February 27, 2017

New Droplet-on-Tape Method Assists Biochemical Research at X-Ray Lasers

A research collaboration designed a new assembly-line system that rapidly replaces exposed samples and allows the team to study reactions in real-time.

Acoustic droplet ejection allows scientists to deposit nanoliters of sample directly into the X-ray beam, considerably increasing the efficiency of sample consumption. A femtosecond pulse from an X-ray free-electron laser then intersects with a droplet that contains protein crystals. (SLAC National Accelerator Laboratory)

Biological samples studied with intense X-rays at free-electron lasers are destroyed within nanoseconds after they are exposed. Because of this, the samples need to be continually refreshed to allow the many images needed for an experiment to be obtained. Conventional methods use jets that supply a continuous stream of samples, but this can be very wasteful as the X-rays only interact with a tiny fraction of the injected material.

To help address this issue, scientists at the Department of Energy's Lawrence Berkeley National Laboratory, SLAC National Accelerator Laboratory, Brookhaven National Laboratory, and other institutes designed a new assembly-line system that rapidly replaces exposed samples by moving droplets along a miniature conveyor belt, timed to coincide with the arrival of the X-ray pulses. The droplet-on-tape system now allows the team to study the biochemical reactions in real-time from microseconds to seconds, revealing the stages of these complex reactions.

In their approach, protein solution or crystals are precisely deposited in tiny liquid drops, made as ultrasound waves push the liquid onto a moving tape. As the drops move forward, they are hit with pulses of visible light or treated with oxygen gas, which triggers different chemical reactions depending on the sample studied. This allows the study of processes such as photosynthesis, which determines how plants absorb light from the sun and convert it into useable energy.

Finally, powerful X-ray pulses from SLAC’s X-ray laser, the Linac Coherent Light Source (LCLS), probe the drops. In this study published in Nature Methods, the X-ray light scattered from the sample onto two different detectors simultaneously, one for X-ray crystallography and the other for X-ray emission spectroscopy. These are two complementary methods that provide information about the geometric and electronic structure of the catalytic sites of the proteins and allowed them to watch with atomic precision how the protein structures changed during the reaction.

Below, see the conveyor belt in action at LCLS, a Department of Energy Office of Science User Facility.

Droplet-on-tape conveyor belt system delivers samples at the Linac Coherent Light Source (LCLS). (SLAC National Accelerator Laboratory)

Citation: Fuller et al., Nature Methods, 27 February 2017 (10.1038/nmeth.4195)

For questions or comments, contact the SLAC Office of Communications at communications@slac.stanford.edu.


SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, Calif., SLAC is operated by Stanford University for the U.S. Department of Energy's Office of Science.

SLAC National Accelerator Laboratory is supported by the Office of Science of the U.S. Department of Energy. The Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

As the drops move forward, they are hit with pulses of visible light or treated with oxygen gas, which triggers different chemical reactions depending on the sample studied. (SLAC National Accelerator Laboratory)
Dig Deeper

Related stories

News Feature

The results offer important implications for astrophysics and nuclear fusion research.

NIF experiment
Press Release

After decades of effort, scientists have finally seen the process by which nature creates the oxygen we breathe using SLAC’s X-ray laser.

Photosystem II
Press Release

New SLAC-Stanford Battery Center bridges the gaps between discovering, manufacturing and deploying innovative energy storage solutions. 

Illustration showing a battery researcher at left, a battery at center and a grid of battery applications at right.
News Feature

The results offer important implications for astrophysics and nuclear fusion research.

NIF experiment
Press Release

After decades of effort, scientists have finally seen the process by which nature creates the oxygen we breathe using SLAC’s X-ray laser.

Photosystem II
Press Release

New SLAC-Stanford Battery Center bridges the gaps between discovering, manufacturing and deploying innovative energy storage solutions. 

Illustration showing a battery researcher at left, a battery at center and a grid of battery applications at right.
News Feature

The SLAC-Stanford team pulled hydrogen directly from ocean waters. Their work could help efforts to generate low-carbon fuel for electric grids, cars, boats and...

This photograph shows ocean water funneling over rocks on about half of the photograph and deeper ocean water on the other part of the photograph. It is a view of the ocean from above, in the sky.
News Feature

SLAC researcher Sadasivan Shankar talks about a new environmental effort starting at the lab – building a roadmap that will help researchers improve the...

Sadasivan Shankar
News Feature

This ‘beautiful’ herringbone-like pattern could give rise to unique features that scientists are just starting to explore.

An illustration of a dramatic, herringbone-like pattern in the atomic lattice of a newly created quantum material. Against a black background, calcium atoms are seen as light blue spheres, cobalt atoms in dark blue and oxygen atoms in red. Lines connecting the oxygen atoms represent the atomic lattice.