Separation between R375 and αC helix described by principal component analysis.

Top: Three-dimensional projections of the second principal component of FKBP12-ALK2^WT (left) and ALK2^WT-Phosp (right) using frame set 2 trajectories. Projections of the R-Component vectors onto the alpha carbons of each residue are shown as yellow conical tipped arrows. Backbone fluctuation is displayed as red transparent ribbon overlays. The region of αC helix responsible for the steric barrier to Arg flipping is highlighted with red glowing rectangles. Bottom: Natural log of R375 to αC helix separation for first 15 principal components of FKBP12-ALK2^WT (teal) and ALK2^WT-Phosp (orange), taken over trajectory subsets indicated in the previous wavelet analysis figure. The diagram of the R375 and αC helix separation calculation is shown on the right.