Backrub changes for Ser/Thr vs. Asn/Asp α-Helix N-caps.

Distances are after superposition into the same reference frame using 4 Cαs (N-cap i−1 and i+1 to i+3).
Distances for BRDEE for atoms at or beyond Cα i±1 are not shown (marked as “—”) because, by construction, those atoms are not moved by BRDEE.
The signs of the backrub rotation angles and Δτ values are in terms of Ser/Thr→Asn/Asp.
For average crystal structures, average sidechains (based on average Cβ positions and χ dihedral angles) were added in KiNG. The τ value used for each Δτ is an average across the crystal structure ensemble; this was preferable to measuring τ values directly from the average structures because the average coordinates before the i−1 Cα were unreliable due to variability within the crystal structure ensemble.
For input to BRDEE, ideal sidechains were added in KiNG to ideal helices. The τ value used for each Δτ is taken directly from the lowest-energy computed structure.
S/T HB and N/D HB are Ser/Thr and Asn/Asp H-bond lengths from the i sidechain O to the i+3 mainchain H. For crystal structures, an average ± standard deviation across the set of examples in this data set is given. For BRDEE, the value is taken directly from the final model.