Figure 4: DFT optimized conformations of 3a-c and analogues 9–11. | Nature Communications

Figure 4: DFT optimized conformations of 3a-c and analogues 9–11.

From: Stabilizing short-lived Schiff base derivatives of 5-aminouracils that activate mucosal-associated invariant T cells

Figure 4

(a) Optimized conformers of 3a–c and (b) optimized conformers of 9–11, which are analogues of 3c. Dihedral angles (red) and ψ (blue) define the angles formed by 5,6-substituents centred at uracil C5-C6 and 5-substituent to uracil C5-C4, respectively. In order to visualize the twisting of these substituents, the LUMOs (with orbital phases in cyan and blue) are shown for clarity. The incorporation of a methyl group to 3c (that is, 3a, 9 or 10) resulted in a twisting of the C-5 substituent relative to the ring and an inversion of the LUMO phase at the carbonyl carbon (3a and 10). These changes likely impact the ability of the ligands to form non-covalent interactions with MR1 and MAIT TCR (Fig. 1), as well as their reactivity towards the formation of Schiff base with K43 of MR1. (c,d) Plots illustrating the structural similarity of the compounds based on the dihedral angles (red) and ψ (blue), and the distances d1 (purple) and d2 (green).

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