Molecular Models Illustrating the Possible Distributions of ‘Holes’ in Simple Systematically Staggered Arrays of Type I Collagen Molecules in Native-Type Fibrils

Abstract

Clear 3/8″ Lucite rod models at a scale of 1″ = D (the native-type period), and using four different colored ribbon markers to indicate one set of ‘equivalent bands’ in the SLS band pattern, clearly show the possible distribution of ‘holes’ and staining loci in native-type fibrils. Close-packed ordered arrays of the 4.4″ long rods (based on the Hodge-Petruska model) in which nearest neighbors are systematically staggered by D must have ordered distributions of the 0.6D long ‘holes’. In one of the two simplest cases, holes occur singly, and are separated laterally by two molecular diameters. In the other case, contiguous holes form transversely continuous channels or slots within the fibril. Electron micrographs of both fish bone and embryonic chick bone clearly show that at least the initial mineralization is intrafibrillar in these systems.