Sciencehttp://dx.doi.org/10.1126/science.1234273 (2013)

Credit: © AAAS 2013

X-ray diffraction, the materials analysis technique used to reveal the structure of DNA in the 1950s, is receiving renewed interest, especially for protein crystallography. One reason for this is the advent of free-electron lasers, which can provide short, intense X-ray pulses. Although X-ray diffraction is useful for determining structural information, other techniques such as nonresonant X-ray emission spectroscopy, which probes electron levels, can provide additional information about a sample. Now, Jan Kern and colleagues from the USA, Germany, Sweden and France have used sub-50-fs X-ray pulses produced at the Linac Coherent Light Source at Stanford, USA, to conduct simultaneous X-ray diffraction and X-ray emission spectroscopy measurements of microcrystals of photosystem II at room temperature. Photosystem II is a metalloenzyme that plays a critical role in photosynthesis; it is found in green plants, algae and cyanobacteria. The researchers report that the photosystem II crystals remained intact during measurements and hope that the technique can be used for time-resolved studies of light-driven structural changes.