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1H-nmr studies of polyoxyethylene-bound homo-oligo-L-methionines

✍ Scribed by Anthony A. Ribeiro; Robert P. Saltman; Murray Goodman; Manfred Mutter

Publisher
Wiley (John Wiley & Sons)
Year
1982
Tongue
English
Weight
823 KB
Volume
21
Category
Article
ISSN
0006-3525

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✦ Synopsis

The use of 'H-nmr spectroscopy is demonstrated to be a useful analytical method to characterize the structure of synthetic peptides attached to soluble, macromolecular polyoxyethylene (POE) supports in the liquid-phase method (LPM) of peptide synthesis. We report an extensive 360-MHz lH-nmr study of POE-bound homo-oligo-L-methionine peptides. A combination of high field and selective saturation or Redfield pulse methods allows resolution of individual backbone NH and a-CH resonances of dilute peptides in the presence of strong resonances from macromolecular POE and/or protonated solvents. The nmr spectra for the POE-bound peptides in CDC13 are qualitatively similar to those of the low-molecular-weight Boc-L-Met,-OMe peptide esters. This corroborates other observations that POE has little effect on peptide structure. The backbone a-CH region of peptides is overlapped by signals from the terminal oxyethylene group of POE, but the peptide side-chain and lowfield backbone NH resonances are well resolved. In trifluoroethanol the Boc-&Met),-NH-POE heptamer and octamer adopt the right-handed a-helical structure, and the present nmr studies provide evidence for two strong intramolecular hydrogen bonds to stabilize the helices. In water, the N-deblocked derivatives, (L-Met),-NH-POE oligomers adopt P-sheet structure and manifest well-resolved nonequivalent NH resonances with 6-7 Hz 3 J ~~. c ~ coupling constants.

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