Interação entre polieletrólitos e macromoléculas heterogeneamente carregadas.
Carregando...
Data
2020-02-07
Autores
Marques, Luan celso
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Estadual Paulista (Unesp)
Resumo
Sabe-se que vários processos biológicos são mediados por interações entre polieletrólitos e proteínas, como a interação entre as proteínas histonas e a molécula de DNA no nucleossomo. Outro exemplo importante é a formação de complexos solúveis de glicosaminoglicanos (GAGs) em proteínas, como o complexo formado por heparina (Hp) e albumina sérica bovina (BSA). Neste caso, a agregação é dada principalmente por interações eletrostáticas, como observado em estudos experimentais que constataram a dependência da formação do complexo Hp-BSA com o pH e a força iônica da solução. Este estudo tem como objetivo investigar a interação entre os polieletrólitos e macromoléculas com distribuições de cargas heterogêneas, como proteínas, por meio de simulações de Metropolis Monte Carlo. A proteína foi representada como uma cavidade esférica com uma distribuição de carga arbitrária. O polieletrólito foi modelado por uma cadeia de esferas rígidas carregadas conectadas por um potencial harmônico. A solução eletrolítica foi representada implicitamente através da teoria de Debye-Hückel, onde a interação eletrostática entre os monômeros do polieletrólito é dada pelo potencial de Coulomb. A interação entre o polieletrólito e a proteína é calculada usando o modelo proposto por Kirkwood. Os efeitos da concentração de sal, distribuição de carga da proteína e comprimento de polieletrólito nas propriedades energéticas e conformacionais do polímero foram investigados. Analisando a dependência da energia de ligação média e o raio de giro com a força iônica, foi possível identificar transições descontínuas entre os estados ligados e não ligados do polímero.
It is known that several biological processes are mediated by interactions between polyelectrolytes and proteins, such as the interaction between histone proteins and DNA molecule in the nucleosome. Another important example is the aggregation of glycosaminoglycans (GAGs) into proteins, such as the complex formed by heparin (Hp) and bovine serum albumin (BSA). In this case, the aggregation is mainly given by electrostatic interactions as observed in experimental studies which contacted the dependence of the formation of the Hp-BSA complex with the pH and ionic strength of the solution. This study aims to investigate the interaction between the polyelectrolytes and macromolecules with heterogeneous charge distributions, like proteins, by means of Metropolis Monte Carlo simulations. The protein was represented as a spherical cavity with an arbitrary point-like charge distribution. The polyelectrolyte was modeled by a chain of charged hard spheres connected by a harmonic potential. The electrolyte solution was represented implicitly through the Debye-Hückel theory, where the electrostatic interaction among the monomers of the polyelectrolyte is given by the screened Coulomb potential. The interaction between the polyelectrolyte and the protein is calculated using the model proposed by Kirkwood. The effects of salt concentration, charge distribution of the protein and polyelectrolyte length on the energetic and conformational properties of the polymer were investigated. Analyzing the dependence of the mean binding energy and the radius of gyration with the ionic strength, it was possible to identify discontinuous transitions between bound and unbound states of polymer.
It is known that several biological processes are mediated by interactions between polyelectrolytes and proteins, such as the interaction between histone proteins and DNA molecule in the nucleosome. Another important example is the aggregation of glycosaminoglycans (GAGs) into proteins, such as the complex formed by heparin (Hp) and bovine serum albumin (BSA). In this case, the aggregation is mainly given by electrostatic interactions as observed in experimental studies which contacted the dependence of the formation of the Hp-BSA complex with the pH and ionic strength of the solution. This study aims to investigate the interaction between the polyelectrolytes and macromolecules with heterogeneous charge distributions, like proteins, by means of Metropolis Monte Carlo simulations. The protein was represented as a spherical cavity with an arbitrary point-like charge distribution. The polyelectrolyte was modeled by a chain of charged hard spheres connected by a harmonic potential. The electrolyte solution was represented implicitly through the Debye-Hückel theory, where the electrostatic interaction among the monomers of the polyelectrolyte is given by the screened Coulomb potential. The interaction between the polyelectrolyte and the protein is calculated using the model proposed by Kirkwood. The effects of salt concentration, charge distribution of the protein and polyelectrolyte length on the energetic and conformational properties of the polymer were investigated. Analyzing the dependence of the mean binding energy and the radius of gyration with the ionic strength, it was possible to identify discontinuous transitions between bound and unbound states of polymer.
Descrição
Palavras-chave
Polímeros, Interação eletrostática, Adsorção, Distribuição heterogênea de cargas, Polyelectrolytes, Electrostatic interaction, Adsorption, Heterogeneous charge distribution