README for Figure 3B

*** This file contains the raw data obtained from tethered particle motion experiments shown in Figure 3B of:
Article: Modulation of archaean hypernucleosome structure and stability by Mg2+
Authors: Ilias Zarguit, Marc K. M. Cajili, Bert van Erp, Samuel Schwab, Nico van der Vis, Marianne Bakker, John van Noort, and Remus T. Dame
Corresponding author: rtdame@chem.leidenuniv.nl

Legend Figure 3: Mg2+ promotes archaeal hypernucleosome formation. A) Titration experiments with increasing MgCl2 at concentrations of 5 nM HTkA and 0.5 nM HTkB reveal an Mg2+ concentration-dependent increase of archaeal nucleosome formation. B) Mg2+ titration experiments with 5 nM HTkA in which the K+ concentration was reduced to adjust for the addition of Mg2+, maintaining a constant ionic strength throughout the Mg2+ titration C) To further elucidate the effect of the ionic strength, a titration in 5 nM HTkA was conducted in the absence of Mg²⁺ while increasing K⁺ concentration to achieve the same ionic strength (blue line). These results show that the compaction can be attributed directly to Mg²⁺ rather than to changes in ionic strength. Each measurement (N ≥ 100) was performed in duplicates, with the error bars representing the error propagated standard deviation. Dashed lines are added to guide the eye.

*** The data were obtained using tethered particle motion as described in the associated article. 

*** Each individual sheet contains data obtained for each concentration of Mg2+ (as indicated in the sheet name), with decreasing amount of K+ to compensate for the change in ionic strength. The sheet "Averaged Values" contains the average plotted in Figure 3B.  
Each sheet contains data from individual tethered DNA molecules or protein-DNA complexes, with each row corresponding to one bead/tether.

Column A: Root mean square = RMS in nm
Column B: Anisotropy = Anisotropic ratio (movement in x-direction/movement in y-direction)
Column C: Stdev = Standard deviation
Column G: Fit parameters = The mean and standard deviation values obtained from fitting a normal distribution to the root mean square values (column A)

The values given in column B and C are tether quality criteria and used for data filtering as described in the associated article.
Histograms showing the distribution of the root mean square values are shown together with the fit and a kernel density estimator.
