To get a clearer view of protein monolayers using XFEL, the team will need to improve the resolution to 1 to 3 angstroms, as well as take images of the proteins at angles, efforts that are currently underway.
Not Your Family's Crystal
Researchers have been using X-ray crystallography for more than 60 years to determine the shape and form of proteins that form the widgets and gears of a living organism's cells. The conventional method requires, however, that proteins stack into a large crystal, similar to how oranges stack in a crate. The structure of more than 80,000 proteins have been determined this way, leading to breakthroughs in understanding of diseases, pathogens, and how organisms grow and develop.
But many proteins found in nature do not stack easily. Some jut from the fatty membranes that cover cells, detecting and interacting with other cells and objects, such as viruses or bacteria, in the surrounding area. These proteins are not used to having others of their kind stack on top. These so-called membrane proteins make up about 25 percent of all proteins, but only 2 percent of proteins that researchers have determined structures for.
Researchers in the last decade have been pursuing the idea that one sheet of proteins could be visualized if the X-rays were bright enough and flashed on and off quickly enough to limit the damage. Two years ago, scientists demonstrated they could use XFEL technology on crystals of proteins about 15 to 20 sheets thick.
Evans, Frank and their team wanted to push this further. The team worked on a way to create one-sheet-thick crystals of two different proteins -- a protein called streptavidin and a membrane protein called bacteriodopsin. The structures of both proteins are well-known to scientists, which gave the team something to compare their results to.
The team shined the super-bright X-rays for a brief moment -- abou
|Contact: Mary Beckman|
DOE/Pacific Northwest National Laboratory