For the first time, scientists have shown the creation of a beam of nanodroplets that can deliver a range of biological samples, from cell organelles to single proteins, nearly free from any contaminations, to the focus of an X-ray laser which can be employed to image them.
The experiment was carried out at the Linac Coherent Light Source (LCLS) at the Department of Energy’s SLAC National Accelerator Laboratory and reported in the most recent issue of Science Advances.
By engineering a new sample delivery instrument which uses electrospray ionization technology, researchers have been able to create droplets of about 100 nm in diameter, about 1000x smaller than with earlier methods.
Earlier methods formed droplets millions of times bigger than the sample within it, which caused the buildup of any contaminants, which unavoidably exist in the solution, on top of the sample to be imaged, efficiently concealing it.
With their new instrument, the team was now able to image the Tomato Bushy Stunt Virus, which, at 33 nm in diameter, is considerably smaller than any biological sample formerly studied using the same method.
Filipe Maia of Uppsala University, the study’s corresponding author, said the ability to provide single proteins, unobscured by contaminants, to the beam of an X-ray laser is a landmark in the mission to image separate proteins in-flight. Integrated with the forthcoming high-repetition rate X-ray free-electron lasers at the European XFEL in Hamburg and the LCLS II in California, which create up to a million pulses a second, this result paves the way towards solving the heterogeneous and dynamic structures of biomolecules.