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Type I collagen, the predominant protein of vertebrates, polymerizes with type III and V collagens and non-collagenous molecules into large cable-like fibrils, yet how the fibril interacts with cells and other binding partners remains poorly understood. To help reveal insights into the collagen structure-function relationship, a data base was assembled including hundreds of type I collagen ligand binding sites and mutations on a twodimensional model of the fibril. Visual examination of the distribution of functional sites, and statistical analysis of mutation distributions on the fibril suggest it is organized into two domains. The "cell interaction domain" is proposed to regulate dynamic aspects of collagen biology, including integrin-mediated cell interactions and fibril remodeling. The "matrix interaction domain" may assume a structural role, mediating collagen cross-linking, proteoglycan interactions, and tissue mineralization. Molecular modeling was used to superimpose the positions of functional sites and mutations from the two-dimensional fibril map onto a three-dimensional x-ray diffraction structure of the collagen microfibril in situ, indicating the existence of domains in the native fibril. Sequence searches revealed that major fibril domain elements are conserved in type I collagens through evolution and in the type II/XI collagen fibril predominant in cartilage. Moreover, the fibril domain model provides potential insights into the genotype-phenotype relationship for several classes of human connective tissue diseases, mechanisms of integrin clustering by fibrils, the polarity of fibril assembly, heterotypic fibril function, and connective tissue pathology in diabetes and aging.Type I collagen is the most abundant protein in humans and other vertebrates, comprising much of the fibrous extracellular matrix scaffold of bones, tendons, skin, and many other tissues (1-4). In general, type I collagen and its binding partners are proposed to provide mechanical strength and form to tissues. Collagenous scaffolds are laid down and remodeled by cells and are also a predominant substrate for cell interactions, migration, and differentiation. Consequently, various debilitating human diseases are associated with type I collagen mutations, including osteogenesis imperfecta (OI, 2 brittle bone disease), Ehlers Danlos syndrome, vascular disorders, and others (3, 5). Type I collagen is also employed in human medicine as hemostatic sponges and implants to repair wounds and in tissue engineering applications as scaffolds (6).Type I collagen is synthesized in the endoplasmic reticulum as ␣1 and ␣2 procollagen chains, each encoded by separate genes that are translated into proteins somewhat longer than 1000 amino acid residues (3, 7). Nucleation domains on the C-terminal propeptide promote the polymerization of two ␣1 and one ␣2 chains into the procollagen triple helical monomer (Fig. 1, A and B). The triple helical domain of procollagen is composed of contiguous glycine-X-Y tri-peptide repeats, with the obligate glyci...

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The fine hair adhesive system found in nature is capable of reversibly adhering to just about any surface. This dry adhesive, best demonstrated in the pad of the gecko, makes use of a multilevel conformal structure to greatly increase inelastic surface contact, enhancing short range interactions and producing significant amounts of attractive forces. Recent work has attempted to reproduce and test the terminal submicrometre 'hairs' of the system. Here we report the first batch fabricated multi-scale conformal system to mimic nature's dry adhesive. The approach makes use of massively parallel MEMS processing technology to produce 20-150 µm platforms, supported by single slender pillars, and coated with ∼2 µm long, ∼200 nm diameter, organic looking polymer nanorods, or 'organorods'. To characterize the structures a new mesoscale nanoindenter adhesion test technique has been developed. Experiments indicate significantly improved adhesion with the multiscale system. Additional processing caused a hydrophilic to hydrophobic transformation of the surface and testing indicated further improvement in adhesion.

A synthetic, fully reversible, switchable, gecko‐inspired adhesive is presented. The biomimetic system is composed of flexible nickel paddles coated with aligned vertical polymeric nanorods. When subjected to a magnetic field, adhesion decreases by a factor of 40. The ability of the adhesive to controllably stick and release from a surface could enable technologies from ubiquitous latching systems to climbing microrobotics.