Conjecture on the lateral growth of Type I collagen fibrils
Whatever the origin and condition of extraction of type I collagen fibrils, in vitro as well as in vivo, the radii of their circular circular cross sections stay distributed in a range going from 50 to 100 nm for the most part of them. Jean Charvolin and Jean-Francois Sadoc from the solid state physique laboratory at the Paris-Sud University propose therefore that, once the growth of the fibrils has been triggered by external biological factors, their lateral size be limited by internal physical stresses generated during the growth. Their conjecture is based on the remark that the assembly of the long triple helices building a fibril is a place of conflict between two incompatible requirements: (1) a double-twist around the fibril axis induced by the chirality of those molecules, and (2) a periodic layering normal to the fibril axis associated with their Hodge-Petrushka staggering.