Photobleaching refers to what?

• A. Too much exposure to light destroys the fluorochrome molecule
• B. A brighter emission under high intensity
• C. Quenching by quencher molecules
• D. Photoblinking of fluorophore

Answer: (A)

Photobleaching is the irreversible loss of fluorescence from a fluorochrome caused by exposure to excitation light. When fluorophores are illuminated for too long or at too high an intensity, chemical changes occur that permanently destroy their ability to emit light, so the signal fades over time. This is a key concern in immunohistochemistry imaging because it can make signals appear weaker or vanish during observation or documentation.

Different dyes vary in how quickly they bleach; factors like exposure duration, light intensity, and the presence of oxygen influence the rate. To minimize bleaching, use antifade mounting media, keep exposure times short, lower illumination power, and acquire images efficiently.

Photobleaching is distinct from photoblinking (temporary on/off emission) and from quenching (reversible or non-destructive reduction of signal by other molecules). The option describing destruction of the fluorochrome by light best matches the concept.