Figure 3
Quantifying domain size and chromatin packing behavior at the domain boundaries. Chromatin packing domains are structurally heterogeneous and anisotropic. (A) ChromSTEM grayscale tomogram for one field of view of an A549 cell. The color bar represents chromatin mass density. (B, C) Local chromatin maxima map estimated from enhanced chromatin density projection shown in (B) was utilized to find chromatin domain centers shown in (C). (D) 3D rendering of the surface of chromatin density in a region containing the packing domain of interest (orange square in C). (E) The average 2D mass scaling curve of the chromatin domain within the region of interest (orange square in C). For one domain, the mass scaling curve is resampled from all loci within the domain center identified in (C). The mass scaling analysis is conducted starting from the domain center. The MS curve starts with D < 3 (blue dashed line) and transitions to values closer to D = 3 beyond the potential domain boundary (red asterisk at 110 nm). (F) Radial distribution of chromatin density or radial CVC for the same domain. The radial CVC initially decreases slowly within the domain regime. As the length scale approaches the potential domain boundary (red asterisk at 130 nm), the radial CVC rapidly dips which is followed by a recovery, due to the presence of other domains at those length scales. (G) The distribution of Rf, the radius of packing domains, for A549 cells. The mean Rf is 80.6 nm, and the median along with the lower and upper quartile is 74 (58–93) nm.
