title: Conformation and orientation of tetraalanine in a lyotropic liquid crystal studied by nuclear magnetic resonance.
abstract: The (1)H NMR spectra of two isotopomers of tetraalanine deuterated on the two external methyl groups and on the two internal ones, respectively, were recorded in the lyotropic solvent cesium pentadecafluorooctanoate (CsPFO)/water. Eight dipolar couplings could be estimated from the spectra. The set of dipolar couplings was fitted assuming that one rigid conformer is present. Of the four major conformers considered, selected on the basis of theoretical calculations, the one characterized by the two couples of internal dihedral angles in the Ramachandran region of PPII resulted to be the only one to fit the set of couplings within experimental error. The data indicate that the molecule is oriented with the long molecular axis tilted with respect to the surface of the micelles formed by CsPFO.
authors.affiliation: Istituto per i Processi Chimico-Fisici, Consiglio Nazionale delle Ricerche, Area della Ricerca di Pisa, via G. Moruzzi 1, 56124 Pisa, Italy.
authors.forename: Silvia
authors.initials: S
authors.lastname: Pizzanelli
authors.forename: Susanna
authors.initials: S
authors.lastname: Monti
authors.forename: Claudia
authors.initials: C
authors.lastname: Forte
mesh_terms: D000409:Alanine / Q000737:chemistry*; D050866:Liquid Crystals / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008823:Micelles; D008958:Models, Molecular; D008968:Molecular Conformation; D009842:Oligopeptides / Q000737:chemistry*; D012997:Solvents
chemical_list: D008823:Micelles; D009842:Oligopeptides; D012997:Solvents; D000409:Alanine