Revealing low-dose radiation damage using single-crystal spectroscopy

Abstract

The structural information and functional insight obtained from X-ray crystallography can be enhanced by the use of complementary spectroscopies. Here the information that can be obtained from spectroscopic methods commonly used in conjunction with X-ray crystallography and best-practice single-crystal UV-Vis absorption data collection are briefly reviewed. Using data collected with the in situ system at the Swiss Light Source, the time and dose scales of low-dose X-ray-induced radiation damage and solvated electron generation in metalloproteins at 100 K are investigated. The effect of dose rate on these scales is also discussed.

Kinetic Modeling of the X-ray-Induced Damage to a Metalloprotein

“…Note the rates we compare range from 126 kGy/s (monochromatic) to 4,500 kGy/s (pink beam, during the pulse), much higher than those considered earlier. 17 We consider three typical rates: monochromatic beam, characteristic of ID beamlines at a 3 rd generation synchrotron source; pink beam, produced at ID beamlines without the use of a monochromator; and an x-ray free electron laser beam, such as the one generated at LCLS. Experimentally, we observed greater than ~6.7×10 6 photons/µm 2 to ~1.1×10 7 photons/µm 2 (corresponding to 7.6×10 3 Gy to 1.3×10 4 Gy, note that this was calculated using the full sample thickness at an energy of 7.1keV) as the dosage limit for 5% damage from ~1mm of sample (monochromatic beam), 5 while the model calculations for such a thickness indicate a dosage threshold at ~2.5×10 6 photons/µm 2 (corresponding to 2.8×10 3 Gy, given the same parameters).…”

Recent structural insights into the function of copper nitrite reductases

“…27 Various online spectroscopic techniques have been developed to monitor the redox state of metals in crystals. [80][81][82] Strategies to mitigate such reduction include merging of composite, low dose partial datasets 83 or helical data collection approaches. 84 Use of rapid X-ray detectors and cryogenic temperatures -typically 100 K -minimises but does not eliminate the effects of photoreduction or radiation damage to crystals.…”

Outrunning free radicals in room-temperature macromolecular crystallography

“…At 100 K aqueous electrons can move through the unit cell and rapidly react, with the result that their spectroscopic signature rapidly reaches a maximum (at $45 kGy; Owen et al, 2011) and then decays (Fig. 4).…”