Conformational investigations on glycosylated threonine-oligopeptides of increasing chain length.
Stepwise solution syntheses are described of the homo-oligomers Z-(Thr)n-NHCH3 (n=1-4, I1-4), Z-¿[Gal(Ac)4beta]Thr¿n-NHCH3(n=1-5, II1-5) and Z-[(Galbeta)Thr]n-NHCH3 (n=1-5, III1-5). Members of the III1-5 series were obtained by de-acetylation of the corresponding oligomers of the II1-5 series. The conformational preferences of the terminally protected homo-peptides of the three series were investigated by FT-IR absorption spectroscopy both in the solid state and in CDCl3 solution, at various concentrations. Proton NMR measurements in CDCl3 and in DMSO-d6 were also carried out and the effect of temperature variation on the chemical shifts of amide protons was determined in DMSO-d6 (range 298-335 K) and in CDCl3 (range 298-320K). CD spectra were recorded in water and in TFE. Solubility problems prevented measurements in CDCl3 solution for Z-(Thr)4-NHCH3 and for the entire III1-5 series. The existence of unordered structures in the carbohydrate-free oligomers and of more or less extended, organized structures in the glycosylated derivatives is indicated by the NMR and IR measurements. The sugar moieties apparently show a structure-inducing effect on the peptide chain.
Biondi
L
L
Biopolymer Research Centre, CNR, Department of Organic Chemistry, University of Padova, Italy.
Filira
F
F
Gobbo
M
M
Pavin
E
E
Rocchi
R
R
D006031:Glycosylation; D009842:Oligopeptides / Q000737:chemistry*; D011487:Protein Conformation; D013057:Spectrum Analysis; D013912:Threonine / Q000737:chemistry*
D009842:Oligopeptides; D013912:Threonine