Synthetic peptide fibre. Molecular model of a synthetic collagen-like peptide fibre, showing three different ways of representing the structure. Peptides are small molecules formed from amino acids. Peptides can be linked together to form proteins. Collagen is a long, fibrous, structural protein that usually takes the form of a triple helix, as seen here. Synthetic peptide collagen chains have a range of medical uses, such as in skin grafts and cosmetic surgery. 674 atoms are shown in this model. The secondary structure (red, yellow, pink helices) is overlaid on tubular and space-filled molecular models.