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Deciphering the Role of π-Interactions in Polyelectrolyte Complexes Using Rationally Designed Peptides.
Sara Tabandeh1, Cristina Elisabeth Lemus2, Lorraine Leon1,3
1Department of Materials Science and Engineering, University of Central Florida, Orlando, FL 32816, USA.
Polymers
|July 2, 2021
Summary
Polypeptide sequences with π-interactions form stable complexes, not liquid condensates. Fluorine substitution disrupts these interactions, reducing stability and hydrogen bonding in these protein-mimetic structures.
Area of Science:
- Biochemistry
- Materials Science
- Polymer Chemistry
Background:
- Electrostatic and π-interactions are crucial for protein liquid-liquid phase separation and membraneless organelle formation.
- Peptide sequence patterning offers a method to create protein-like structures with controlled chemical properties and interactions.
Purpose of the Study:
- To investigate the role of π-interactions in the phase separation and secondary structure formation of polyelectrolyte complexes.
- To explore how charge density and fluorine substitution on phenylalanine affect these interactions and complex properties.
Main Methods:
- Design and synthesis of oppositely charged polypeptides incorporating phenylalanine, lysine, and glutamic acid.
- Characterization using MALDI-TOF mass spectroscopy, 1H NMR, and circular dichroism (CD).
- Analysis of secondary structures via FTIR spectroscopy and complex stability via critical salt concentration measurements. UV-vis spectroscopy was used for encapsulation studies.
Main Results:
- Polyelectrolyte complexes formed solid precipitates, not liquid condensates, indicating strong inter-sequence interactions.
- Secondary structures revealed hydrogen-bonded formations with a β-sheet signal.
- Fluorine substitution reduced hydrogen bonding by inhibiting π-interactions.
- π-interactions enhanced complex stability against salt, with higher critical salt concentrations observed for sequences with more phenylalanine residues.
- Sequences with π-interactions and increased charge density efficiently encapsulated small molecules with π-bonds.
Conclusions:
- The study highlights the complex interplay of ionic, hydrophobic, hydrogen bonding, and π-interactions in polyelectrolyte complex formation.
- Findings enhance the understanding of phase separation phenomena in protein-mimetic systems.
- π-interactions play a significant role in stabilizing polyelectrolyte complexes and influencing their structural properties.
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