Selection of side-chain carbons in a high-molecular-weight, hydrophobic peptide using solid-state spectral editing methods.

Solid-state spectral editing techniques have been used by others to simplify 13C CPMAS spectra of small organic molecules, synthetic organic polymers, and coals. One approach utilizes experiments such as cross-polarization-with-polarization-inversion and cross-polarization-with-depolarization to generate subspectra. This work shows that this particular methodology is also applicable to natural-abundance 13C CPMAS NMR studies of high-molecular-weight biopolymers. The editing experiments are demonstrated first with model peptides and then with alpha-elastin, a high-molecular-weight peptidyl preparation obtained from the elastic fibers in mammalian tissue. The latter has a predominance of small, nonpolar residues, which is evident in the crowded aliphatic region of typical 13C CPMAS spectra. Spectral editing is particularly useful for simplifying he aliphatic region of the NMR spectrum of this elastin preparation.