Peptide models XXIV: An ab initio study on N-formyl-L-prolinamide with trans peptide bond. The existence or non-existence of aL and e L conformations

H.A.BALDONI; A M RODRIGUEZ; G.ZAMARBIDE; ENRIZ R.D.; O.FARKAS; L.TORDAY; C.SOSA; I.JAKLI; A. PERCZEL; M.HOLLOSI; I.G.CSIZMADIA

JOURNAL OF MOLECULAR STRUCTURE THEOCHEM

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 1999 vol. 465 p. 465 - 479

0166-1280

N-formyl-L-prolinamide was subjected to geometry optimization at three levels of theory: HF/3-21G, HF/6-31G (d) and B3LYP/6-31G (d). At all three levels of computation the global minimum was g L (inverse g -Turn) backbone conformation with two ring-puckered forms ??UP?? and ??DOWN??. At HF/3-21G level of theory three backbone conformations were found g L, e L, and aL. At higher levels of theory the e L, and aL conformations disappeared. The ??UP?? and ??DOWN?? ring-puckered forms, in the g L backbone conformation, led to practically identical vibrational spectra at the B3LYP/6-31G (d) level of theory