Hydrogen Bonds Visualized

Abstract

Hydrogen bonds are ubiquitous—and universally important—in chemistry. They give water its unique properties, speed or slow reactions, and hold together the three-dimensional shapes of DNA, proteins, and other supramolecular structures. But chemists have never actually seen them. Now, with high-resolution atomic force microscopy (AFM), they have (Science 2013, DOI: 10.1126/science.1242603). The stunning images should enhance understanding of hydrogen bonds’ hitherto elusive properties. AFM has produced several pinup molecular images over the past several years—showing the atoms and bonds in single molecules of pentacene, revealing the bond order of complex molecules, and exposing before and after pictures of molecules undergoing a chemical reaction. Hydrogen bonds are another big win for the technique. Roughly defined, these bonds are weak attractive interactions between an atom or group of atoms and a hydrogen that is covalently bonded to an atom that is more electronegative than hydrogen (Pure Appl. Chem...