Synchrotron SAXS data from solutions of Immunoglobulin G1 in 100 mM glycine-HCl, pH 2 were collected on the BL-10C beam line at the Photon Factory (PF), High Energy Accelerator Research Organization (KEK; Tsukuba, Japan) using a Pilatus3 2M detector at a sample-detector distance of 2 m and at a wavelength of λ = 0.1 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 150.00 μl sample at 7 mg/ml was injected at a 0.05 ml/min flow rate onto a GE Superdex 200 10/300 column at 25°C. 64 successive 20 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.
Due to the weak scatterings at the low protein concentration and potential flow-cell fouling issues, undersubtraction of the background was seen for the preprocessing data. This was corrected by removing a small constant background from I(s), assuming that the scattering at higher-s obeys Porod’s law. This assumption holds when the scatterer is globular. The analytical ultracentrifugation indicates that this protein is globular.
s, nm-1
