Theory of pattern and pH effects in complex coacervation

Knoerdel, Ashley R

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https://hdl.handle.net/2142/121402 Copy

Description

Title

Theory of pattern and pH effects in complex coacervation

Author(s)

Knoerdel, Ashley R

Issue Date

2023-05-30

Director of Research (if dissertation) or Advisor (if thesis)

Sing, Charles E

Doctoral Committee Chair(s)

Sing, Charles E

Committee Member(s)

• Statt, Antonia
• Gruebele, Martin
• Pogorelov, Taras

Department of Study

School of Molecular & Cell Bio

Discipline

Biophysics & Quant Biology

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• pH
• sequence effects
• complex coacervation
• hydrophobicity

Abstract

Oppositely-charged polyelectrolytes can undergo an associative phase separation in a process known as polymeric complex coacervation. This phenomenon is driven by the electrostatic attraction between polyanion and polycation species, leading to the formation of a polymer-dense coacervate phase and a coexisting polymerdilute supernatant phase. This phase separation can be influenced by chemical and physical molecular features such as hydrophobicity, charge density, and polyelectrolyte lengths. Lately, there has been intense interest in tuning this phase behavior using chemical and molecular features. A large amount of theoretical modeling of complex coacervation has been performed such as the Voorn-Overbeek theory, random phase approximation, polymer field theory, and the transfer matrix theory. These theories have given many physical insights into coacervation, but most of these approaches are applicable to polymers with low charge density instead of high charge density. My work has led to the expansion of the transfer matrix theory to develop a transfer matrix that works well in the low and high charge regimes as well as describing the affect molecular features have on complex coacervation. This approach maps the complicated three-dimension system to a one-dimension adsorption model, and solves for the adsorption model partition function using a transfer matrix approach. We show that there is good qualitative matching with our theoretical expansion with previously developed simulations of bulk phase separation. We also capture the effects of weak polyelectrolytes, hydrophobicity, chain length asymmetry, and patterned polyelectrolytes on phase separation using this approach. Results suggest that the formation of the coacervate phase is highly sensitive to local electrostatics and system environment. My expansion of the transfer matrix approach is able to capture a wide range of charge densities, sequence effects, chain length asymmetry, and is no longer limited to strong polyelectrolytes. This work provides the necessary building blocks to begin building a single theory capable of describing a sequenced polyelectrolyte system with a dependence on pH, hydrophobicity, and chain length asymmetry. An example of such a system is intrinsically disordered proteins that are able to phase separate inside of the cell to form membraneless compartments. My work has led to the expansion of the transfer matrix theory to develop a transfer matrix that works well in the low and high charge regimes as well as describing the affect molecular features have on complex coacervation. This approach maps the complicated three-dimension system to a one-dimension adsorption model, and solves for the adsorption model partition function using a transfer matrix approach. We show that there is good qualitative matching with our theoretical expansion with previously developed simulations of bulk phase separation. We also capture the effects of weak polyelectrolytes, hydrophobicity, chain length asymmetry, and patterned polyelectrolytes on phase separation using this approach. Results suggest that the formation of the coacervate phase is highly sensitive to local electrostatics and system environment. My expansion of the transfer matrix approach is able to capture a wide range of charge densities, sequence effects, chain length asymmetry, and is no longer limited to strong polyelectrolytes. This work provides the necessary building blocks to begin building a single theory capable of describing a sequenced polyelectrolyte system with a dependence on pH, hydrophobicity, and chain length asymmetry. An example of such a system is intrinsically disordered proteins that are able to phase separate inside of the cell to form membraneless compartments.

Graduation Semester

2023-08

Type of Resource

Thesis

Copyright and License Information

Copyright 2023 Ashley Knoerdel

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