Define the comparison
An increase in pHrodo fluorescence indicates a stronger acid-dependent signal under the assay conditions. To compare antibodies, record protein concentration, labeling density, post-labeling binding, cell number and acquisition settings. Equal dye input does not ensure equal labeling density, and an endpoint ranking can also reflect differences in acidification kinetics.
Match each control to a question
Blanks and negative controls answer different questions. Establish detection background with unstained samples, then use matched labeled controls to assess target-associated signal.
| Control | Purpose | Interpretation limit |
|---|---|---|
| Unstained cells / cell-free wells | Separate cellular autofluorescence from medium and reagent background. | Does not replace a labeled-antibody negative control. |
| Target-negative or knockout cells | Assess dependence on target expression. | Uptake and acidification may differ between cell models. |
| Matched labeled isotype | Assess Fc-associated uptake and nonspecific background. | Match concentration, labeling density and formulation where possible. |
| Independent localization or uptake readout | Check entry into cells independently of acid-dependent brightness. | Total cell-associated fluorescence can include surface binding. |
| Acidification perturbation and vehicle | Assess dependence on an acidic environment. | Perturbation may also affect uptake, cell health and trafficking. |
Report the metric used by the platform
For plate assays, also record viable cell number or an independent measure of cell abundance. For flow cytometry, report median fluorescence and positive fraction within a consistent live-singlet gate. For imaging, report per-cell signal, intracellular puncta or localization rather than one bright field. Time courses reveal onset, growth and plateaus; a plateau does not by itself establish complete internalization.
Keep the readout distinct from the biological quantity
After subtracting matched background, compare relative fluorescence under consistent acquisition conditions. An acidic positive control checks conjugate responsiveness, but dividing cell signal by the acidic maximum does not directly give percent internalization. Absolute pH measurement additionally requires an appropriate reference readout and calibration within the assay system.
Related products and documentation
- pH560 Red TFP ester · QH-17-1005 · Request documentation
- pH560 Red maleimide · QH-17-1004 · Request documentation
- pH630 Deep Red TFP ester · QH-17-1001 · Request documentation
- pH630 Deep Red maleimide · QH-17-1002 · Request documentation
- pHAb Amine Reactive Dye · QH-17-2001 · Request documentation
- pHAb Thiol Reactive Dye · QH-17-2002 · Request documentation
- pH630 Deep Red anti-human labeling reagent · QH-17-1003 · Request documentation
Further reading
- pHrodo selection for antibody internalization
- Troubleshooting pHrodo background and weak signal
- Sample setup and controls for pH630 human-antibody labeling