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The Role of Charge Regulation in Weak Polyampholytes
Lunkad, Raju ; Košovan, Peter (advisor) ; de Sousa Dias, Rita (referee) ; Gonzalez, Jose Luis Garces (referee)
A weak polyampholyte is a polymer that consists of both acid and base groups along the chain. In aqueous solutions, these groups dissociate in a certain pH range, leading to a dramatic change in the overall charge of the polyampholyte from positive to negative as the pH increases. The ability of weak ampholytes to switch their charge in response to changes in pH makes them useful in various applications. Despite the considerable research on weak polyampholytes, the understanding of some aspects is still insufficient. To address this, I systematically investigated the charge regulation of weak polyam- pholytes, specifically peptides, both in solution and during their interaction with polyelectrolytes. Furthermore, I also looked at the charge regulation of polyzwitterions. All these studies were carried out using a simple coarse-grained bead-spring model in Langevin dynamics simulations. In addition, I used the constant-pH ensemble to account for the ionization reactions of acid and base groups in the implicit solvent. Through our simulations, we made significant advancements in understanding how charges and the ionization states of acid and base groups in various peptides and polyzwitterions respond to pH changes. By comparing simulation results with the ideal results predicted by the...
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