+Present address: Sviluppo Terapie Innovative, IRCCS AOU San Martino-IST, Genova, Italy.

1Supplementary material is available from the IUCr electronic archives (Reference: KK5149 ). Services for accessing this material are described at the back of the journal.

2The data presented here, as well as the BSA patterns, were recorded during a measuring session in 2010. Since then, the accumulation of material leading to the capillary fouling problem has been experimentally addressed. A cleaning device has been designed and installed on the SWING beamline (P. Roblin & J. Pérez, Synchrotron Soleil), so that the measuring cell goes through one or several cleaning cycles involving water flushing, detergent and again water flushing before elution buffer flows again through the cell at the end of each SE-HPLC-SAXS run. This and careful tuning of X-ray exposure time has significantly improved the situation, without completely eliminating capillary fouling in all cases. To date, fouling is not as serious an issue as shown here, and the I(t) versus t plot and baseline evaluation provides an objective assessment of data quality.