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. 2025 May 19;18(5):e70161. doi: 10.1111/1751-7915.70161

FIGURE 2.

FIGURE 2

Microcalorimetric titrations of dopamine, epinephrine, serotonin and norepinephrine to the TlpQ‐LBD. (a) Titration of 80 μM TlpQ‐LBD with aliquots of 10 mM dopamine. (b) Titration of 40 μM TlpQ‐LBD with aliquots of 10 mM epinephrine. (c) Competition assays: Titration of 18 μM TlpQ‐LBD with aliquots of 250 μM spermidine (Spe) in the absence and presence of 10 mM serotonin (Ser) or norepinephrine (Noe). Protein and ligand solutions were in 3 mM Tris, 3 mM PIPES, 3 mM MES, 150 mM NaCl, 10% (v/v) glycerol, pH 7.0. Experiments were conducted on a VP‐microcalorimeter (Microcal, Amherst, MA, USA) at 25°C (for dopamine) and at 10°C (for remaining compounds). Upper panels: Raw titration data. Lower panels: Integrated, concentration‐normalised and dilution‐heat‐corrected raw data fitted with the ‘one‐binding‐site’ model of the MicroCal version of ORIGIN (Microcal, Amherst, MA, USA). The corresponding binding parameters are shown in Table S1. (d) Structure of the TlpQ ligands identified.