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significant when it is greater or equal to twice of the standard deviation for all the chemicalshifts variations of the spectra. Compounds that cause a significant variation of marks thatcorrespond to active site residues are considered as NMR hit. Compound mixturesproducing significant chemical shift variations were subsequently deconvoluted (10 hits).The NMR hits were used to select another set of fragment (52 compounds). We produced alarge number of CypD crystals which are suitable for soaking [1]. The soaking conditionswere demonstrated to be robust for use with a variety of fragments. CypD crystals weresoaked with 52 compounds, and the X-ray structures for the crystals were obtained. Cootwas used to fit into the Fo-Fc electron density maps that were calculated after initialrefinement against an unliganded CypD structure (2BIT.pdb). Protein-ligand structures ofbound fragments were subjected to further refinement steps. Multiple low affinity fragmenthits were identified that bind the hydrophobic pocket, the Abu pocket, and some werefound to be multibinders. The output from this fragment screening process was a set ofexperimentally determined binding modes for several fragments bound to CypD (14 hits,Figure 1).Fig. 1. Examples of complexes of CypD with 5 fragments (superposition): the protein andthe ligands are represented by their surface.This information was used to design different ligands which are composed of the differentfragments connected by different linker. We were able to find some molecules(peptidomimetics) with inhibition around 500 nM against the Cyp’s peptidyl-prolylisomerase activity [2] and with a micromolar activity against the HCV virus. The process todevelop nanomolar compounds is ongoing and it should afford new chemical tools to treatpatients with an HCV infection.AcknowledgmentsSupported by grant ANR Jeune Chercheur “Fragscreens”, ANRS (2009-139) and Région Languedoc-Roussillon “Chercheur d’Avenir” (Source of Money).References1. Schlatter, D., Thoma, R., Küng, E., Stihle, M., Müller, F., Borroni, E., Cesura, A., Hennig, M. ActaCrystallographica Section D, D61, 513-519 (2005).2. Kofron, J.L., Kuzmic, P., Kishore, V., Colon-Bonilla, E., Rich, D.H. Biochemistry 30, 6127-6134(1991).229