Figure 5. The glycocalyx exhibits a nanoscale architecture with sugar residues exhibiting a maximal density some distance away from the membrane.

(A) Nine representative localization distributions from single 90×30 nm windows along a single wall of GalNAz (G) or Sia (S)-labeled tubules. Top row depicts examples of exponential- or half-Gaussian-like distributions, middle row depicts Gaussian-like distributions, and bottom row depicts uniform-like distributions. (B) Schematic of analysis workflow for comparing possible ground truth sugar distributions with experimental localizations. (C) R² values from QQ analysis shown binned as violin plots. Each of the twelve columns represents a comparison of two distributions (see x-axis labels). Analysis of GalNAz-labeled tubules is shown on top, and analysis of Sia-labeled tubules is shown on bottom. P-values are derived from t-tests of the means and standard deviations of the violin plots shown. Error bars: SEM; * = p < 0.05; *** = p < 0.0005. (D) Quantification of glycocalyx microheterogeneity along a single tubule wall. Values close to zero for R²_{ideal, exp} minus R²_{ideal, realistic} indicate good agreement between the experimental localization distribution and the simulated distribution to which it was compared. Arrowheads indicate example positions where the experimental data has a non-Gaussian sugar distribution.