Synchrotron SAXS data from solutions RNA Xist A-repeats in 25 mM K-HEPES, 0.1 mM Na-EDTA, 150 mM KCl, 15 mM MgCl2, pH 7 (Liu buffer) were collected on the EMBL P12 beam line at PETRA III (DESY, Hamburg, Germany) using a Pilatus 6M detector at a sample-detector distance of 3 m and at a wavelength of λ = 0.124 nm (I(s) vs s, where s = 4πsinθ/λ, and 2θ is the scattering angle). One solute concentration of 1.37 mg/ml was measured at 25°C. One 0.145 second frame was collected. The data were normalized to the intensity of the transmitted beam and radially averaged; the scattering of the solvent-blank was subtracted.