title: Revisiting the localisation of Zn(2+) cations sorbed on pathological apatite calcifications made through X-ray absorption spectroscopy.
abstract: The role of oligo-elements such as Zn in the genesis of pathological calcifications is widely debated in the literature. An essential element of discussion is given by their localisation either at the surface or within the Ca apatite crystalline network. To determine the localisation, X-ray absorption experiments have been performed at SOLEIL. The Exafs results suggest that Zn atoms, present in the Zn(2+) form, are bound to about 4 O atoms at a distance of 2.00 A, while the interatomic distance R(CaO) ranges between 2.35 A and 2.71 A. Taking into account the content of Zn (around 1000 ppm) and the difference in ionic radius between Zn(2+) (0.074 nm) and Ca(2+) (0.099 nm), a significant longer interatomic distance would be expected in the case of Zn replacing Ca within the apatite crystalline network. We thus conclude that Zn atoms are localised at the surface and not in the apatite nanocrystal structure. Such structural result has essential biological implications for at least two reasons. Some oligoelements have a marked effect on the transformation of chemical phases, and may modify the morphology of crystals. These are both major issues because, in the case of kidney stones, the medical treatment depends strongly on the precise chemical phase and on the morphology of the biological entities at both macroscopic and mesoscopic scales.
authors.affiliation: Laboratoire de Physique des Solides, Bat. 510, Université Paris Sud, 91405 Orsay, France. bazin@lps.u-psud.fr
authors.forename: Dominique
authors.initials: D
authors.lastname: Bazin
authors.forename: Xavier
authors.initials: X
authors.lastname: Carpentier
authors.forename: Isabelle
authors.initials: I
authors.lastname: Brocheriou
authors.forename: Peter
authors.initials: P
authors.lastname: Dorfmuller
authors.forename: Stephane
authors.initials: S
authors.lastname: Aubert
authors.forename: Christine
authors.initials: C
authors.lastname: Chappard
authors.forename: Dominique
authors.initials: D
authors.lastname: Thiaudière
authors.forename: Solenn
authors.initials: S
authors.lastname: Reguer
authors.forename: Glenn
authors.initials: G
authors.lastname: Waychunas
authors.forename: Paul
authors.initials: P
authors.lastname: Jungers
authors.forename: Michel
authors.initials: M
authors.lastname: Daudon
mesh_terms: D015502:Absorptiometry, Photon / Q000379:methods*; D000042:Absorption; D001031:Apatites / Q000737:chemistry*; D002114:Calcinosis; D006801:Humans; D007669:Kidney Calculi / Q000737:chemistry*; D015032:Zinc / Q000737:chemistry*
chemical_list: D001031:Apatites; D015032:Zinc