CRAMPS NMR of H-1 was used for the structural analysis of some natural silk fibroins such as Tussah Antheraea pernyi and Bombyx mori in the solid state. We were able to resolve all expected H-1 NMR resonances. When tied to the resolution of C-13 NMR via 2D H-1-C-13 HETCOR experiments, overlapping proton resonance under CRAMPS are able to be further resolved. The simplified H-1 signals of these natural proteins could be successfully assigned on the basis of the conformation-dependent H-1 chemical shifts of model polypeptides. The H-1 chemical shift of the H-alpha signals of Tussah A. pernyi fibroin adopting an alpha -helix conformation (4.0 ppm) agrees with that of alpha -helical poly(L-alanine) (3.9 ppm) to within +/-0.1 ppm. A well-defined poly(L-alanylglycine), [Ala-Gly](12), was used as a model polypeptide of B. mori silk fibroin. The H-1 CRAMPS spectra of B. mori fibroins adopting the silk I or silk II form were similar to those of [Ala-Gly](12) adopting a corresponding conformation. The H-alpha chemical shifts of the silk I fibroin were 3.9 ppm (singletlike) whereas those of the silk II fibroin exhibited peaks at 5.0 and 3.9 ppm. Further, we found that the H-1 chemical shift of side chains in silk I was downfield by 0.4 ppm compared with that in silk II. Thus, it is possible to assign the H-1 CRAMPS NMR spectra of natural proteins such as silk fibroins using model polypeptides of known structure as references.