RECENT DEVELOPMENTS IN RETRO PEPTIDES AND PROTEINS - AN ONGOING TOPOCHEMICAL EXPLORATION

Main-chain peptidomimetics based on peptide-bond reversal and inversio n of chirality represent important structural alterations for peptides and proteins, and are highly significant for biotechnology; these mod ifications have been widely applied: the D-HIV-protease dimer cleaves only all-D substrate; an all-D-hexapeptide opioid is able to produce a nalgesia following intraperitoneal administration. Antigenicity and im munogenicity can be achieved by metabolically stable antigens such as all-D- and retro-inverso-isomers of natural antigenic peptides. Isomer s, including the retro- and retro-inverso- forms, of hybrid peptides d erived from cercropin A and melittin, maintain antimicrobial activity. Therefore, an insight is provided into structure-activity relationshi ps and the rational design of biologically important isomeric peptides .