Real-time crystallographic studies of the adenine riboswitch using an X-ray free-electron laser.

Structures of the four reaction states of the adenine riboswitch aptamer domain, including a transient intermediate state were solved by serial femtosecond crystallography. The structures not only demonstrate the use of X-ray free-electron lasers for RNA crystallography but have also proven that transient states can be determined in real time by mix-and-inject crystallography. These results illustrate the structural basis for the ligand-induced conformational changes associated with the molecular 'switch'. Published 2017. This article is a U.S. Government work and is in the public domain in the USA.