Estudo por simulação computacional da interação entre polianfóteros fracos e macroíons cilíndricos
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Data
2013-03-01
Autores
Caetano, Daniel Lucas Zago [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
Polianfóteros são cadeias poliméricas de monômeros que são caracterizadas pela presença tanto de grupos ácidos quanto de grupos básicos ao longo da sua cadeia. A interação entre polianfóteros e macroons carregados tem sido investigada por um grande número de estudos teóricos e experimentais. Este interesse e devido a sua importância em uma ampla variedade de sistemas biológicos e tecnológicos, tais como a estabilização/desestabilização de soluções coloidais, a associação entre DNA e prote nas histonas e o desenvolvimento de formas de terapia gênica não-viral pela associação DNA-polications. O propósito deste estudo é, portanto, investigar as propriedades conformacionais e o processo de adsor ção/dessorção de polianfóteros fracos sobre macroíons cilíndricos carregados negativamente por meio de simulações de Monte Carlo associadas ao algoritmo de Metropolis. O macroíon foi representado simplesmente por um cilindro infinito rígido, com uma densidade de carga uniforme sobre seu eixo. O polianf ótero foi representado por uma cadeia de Nesferas rígidas, conectadas por ligações harmônicas e a solu ção eletrolítica foi tratada pela teoria de Debye-Hückel. A fração de monômeros carregados é calculada tanto para a cadeia livre em solução quanto na presença do macroíon. As propriedades conformacionais da cadeia adsorvida, como por exemplo, raio de giro, número médio de monômeros em trains, em loops e em tails, em função da força iônica também são calculadas. Verifica-se que a presença de um macroíon carregado negativamente modi ca as propriedades acido/base do polianfótero fraco e que o efeito de regulação de carga afeta o processo de adsorção
Polyampholytes are polymer chains of monomers which are characterized by the pre-sence of both acid and basic groups along their chain. The adsorption of polyampholyte chains onto charged macroions has been the subject of a large number of theoretical and experimental studies. This interest is due to its importance in a wide variety of biological and technological systems, such as the stabilization and destabilization of colloidal solutions, the association of DNA with histone proteins and the development of forms of non-viral gene therapy by DNA-polycations interaction. This study aims, therefore, at investigating the conformational properties and the adsorption/desorption process of weak polyampholytes onto negatively charged rod-like macroion by means of Metropolis Monte Carlo simulations. The macroion was represented simply by an in nity rigid cylinder with uniform charge density on its axis. The polyampholyte was represented by a chain with Ncharged hard spheres connected by harmonic bonds, and the electrolyte solution was treated by the Debye-H uckel theory. The degree of ionization of the monomer is calculated both for the free chain in solution and for the adsorbed chain. The conformational properties of the adsorbed chain, such as radius of gyration, the average number of monomers in trains, in loops and in tails, in function of the ionic strength are also provided. It is found that the presence of one negatively charged macroion modi es the acid/base properties of the weak polyampholyte and that the e ect of charge regulation a ects the adsorption process
Polyampholytes are polymer chains of monomers which are characterized by the pre-sence of both acid and basic groups along their chain. The adsorption of polyampholyte chains onto charged macroions has been the subject of a large number of theoretical and experimental studies. This interest is due to its importance in a wide variety of biological and technological systems, such as the stabilization and destabilization of colloidal solutions, the association of DNA with histone proteins and the development of forms of non-viral gene therapy by DNA-polycations interaction. This study aims, therefore, at investigating the conformational properties and the adsorption/desorption process of weak polyampholytes onto negatively charged rod-like macroion by means of Metropolis Monte Carlo simulations. The macroion was represented simply by an in nity rigid cylinder with uniform charge density on its axis. The polyampholyte was represented by a chain with Ncharged hard spheres connected by harmonic bonds, and the electrolyte solution was treated by the Debye-H uckel theory. The degree of ionization of the monomer is calculated both for the free chain in solution and for the adsorbed chain. The conformational properties of the adsorbed chain, such as radius of gyration, the average number of monomers in trains, in loops and in tails, in function of the ionic strength are also provided. It is found that the presence of one negatively charged macroion modi es the acid/base properties of the weak polyampholyte and that the e ect of charge regulation a ects the adsorption process
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Palavras-chave
Biofísica, Biologia molecular, Metodo de Monte Carlo, Polimeros, Polieletrolitos, Biophysics
Como citar
CAETANO, Daniel Lucas Zago. Estudo por simulação computacional da interação entre polianfóteros fracos e macroíons cilíndricos: Daniel Lucas Zago Caetano. -. 2013. 92 f. Dissertação (mestrado) - Universidade Estadual Paulista Julio de Mesquita Filho. Instituto de Biociências, Letras e Ciências Exatas de São José do Rio Preto, 2013.