The spurious pre-edge features in Fig. are perhaps easy to identify as such, and therefore to discount, but this may not be true in more complex systems. For example, metal-ligand hybridization in organometallic systems can provide an intensity borrowing mechanism leading to the appearance of weakly-allowed 1s → 3d pre-edge transitions. Even for main features in the methionine spectrum in Fig. , agreement between LR-TDDFT and TDKS is less quantitative than what we observed previously for acetone. This is a direct reflection of the appearance of N(1s) → continuum transitions in the TDKS spectrum that are excluded from the LR-TDDFT spectrum by virtue of the active space that is used to model the oxygen K-edge.