Fig. 15.

The effect of packing. (a) and (b) Experimental Cα and Cβ chemical shifts (ppm) for all alanines in the training set in β-sheets (red dots), helixes (blue dots) and coil states (green dots) showing separately values for (a) exposed residues (${\rho }_i^{C\alpha }<0.1$) and (b) buried residues (${\rho }_i^{C\alpha }>0.2$). (c) The parameter, $A_I^{n,s}$, in Eq. (11) for the simple model (same value for all residue types) scaled by the corresponding standard deviation, ${\sigma }_0^{n,s}$, for the observed shifts demonstrating the effect of packing for different atom types and secondary structures.