More Bone Microscopy

Consider:

collagen fibril
naked collagen fibril
coated collagen fibril

At left is a coated fibril with collagen molecules shaped hexagonally ( blue blobs) surrounded by a water-mineral composite consisting of bone glue, HA mineral crystals, and water where ratio of mineral to the rest depends on age of the fibril. This fibril over time will crystallize completely, and the organic collagen will die. At that point the fibril becomes part of the overall mineral matrix of the cortical (hard) bone.

A newborn fibril is naked in the sense that as it ages HA crystals will commence to form on
its outside skin(note the HA mineral bumps on the outside of these fibrils). Thus we refer to coated fibrils (at left). As the fibril ages HA rings (mineralized rings) commence to form around the fibril and these HA rings will continue to multiply until they bump into those of an adjoining fibril.

The above is essential knowledge to the Planck finding that the strength of these microscopic structures appears to depend upon the shape and volume of the HA crystals, both internal in the fibril, and the the crystals that make up the outer coating. Last post I'd speculated whether shape and volume might be affected by exercise.

You may view the interesting academic exercise as to how these conclusions are reached by reading the Planck piece:

http://www.mpie.de/index.php?id=2697

but, essentially, they model the structure mathematically, calculate the "elastic properties"(strength) of the collagen molecule-water composite inside the naked fibril, repeat the calculations for a coated fibril and one with HA rings, and finally compare these calculations to determine differences in "elastic properties" or strength. The conclusion basically is that the naked fibril has little strength compared to the coated fibrils. But, there is more.

Similarly to the manner in which astronomers can measure the size of the known universe by measuring our distance from a super novae, these physicists can arrive at some amazing conclusions provided they have made a few measurements. Continue next post.

Training: whenever we believe the weather could hardly get worse, its does. Off.