Each AzTG derivative was assessed by its ability to inhibit SERCA ATPase activity under conditions inducing either the trans-configuration (kept in the dark) or the cis-configuration (subjected to illumination with UV light). Crucially, all derivatives demonstrated a degree of optical control over their inhibitory abilities, displaying an ~2-fold difference in IC50 value between their cis-and trans-configurations (Figure , Table ). Furthermore, this difference can be attributed solely to the conformational state of the incorporated photoswitch group, as no change in dose-inhibition response was observed for underivatized TG subjected to UV illumination. Importantly, each AzTG derivative (differentiated only by the length of the carbon linker between the TG skeleton and the photoswitch group) exhibited distinct overall and photoisomer-dependent inhibitory properties. AzTG-2, containing the shortest linker, demonstrated substantially lower potency compared to the other compounds, with both the cis-and trans-configuration possessing micromolar IC50 values. Increased linker length correlated with significantly improved potency, however, with each photoisomer of both AzTG-4 and AzTG-6 exhibiting an IC50 value in the nanomolar range (of the derivatives, trans-AzTG-4 displayed the highest potency with an IC50 of 280 nM).