  Collagen fibrils, cable-like assemblies of long biological molecules, are
dominant components of connective tissues. Their determinant morphological and
functional roles motivated a large number of studies concerning their formation
and structure. However, these two points are still open questions and,
particularly, that of their organization which is certainly dense but not
strictly that of a crystal. We examine here how the algorithm of phyllotaxis
could contribute to the analysis of the structure of collagen fibrils. Such an
algorithm indeed leads to organizations giving to each element of the assembly
the most homogeneous and isotropic dense environment in a situation of
cylindrical symmetry. The scattered intensity expected from a phyllotactic
distribution of triple helices in collagen fibrils well agrees with the major
features observed along the equatorial direction of their X ray patterns.
Following this approach, the aggregation of triple helices in fibrils should be
considered within the frame of soft condensed matter studies rather than that
of molecular crystal studies.
