Scientists have devised a simple technique for shielding biologically important molecules from degradation, which could open the door to longer-lasting drugs.

Short chains of amino acids called peptides help to control processes ranging from food intake to communication between neurons. But many natural enzymes in the body snip peptides apart, limiting their use in medicine. E. James Petersson at the University of Pennsylvania in Philadelphia and his colleagues tried a simple fix: substituting sulfur for the oxygen atom located at a peptide bond often sliced by enzymes.

Making the atomic swap in glucagon-like peptide-1, which helps to regulate blood-sugar levels and appetite, rendered the modified peptide as much as 750 times more stable than the natural variety. Rats treated with the more durable form of the peptide had smaller blood-sugar spikes after meals than rats treated with the naturally occurring peptide.