Conformational investigations on glycosylated threonine-oligopeptides of increasing chain length

✍ Scribed by Laura Biondi; Fernando Filira; Marina Gobbo; Enrico Pavin; Raniero Rocchi

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 180 KB
• Volume: 4
• Category: Article
• ISSN: 1075-2617
• DOI: 10.1002/(sici)1099-1387(199802)4:1<58::aid-psc129>3.0.co;2-b

✦ Synopsis

Stepwise solution syntheses are described of the homo-oligomers Z-(Thr) n -NHCH 3 (n1±4,

Members of the III 1±5 series were obtained by de-acetylation of the corresponding oligomers of the II 1±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 CDCl 3 solution, at various concentrations. Proton NMR measurements in CDCl 3 and in DMSO-d 6 were also carried out and the effect of temperature variation on the chemical shifts of amide protons was determined in DMSO-d 6 (range 298±335 K) and in CDCl 3 (range 298± 320K). CD spectra were recorded in water and in TFE. Solubility problems prevented measurements in CDCl 3 solution for Z-(Thr) 4 -NHCH 3 and for the entire III 1±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.