Conformational analyses of polyoxyethylene-bound homo-oligo-L-glutamates in a helix-supporting environment trifluoroethanol

A detailed conformational analysis of C-terminal polyoxyethylene-bound homo-oligo-L -glutamates (dimer, penta-heptamer) with N-terminal blocking groups, X = Boc, Ac, or pGlu, was carried out in the helix-supporting environment, trifluorethanol, using ¹H-nmr spectroscopy to observe backbone NH resonances. The nmr structural investigations for the three glutamate POE series were based on the assignment of individual amide NH resonances through deuteration, analyses of vicinal coupling constants (³J_NH-α-CH), measurements of the temperature-dependence of NH chemical shifts, saturation-transfer experiments, stable free radical titration studies, and titration experiments using a denaturing solvent (DMSO). From these investigations, a detailed picture was derived for the possible conformations of these POE-peptides.