Isoflurane concentration–dependent changes in chemical shift of the postsynaptic density protein-95, Drosophila disc large tumor suppressor, and zonula occludens-1 (PDZ) domains of postsynaptic density protein-95. (A) A representative ¹⁵N-¹H Heteronuclear Single Quantum Coherence spectrum of the ¹⁵N-labeled PDZ1–3 of rat source postsynaptic density protein-95 (residues 61–393) showing 230 assigned residues. (B) Representative ¹H chemical shift changes of residues in the PDZ1–3 as a function of isoflurane concentrations. (C) Structures of PDZ1–3 mapped with the combined chemical shifts induced by isoflurane. Residues-experienced chemical shift changes are highlighted in red (Δδ ≥ 0.03 ppm), green (Δδ ~ 0.02–0.03 ppm), and orange (Δδ ~ 0.01–0.02 ppm). Isoflurane concentration was calibrated with the external reference of trifluoroacetic acid.