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  4. A Monte Carlo Study of Weak Polyampholytes:  Stiffness and Primary Structure Influences on Titration Curves and Chain Conformations
 
research article

A Monte Carlo Study of Weak Polyampholytes:  Stiffness and Primary Structure Influences on Titration Curves and Chain Conformations

Ulrich, Serge
•
Seijo, Marianne  
•
Stoll, Serge
2007
The Journal of Physical Chemistry B

The conformation and titrn. curves of weak polyampholytes are examd. using Monte Carlo simulations with screened Coulomb potentials in the Grand Canonical ensemble. Two different types of monomers are considered. Depending on the soln. pH, monomers A are weak acidic sites that can either be neg. charged or uncharged (as carboxylic groups), whereas monomers B are weak basic sites that can either be pos. charged or uncharged (as amino groups). The influence of the chain stiffness, primary structure, and ionic concn. on the acid/base properties of the polyampholyte chains are systematically investigated. By adjusting the pH values, titrn. curves and then the fractions of pos. and neg. ionized charged monomers are calcd. Stiffness influence is estd. by comparing two models of chain: a fully flexible and a rod-like polyampholyte. Different primary structures such as statistical (diblock, octablock, and alternating) and random polyampholytes are also considered. We demonstrate that the primary structure plays important roles in the acid/base properties as well as the charge distribution along the polymer backbone of a statistical rod-like polyampholyte. When flexible polyampholytes are considered, polyampholyte conformations promote the attractive electrostatic interactions between pos. and neg. charged monomers, hence leading to more or less compact conformations and acid/base properties relatively different in comparison to the rod-like polyampholytes. Various conformations such as extended, globular, and pearl-necklace conformations are found in good agreement with the literature by adjusting the interaction parameter between monomers and monomer stoichiometry.

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Type
research article
DOI
10.1021/jp0688658
Author(s)
Ulrich, Serge
Seijo, Marianne  
Stoll, Serge
Date Issued

2007

Published in
The Journal of Physical Chemistry B
Volume

111

Issue

29

Start page

8459

End page

8467

Subjects

Monte Carlo simulation

•

stiffness

•

primary structure

•

titration curves

•

weak polyampholytes

•

amphoteric

Editorial or Peer reviewed

REVIEWED

Written at

OTHER

EPFL units
ISIC  
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/63336
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