Application of fluorescence imaged microdeformation (FIMD) to murine erythrocytes. (A) Erythrocyte with fluorescently labeled lipid bilayer is aspirated by a micropipette (upper panel). For scale reference, the diameter of the micropipette is 1.5 μm. The lipid bilayer exhibited a uniform density profile along the deformation projection, indicating its fluidity (lower panel). ρe and ρc are defined as the densities at the pipette entrance and at the cap of the projection, respectively. (B) ρe/ρc is plotted against the dimensionless projection length, L/Rp for the FIMD of F-actin and the lipid bilayer of mouse red cells. L is the projection length and Rp is the radius of the pipette. Data were fitted by straight lines with a y-intercept = 1. γ is defined as the slope of the FIMD analysis and indicates the degree of cytoskeletal association. As γ of a protein approaches γ of F-actin, a greater degree of cytoskeletal association is indicated. (C) Histogram showing the γ of lipid bilayer and cytoskeletal F-actin.
