Synchrotron SAXS data from solutions of P2X7 ballast domain in 20 mM HEPES pH 7.5, 150 mM NaCl, 5 mM CaCl2, 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). In-line size-exclusion chromatography (SEC) SAS was employed. The SEC parameters were as follows: A 35.00 μl sample at 8 mg/ml was injected at a 0.35 ml/min flow rate onto a GE Superdex 200 Increase 5/150 column at 10°C. 2880 successive 0.245 second frames were collected. The data were normalized to the intensity of the transmitted beam and radially averaged; the scattering of the solvent-blank was subtracted.