VO2+-hydroxyapatite complexes as models for vanadyl coordination to phosphate in bone.
We describe a 1D and 2D ESEEM investigation of VO2+adsorbed on hydroxyapatite (HA) at different concentrations and compare with VO2+-triphosphate (TPH) complexes studied previously in detail, in an effort to provide more insight into the structure of VO2+coordination in bone. Structures of this interaction are important because of the role of bone in the long-term storage of administered vanadium, and the likely role of bone in the steady-state release of vanadium leading to the chronic insulin-enhancing anti-diabetic effects of vanadyl complexes. Three similar sets of cross-peaks from phosphorus nuclei observed in the31P HYSCORE spectra of VO2+-HA, VO2+-TPH, and VO2+-bone suggest a common tridentate binding motif for triphosphate moieties to the vanadyl ion. The similarities between the systems present the possibility thatin vivovanadyl coordination in bone is relatively uniform. Experiments with HA samples containing different amounts of adsorbed VO2+demonstrate additional peculiarities of the ion-adsorbent interaction which can be expectedin vivo. HYSCORE spectra of HA samples show varying relative intensities of31P lines from phosphate ligands and1H lines, especially lines from protons of coordinated water molecules. This result suggests that the number of equatorial phosphate ligands in HA could be different depending on the water content of the sample and the VO2+concentration; complexes of different structure probably contribute to the spectra of VO2+-HA. Similar behavior can be also expectedin vivoduring VO2+accumulation in bones.
Department of Veterinary Clinical Medicine, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
Sergei A
SA
Dikanov
Medicinal Inorganic Chemistry Group, Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC, Canada, V6T 1Z1, and Faculty of Pharmaceutical Sciences, University of British Columbia, 2146 Main Mall, Vancouver, BC, Canada, V6T 1Z3.
Barry D
BD
Liboiron
Medicinal Inorganic Chemistry Group, Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC, Canada, V6T 1Z1, and Faculty of Pharmaceutical Sciences, University of British Columbia, 2146 Main Mall, Vancouver, BC, Canada, V6T 1Z3.
Chris
C
Orvig
EPR; bones; diabetes; hydroxyapatite; oxovanadium(IV); two-dimensional ESEEM