Solid-State NMR Spectroscopy and Isotopic Labeling Target Abundant Dipeptide Sequences in Elastin's Hydrophobic Domains.

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 15N-¹H 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 ¹HN and 15N temperature coefficients indicate that discrete secondary structures are present, even among significant populations with rapid conformational fluctuations typical of a random coil. 13C-15N couplings and the 13C 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. [ABSTRACT FROM AUTHOR]