The overall aim of the effort is to share real world crystallization data in a fashion designed to attract image analysis experts from the non crystallographic community to contribute in this arena. As a community we can use the results to select those methods most appropriate and practical for immediate use as well as encouraging further development of successful methods.

What is a Protein Crystal?

A crystal is a three-dimensional ordered stacking of atoms. As a simple case, divide a volume into equal cubes, and place an atom at center of each of these cubes. The result would then be a simple cubic crystal of these atoms. Slightly more complicated packings involve placing additional atoms — possibly of different types — on the vertices or faces of the cubes. Such ordered arrangements result in everyday crystals, such as ice, table salt and sugar.

Proteins are molecules made of smaller components (called amino acids) tied to one another in a chain which folds into a complex shape. This shape enables a protein to carry out a variety of functions in all organisms. Although the properties of the amino acids are well known, computing the structure of a protein is combinatorially complex. Other methods for obtaining protein structures have thus been devised.

Like table salt, proteins can also form ordered crystalline packings, although they don’t do so readily. Most proteins have evolved to be recalcitrant to crystallization, as they only carry out their biological function when non-crystallized. Yet such crystals are very useful: they enable one to determine the three-dimensional structure of a protein through X-ray crystallography. In fact, about 90% of all known protein structures have been obtained this way.

Once a protein structure is known, its biological function can be understood, which may lead to the development of new therapeutic treatments. Obtaining protein crystals is thus an important first step to uncovering the origin of life and to curing diseases.

Because proteins do not crystallize readily, thousands of different experiments must typically be run for up to two months before a single (if any) crystal forms. Although identifying this crystal is acutely important, the observational data can be overwhelming for a human to sieve through. Characterizing experimental outcomes other than crystals can also provide insights about a protein, but are often neglected due to the arduousness of the task. Devising a reliable, automated tool for analyzing the results of protein crystallization experiments would thus not only guarantee that crystals are not passed over, but also enable scientific questions about proteins to be asked.

Contributing Images

To contribute images please contact: patrick.charbonneau@duke.edu