TITLE:
Thermal, infrared spectroscopy and molecular modeling characterization of bone: An insight in the apatite-collagen type I interaction
AUTHORS:
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
KEYWORDS:
Bone, Collagen Type I; Apatite; Differential Scanning Calorimetry (DSC); Molecular Modeling; Fourier Transform Infrared (FTIR) Spectroscopy
JOURNAL NAME:
Advances in Biological Chemistry,
Vol.3 No.2,
April
30,
2013
ABSTRACT: 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.