The alanine model dipeptide Ac-Ala-NH2 exists as a mixture of C-7(eq) and C-5 conformers

作者：Cabezas Carlos; Varela Marcelino; Cortijo Vanessa; Jimenez Ana I; Pena Isabel; Daly Adam M; Lopez Juan C; Cativiela Carlos; Alonso Jose L^*

来源：Physical Chemistry Chemical Physics, 2013, 15(7): 2580-2585.

DOI：10.1039/c2cp43924g

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-NH2). This compound was vaporized by laser ablation and shown to exist as a mixture of C-7(eq) and C-5 conformers stabilized by a CO center dot center dot center dot HN intramolecular hydrogen bond closing a seven- or a five-membered ring, respectively. The complicated quadrupole hyperfine structure originated from two N-14 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.

• 出版日期2013