(a) Time dependence of X-ray reflectivity profiles. The data were divided by the Fresnel reflectivity of the air/buffer interface. The continuous lines are the fit to the data. The triangles and circles are the data measured by the angle-scan reflectometer at SPring-8 before and 7–152 s after LSZ injection, respectively. The dashed gray curve represents the simulated profile of native LSZ whose electron density profile is shown in (b). (b) Electron density profiles corresponding to the fits to the data. The dashed lines are those for 7–152 s after protein injection measured by the angle-scan reflectometer. The gray area represents the simulated profile of native LSZ with a side-on orientation (Tiemeyer et al., 2010).