Radiation damage is a serious problem for most of BioSAXS studies. It may happen 8 in 10 studied samples. An accumulation of aggregates (through formation of radicals) interferes with the small-angle region of protein scattering curves due to the high intense X-ray beam of the ESRF.

 However, some solutions exist to avoid or reduce radiation damages.

  • more evident and simplest action is to reduce beam intensity by decreasing transmission (from 100%) to for example 30%, or decrease time per frame (from 2s to 0.5s for example);
  • other approche is to add some free radical scavengers as EDTA, DTT or cryoprotectants such as glycerol, PEG or some sugars (e.g, glucose) providing that a given protein is behaving well once added

For samples which support well reducing agents and/or cryoprotectants, it is recommended to add after concentration measurement into a final concentration about 1- 2 % of cryoprotectant or about 2 mM of reducing agents (1M DTT stock aliquots can be found in the –20°C lower drawer).