Acridine orange is a fluorescent dye used to bind:
**Core Concept**
Acridine orange is a fluorescent dye that binds to nucleic acids, particularly in the context of cell viability and apoptosis assays. This property allows researchers to assess the integrity of cellular DNA and RNA.
**Why the Correct Answer is Right**
Acridine orange intercalates into the DNA double helix, emitting a green fluorescence when it binds to live cells. However, when the cells undergo apoptosis or have compromised cell membranes, the dye can penetrate the cells and bind to RNA, emitting a red fluorescence. This shift in fluorescence is indicative of cellular damage or death. The dye's ability to bind to nucleic acids is due to its planar, aromatic structure, which allows it to insert between the base pairs of DNA.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because while acridine orange can bind to other cellular components, its primary interaction is with nucleic acids.
**Option B:** This option is incorrect because there is no established relationship between acridine orange and the mentioned cellular component.
**Clinical Pearl / High-Yield Fact**
When using acridine orange in fluorescence microscopy, it's essential to note that the dye can also bind to other cellular structures, such as mitochondria, and can accumulate in lysosomes, which can lead to false-positive results.
**Correct Answer:** C. Nucleic acids