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Figure 2 | BMC Biophysics

Figure 2

From: Pulling chromatin apart: Unstacking or Unwrapping?

Figure 2

Model for the array stretching under pulling force. (A) Geometrical model of the array predicted from the two angle model for a NRL of 197 bp for different values of the αangle. For each of the five colors (blue, green, yellow, orange and red), the contacts between DNA and the histone core are different. A schematic representation of the location of those contacts (SHL) is presented in black. On each colored nucleosome, SHL are shown in black when there is a physical contact between DNA and the histones and in grey if this contact is disrupted. In blue, the interaction between DNA and the core histones is disrupted at SHL 6.5, 5.5 and 4.5 (resp. -6.5, -5.5 and -4.5). In green, the interaction between DNA and the core histones is disrupted at SHL 6.5 and 5.5 (respectively, -6.5 and -5.5). In yellow, the interaction between DNA and the core histones is disrupted at SHL 6.5 only (respectively, -6.5 ). In orange, no interaction in between DNA and the histones are disrupted. In the red conformation, the linker histone (represented as a black dot) interacts with the entry and exit DNA linker so that the negative crossing is stabilized. (B) Summary of the experimental results presented in Kruithof et al.[3]. The extension of the array is plotted as a function of the pulling force. The red curve corresponds to the H5 containing array. The orange/yellow/green curve corresponds to the array without LH, in the presence of Mg2+. The green/blue curves show the hysteretic behaviour obtained without LH when magnesium has been depleted. The black arrows indicate the curve obtained while increasing (respectively, decreasing) the applied force.

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