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. 2013 Nov 30;42(4):2624–2636. doi: 10.1093/nar/gkt1231

Figure 4.

Figure 4.

(A), (B) AFM imaging of SpoIIIE–DNA complexes on circular DNA. Orange arrow indicates free SpoIIIE and green arrows indicate SpoIIIE bound to DNA. (C) Cross-section values of height and length of a representative DNA (grey line), free SpoIIIE (orange solid line) and DNA-bound SpoIIIE complexes (green solid line). (D), (E) Lateral distribution of sizes of free and DNA-bound SpoIIIE complexes in two directions. A Gaussian distribution was fitted to the experimental height data measured in the two normal directions (parallel and perpendicular to DNA in DNA-bound complexes and x-y for unbound complexes) and the FWHM of the height profile was computed to estimate the diameter of free and DNA-bound hexamers. The mean FWHM (in x and y directions) were (nm): 14.70 ± 1.13 and 14.56 ± 1.06 for free SpoIIIE particles and 15.47 ± 1.05 and 15.08 ± 1.47 for DNA-bound SpoIIIE. Mean FWHM (in both directions combined) were (nm): 14.63 ± 1.07 nm for free SpoIIIE and 15.27 ± 1.27 for DNA-bound particles. These reported values were employed to test statistically the differences between the mean lateral sizes of free and DNA-bound SpoIIIE described in the main text [Equation (4), ‘Materials and Methods’ section].