Nuclear Magnetic Resonance Relaxation Studies of Plant Polyester Dynamics. 1. Cutin from Limes

Magic angle spinning (MAS) ¹³C NMR results are reported for intact lime cuticle and its two major components, cutin and wax. DPMAS and CPMAS experiments permit determination of the numbers of relatively mobile and immobile carbons in each biopolymer sample. T_1p(C) and T₁(C) relaxation experiments characterize kilohertz- and megahertz-regime motions, respectively; they indicate that motional restrictions are present at cross-links of the cutin polymer and along alkyl chains of the wax alone. Values of 〈T_1p(C)〉 and 〈T₁(C)〉, which differ significantly for analogous carbon sites of cutin and wax individually, approach common values for the two materials in the intact lime cuticle. These results, together with measurements of T_1p,(H), provide evidence for hydrophobic association within the plant cuticle of the long aliphatic chains of cutin and wax.