NUCLEAR MAGNETIC-RESONANCE STUDIES OF CUTIN, AN INSOLUBLE PLANT POLYESTER

High-resolution 13C NMR studies have been conducted for cutin, a biopolyester that forms the structural component of the protective cuticle in terrestrial plants. With use of cross polarization-magic angle spinning (CPMAS) methods, the cutin structure is found to include methylene, methine, alkene, arene, keto, and ester functional groups. In addition, several types of mobile aliphatic carbons are observed by direct polarization (DP) methods. Estimates of the relative composition of each carbon type are also available from appropriate comparisons of CPMAS and DPMAS spectra. A combination of 13C T1, 1H T1ρ, and line-width measurements suggests that cutin is a moderately flexible netting, with motional constraints at particular cross-link sites. A preliminary structural model is proposed to account for the compositional and dynamic information obtained from 13C NMR experments.