Author(s)

Alejandro Heredia, Maria Colin-Garcia, Miguel A. Peña-Rico, Luis F. L. Aguirre Beltrán, José Grácio, Flavio F. Contreras-Torres, Andrés Rodríguez-Galván, Lauro Bucio, Vladimir A. Basiuk

Departamento de Estado Sólido, Instituto de Física, Universidad Nacional Autónoma de México (UNAM), D.F. México, México.
Departamento de Fisica de Plasmas y de Intearcción de Radiación con la Materia, Instituto de Ciencias Nucleares, UNAM, D.F. México, México.
Departamento de Radiaciones y Radioquímica, Instituto de Ciencias Nucleares, UNAM, D.F. México, México.
Instituto de Biotecnología, UNAM, D.F. México, México.
Nanotechnology Research Division, Centre for Mechanical Technology & Automation, University of Aveiro, Aveiro, Portugal.
S.I.O.V. Instituto de Geología, UNAM, D.F. México, México.

An insight into the interaction of collagen type I with apatite in bone tissue was performed by using differential scanning calorimetry, Fourier transform infrared spectroscopy, and molecular modeling. Scanning electron microscopy shows that bone organic content incinerate gradually through the different temperatures studied. We suggest that the amide regions of the type I collagen molecule (mainly C=O groups of the peptide bonds) will be important in the control of the interactions with the apatite from bone. The amide I infrared bands of the collagen type I change when interacting to apatite, what might confirm our assumption. Bone tissue results in a loss of thermal stability compared to the collagen studied apart, as a consequence of the degradation and further combustion of the collagen in contact with the apatite microcrystals in bone. The thermal behavior of bone is very distinctive. Its main typical combustion temperature is at 360°C with a shoulder at 550°C compared to the thermal behavior of collagen, with the mean combustion peak at ca. 500°C. Our studies with molecular mechanics (MM+ force field) showed different interaction energies of the collagen-like molecule and different models of the apatite crystal planes. We used models of the apatite (100) and (001) planes; additional two planes (001) were explored

with phosphate-rich and calcium-rich faces; an energetic preference was found in the latter case. We preliminary conclude that the peptide bond of collagen type I is modified when the molecule interacts with the apatite, producing a decrease in the main peak from ca. 500°C in collagen, up to 350°C in bone. The combustion might be related to collagen type I, as the ΔH energies present only small variations between mineralized and non-mineralized samples. The data obtained here give a molecular perspective into the structural properties of bone and the change in collagen properties caused by the interaction with the apatite. Our study can be useful to understand the biological synthesis of minerals as well as the organic-inorganic interaction and the synthesis of apatite implant materials.

Bone, Collagen Type I; Apatite; Differential Scanning Calorimetry (DSC); Molecular Modeling; Fourier Transform Infrared (FTIR) Spectroscopy

Heredia, A. , Colin-Garcia, M. , Peña-Rico, M. , Beltrán, L. , Grácio, J. , Contreras-Torres, F. , Rodríguez-Galván, A. , Bucio, L. and Basiuk, V. (2013) Thermal, infrared spectroscopy and molecular modeling characterization of bone: An insight in the apatite-collagen type I interaction. Advances in Biological Chemistry, 3, 215-223. doi: 10.4236/abc.2013.32027.