1.3 The partial double bond feature is a result of partial sharing(resonance)of electrons between the carbonyl oxygen and amide nitrogen 1.1.4 The atoms attached to the peptide bond are coplanar with the oxygen and hydrogen atom in trans positions. 1.2 X-ray studies of a-keratin(the fibrous protein ma king up hair and wool) revealed a repeating unit of 5.4 A(Astury in the 1930s)1.1.3 The partial double bond feature is a result of partial sharing (resonance) of electrons between the carbonyl oxygen and amide nitrogen. 1.1.4 The atoms attached to the peptide bond are coplanar with the oxygen and hydrogen atom in trans positions. 1.2 X-ray studies of a-keratin (the fibrous protein making up hair and wool) revealed a repeating unit of 5.4 Å (Astury in the 1930s)