Intramolecular cross-linking is predicted to stabilize the folded state of peptides and proteins most effectively if the cross-linker provides a rigid link that is well-matched in end-to-end distance with attachment sites in the peptide or protein. We describe a thiol-reactive sulfonated alkyne-based cross-linker that is demonstrably more effective than more flexible counterparts. Exceptional stabilization of helical structure in short peptides is obtained.