Projects
PCDF 1 - The PROTEIN mission
The Protein Crystallisation Diagnostics Facility PCDF is an instrument developped by the European Space Agency to study the crystallization of proteins in microgravity.
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Structural biologists need protein crystals to determine the structure of these proteins by X-ray or neutron crystallography. Protein crystals are also important for the formulation of protein-based drugs, such as insulin or in industrial processes e.g. in the food industry.
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Usually, crystals with very specific properties are required. For X-ray or neutron crystallography for instance, one needs fairly large and prefect crystals. At present, we don't understand the crystallization process well enough to always get crystals with the required properties. Also, there are many proteins (and other macromolecules) that resist all crystallization attempts.
The aim of this project is therefore to study the crystallization process itself, to gain better understanding and better control.
When a protein crystal is growing from a supersaturated solution, it absorbs molecules from the solution around it. Therefore, the local concentration of the solution around the growing crystal is a bit lower than in the rest of the solution. This local concentration gradient is at the same time a density gradient: the solution containing a lower concentration is lighter. On earth, gravity causes convection, which eliminates the concentration gradient. In microgravity, there is no convention and therefore the concentration gradient around the growing crystal remains undisturbed. This situation allows us to focus on all the other processes that occur during crystal growth. If these other processes can be understood and controlled, we can use this knowledge to improve crystals grown on earth, and maybe identify a set of rules to predict whether or not a protein will yield better crystals in microgravity.
During the PROTEIN mission, the first one for the PCDF instrument, we will study the protein glucose isomerase. The dynamic light scattering diagnostic will be used to study the pre-nucleation and nucleation events, whereas the Mach-Zehnder interferometer will be used for observing the protein concentration gradients around the growing crystals. A still camera will be used to observe the number of crystals that occur and the speed at which they grow. Using the possibilities to change the temperature and to change concentrations by injection, we will investigate a wide range of conditions.
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