Polymer conformational entropy as the driver of complex coacervation

Area of Science:

• Biomolecular Sciences
• Polymer Physics
• Biophysics

Background:

• Complex coacervation is a fundamental process in biomolecular systems.
• Understanding its driving mechanisms remains a challenge.
• Archetypal systems offer insights into general principles.

Purpose of the Study:

• Investigate the condensation transition and pretransitional behavior of polyuridylic acid (PolyU) and cationic peptides.
• Determine the role of peptide-PolyU interactions in driving coacervation.
• Develop a model to explain the observed phase behavior.

Main Methods:

• Static and dynamic light scattering
• Confocal microscopy
• Phenomenological modeling

Main Results:

• Peptide addition reduces PolyU coil size via intrachain bonds in the dilute phase.
• Sticky-reptation kinetics in the dense phase indicate interchain bonding.
• Loss of PolyU conformational entropy is identified as the main driver of condensation.
• The phenomenological model accurately predicts molecular partitioning between phases.

Conclusions:

• Peptide-induced conformational constraints on PolyU are crucial for complex coacervation.
• The loss of conformational entropy is a key thermodynamic driver.
• Coil conformational relaxation may be a general principle in complex coacervation.