Effective scavenging at cryotemperatures: further increasing the dose tolerance of protein crystals

J. Synchrotron Rad. (2011). 18, 346-357 (doi.org/10.1107/S0909049511007163)

Electron density maps of the Cys6–Cys127 bond in lysozyme after doses of 2.3 MGy, 12.3 MGy and 22.3 MGy, showing a nearby bound ordered nitrate ion being reduced to NO₂ and then NO by X-ray induced electrons, and thus affording protection to the neighbouring disulfide bond.

Certain radical scavengers can reduce the rate of X-ray induced radiation damage to macromolecular crystals during both room temperature and cryotemperature (100 K) data collection. In HEWL crystals held at 100 K, sodium nitrate, an electron scavenger, was found to double the dose (Gy = J kg⁻¹) tolerance as judged from the rate of total diffraction intensity loss, and increase it by over 5 times when considering structural damage to the disulfide bonds. The sequential electron density maps show the radiation chemistry mechanism at work.