No side groups are involved in 2° structure H-bonding. Which atoms are directly involved in α - helix and β -sheet H-bonding?

Answer 1

Only the N–H and C=O bonds of the amide linkages (-NH–CO-) between amino acids that hold the peptide together are directly involved in α-helix and β-sheet hydrogen bonding. The H atom of the N–H group of one amide linkage forms a hydrogen bond by interacting with the O atom of the C=O group of another amide linkage.