Stapled peptides and proteins with enhanced stability are of great importance in medicinal chemistry and chemical biology. Now Goncalo Bernardes' group has developed a new oxetane-bis-alkylating reagent which reacts directly with disulfide-bridged peptides or proteins under physiological conditions and replaces the unstable disulfide bridge by a stable tether. The modified peptides and proteins are then more stable but still preserve their biological activity. The reagent has a great potential in stabilizing peptide or protein tertiary structures for structural biology or medicinal chemistry.