The 300 keV cryo-electron microscope (cryo-EM) installation at SOLEIL has just been completed and is now available to scientists who have applied through a call for proposals. The first user team, from the Membrane Proteins and Membrane Systems Laboratory (I2BC, Gif-sur-Yvette), was supported at SOLEIL on January 11 and 12, 2025.
After the delivery of the various components of the Titan Krios cryo-EM (®ThermoFisher) in March 2024, the teams from SOLEIL, Thermo Fisher Scientific, and Climascience coordinated to ensure the new equipment would be accessible to users by the end of the year. Thermo Fisher Scientific was responsible for assembling the cryo-EM, funded under the PIA3 - EQUIPEX+ FRANCE-CRYO-EM project. Climascience built the room dedicated to cryo-EM in the synchrotron building. And the POLARIS* team is responsible for operating the cryo-EM for academic and industrial users.
These "installation" steps were completed in December, while initial tests by expert users were conducted starting in early autumn. As the results obtained met the expected specifications, it became possible to move to the next step: welcoming the first users whose projects were selected by the members of the Biology-Health Program Committee.

In the cryo-EM control room: from left to right, the users: Christelle Saade and Thibaud Dieudonné from the I2BC, and Eric Larquet, microscope operational manager.
This milestone was achieved on January 11, 2025. The first project was methodological: comparing images of a small asymmetric membrane protein (Drs2/Cdc50, a yeast phospholipid transporter) obtained with SOLEIL's microscope, named POLARIS, to those provided by the I2BC 200 keV microscope.

Thibaud, preparing to launch the data collection: micrographs of the grids containing the protein being studied.
A new project submission process, called "Rolling-access," has been implemented for access to this instrument. This process allows continuous submission of projects with selection every two months, distinguishing it from the access methods for beamlines, which follow project submission calendars.

Pierre Legrand, head of POLARIS, sets up the samples for the measurements.
* The POLARIS team mainly consists of 5 people: Andrew Thompson, former scientific director of SOLEIL, consultant; Eric Larquet, CNRS/I2BC engineer, seconded 80% to SOLEIL; Heddy Soufari, CEA/I2BC engineer, seconded 80% to SOLEIL; Tatiana Isabet, industrial liaison engineer; Pierre Legrand, head of the PROXIMA-1 beamline and POLARIS.