Isotopic labeling strategies are coupled with solid-state NMR spectroscopy to characterize elastin's abundant glycines (Gly) and prolines (Pro) and the sequences that include these residues. Elastin is prepared with isotopic labels at Gly, Pro, and Val-three of its four most abundant amino acids. Solid-state N-15-H-1 nuclear magnetic resonance (NMR) spectra show four resolved glycine populations, whereas three features are observed for the prolines. Selection of the Val-Pro and Gly-Gly pairs found exclusively and abundantly in the hydrophobic domains confirms these assignments and also provides more information on the conformational ensembles of elastin. The H-1(N) and N-15 temperature coefficients indicate that discrete secondary structures are present, even among significant populations with rapid conformational fluctuations typical of a random coil. C-13-N-15 couplings and the C-13 chemical shift anisotropy (CSA) are also utilized to confirm assignments and structure, respectively. Implications for the evolving conformational ensemble model for elastin are also discussed.