Using LysoSensor Yellow/Blue DND-160 to sense acidic pH under high hydrostatic pressures.

LysoSensor Yellow/Blue DND-160, a dual-wavelength fluorophore commonly used for sensing pH in acidic organelles, possesses solvatochromic behavior believed to originate from an intramolecular charge transfer (ICT). Given this, we investigated whether DND-160 can be used for acidic pH sensing under hydrostatic pressures up to 510 atm, a range suitable for studying a wide variety of cellular processes. We found that the emission spectrum of the protonated form does not exhibit sensitivity to pressure, whereas the deprotonated form shows a piezochromic shift consistent with increased ICT character. Although pressure effects on the apparent pKa are buffer solvent dependent, DND-160 retains two-state behavior, making it a useful acidic pH probe under pressure.