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Global radiation damage: temperature dependence, time dependence and how to outrun it.

ABSTRACT: A series of studies that provide a consistent and illuminating picture of global radiation damage to protein crystals, especially at temperatures above ∼200 K, are described. The radiation sensitivity shows a transition near 200 K, above which it appears to be limited by solvent-coupled diffusive processes. Consistent with this interpretation, a component of global damage proceeds on timescales of several minutes at 180 K, decreasing to seconds near room temperature. As a result, data collection times of order 1 s allow up to half of global damage to be outrun at 260 K. Much larger damage reductions near room temperature should be feasible using larger dose rates delivered using microfocused beams, enabling a significant expansion of structural studies of proteins under more nearly native conditions.

SUBMITTER: Warkentin M

PROVIDER: S-EPMC3526918 | biostudies-literature | 2013 Jan

REPOSITORIES: biostudies-literature

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Global radiation damage: temperature dependence, time dependence and how to outrun it.

Warkentin Matthew M Hopkins Jesse B JB Badeau Ryan R Mulichak Anne M AM Keefe Lisa J LJ Thorne Robert E RE

Journal of synchrotron radiation 20121129 Pt 1

A series of studies that provide a consistent and illuminating picture of global radiation damage to protein crystals, especially at temperatures above ∼200 K, are described. The radiation sensitivity shows a transition near 200 K, above which it appears to be limited by solvent-coupled diffusive processes. Consistent with this interpretation, a component of global damage proceeds on timescales of several minutes at 180 K, decreasing to seconds near room temperature. As a result, data collection ...[more]

PMID: 23254651

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Project description:The local Fourier-space relation between diffracted intensity I, diffraction wavevector q and dose D, , is key to probing and understanding radiation damage by X-rays and energetic particles in both diffraction and imaging experiments. The models used in protein crystallography for the last 50 years provide good fits to experimental I(q) versus nominal dose data, but have unclear physical significance. More recently, a fit to diffraction and imaging experiments suggested that the maximum tolerable dose varies as q -1 or linearly with resolution. Here, it is shown that crystallographic data have been strongly perturbed by the effects of spatially nonuniform crystal irradiation and diffraction during data collection. Reanalysis shows that these data are consistent with a purely exponential local dose dependence, = I 0(q)exp[-D/D e(q)], where D e(q) ? q ? with ? ? 1.7. A physics-based model for radiation damage, in which damage events occurring at random locations within a sample each cause energy deposition and blurring of the electron density within a small volume, predicts this exponential variation with dose for all q values and a decay exponent ? ? 2 in two and three dimensions, roughly consistent with both diffraction and imaging experiments over more than two orders of magnitude in resolution. The B-factor model used to account for radiation damage in crystallographic scaling programs is consistent with ? = 2, but may not accurately capture the dose dependencies of structure factors under typical nonuniform illumination conditions. The strong q dependence of radiation-induced diffraction decays implies that the previously proposed 20-30?MGy dose limit for protein crystallography should be replaced by a resolution-dependent dose limit that, for atomic resolution data sets, will be much smaller. The results suggest that the physics underlying basic experimental trends in radiation damage at T ? 100?K is straightforward and universal. Deviations of the local I(q, D) from strictly exponential behavior may provide mechanistic insights, especially into the radiation-damage processes responsible for the greatly increased radiation sensitivity observed at T ? 300?K.

Dataset Information

Global radiation damage: temperature dependence, time dependence and how to outrun it.

Publications

Global radiation damage: temperature dependence, time dependence and how to outrun it.

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