VO(2+)-hydroxyapatite complexes as models for vanadyl coordination to phosphate in bone.

ABSTRACT: We describe a 1D and 2D ESEEM investigation of VO(2+) adsorbed on hydroxyapatite (HA) at different concentrations and compare with VO(2+)-triphosphate (TPH) complexes studied previously in detail, in an effort to provide more insight into the structure of VO(2+)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 the (31)P HYSCORE spectra of VO(2+)-HA, VO(2+)-TPH, and VO(2+)-bone suggest a common tridentate binding motif for triphosphate moieties to the vanadyl ion. The similarities between the systems present the possibility that in vivo vanadyl coordination in bone is relatively uniform. Experiments with HA samples containing different amounts of adsorbed VO(2+) demonstrate additional peculiarities of the ion-adsorbent interaction which can be expected in vivo. HYSCORE spectra of HA samples show varying relative intensities of (31)P lines from phosphate ligands and (1)H 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 VO(2+) concentration; complexes of different structure probably contribute to the spectra of VO(2+)-HA. Similar behavior can be also expected in vivo during VO(2+) accumulation in bones.

SUBMITTER: Dikanov SA 

PROVIDER: S-EPMC4016957 | biostudies-literature | 2013 Sep

REPOSITORIES: biostudies-literature