Fig. 2: sDarken Sensor variants.
From: Next generation genetically encoded fluorescent sensors for serotonin
a Expression of L-sDarken in HEK cells. Fluorescence before and after the application of 160 µM 5-HT. Scale bar 10 µm. b Expression of H-sDarken in HEK cells. Fluorescence change before and after the application of 800 nM 5-HT. Scale bar 10 µm. c Dose response curve of sDarken, L-sDarken and H-sDarken measured in response to different 5-HT concentrations. Group data n = 20 from 3 replicates. Error bars represent ±SEM. d (i) Fluorescence change of L-sDarken to application of serotonin (160 µM), similar substances or neurotransmitters, if not mentioned differently 10 µM were applied (n = 10). 8-OHDPAT 300 µM. (ii) Fluorescence change of H-sDarken to application of serotonin, similar substances or neurotransmitters if not mentioned differently 10 µM were applied (n = 10). Box represents the 25% percentile to the 75% percentile. The line in the middle of the box represents the median. One-Way ANOVA Multiple Comparison, ***p < 0.001. e Measurement of photostability. Normalized fluorescence during continuous illumination with blue light (1.8 mW/mm2) for 10 min in HEK cells expressing sensor variants or eGFP-CAAX. f Fluorescence intensity profile measured along the white line in one example cell. Scale bar 10 µm. g Two-photon image (maximum intensity projection of a z-stack) of a CA1 neuron expressing sDarken (green) and the red cytosolic fluorophore tdimer2 (magenta). Insert shows a magnified view of the membrane-localized expression of Darken along the apical dendrite. h Time course of sDarken, H-sDarken, L-sDarken and tdimer2 fluorescent signals imaged during 1 min of continuous 2-photon excitation.
