloretin increases strongly the anisotropy on the surface as well as at the bilayer core, while between 15 ºC to 19 ºC, phloretin and barbaloin increase the mobility and the fluidity at the bilayer core. For high temperature (35 ºC to 45 ºC) the presence of phloretin apparently did not alter the hydration, but changed significantly the packing and the motional diffusion of the lipid polar heads; while barbaloin increased the hydration on the surface as well as the bilayer core, but produced great structural changes (“folds”) mainly at the end of the hydrocarbon... (Complete abstract click electronic access below)
Phloretin (3-(4-Hydroxyphenyl)-1-(2,4,6-trihydroxyphenyl)-1-propanone) is a dihydrochalcone present mainly in apples, which lately has been used for medical and cosmetic purposes. It has been shown that phloretin interacts with neutral and charged model membranes, changing the hydration, which is important as for bilayer stability as for its permeability properties. In this work, the effect of phloretin was studied in negatively charged DMPG (dimyristoylphosphatidylglycerol) liposomes (vesicles) at low ionic strength (10mM Hepes pH 7.4 + 2 mM NaCI). The results were compared with the biomolecule barbaloin (10-glucopyranosyl-1,8-dihydroxy-3-(hydroxymethyl)-9(10H)-anthracenone), - a known active ingredient extracted from leaves of different Aloe plants -, because this glycosilated anthraquinone has showed to interact strongly with DMPG vesicles at low ionic strength. The dynamics and structural changes were monitored by ESR (electron spin resonance), using spin labels incorporated in the membranes. The data were analyzed by using parameters measured directly on the spectra and by simulated parameters (solutions of the stochastic Liouville equation for a set of magnetic spins). The ESR results for the interval between 5 ºC and 10 ºC showed that phloretin increases strongly the anisotropy on the surface as well as at the bilayer core, while between 15 ºC to 19 ºC, phloretin and barbaloin increase the mobility and the fluidity at the bilayer core. For high temperature (35 ºC to 45 ºC) the presence of phloretin apparently did not alter the hydration, but changed significantly the packing and the motional diffusion of the lipid polar heads; while barbaloin increased the hydration on the surface as well as the bilayer core, but produced great structural changes (“folds”) mainly at the end of the hydrocarbon... (Complete abstract click electronic access below)
Descrição
Palavras-chave
Biomoléculas, Lipossomos, Membranas (Biologia), Phloretin, Barbaloin
Como citar
ARIMA, Anderson Akira. Estudo comparativo entre as alterações produzidas pelas biomoléculas floretina e barbaloína na estrutura e na hidratação de membranas modelo negativamente carregadas de DMPG. 2010. 101 f. Dissertação (mestrado) - Universidade Estadual Paulista, Faculdade de Medicina Veterinaria e Zootecnia, 2010.