Fig 2.

(A) Definition of the axis systems used to describe the DECODER spectrum, where MOL is the molecular axis system, i.e., the peptide plane, with the z axis perpendicular to the peptide plane. FAS denotes the fiber axis system, with the z axis along the fiber direction. The orientation of a peptide plane toward the fiber axis is given by two Euler angles (α_F, β_F). Note that in the extended conformation of the peptide shown, the x_MOL is approximately along the chain direction. In less-extended β sheet conformations, an angle of up to 23° may be observed. (B and C) Experimental 1D ¹³C spectra of 1-¹³C alanine and 1-¹³C glycine-labeled spider dragline silk, respectively, of oriented samples from N. edulis, for three sample orientations. The bottom trace is from an unoriented sample of 1-¹³C glycine-labeled silk and serves as an example of a nonoriented sample. Note that DECODER is insensitive to the size of (possibly) ordered microdomains but gives an integral over the entire sample volume.