We have recorded high-resolution l3C-nmr spectra of collagen fibrils in the solid state by the cross-polarization-magic-angle-spinning (CP-MAS) method and analyzed the spectra with reference to those of collagenlike polypetides. We used two kinds of model polypeptides to obtain reference 13C chemical shifts of major amino acid residues of collagen (Gly, Pro, Ala, and Hyp): the 3,-helical polypeptides [(GlyIJI, (Pro)JI, (Hyp),, and (Ala-Gly-Gly).II],
and the triple-helical polypeptides [(Pro--Gly-Pro), and (Pr+Ala-Gly)n]. Examination of the I3C chemical shifts of these polypeptides, together with our previous data, showed that the 13C chemical shifts of individual amino acid residues are the same, within experimental error (k0.5 ppm), among different polypeptides with different primary sequences, if the conformations are the same. We found that the I3C chemical shifts of Ala residues of the 3,-helical (Ala-Gly--Gly), and triplehelical (Pro-Ala--Gly), are significantly displaced, compared with those of the a-helix, &sheet, and silk I form, and can be utilized as excellent probes to examine conformational features of collagen-like polypeptides. Further, the I3C chemical shifts of Gly and Pro residues in the triple-helical polypeptides are substantially displaced from those found in (Gly),II and fPro),II of the 3,-helix, reflecting further conformational change from the 3,-helix to the supercoiled triple helix. In particular, the I3C chemical shifts of Gly C =O carbons of the triple-helical polypeptides are substantially displaced upfield (4.1-5.1 ppm), with respect to those of the 3,-helical polypeptides. These displacements are interpreted by that Gly C=O of the former is not involved in NH . . . O=C hydrogen bonds, while this carbon of the latter is linked by these kinds of hydrogen bonds.