title: Conformations of cis- and trans-2,3-methanomethionine stereoisomers in the tripeptide mimic system Ac[cyclo-M]NHiPr.
abstract: Quenched molecular dynamics (QMD) was used to simulate low-energy conformers of the tripeptide mimics Ac¿cyclo-Met¿NHiPr, where the 2.3-methanomethionine is the cis-derivative (2R,3S)-cyclo-Met and the trans-derivative (2R,3R)-cyclo-Met. Variations of the favored omicron, upsilon values. and differences between the simulated preferred conformations for the two structures, were rationalized and discussed. Physical data for the cis-derivative (NMR, CD and FT-IR) gave no conclusive evidence for any preferred conformation. However for the trans-derivative, Ac¿(2R,3R)-cyclo-Met¿NHiPr, the physical data suggests that a conformer with partial helical structure is favored. This work provides details of how the rigidly constrained side chain and cyclopropane of 2,3-methanoamino acids can be used to manipulate phi, psi values in a logical fashion.
authors.affiliation: Department of Chemistry, Texas A & M University, College Station, USA. burgess@chemvx.tamu.edu
authors.forename: K
authors.initials: K
authors.lastname: Burgess
authors.forename: C Y
authors.initials: CY
authors.lastname: Ke
mesh_terms: D055598:Chemical Phenomena; D002627:Chemistry, Physical; D002942:Circular Dichroism; D003521:Cyclopropanes / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008715:Methionine / Q000031:analogs & derivatives* / Q000737:chemistry; D008958:Models, Molecular; D015394:Molecular Structure; D009842:Oligopeptides / Q000737:chemistry*; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017550:Spectroscopy, Fourier Transform Infrared; D013237:Stereoisomerism
chemical_list: D003521:Cyclopropanes; D009842:Oligopeptides; C106781:acetyl(cyclo-methionine)isopropylamide; C083932:2,3-methanomethionine; D008715:Methionine