Dynamic frustrated charge hotspots created by charge density modulation sequester globular proteins into complex...

Area of Science:

• Biomaterials Science
• Supramolecular Chemistry
• Synthetic Biology

Background:

• Biological condensates form via scaffold-client interactions, crucial for cellular organization.
• Replicating these interactions in synthetic systems is key for understanding biological processes and creating artificial organelles.
• Existing synthetic scaffolds often lack the nuanced interactions found in natural systems.

Purpose of the Study:

• To develop a simple strategy for sequestering globular proteins into synthetic polypeptide-based complex coacervates.
• To recapitulate scaffold-client interactions found in biological condensates using synthetic materials.
• To investigate the tunability of coacervate properties through rational design.

Main Methods:

• Reduced linear charge density (σ) polyanions (polyethylene glycol-b-poly(aspartic acids)) were synthesized.
• Complex coacervates were formed using reduced-σ polyanions and homo-poly-l-lysine (polycation).
• Protein sequestration efficiency was measured, and interactions were probed using fluorescence recovery after photobleaching (FRAP).

Main Results:

• Complex coacervates efficiently sequestered various globular proteins (>80% encapsulation efficiency).
• Protein sequestration was primarily driven by electrostatic interactions, dependent on ionic strength and protein charge.
• Dynamic frustrated charges within the coacervates were identified as the origin of electrostatic interaction with proteins.
• FRAP measurements indicated that protein interaction alters coacervate dynamics, demonstrating tunable physical properties.

Conclusions:

• A rational design approach for scaffold-client interactions in synthetic coacervates was established.
• The synthetic coacervates effectively mimic biological condensate functions, serving as scaffolds for globular proteins.
• This work provides a foundation for developing artificial organelles and advancing basic life-science research.