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Scanning tunnelling microscopy of collagen I reveals filament bundles to be arranged in a left-handed helix.

Collagen I is the most abundant protein found in the body. Its quaternary structure has been extensively characterised and consists of filaments arranged into bundles. In this study we used scanning tunnelling microscopy to image the collagen I filaments and fibrils directly. The images suggested that filaments are arranged into a left-handed helical structure with a periodicity of about 10nm. Such a structure potentially adds increased tensile strength to the collagen fibrils.