title: Halogen bonds in biological molecules.
abstract: Short oxygen-halogen interactions have been known in organic chemistry since the 1950s and recently have been exploited in the design of supramolecular assemblies. The present survey of protein and nucleic acid structures reveals similar halogen bonds as potentially stabilizing inter- and intramolecular interactions that can affect ligand binding and molecular folding. A halogen bond in biomolecules can be defined as a short C-X...O-Y interaction (C-X is a carbon-bonded chlorine, bromine, or iodine, and O-Y is a carbonyl, hydroxyl, charged carboxylate, or phosphate group), where the X...O distance is less than or equal to the sums of the respective van der Waals radii (3.27 A for Cl...O, 3.37 A for Br...O, and 3.50 A for I...O) and can conform to the geometry seen in small molecules, with the C-X...O angle approximately 165 degrees (consistent with a strong directional polarization of the halogen) and the X...O-Y angle approximately 120 degrees . Alternative geometries can be imposed by the more complex environment found in biomolecules, depending on which of the two types of donor systems are involved in the interaction: (i) the lone pair electrons of oxygen (and, to a lesser extent, nitrogen and sulfur) atoms or (ii) the delocalized pi -electrons of peptide bonds or carboxylate or amide groups. Thus, the specific geometry and diversity of the interacting partners of halogen bonds offer new and versatile tools for the design of ligands as drugs and materials in nanotechnology.
authors.affiliation: Institut de Biologie Moléculaire et Cellulaire, Centre National de la Recherche Scientifique, Unité Propre de Recherche 9002, Université Louis Pasteur, 15 Rue René Descartes, F-67084 Strasbourg, France. p.auffinger@ibmc.u-stasbg.fr
authors.forename: Pascal
authors.initials: P
authors.lastname: Auffinger
authors.forename: Franklin A
authors.initials: FA
authors.lastname: Hays
authors.forename: Eric
authors.initials: E
authors.lastname: Westhof
authors.forename: P Shing
authors.initials: PS
authors.lastname: Ho
mesh_terms: D003596:Cytosine / Q000737:chemistry*; D006219:Halogens / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D055672:Static Electricity; D014529:Uridine / Q000737:chemistry*
chemical_list: D006219:Halogens; D003596:Cytosine; D014529:Uridine