Extended Data Figure 10. Membrane flickering spectroscopy amplitude analysis.

(a) To justify our choice of modes for fitting Eq. S4, we calculated the residuals of mean square fluctuation amplitudes at different ranges of modes for the same RBC. The figure shows that the residues derived from fitting modes above 20 increase steadily, suggesting a systematic error in fitting modes above 20. Our range of modes (8-20) seems the most convincing range, as well as range 5-20, with no systematic deviations.

By studying the dynamics of modes it is possible to extract the viscosity of the cell interior, and this analysis can be used as further proof of the method. From the timescale of decorrelation of mode amplitudes, it is possible to obtain the viscosity of the RBC interior, using the values of tension and bending modulus obtained from the static spectrum of the same cell. This is achieved by fitting the relaxation time with Eq. S7. The viscosity is statistically the same, across the non-Dantu and Dantu groups which have statistically different tension values. This is thus a further independent check confirming the static study is measuring tension values reliably. (b) The viscosities of RBCs with extreme low and high tension are not significantly different (p value=0.14, two-sided Mann-Whitney U test). The fit in the inset shows data from one of the RBCs in the sample. (c) The relaxation times, plotted vs q_x, modes 5-11, are represented for both the low- and high-tension RBCs; the trend is 1/q consistent with the limiting behaviour of Eq. S7 for $\left(\sigma \gg \kappa q_x^2\right)$. The range of modes that can be studied dynamically is limited by the camera acquisition rate, as well as by the other factors that limit also the static analysis.