Spectral analysis of erythrocyte flickering in the 0.3–4-μ${\mathrm{m}}^{\mathrm{-}1}$ regime by microinterferometry combined with fast image processing

Reflection interference microscopy in combination with real-time image processing was applied to determine the spatial spectrum of the mean-square amplitude of erythrocyte flickering in the wave-vector regime 0.3≤q≤4 μ${\mathrm{m}}^{\mathrm{-}1}$. The mean-square amplitude scales as ${\mathit{q}}^{4\pm \mathrm{\epsilon }}$ for q≥0.7 μ${\mathrm{m}}^{\mathrm{-}1}$, suggesting that flickering is dominated mainly by bending stiffness. We measured a bending modulus of ${\mathit{K}}_{\mathit{c}}$=(2±0.5)×${10}^{\mathrm{-}20}$ N m as compared to ${\mathit{K}}_{\mathit{c}}$=(5±1.5)×${10}^{\mathrm{-}20}$ N m found for dimyristoylphosphatidylcholine (DMPC) vesicles with the same technique.