¹³C‐¹H magnetic double‐resonance study of fetal enamel matrix proteins

Recently developed 13 C‐ 1 H nuclear magnetic double‐resonance techniques have been used to study proteins in the intact fetal enamel matrix. Enamel protein chains undergoing rapid, almost isotropic motion were detected in scalar decoupled 13 C‐nmr spectra, while motionally restricted enamel protein chains were principally observed in proton‐enhanced spectra. The latter spectra were obtained using a matched Hartmann‐Hahn contact to transfer polarization from protons to carbons (cross‐polarization). Both mobile and motionally restricted enamel protein chains were observed in dipolar decoupled 13 C‐nmr spectra. A comparison of integrated intensities obtained from the scalar decoupled and dipolar decoupled spectra showed that 70% of the fetal enamel protein chains exhibit rapid, nearly isotropic molecular motion (τ ≲ 10 −6 sec), while the remaining 30% are rigid or undergo only anisotropic molecular motion.