Oxygen additions in serial femtosecond crystallographic protein structures

• Published in: Protein science Vol. 25; no. 10; pp. 1797 - 1802
• Main Author: Wang, Jimin
• Format: Journal Article
• Language: English
• Published: United States Wiley Subscription Services, Inc 01.10.2016; John Wiley and Sons Inc
• Subjects: cryroprotectants; Crystallography, X-Ray; dirty diffraction data; dirty enzyme; free radical amplifiers; free radical chain reaction; Models, Molecular; Oxygen; Oxygen - chemistry; Proteins - chemistry; radiation chemistry; serial femtosecond crystallography; SFX; XFEL; X‐ray free‐electron laser; dirty enzyme; free radical chain reaction; SFX; radiation chemistry; dirty diffraction data; free radical amplifiers; cryroprotectants; X-ray free-electron laser; XFEL; serial femtosecond crystallography
• ISSN: 0961-8368; 1469-896X
• DOI: 10.1002/pro.2987

In principle, serial femtosecond crystallography (SFX) could yield data sets that are completely free of the effects caused by slow, radiation‐induced chemical reactions, for example, oxygen additions, responsible for radiation damage. However, experimental evidence is presented here that SFX data sets obtained by techniques that expose different parts of the same specimen to single pulses of radiation do not have this property, even if the specimen in question is frozen. The diffraction image of each such crystal obtained with the first pulse of radiation is certain to represent the structure of a protein that has not been modified chemically, but all of the images obtained subsequently from the same crystal will represent structures that have been modified to a lesser or greater extent by oxygen additions because of the rapid diffusion of oxygenic free radicals through the specimen. The higher the level of oxygen additions a crystal suffers during data collection, the poorer the statistical quality of data set obtained from it will, and the higher the free R‐factors of the resulting structural model.