Figure 4.

Standard calibration curve for the LysoSensor Yellow/Blue pH indicator dye. CHO cells were incubated for 12 h with LysoSensor Yellow/Blue dextran, and equilibrated with MES calibration buffers (pH from 4.5 to 7.0) containing nigericin and monensin. Indicator emissions at 450 and 530 nm from endocytic vesicles were measured with confocal microscopy using a 360 nm excitation wavelength. The 530/450 nm fluorescence ratio (R/G) of these endocytic vesicles was measured as described in the Materials and Methods.