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 and isomers at the Xaa-Pro imide bonds are detected in two-dimensional C nuclear magnetic resonance (NMR) experiments. One- and two-dimensional C 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 isomerization of its abundant prolines provides an additional mechanism of fiber elongation in tissue.