Detection of Labile Conformations of Elastin's Prolines by Solid-State Nuclear Magnetic Resonance and Fourier Transform Infrared Techniques.

Samples of native elastin are prepared with high levels of enrichment at its prolines, which are believed to play a major role in the elasticity of elastin. Major and minor populations of trans and cis isomers at the Xaa-Pro imide bonds are detected in two-dimensional 13C nuclear magnetic resonance (NMR) experiments. One- and two-dimensional 13C NMR and isotope-edited Fourier transform infrared experiments are also used to identify the prolines' folded and unfolded states, type II β-turn and random coil, respectively, at physiological temperatures. This study provides new details about elastin's conformational ensemble. In addition, the cis-trans isomerization of its abundant prolines provides an additional mechanism of fiber elongation in tissue.