title: High-performance liquid chromatography and nuclear magnetic resonance study of linear tetrapeptides and octapeptides containing N-methylated amino acid residues.
abstract: Chromatographic behavior of a series of N-methylated tetra and octapeptides on a reversed-phase sorbent was studied considering the information obtained on these compounds by NMR spectroscopy. The modified tetrapeptides were derived from GFFY-NH2, GFFF-NH2 and GFFH-NH2 primary structures by N-methylation at various peptide bond positions. Similarly, the N-methylated octapeptides were based on TPK(Pac)T C-terminally elongated forms of GFFY and GFFF. It was found that many studied N-methylated peptides provide broad peaks as a consequence of cis/trans isomerism of the R1CON(CH3)R2 peptide bond. The extent of the peak spreading depends on the following important factors: the nature of the surrounding amino acid residues, the location of the modified peptide bond within the peptide chain, temperature, and mobile phase flow-rate. All these aspects were critically evaluated. Nearly complete separation of the individual conformers of GF(NMe)FY-NH2 was obtained applying fast chromatography on short column packed with 20-30 microm reversed-phase sorbent.
authors.affiliation: Institute of Chemical Technology, Department of Analytical Chemistry, Technická 5, 166 28 Prague 6, Czech Republic.
authors.forename: David
authors.initials: D
authors.lastname: Sýkora
authors.forename: Lenka
authors.initials: L
authors.lastname: Záková
authors.forename: Milos
authors.initials: M
authors.lastname: Budesínský
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D009682:Magnetic Resonance Spectroscopy; D008745:Methylation; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000737:chemistry*; D011522:Protons; D012997:Solvents; D013237:Stereoisomerism; D013696:Temperature
chemical_list: D000596:Amino Acids; D009842:Oligopeptides; D011522:Protons; D012997:Solvents