Cross-polarization 13C nuclear magnetic resonance spectroscopy of collagen

Abstract

Natural abundance 13C nuclear magnetic resonance (nmr) spectra have been obtained for samples of a variety of native collagens by use of cross-polarization (CP) techniques which permit high resolution natural abundance 13C nmr spectra of solids to be obtained with high sensitivity. The CP 13C nmr spectra of lyophilized skin and tendon collagens consisted of two broad resonance envelopes spanning a five kHz range. Hydrated tendon collagen gave rise to a CP spectrum very similar to that obtained for the lyophilized sample, indicating that it retains its solid-like properties. In contrast, hydrated skin collagen became denatured under the conditions of the CP experiment and subsequently gave rise to a conventional high-resolution Fourier transform (FT) nmr spectrum. The CP 13C nmr spectrum of ivory was similar to those of lyophilized skin and tendon collagens, demonstrating the solid-like character of the collagen in dentine, whereas the CP spectrum of bovine nasal cartilage reflected the presence of highly mobile proteoglycan components in addition to relatively rigid collagen molecules. In the case of ivory, the resolution of the CP spectrum was enhanced by “magic angle” spinning to a degree approaching that of conventional FT 13C nmr spectra of denatured collagen in solution. Because of its ability to probe the dynamic properties of solid-like biological molecules, CP 13C nmr spectroscopy should be a valuable investigative tool for future studies.