title: Crystal structure of monoclinic calcium pyrophosphate dihydrate (m-CPPD) involved in inflammatory reactions and osteoarthritis.
abstract: Pure monoclinic calcium pyrophosphate dihydrate (m-CPPD) has been synthesized and characterized by synchrotron powder X-ray diffraction and neutron diffraction. Rietveld refinement of complementary diffraction data has, for the first time, allowed the crystal structure of m-CPPD to be solved. The monoclinic system P2(1)/n was confirmed and unit-cell parameters determined: a = 12.60842 (4), b = 9.24278 (4), c = 6.74885 (2) Å and β = 104.9916 (3)°. Neutron diffraction data especially have allowed the precise determination of the position of H atoms in the structure. The relationship between the m-CPPD crystal structure and that of the triclinic calcium pyrophosphate dihydrate (t-CPPD) phase as well as other pyrophosphate phases involving other divalent cations are discussed by considering the inflammatory potential of these phases and/or their involvement in different diseases. These original structural data represent a key step in the understanding of the mechanisms of crystal formation involved in different types of arthritis and to improve early detection of calcium pyrophosphate (CPP) phases in vivo.
authors.affiliation: CIRIMAT, UMR 5085 INPT-CNRS-UPS, Université de Toulouse, INPT-ENSIACET, Toulouse, France.
authors.forename: Pierre
authors.initials: P
authors.lastname: Gras
authors.affiliation: CIRIMAT, UMR 5085 INPT-CNRS-UPS, Université de Toulouse, INPT-ENSIACET, Toulouse, France.
authors.forename: Christian
authors.initials: C
authors.lastname: Rey
authors.affiliation: Laboratoire Léon Brillouin, CEA Saclay, Gif-sur-Yvette, France.
authors.forename: Gilles
authors.initials: G
authors.lastname: André
authors.affiliation: CIRIMAT, UMR 5085 INPT-CNRS-UPS, Université de Toulouse, INPT-ENSIACET, Toulouse, France.
authors.forename: Cédric
authors.initials: C
authors.lastname: Charvillat
authors.affiliation: CIRIMAT, UMR 5085 INPT-CNRS-UPS, Université de Toulouse, Université Paul Sabatier , Toulouse, France.
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Sarda
authors.affiliation: CIRIMAT, UMR 5085 INPT-CNRS-UPS, Université de Toulouse, INPT-ENSIACET, Toulouse, France.
authors.forename: Christèle
authors.initials: C
authors.lastname: Combes
mesh_terms: D002131:Calcium Pyrophosphate / Q000138:chemical synthesis* / Q000737:chemistry*; D003460:Crystallization; D007249:Inflammation / Q000378:metabolism; D010003:Osteoarthritis / Q000378:metabolism; D017356:Synchrotrons; D014961:X-Ray Diffraction
chemical_list: D002131:Calcium Pyrophosphate
keywords: calcium pyrophosphate dihydrate; neutron diffraction; osteoarthritis; structure refinement; synchrotron X-ray diffraction