Mass Spectrometry for Single-Particle Imaging of Dipole Oriented Protein Complexes

The European XFEL has just entered user operation. With its unparalleled peak brilliance and repetition rate, European XFEL has the potential to further applications in single particle imaging (SPI), thus far limited to large viral particles at X-ray fee-electron lasers (XFEL). SPI will allow imaging protein complexes without the need for crystallization. This eventually renders transient conformational states accessible for high resolution structural studies, yielding molecular movies of biomolecular machines. A major bottleneck is the wealth of data required to reconstruct a single structure leading to long processing times. This is currently also a problem in electron microscopy (EM). MS SPIDOC will overcome this data challenge by developing a native mass spectrometry (MS) system for sample delivery called X-MS-I. It will provide mass- and conformation-selected biomolecules that are oriented along their dipole axis upon imaging. This will enable structural reconstruction from much smaller datasets, speeding up the analysis time tremendously. Moreover, the system features low sample consumption and a controlled low background, easing pattern identification.

© European XFEL / Jan Hosan
The experiment station SPB/SFX will be used to investigate crystalline and non-crystalline matter. A particular emphasis is placed on the determination of three-dimensional structures of biological objects. Examples are biological molecules including crystals of macromolecules and macromolecular complexes as well as viruses, organelles, and cells. (Photo: European XFEL / Jan Hosan)

The main objectives of the project are:

• Deliver mass and conformation separated biomolecules for SPI.

• Orient proteins for SPI.

• Image protein complex unfolding

• Exploit potential of protein orientation for other applications.

The MS SPIDOC consortium combines internationally leading expertise in different fields relevant to the project: Instrument design and development, computer simulations as well as working with biomolecules in the gas phase and on SPI are combined to implement the novel sample environment at the next generation XFEL facility. New components and methods will be opened to the market and thereby strengthen the European Research Area (ERA) and industry. This early stage, high-risk project will give rise to a new technology with major impact on how to derive structures of biomolecules.