Fig. 3.

Multi-temperature experiments reveal a global hinge motion and local rearrangements. (A) Schematic of multi-crystal, multi-temperature diffraction experiment. (B and C) The primary structural mode from SVD of the pairwise $C_{\alpha }$ distances describes 88% of the variance among experimental structures. (B) Plot of the temperature dependence of the first left singular vector. (C) Heatmap of the contribution of each pairwise distance in the first right singular vector. Residues 38 to 88 are indicated with an orange bar and residues 120 to 130 are indicated with a yellow bar. (D) Structure of ecDHFR with arrows to depict displacements greater than 0.1 Å of $C_{\alpha }$ atoms between 310 and 270 K refined models. The arrows are enlarged 10-fold relative to the corresponding displacements. Residues 38 to 88 are shown in orange, residues 120 to 130 are shown in yellow, and the distance between Asn23-$C_{\alpha }$ and Pro53-$C_{\alpha }$ (hinge distance) is shown as a dashed line. (E) Plot of the hinge distance as a function of temperature. Data points are shown for each independent crystal and the mean $\pm$ SE at each temperature. (F) Structure and $2m{F}_o-D{F}_c$ map for the 290 K consensus structure for Asp127 and Tyr128. The 1.0$\sigma$ isocontour plot of the $2m{F}_o-D{F}_c$ map in the plane of the backbone carbonyl is shown for the consensus structures at each temperature. (G) Schematic for the single-crystal, multi-temperature diffraction experiment. (H) Overview of the temperature-resolved isomorphous difference map between the 280 and 310 K datasets. (I–K) Insets highlighting regions of the difference map. All maps are carved within 2 Å of the displayed atoms, and arrows highlight the structural changes.