title: An experimental charge density of HEPES.
abstract: We report the experimental charge density of HEPES [4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid], which is a common buffering agent. The structure was refined using the Hansen-Coppens formalism. The ability of the HEPES molecule to form stable intermolecular interactions and intermolecular hydrogen bonds in the crystal structure is discussed in terms of its buffering properties. The protonation mode observed in the crystal structure is different from that expected in solution, suggesting that additional factors must be taken into consideration in order to explain the solution properties of the compound. As ordered HEPES molecules are found in the active sites of proteins in several protein crystal structures, our results will allow for quantitative analysis of the electrostatic potential of the interacting surfaces of those proteins.
authors.affiliation: Department of Chemistry, Warsaw University, Pasteura 1, 02-093 Warszawa, Poland.
authors.forename: Paweł
authors.initials: P
authors.lastname: Sledź
authors.forename: Radosław
authors.initials: R
authors.lastname: Kamiński
authors.forename: Maksymilian
authors.initials: M
authors.lastname: Chruszcz
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Zimmerman
authors.forename: Wladek
authors.initials: W
authors.lastname: Minor
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Woźniak
mesh_terms: D002021:Buffers; D018360:Crystallography, X-Ray; D006531:HEPES / Q000737:chemistry*; D006860:Hydrogen Bonding; D008958:Models, Molecular; D008968:Molecular Conformation; D011522:Protons; D055672:Static Electricity
chemical_list: D002021:Buffers; D011522:Protons; D006531:HEPES