Normal red blood cells' shape stabilized by membrane's in-plane ordering.

Area of Science:

• Biophysics
• Cell Biology
• Materials Science

Background:

• Red blood cells (RBCs) are vital for oxygen transport, with their discocyte shape optimizing flow.
• Existing models predict a narrow stability range for discocyte shapes, contradicting experimental observations.

Purpose of the Study:

• To reconcile the discrepancy between theoretical predictions and experimental data on red blood cell discocyte shape stability.
• To investigate the role of membrane in-plane ordering in stabilizing RBC shapes.

Main Methods:

• Utilized a hybrid Helfrich-Landau mesoscopic approach to model RBC structures.
• Incorporated in-plane ordering effects into theoretical membrane-shape models.

Main Results:

• Demonstrated that considering membrane in-plane ordering broadens the stability window for RBC discocyte shapes.
• Identified an extrinsic curvature free energy term as a key stabilizer of discocyte shapes.
• Showed that extrinsic curvature's stabilizing effect is significantly enhanced near the nematic order-disorder phase transition.

Conclusions:

• The study provides a theoretical framework that explains the experimentally observed broad range of stable red blood cell discocyte shapes.
• In-plane membrane ordering and extrinsic curvature are critical factors in RBC shape determination and stability.