No AbstractScience EditorThere’s a lot of give, stretch and elasticity to large blood vessels, tendons, ligaments and heart muscle. That compliant behavior is the work of a yellowish mucoprotein called elastin, the main connective-tissue protein of such stretchable structures. Elastin’s main enemy in the body is pulmonary emphysema, which leaves its victims wheezing and gasping not just for breath but for therapeutic snortfuls of pure inhaled oxygen.