The bond that determines the secondary structure of proteins is hydrogen bond. Depending on hydrogen bonding, two main types of secondary structure are the -helix and the -sheet.
The -helix is a right-handed coiled strand. The side-chain substituents of the amino acid groups in an a-helix extend to the outside. Hydrogen bonds form between the oxygen of the of each peptide bond in the strand and the hydrogen of the group of the peptide bond four amino acids below it in the helix.
The hydrogen bonding in a -sheet is between strands (inter-strand) rather than within strands (intra-strand). The sheet conformation consists of pairs of strands lying side-by-side