Structure and dynamics of silk fibroin studied with 13C, 15N and 2H solid state NMR

1-¹³C]Gly, L-1-¹³C]Ala, ¹⁵N]Gly, L-¹⁵N]Ala, 2,2-²H₂]Gly, L-3,3-²H₂]Ser and 3,3,3-²H₃]Ala labeled silk fibroin fibers from Bombyx mori and Samia cynthia ricini silkworms were prepared in order to analyze structure of backbone and dynamics of side chain. The torsion angles ϕ and Ψ were determined from the angular dependent ¹³C and ¹⁵N solid state NMR spectra for uniaxially oriented fiber samples. In addition, the characteristic side chain dynamics of Ser residue determined from solid state ²H NMR measurements was compared with those of Ala and Gly residues.