Multinuclear magnetic resonance studies of collagen molecular structure and dynamics

✍ Scribed by D. A. Torchia; Y. Hiyama; S. K. Sarkar; C. E. Sullivan; P. E. Young

• Publisher: Wiley (John Wiley & Sons)
• Year: 1985
• Tongue: English
• Weight: 604 KB
• Volume: 24
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.360240107

✦ Synopsis

We have measured the percentages of cis and trans Gly-Pro and X-Hyp peptide bonds in thermally unfolded type I collagen. W-nmr solution spectra show that 16% of the Gly-Pro and 8% of the X-Hyp bonds are cis in unfolded chick calvaria collagen. These results support the hypothesis that cis-trans isomerization is the rate-limiting step in the propagation of the collagen triple helix. We have used multinuclear solid-state nmr to study the molecular dynamics of the collagen backbone in tendon, demineralized bone, and intact bone as a function of temperature, hydration, and pH. These studies show that collagen backbone motions are characterized by a broad distribution of correlation times, T, covering the range from 1 0 -4 to s. In the case of nonmineralized collagen, the root-mean-square fluctuations in azimuthal angle, yrms, range from ca. 10" when Ts to ca. 30" when T < lo-' s; in the case of bone collagen, yIms values are about half as large as those found in nonmineralized collagen. Backbone motions are negligible at temperatures below -25°C. This is also the case at 22°C when demineralized bone collagen is lyophilized. In contrast, flexibility of hydrated demineralized bone collagen greatly increases as pH is lowered from 7 to 2. The more limited flexibility observed at neutral pH is a consequence of the intermolecular interactions that contribute to fibril organization and strength. However, the fibrils retain significant flexibility at physiological pH, enabling them to distribute stress and dissipate mechanical energy.