Ordering in dense fiber bundles, the phyllotactic solution and its application to collagen fibrils

TL;DR

This paper explores how phyllotaxis, a non-traditional packing pattern, explains the apparent contradiction between high-symmetry cross sections and lower-symmetry molecular arrangements in dense collagen fibril bundles.

Contribution

It introduces phyllotaxis as a novel framework to understand molecular packing in collagen fibrils, linking symmetry and order beyond classical crystallography.

Findings

Phyllotaxis explains the high symmetry of fibril cross sections.

Lateral order in collagen fibrils extends beyond classical crystal symmetry.

The model provides a new interpretation of experimental data on collagen structure.

Abstract

The shape of the cross section of a dense fiber bundle is related to the symmetry of its molecular packing. However, this statement might be belied by type I collagen fibrils which have a rounded section of high symmetry while structural studies suggest that their molecules are assembled with a long range lateral order of lower symmetry. We examine how phyllotaxis, which is a non conventional crystallographic solution to packing efficiency in situations of high radial symmetry, can establish a link between those two apparently conflicting points. The lateral order imposed by the algorithm of phyllotaxis, which implies an enlargement of the notion of long range lateral order beyond that used for classical crystals, provides a basis for a new analysis of the experimental data.