Non-uniform distribution of myosin-mediated forces governs red blood cell membrane curvature through tension modulation
Fig 5
Heterogeneous forces in the RBC dimple and rim.
The applied force densities at the RBC dimple and rim regions regulate the shape error. (A, upper) Schematic of a biconcave RBC with a large force density (red arrows) at the dimple and a small force density (gray arrows) at the rim region. Schematic is overlaid on an RZ view of the center of an RBC from a confocal Z-stack of an RBC stained for the membrane marker glycophorin A. (A, lower) The applied force density along the membrane as a function of the arclength (Eq. S24 in S1 Text). (B) Heat map shows the calculated shape error (Eq 8) for a range of the force densities at the dimple (Fdimple) and rim (Frim) regions. We stopped the simulations when the height at the dimple tends to zero (hmin→ 0). The marked point X shows the case that has the lowest value of the error in the heat map at Fdimple = 4.05 pN/μm2 and Frim = 0.28 pN/μm2 (ϵtotal ~ 4.1%) with V = 85.61 μm3. A comparison between the parametric shape of an RBC (dotted blue line) and the shape obtained from the simulation at point X (dashed red line) is shown in the lower panel. (C) The shape error as a function of force density at the dimple (Fdimple) for five different values of the applied force density at the rim region. The dotted purple line shows a discontinuous transition in the shape error with increasing the dimple force density for Frim = 2 pN/μm2. Similar to Fig 4B, independent of the value of Frim, the total error is a nonmonotonic function of the dimple force density (Fdimple).