Glycyl radicals are produced by hydrogen abstraction from the Cα of glycine. They are reasonably stable compared to other types of amino acid Cα radicals and were observed in EPR of collagen subjected to gamma rays . Molecular dynamics indicate that the formation of a glycyl radical is accompanied by large changes in the backbone dihedral angles , which we propose underlie the disruption of hydrogen bonding in pigmented cartilage observed in the current study.