Molecular Probes pH indicator dextrans, in order of decreasing pKa—Table 20.3

Dye Cat # pKa * Measurement Wavelengths Application Notes
SNARFD3303, D3304~7.5Emission ratio 580/640 nm excited at 514 or 488 nm
  • Best conjugate for ratiometric emission measurements
BCECFD1878, D1880~7.0Excitation ratio 490/440 nm detected at 530 nm
  • Best conjugate for ratiometric excitation measurements
FluoresceinD1821, D1823, D1844, D3305~6.4Excitation ratio 490/450 nm detected at 520 nm
  • Fluorescence is strongly quenched upon uptake into acidic organelles
Fluorescein and tetramethylrhodamineD1951~6.4Excitation ratio 495/555 nm detected at 580 nm †
  • Conjugate incorporating both pH-sensitive and pH-insensitive fluorescent dyes
pHrodoP10361NA ‡Emission at 585 nm when excited at 540–560 nm
  • Best conjugate for measurements requiring broad-range pH sensitivity
Oregon Green 488D7170, D7172~4.7Excitation ratio 490/440 nm detected at 520 nm
  • Good photostability
  • Optimum pH sensitivity for measurements in lysosomes and late endosomes
Oregon Green 514D7176~4.7Excitation ratio 510/450 nm detected at 530 nm
  • Excellent photostability
  • Optimum pH sensitivity for measurements in lysosomes and late endosomes
LysoSensor Yellow/BlueL22460~4.2Excitation ratio 340/400 nm detected at 520 nm; emission ratio 450/510 nm excited at 365 nm
  • Options for dual excitation or dual emission ratio measurements
  • Optimum pH sensitivity for measurements in lysosomes and late endosomes
* pKa values are those determined for the free dyes. Actual values for dextran conjugates may differ by up to +/– 0.3 pH units and may vary with production lots. † Ratiometric emission measurements at 520/580 nm (with excitation at 495 nm) are also possible in principle; however, the response may be complicated by fluorescence resonance energy transfer. ‡ NA = Not applicable. pHrodo pH indicator exhibits a complex pH titration profile. Decreasing pH (from pH 9 to pH 2) produces a continuous (but nonlinear) fluorescence increase.
For Research Use Only. Not for use in diagnostic procedures.