The Protein Crystallisation Diagnostics Facility (PCDF) on Board ESA Columbus Laboratory

Abstract

Crystals of proteins or macromolecules are at the basis of X-ray crystallography to reveal structural information necessary for the understanding of their likely mode of action. However, the structural resolution is strongly dependent on the crystalline quality, which is known to be related to gravity dependent processes. The facilities and instruments used so far to grow crystals in space have mostly focused on the growing of crystals for detailed post-flight analysis on ground, and less on the understanding of phenomena associated to the crystallisation processes. The Protein Crystallisation Diagnostics Facility (PCDF), developed by Astrium under contract of the European Space Agency (ESA), allows to study with several diagnostics means in situ the crystallisation of macromolecules over long periods in microgravity. In addition, several ground models with PCDF similar capabilities were developed to allow scientists to prepare their experiments. The PCDF is installed in the European Drawer Rack (EDR), on board ESA’s Columbus Laboratory module launched in February 2008 to the International Space Station (ISS) for research in microgravity on protein nucleation and assembling sequences. The PCDF configuration for this first mission accommodates four reactors, using the batch crystallization technique. Individual process control for temperature and concentration will allow several crystallizations of solutions to be performed. Each reactor will be observed by several optical diagnostics, including video microscopy, dynamic light scattering, and Mach–Zehnder interferometry. This paper presents the overall PCDF design and details the different diagnostics allowing the scientific community to use the PCDF in orbit for microgravity research on molecule assemblies grown from solutions.