| INTERNATIONAL JOURNAL OF ORAL-MEDICAL SCIENCES | |
| Vol. 7 No. 1 September - 2008 | |
| ISSN: 1347-9733 UBIC: 136-M | |
| Abstract | |
| Conformational analysis of three types of pamidronate/calcium (Ca) complex model was performed using a molecular mechanics method with a standard
MM3 force field. Three types of pamidronate/Ca-complexes were designed. Namely, one calcium atom was connected to two oxygen atoms of different P-O bonds [Ca-complex (I)],
one calcium atom was connected to two oxygen atoms of the same P-O bond at one end of the molecule [Ca-complex (II)], and one calcium atom was connected to two oxygen
atoms of the same P-O bond at both ends of the molecule [Ca-complex (III)]. Three-dimensional imaging clearly showed the steric conformation of each compound. Ca-complex
(I) showed the lowest steric energy and Ca-complex (III) showed the highest steric energy among the three types of Ca-complexes. The Ca-O bond lengths of Ca-complexes (II)
and (III) were shorter than that of Ca-complex (I). The P-O bond lengths of Ca-complexes (II) and (III) were longer than that of Ca-complex (I). The O-Ca-O dihedral angles
of Ca-complexes (II) and (III) decreased approximately 30% from that of Ca-complex (I). These data suggested that the Ca-complex (I) was most stable and that the structure
of Ca-complex (I) had the highest possibility when pamidronate reacted with a calcium atom. The structure of Ca-complex (III) has the lowest possibility. The present
results revealed the stable structures of Ca-complexes using molecular mechanics calculations, a useful tool for obtaining geometrical information about molecules.
Keywords: bisphosphonate, molecular mechanics calculation, steric energy, bond length, dihedral angle. |
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