Radiation Damage in Macromolecular Crystallography—An Experimentalist’s View

Helena Taberman

doi:10.3390/cryst8040157

Abstract

Radiation damage still remains a major limitation and challenge in macromolecular X-ray crystallography. Some of the high-intensity radiation used for diffraction data collection experiments is absorbed by the crystals, generating free radicals. These give rise to radiation damage even at cryotemperatures (~100 K), which can lead to incorrect biological conclusions being drawn from the resulting structure, or even prevent structure solution entirely. Investigation of mitigation strategies and the effects caused by radiation damage has been extensive over the past fifteen years. Here, recent understanding of the physical and chemical phenomena of radiation damage is described, along with the global effects inflicted on the collected data and the specific effects observed in the solved structure. Furthermore, this review aims to summarise the progress made in radiation damage studies in macromolecular crystallography from the experimentalist’s point of view and to give an introduction to the current literature.

Highlights

Macromolecular crystallography (MX) has been the most employed technique to solve three-dimensional structures of proteins at atomic resolution to date
Free radicals are generated when X-rays are absorbed by macromolecular crystals
Radiation damage continues to be an intrinsic part of X-ray crystallography, but owing to continuous systematic research, significant progress has been made in our knowledge and understanding of it in MX

Summary

Introduction

Macromolecular crystallography (MX) has been the most employed technique to solve three-dimensional structures of proteins at atomic resolution to date. Global radiation damage is observed as a loss of diffraction intensity, with the weakest higher resolution reflections fading first, an increase in unit-cell volume, and higher Wilson B-factors, all due to the overall increase in non-isomorphism in the crystal [2,3,4]. These effects can preclude structure solution by, for example, causing both deterioration in the quality of the resulting electron density and incompleteness of the data. Is a summary of some of the ongoing efforts over the past 15 years to establish strategies for reducing the occurrence and manifestation of radiation damage from the bird’s-eye view of an experimental structural biologist

Crystallisation

Cryocrystallography

Mechanisms of Radiation Damage

Data Collection Methods

Data Collection Parameters

Structure Solution and Interpretation

Findings

Conclusions