Synchrotron SAXS data from solutions of RNA Xist A-repeats in 10 mM NaH2PO4/Na2HPO4, 100 mM NaCl, 0.02 mM EDTA, 0.02% azide, pH 6 (Duszczyk 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 1.56 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.