Molecular Biophysics Uppsala - A VR Centre of Excellence

A Center of Excellence of the Swedish Research Council

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The laboratory promotes research and discoveries at the frontiers of photon science by exploring and exploiting photon-material interactions on extremely short time scales, at extremely high photon frequencies, and in extremely strong photon fields. We produced the scientific justification in biomolecular imaging for building X-ray free-electron lasers, including the LCLS at Stanford, the European XFEL in Hamburg and other facilities currently under construction.

The Linac Coherent Light Source and a diffraction pattern of a single mimivirus particle.

Single mimivirus imaging with an X-ray Laser

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Intense and ultrafast X-ray laser pulses have been used to collect diffraction data from single mimivirus particles. Using the "diffraction before destruction" concept, structural information has been collected before the virus particles have been vaporized. These outstanding results obtained by our group have been published in Nature 470, 78-81 (2011) . Further information can be accessed under Research.

Rendering of a mimivirus electronmicrograph

Reconstructed image of a mimivirus from a single X-ray exposure at the LCLS

High-field soft X-rays

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We have reached into the high field regime at soft X-ray frequencies at FLASH, where we focused extremely short (15 fs) pulses to a micrometer size spot. The power density of the radiation reached more than 10¹⁷ W/cm², which would be similar to the power density of all the sun light hitting the Earth focused to a spot of only 1 cm².

Two unexpected results emerge. At these intensities, metallic samples become transiently transparent to radiation and damage becomes less dominant. This is good news for imaging single particles with ultra-intense X-ray pulses. At the same time, high energy ions are ejected as the samples blow up, reaching energies enough to even facilitate nuclear reactions. These results have been reported in Phys. Rev. E83, 016403 (2011) and indicate that developments at X-ray lasers could, in principle, lead to a fusion between structural sciences and fusion physics.

Crater in a Niobium Deuteride crystal formed by an intense ultrashort X-ray pulse

Scientific Impact

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A decade ago, we have suggested in Nature 406, 752–757 (2000) that femtosecond pulses from a free-electron laser could provide sufficiently short but intense X-ray doses to collect useful structural information from single particles before significant radiation damage could occur. This new approach is demonstrated by two experiments published in Nature recently, reporting on high-resolution diffraction from protein nanocrystals, and from non-crystalline virus particles. Below are some of the early press releases:

followed by a lot more coverage.

Femtosecond X-ray nanocrystallography

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Our theoretical study on the feasibility of nanocrystal imaging using intense and ultrashort X-ray pulses has been published in ACS Nano 5, 139-146 (2011). We study radiation damage in biological nanocrystals and establish conditions for ultrafast single-shot nanocrystallography diffraction experiments as a function of X-ray fluence, pulse duration, and the size of nanocrystals.

Urea nanocrystal and its diffraction pattern

In our recent experiment on nanocrystalsat the LCLS (Nature 470, 73-77, 2011) we tested this concept by imaging one of the largest membrane proteins (Photosystem I).

Nanocrystallography using ultrafast X-ray pulses has the potential to open up a new route in protein crystallography to solve atomic structures of many systems that remain inaccessible using conventional X-ray sources.

Photosystem I diffraction pattern

Photosystem I structure from LCLS