title: Characterization of water wires inside hydrophobic tubular peptide structures.
abstract: The crystallographic observation of a hydrophobic, empty channel (diameter approximately 5.2 A) in the peptide Boc-(D)Pro-Aib-Leu-Aib-Val-OMe, prompted the investigation of the analog Boc-(D)Pro-Aib-Val-Aib-Val-OMe in which the side chain at position 3 was shortened, resulting in the structure of a channel (diameter approximately 7.5 A) containing a one-dimensional wire of water molecules. Crystallization in the space group P6(5) facilitates formation of a pore lined entirely by hydrocarbon side chains. Two forms of the entrapped water wires, with O...O separations of 3.5 and 2.6 A, are discussed. A lone hydrogen bond between the adjacent pairs of water molecules in the wire, with no strong interactions between the second water hydrogen and the hydrophobic walls of the channel, is a feature of the one-dimensional array. The structure provides the first crystallographic characterization of a water wire in a hydrophobic channel with implications in water and proton transport in membranes and carbon nanotubes.
authors: Department of Physics, Indian Institute of Science, Bangalore-560012, India.
authors: Upadhyayula S
authors: US
authors: Raghavender
authors: Subrayashastry
authors: S
authors: Aravinda
authors: Narayanaswamy
authors: N
authors: Shamala
authors: Kantharaju
authors: Rajkishor
authors: R
authors: Rai
authors: Padmanabhan
authors: P
authors: Balaram
mesh_terms: D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D057927:Hydrophobic and Hydrophilic Interactions; D008958:Models, Molecular; D010455:Peptides / Q000737:chemistry*; D017434:Protein Structure, Tertiary; D014867:Water / Q000737:chemistry*
chemical_list: D010455:Peptides; D014867:Water