Figure 10.

A model depicting the collagen molecule composed of rigid (black) and flexible (red) regions (A) and a quarter-staggered array of 5 molecules packed laterally that make up the microfibril (B) in the tendon. The numbers under the molecular bar code illustrated in A are the amino acid residue numbers. The flexible and rigid regions shown in A are blown up below the bar code. Initially, under stress the red regions of the molecule are stretched. The banding pattern of the collagen D period is shown in B. The bands a through e represent the positively staining bands characteristic of collagen fibrils seen by electron microscopy that arise from alignment of all the flexible regions in the collagen molecules. The negatively staining bands, showing the hole and overlap regions at the bottom of B, illustrate the penetration of stain into the region of the microfibril devoid of amino acids.