Figure 3
DREEM imaging reveals DNA wrapping around nucleosomes purified from HeLa Cells.
(a–c) Topographic AFM images (left), DREEM phase (middle) and models (right) of nucleosomes purified from HeLa cells. In DREEM phase images, proteins and DNA show negative signals relative to the mica surface, with the proteins producing greater contrast (darker regions). The XY scale bars are at 10 nm. (d) The difference in DREEM phase signals from DNA bound by histones and DNA alone reveals signal transitions from DNA to histones. Left: a contour map of the nucleosome shown in (c). Right panel: Statistical analysis of the DNA DREEM phase signal difference (DNA bound – DNA alone, N = 30) for individual nucleosome complexes. Each bar represents the difference between DREEM phase signals from DNA bound by histone proteins and DNA alone in the same images. The DREEM signals from DNA were obtained by drawing a line over a segment of DNA. The error bars represent standard deviations of DNA signals. The error bars represent standard deviations of the measurement.
