title: Conformational investigations on glycosylated asparagine-oligopeptides of increasing chain length.
abstract: Stepwise solution syntheses of the homo-oligomers Boc-(Asn)n-NHCH3 (n = 1-5; I1-5), Boc-[[GlcNAc(Ac)3beta]Asn]n-NHCH3 (n = 1-8; II1-8), and Boc-[(GlcNAcbeta)Asn]n-NHCH3 (n = 1-8; III1-8) are described. Members of the series III were obtained by deacetylation of the corresponding members of the series II. The conformational preferences of the N-protected homo-peptides of the three series were investigated by spectroscopic techniques. 1H-NMR measurements were carried out in various solvents; the CD spectra were recorded in water, aqueous SDS and TFE. The poor solubility of the oligomers of the three series prevented FT-IR measurements in solution. NMR and IR measurements indicate the existence of unordered structures containing some gamma-turns in the carbohydrate-free oligomers and the presence of beta-turns in the glycosylated oligopeptides, whether acetylated or not. The CD spectra do not indicate the presence of organized structures. The sugar moieties apparently do not have a structure-inducing effect on the asparagine homo-oligomer main chain.
authors.affiliation: Department of Organic Chemistry, University of Padova, Biopolymer Research Centre, CNR, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Biondi
authors.forename: Fernando
authors.initials: F
authors.lastname: Filira
authors.forename: Marina
authors.initials: M
authors.lastname: Gobbo
authors.forename: Raniero
authors.initials: R
authors.lastname: Rocchi
mesh_terms: D001216:Asparagine / Q000737:chemistry*; D002942:Circular Dichroism; D006031:Glycosylation; D009682:Magnetic Resonance Spectroscopy; D009842:Oligopeptides / Q000737:chemistry*; D010452:Peptide Biosynthesis; D011138:Polytetrafluoroethylene; D012967:Sodium Dodecyl Sulfate / Q000737:chemistry; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013055:Spectrophotometry, Infrared; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D009842:Oligopeptides; D012967:Sodium Dodecyl Sulfate; D001216:Asparagine; D011138:Polytetrafluoroethylene