Scientific Highlights & News
Researchers have coaxed a secret out of the vital protein cytochrome c that it kept well-hidden up to now. Measurements at the X-ray free-electron laser SwissFEL reveal structural changes that science had previously ruled out for this kind of biomolecule.
Advances in de novo protein structure determination using long-wavelength native-SAD phasing at SwissFEL
An international team of scientists from the Paul Scherrer Institute and members of the LeadXpro and Heptares pharmaceutical companies led by Karol Nass (Alvra group, SwissFEL) demonstrated a significant advancement in de novo protein structure determination at X-ray free-electron lasers. Their article, published recently in IUCrJ (DOI: 10.1107/S2052252520011379), describes structure determination of a membrane protein and an important drug target (A2A adenosine receptor) by native single-wavelength anomalous diffraction (native-SAD) at SwissFEL with up to ten fold reduction in the required number of indexed images.
The results from the very first user experiment at SwissFEL have just been published in the Proceedings of the National Academy of Sciences (PNAS). The measurements probed the electron transport properties of the cytochrome c protein, which is found in cellular mitochondria. The measurements show that when the Fe atom at the centre of the protein undergoes electronic excitation, for example when it gains or loses and electron, the active centre of the protein undergoes a doming structural rearrangement. This result raises interesting questions about how this structural change is involved in the electron transfer properties of cytochrome c.
Researchers at the Paul Scherrer Institute PSI have succeeded for the first time in recording a light-driven sodium pump from bacterial cells in action. The findings promise progress in developing new methods in neurobiology. The researchers used the new X-ray free-electron laser SwissFEL for their investigations.
The results from the first pilot experiment at Alvra have just been published in Nature Communications. The measurements probed the excited-state character of a Cu-P OLED complex using X-ray emission spectroscopy from the phosphorus atoms in the molecule.
At the Paul Scherrer Institute PSI, researchers have gained insights into a promising material for organic light-emitting diodes (OLEDs). This new understanding at the atomic level will help to develop new lighting materials that have higher light output and also are cost-efficient to manufacture.
The typical mode of operation at XFEL facilities uses the so-called self-amplified spontaneous emission (SASE) process to generate the short, bright X-ray pulses. This mode of operation is stochastic in nature, causing some variance in intensity and spectrum on a shot-to-shot basis, which makes certain types of crystallographic measurements much more challenging.
The high brilliance of new X-ray sources such as X-ray Free Electron Laser opens the way to non-linear spectroscopies. These techniques can probe ultrafast matter dynamics that would otherwise be inaccessible. One of these techniques, Transient Grating, involves the creation of a transient excitation grating by crossing X-ray beams on the sample. Scientists at PSI have realized a demonstration of such crossing by using an innovative approach well suited for the hard X-ray regime.
The first user experiment has taken place the the SwissFEL X-ray free electron laser, officially inaugurating it as the newest user facility at the Paul Scherrer Institute. The experiment, led by Camila Bacellar from EPFL, investigated ultrafast electron transfer dynamics in a protein to try to identify the charge density re-localization after the protein absorbs a photon of UV light. The experiment was performed using the Alvra Prime experimental station, taking advantage of the integrated von Hamos X-ray emission spectrometer to perform both X-ray absorption and emission measurements on the Fe atom, which is located at the centre of the protein.