Synchrotron SAXS data from solutions of a semi-synthetic nucleosome core particle (NCP) in 15 mM HEPES, 200 mM NaCl, pH 7.3 were collected using size-exclusion chromatography SAXS (SEC-SAXS) on the BM29 beam line at the ESRF (Grenoble, France) using a Pilatus 1M detector at a sample-detector distance of 2.9 m and at a wavelength of λ = 0.1 nm (l(s) vs s, where s = 4πsinθ/λ, and 2θ is the scattering angle). SEC-SAXS was performed at 20 °C using the following parameters: Column: Wyatt WTC-030N5; Flow rate: 0.25 mL/min; Sample injection concentration: 2.5 mg/mL; Injection volume: 50 μL. The data were collected through the SEC peak of the sample as a series of 243 x 1 second exposures. Each unsubtracted data frame was normalised to the intensity of the transmitted beam and radially averaged and the scattering of an appropriate solvent-blank was subtracted. The resulting subtracted frames were scaled and averaged to generate the final SAXS profile displayed in this entry.