Observation of the Glycines in Elastin Using ¹³C and ¹⁵N Solid-State NMR Spectroscopy and Isotopic Labeling

We report the solid-state 13C and 15N NMR of insoluble elastin which has been synthesized in vitro with isotopically enriched glycine. Most of the glycines reside in a domain with good cross-polarization (CP) efficiencies, although surprisingly, a portion resides in an environment that is not detectable using CP. Our data indicate that much of the 13C population resides in regions of significant conformational flexibility. To support these conclusions, we present 13C and 15N cross-polarization with magic-angle-spinning (CPMAS) data in conjunction with "direct-polarization", nonspinning CP, and T1 measurements.