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 simplif y C-13 CPMAS spectra of small organic molecules, synthetic organic polymers , and coals. One approach utilizes experiments such as cross-polarization-w ith-polarization-inversion and cross-polarization-with-depolarization to ge nerate subspectra. This work shows that this particular methodology is also applicable to natural-abundance C-13 CPMAS NMR studies of high-molecular- weight biopolymers. The editing experiments are demonstrated first with mod el peptides and then with alpha -elastin, a high-molecular-weight peptidyl preparation obtained from the elastic fibers in mammalian tissue. The latte r has a predominance of small, nonpolar residues, which is evident in the c rowded aliphatic region of typical C-13 CPMAS spectra. Spectral editing is particularly useful for simplifying the aliphatic region of the NMR spectru m of this elastin preparation.