Caracterização espectral e computacional da interação de derivados de benzoil-tiraminas e albumina humana São José do Rio Preto 2017
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Data
2017-09-18
Autores
Camargo, Cintia Ramos [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
A folha de louro verde brasileira, uma especiaria muito apreciada na cozinha local (Aniba riparia, Lauraceae), contém compostos químicos que apresentam derivados de benzoíla chamados riparinas, que possuem propriedades anti-inflamatórias, antimicrobianas e ansiolíticas. No entanto, não está claro qual o tipo de interação que as riparins desempenham com qualquer alvo molecular. Como um alvo rentável, a albumina de soro humano (HSA) é uma das principais proteínas extracelulares, com uma capacidade excepcional para interagir com várias moléculas, e também desempenha um papel crucial no transporte, distribuição e metabolismo de uma grande variedade de ligantes endógenos e exógenos. Para delinear o mecanismo de interação HSA-riparina, a espectroscopia e os métodos computacionais foram aplicados de forma sinérgica. Uma avaliação através de espectroscopia de fluorescência mostrou que a emissão, atribuída ao Trp 214, a 346 nm, diminuiu com as titulações das riparinas. Observou-se um mecanismo de supressão estática na ligação das riparinas à HSA. Os experimentos de fluorescência realizados em 298, 308 e 318 K possibilitaram a realização de análises termodinâmicas que indicassem uma reação espontânea na formação do complexo (ΔG <0). O experimento do balanço entálpico-entrópico e com um cálculo de modelagem molecular revelou que interações hidrofóbicas, ligação de hidrogênio e interações não específicas estão presentes para as riparinas I - III com a HSA. O conjunto de resultados das mudanças da fração de fluorescência obtidos através de Schatchard não foi conclusivo ao estabelecer que tipo de cooperatividade esteja presente na interação. Para esclarecer o complexo HSA-riparinas, a abordagem de Hill foi utilizada para distinguir o índice de afinidade e a constante de ligação. Observou-se uma correspondência entre as estruturas moleculares das riparinas, devido à presença do grupo hidroxila no anel B, com parâmetros termodinâmicos e índice de afinidade. Riparin III realiza uma ligação de hidrogênio intramolecular, que afeta o coeficiente de Hill e a constante de ligação. Portanto, a presença de grupos hidroxila é capaz de modular a interação entre riparinas e HSA. Os experimentos de competição de sítio indicaram o sítio I como sendo o mais acessado, e as ferramentas de modelagem molecular reforçavam os resultados experimentais detalhando a participação de resíduos.
The green Brazilian bay leaf, a spice much prized in local cuisine (Aniba riparia, Lauraceae), contains chemical compounds presenting benzoyl-derivatives named riparins, which have anti-inflammatory, antimicrobial and anxiolytic properties However, it is unclear what kind of interaction riparins perform with any molecular target. As a profitable target, human serum albumin (HSA) is one of the principal extracellular proteins, with an exceptional capacity to interact with several molecules, and it also plays a crucial role in the transport, distribution, and metabolism of a wide variety of endogenous and exogenous ligands. To outline the HSA– riparin interaction mechanism, spectroscopy and computational methods were synergistically applied. An evaluation through fluorescence spectroscopy showed that the emission, attributed to Trp 214, at 346 nm decreased with titrations of riparins. A static quenching mechanism was observed in the binding of riparins to HSA. Fluorescence experiments performed at 298, 308 and 318 K made it possible to conduct thermodynamic analysis indicating a spontaneous reaction in the complex formation (ΔG<0). The enthalpy-entropy balance experiment with a molecular modeling calculation revealed that hydrophobic, hydrogen bond and non-specific interactions are present for riparin I - III with HSA. The set of results from fractional fluorescence changes obtained through Schatchard was inconclusive in establishing what kind of cooperativity is present in the interaction. To shed light upon the HSA-riparins complex, Hill’s approach was utilized to distinguish the index of affinity and the binding constant. A correspondence between the molecular structures of riparins, due to the presence of the hydroxyl group in the B-ring, with thermodynamic parameters and index of affinity were observed. Riparin III performs an intramolecular hydrogen bond, which affects the Hill coefficient and the binding constant. Therefore, the presence of hydroxyl groups is capable of modulating the interaction between riparins and HSA. Site marker competitive experiments indicated Site I as being the most suitable, and the molecular modeling tools reinforced the experimental results detailing the participation of residues.
The green Brazilian bay leaf, a spice much prized in local cuisine (Aniba riparia, Lauraceae), contains chemical compounds presenting benzoyl-derivatives named riparins, which have anti-inflammatory, antimicrobial and anxiolytic properties However, it is unclear what kind of interaction riparins perform with any molecular target. As a profitable target, human serum albumin (HSA) is one of the principal extracellular proteins, with an exceptional capacity to interact with several molecules, and it also plays a crucial role in the transport, distribution, and metabolism of a wide variety of endogenous and exogenous ligands. To outline the HSA– riparin interaction mechanism, spectroscopy and computational methods were synergistically applied. An evaluation through fluorescence spectroscopy showed that the emission, attributed to Trp 214, at 346 nm decreased with titrations of riparins. A static quenching mechanism was observed in the binding of riparins to HSA. Fluorescence experiments performed at 298, 308 and 318 K made it possible to conduct thermodynamic analysis indicating a spontaneous reaction in the complex formation (ΔG<0). The enthalpy-entropy balance experiment with a molecular modeling calculation revealed that hydrophobic, hydrogen bond and non-specific interactions are present for riparin I - III with HSA. The set of results from fractional fluorescence changes obtained through Schatchard was inconclusive in establishing what kind of cooperativity is present in the interaction. To shed light upon the HSA-riparins complex, Hill’s approach was utilized to distinguish the index of affinity and the binding constant. A correspondence between the molecular structures of riparins, due to the presence of the hydroxyl group in the B-ring, with thermodynamic parameters and index of affinity were observed. Riparin III performs an intramolecular hydrogen bond, which affects the Hill coefficient and the binding constant. Therefore, the presence of hydroxyl groups is capable of modulating the interaction between riparins and HSA. Site marker competitive experiments indicated Site I as being the most suitable, and the molecular modeling tools reinforced the experimental results detailing the participation of residues.
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Palavras-chave
riparina, albumina do soro humano, fluorescência, deslocamento de drogas, Riparin, Human serum albumin, Fluorescence, Drug displacement