How is the peptide crossbridge different from the tetrapepti

Solution

A cross bridge is made up of peptides usually pentapeptide though other form can exist they connect tetrapeptide chain side chain at 3 rd amino acid of one chain and 4 amino acid of other.while tetrapeptide side chain consists of four amino acid sequence L alanine ,D glutamic acid L lysine D alanine. Each N acetyl muramic acid of glycan strand is linked to four amino acid by peptide bond.