title: The alanine model dipeptide Ac-Ala-NH2 exists as a mixture of C7(eq) and C5 conformers.
abstract: Microwave spectroscopy has been applied to characterize the conformations adopted in the gas phase by a small peptide derived from alanine, N-acetyl-L-alaninamide (Ac-Ala-NH(2)). This compound was vaporized by laser ablation and shown to exist as a mixture of C(eq)(7) and C(5) conformers stabilized by a CO···HN intramolecular hydrogen bond closing a seven- or a five-membered ring, respectively. The complicated quadrupole hyperfine structure originated from two (14)N nuclei has been completely resolved for both species and the derived nuclear quadrupole coupling constants have been used to determine the Ramachandran angles that describe their molecular shapes.
authors: Grupo de Espectroscopía Molecular (GEM), Edificio Quifima, Laboratorios de Espectroscopia y Bioespectroscopia, Parque Científico UVa, Universidad de Valladolid, 47005 Valladolid, Spain.
authors: Carlos
authors: C
authors: Cabezas
authors: Marcelino
authors: M
authors: Varela
authors: Vanessa
authors: V
authors: Cortijo
authors: Ana I
authors: AI
authors: Jiménez
authors: Isabel
authors: I
authors: Peña
authors: Adam M
authors: AM
authors: Daly
authors: Juan C
authors: JC
authors: López
authors: Carlos
authors: C
authors: Cativiela
authors: José L
authors: JL
authors: Alonso
mesh_terms: D000409:Alanine / Q000031:analogs & derivatives* / Q000737:chemistry*; D004151:Dipeptides / Q000737:chemistry*; D006860:Hydrogen Bonding; D008962:Models, Theoretical; D009584:Nitrogen / Q000737:chemistry
chemical_list: D004151:Dipeptides; C089248:N-acetylalaninamide; D009584:Nitrogen; D000409:Alanine