News & Scientific Highlights

A2A protein

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.

Cyt C structure

Unraveling the structural dynamics of Heme proteins at SwissFEL

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.

CuPCP jet in the Prime chamber

Publication of the very first Pilot experiment results from Alvra

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.

Measured longitudinal phase space of the injected electron beam

First serial femtosecond crystallography experiment using SwissFEL’s large bandwidth X-ray pulses

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.

Figure 1. Layout depicting the experimental conditions at the Alvra experimental station. (b) Fresnel simulation of the Talbot carpet: intensity distribution of the experimental conditions for a 1D diamond phase grating with a 200 nm pitch and 2.985 keV photon energy. The inset (c) shows the detailed structure of the interference pattern in the vicinity of the sample where the pitch is 190 nm

Towards X-ray Transient Grating Spectroscopy at SwissFEL

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.

Cytochrome C

User operation at SwissFEL has begun

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.

First femtosecond protein pump-probe measurements at SwissFEL

A major milestone in the commissioning of SwissFEL has been reached: the first pump-probe experiments on proteins have been successfully carried out. Crystals of several retinal-binding proteins were delivered in a viscous jet system and a femtosecond laser was used to start the isomerization reaction. Microsecond to sub-picosecond snapshots were then collected, catching the retinal proteins shortly after isomerization of the chromophore.

SwissFEL's First Call for Proposals

The first SwissFEL call for proposals took place, deadline for submission was the 15th of September. In this first call for proposals SwissFEL received overwhelming interest from the user community. A total of 47 proposals were submitted for the SwissFEL Alvra experimental station and 26 for the Bernina experimental station. The Proposal Review committee PRC took place on 18-19 October 2018.

First serial femtosecond crystallography (SFX) pilot user experiment at SwissFEL

On the 7th to 12th of August 2018, a collaborative group of scientists from the Paul Scherrer Institute and members of the LeadXpro and Heptares pharmaceutical companies led by Karol Nass (PSI macromolecular crystallography MX-SLS group) performed the first serial femtosecond crystallography (SFX) pilot user experiment at the SwissFEL X-ray free electron laser (XFEL).

First Pilot Experiment at SwissFEL-Alvra: UV photo-induced charge transfer in OLED system

On the 17th of December 2017 SwissFEL saw its first pilot experiment in the Alvra experimental station of the SwissFEL ARAMIS beamline.