SUPRAMOLECULAR ASSEMBLIES |
Lateral Packing of Mineral Crystals in Bone Collagen Fibrils
Christian Burger 1, Hongwen Zhou 1, Hao Wang 2, Igors Sics 1, Benjamin S Hsiao 1*, Benjamin Chu 1, Lila Graham 2 and Melvin Glimcher 2
1 Stony Brook University
2 Harvard Medical School
* To whom correspondence should be addressed. E-mail: bhsiao{at}notes.cc.sunysb.edu.
Submitted on December 26, 2007
Revised on January 30, 2008
Accepted on 25 February 2008
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Abstract |
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Combined small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) studies of intramuscular fish bone (shad and herring) indicate that the lateral packing of nanoscale calcium-phosphate crystals in collagen fibrils can be represented by irregular stacks of platelet-shaped crystals, intercalated with organic layers of collagen molecules. The scattering intensity distribution in this system can be described by a modified Zernike-Prins model, taking preferred orientation effects into account. Using the model, the diffuse fan-shaped SAXS intensity profile, dominating the equatorial region of the scattering pattern, could be quantitatively analyzed as a function of the degree of mineralization. The mineral platelets were found to be very thin (1.5 nm ~ 2.0 nm), having a narrow thickness distribution. The thickness of the organic layers between adjacent mineral platelets within a stack is more broadly distributed with the average value varying from 6 nm to 10 nm, depending on the extent of mineralization. The 2D analytical scheme also leads to quantitative information about the preferred orientation of mineral stacks and the average height of crystals along the crystallographic c-axis.
Key Words:
SAXS, bone, collagen, mineral, orientation, packing
