Synchrotron SAXS data from solutions of Lys63-linked diubiquitin in 20mM HEPES, 150mM NaCl, pH 7.4 were collected on the BL19U2 beam line at the Shanghai Synchrotron Radiation Facilitystorage ring (SSRF: Shanghai, China) using a Pilatus 1M detector at a sample-detector distance of 2.1 m and at a wavelength of λ = 0.1033 nm (I(s) vs s, where s = 4πsin θ/λ and 2θ is the scattering angle). One solute concentration of 2.60 mg/ml (150 µM) was measured at 25°C. 20 successive 1 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.