Synchrotron SAXS data from solutions of calmodulin in 50 mM HEPES, 100 mM NaCl, 2 mM CaCl2, 1 mM TCEP, pH 7.4 were collected on the 12.3.1 (SIBYLS) beam line at the Advanced Light Source (ALS; Berkeley, CA, USA) using a Pilatus3 X 2M detector at a sample-detector distance of 1.5 m and at a wavelength of λ = 0.103 nm (I(s) vs s, where s = 4πsinθ/λ, and 2θ is the scattering angle). One solute concentration of 8.00 mg/ml was measured at 25°C. 800 successive 3 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.