X-ray radiation damage to biological samples: recent progress

Abstract

With the continuing development of beamlines for macromolecular crystallography (MX) over the last few years providing ever higher X‐ray flux densities, it has become even more important to be aware of the effects of radiation damage on the resulting structures. Nine papers in this issue cover a range of aspects related to the physics and chemistry of the manifestations of this damage, as observed in both MX and small‐angle X‐ray scattering (SAXS) on crystals, solutions and tissue samples. The reports include measurements of the heating caused by X‐ray irradiation in ruby microcrystals, low‐dose experiments examining damage rates as a function of incident X‐ray energy up to 30 keV on a metallo‐enzyme using a CdTe detector of high quantum efficiency as well as a theoretical analysis of the gains predicted in diffraction efficiency using these detectors, a SAXS examination of low‐dose radiation exposure effects on the dissociation of a protein complex related to human health, theoretical calculations describing radiation chemistry pathways which aim to explain the specific structural damage widely observed in proteins, investigation of radiation‐induced damage effects in a DNA crystal, a case study on a metallo‐enzyme where structural movements thought to be mechanism related might actually be radiation‐damage‐induced changes, and finally a review describing what X‐ray radiation‐induced cysteine modifications can teach us about protein dynamics and catalysis. These papers, along with some other relevant literature published since the last Journal of Synchrotron Radiation Radiation Damage special issue in 2017, are briefly summarized below.

Probing Trace Elements in Human Tissues with Synchrotron Radiation

“…First, it is important to note that the absorbed doses in SR-based studies of biological samples are extreme. Although radiation-induced damage can occur at doses of just a few grays (1 Gy = 1 J of absorbed radiation energy per 1 kg of absorbing tissue mass), the X-ray exposures in synchrotron-based studies reach the MGy (10 6 Gy) unit scale and higher [41,42]. By comparison, radiation doses from exposures to X-rays or gamma-rays in clinical procedures are below 1 Gy and are measured in units of cGy (10 −2 Gy) in external-beam radiation therapy, and in units of mGy (10 −3 Gy) in conventional diagnostic X-ray imaging and nuclear medicine procedures [43].…”

“…Radiobiology, the study of the interactions of radiation with living systems and the basis of modern radiation treatments of cancer, along with space science and technology, are perhaps the most known applications of this branch of chemistry. A detailed account of photo-reduction reactions in biological XAS studies can be found in the review by George et al [44], while Garman and Weik [42] highlighted some recent research work on assessing radiation damage and mechanisms in DNA, amino acids, and proteins.…”

Image Mosaic Algorithm-Based Analysis of Effects of Low-Dose X-Rays on Blood Immune Cells

“…X-ray projection technology has the characteristics of wide projection surface and convenient operation. It is one of the commonly used imaging diagnostic techniques in medicine [7]. With the increasing application of X-ray technology in medicine, medical image mosaic methods have become a research hotspot and difficulty in medical image processing [8,9].…”

Towards the spatial resolution of metalloprotein charge states by detailed modeling of XFEL crystallographic diffraction

“…Although the ferredoxin and nitrogenase studies were performed on cryopreserved crystals, it is now widely recog-nized that a macromolecular structure consists of an ensemble of conformations (Woldeyes et al, 2014), with crystallography contributing the most relevant information about biological function when the experiment is performed at physiological or room temperature (Keedy et al, 2014(Keedy et al, , 2015Russi et al, 2017;Thomaston et al, 2017). However, dispensing with cryopreservation presents a general challenge, as it is the principal method used to protect against radiation damage (Garman & Weik, 2019). Also, with respect to probing the electronic environment, X-ray crystallography studies are particularly difficult for metalloproteins, as metal centers are photoreduced at very low X-ray doses (Yano et al, 2005;Denisov et al, 2007;Borshchevskiy et al, 2014).…”