Subfibrillar structure of type I collagen observed by atomic force microscopy

Abstract

We have imaged native rat tail and reconstituted bovine dermal type I collagen by atomic force microscopy, obtaining a level of detail comparable to that obtained on the same samples by transmission electron microscopy. The characteristic 60-70 nm D periodicity consists of ridges exhibiting high tip-sample adhesion alternating with 5-15-nm-deep grooves having low adhesion. We also observe an intraperiod or "minor" band consisting of 1-nm-deep grooves, and "microfibrils" arranged parallel to or inclined approximately 5 degrees to the fibril axis. In air collagen fibrils exhibit negligible compression under the forces exerted by the tip. When immersed in water the subfibrillar features disappear and the fibrils become softer, compressing by 5% of their height under an 11-nN force. Material on the surface of the sample sometimes accumulates on the atomic force microscope tip; contrary to expectation such tip contamination can improve as well as reduce resolution.

Association of Type VI Collagen with D-Periodic Collagen Fibrils in Developing Tail Tendons of Mice.

“…Mature collagen fibrils are formed by the polymerization of collagen molecules staggered by D (about 67 nm, 1/4.4 of the molecular length) from each other, and hence showing D-periodicity. The D-periodic repetition of elevated and depressed surfaces along the collagen fibrils, corresponding to overlap (materially dense) and gap (materially sparse) regions, respectively, has been revealed by AFM (BASELT et al, 1993). In the present study, the probable interaction of type VI collagen with D-periodic collagen fibrils through PGs/GAGs was topologically shown by the increase in the depth of the groove after hyaluronidase digestion using AFM imaging.…”

Effect of material and structural factors on fracture behaviour of mineralised collagen microfibril using finite element simulation

“…Experimental work conducted by Orgel, Fratzl and others have proved that all collagen-based tissues are organized into hierarchical structures, where the lowest hierarchical level consists of triple helical collagen molecules (Fratzl, 2008;Orgel et al, 2006;Orgel et al, 2001) and the multiscale structure is defined as TC/fibrils/fibres. Also, other authors have observed a longitudinal microfibrillar structure with a width of 4 -8 nm (Habelitz et al, 2002;Baselt et al, 1993). Three-dimensional image reconstructions of 36 nm-diameter corneal collagen fibrils also showed a 4 nm repeat in a transverse section that was related to the microfibrillar structure (Holmes et al, 2001).…”

Mathematical modeling of collagen turnover in biological tissue

“…The extracellular collagen molecule, procollagen, is made up of three left-handed helix polypeptides, the so-called α-chains, coiled-up in a right-handed helical structure, about 300 nm long and 1.5 nm in diameter (Bella et al, 1994;Orgel et al, 2001;Bhattacharjee & Bansal, 2005). Collagen molecules assemble along a given direction through covalent bonds to form collagen microfibrils, constituting the basic building block of collagen fibrils (Baselt et al, 1993;Hulmes et al, 1995;Orgel et al, 2006Orgel et al, , 2011. The collagen fibrils are gathered in the extracellular matrix to form bundles of collagen fibers.…”