Validation of the temperature sensitivity of ER thermo yellow.
(a) In fixed HeLa cells, the fluorescence of ER thermo yellow also showed the square wave pattern in response to a temperature difference. (b) The temperature sensitivities in 20 mM HEPES buffer solutions (pH = 5.0, 6.0, 7.0 and 8.0) were 4.0%/°C (R2 = 0.96, n = 41), 3.7%/°C (R2 = 0.97, n = 41), 3.7%/°C (R2 = 0.99, n = 38), 3.8%/°C (R2 = 0.98, n = 44), in order. (c) The pink circle is the tip of the needle at a heating spot. Scale bar, 10 μm. (d) The temperature sensitivity in Chang liver, NIH3T3, Brown adipose tissue (BAT) and C2C12 myotube were 3.8%/°C (R2 = 0.85, n = 56), 3.8%/°C (R2 = 0.94, n = 58), 3.8%/°C (R2 = 0.81, n = 50), 3.7%/°C (R2 = 0.96, n = 47), respectively. In Fig. 3b,d, ΔT was determined from the distance between the heating spot and the ROI. The ΔF/Fo was plotted against ΔT.