American Scientist

November-December 2023

Volume: 111 Number: 6

Collagen is the body’s most abundant protein, strengthening bone, teeth, tendons, skin, and the support sheets of the internal organs. Its ropelike structure comes from winding three stands of amino acids into a triple helix. The amino acids are linked together with amide bonds that include carbonyl groups (carbon–oxygen double bonds), and the strands wind into helices because of charge interactions between different amides along the chain. The positively charged regions around the carbon atoms in carbonyls are called π-holes, and they’ve sparked spirited discussions among chemists about their origins. In "“(Don’t) Shut Your π-hole&rdquo," Dean J. Tantillo argues that the debates are productive if they help chemists design experiments to build better drugs, materials, and more. (Illustration by David Goodsell.)