Good question.

I found this reference in "Molecular Biology: A Project Approach"

A phenomenon called photobleaching occurs when ethidium bromide (EtBr) -stained DNA is illuminated by ultraviolet light.... This decreased fluorescence is presumably due to the dissociation of ethidium bromide from the DNA.

Ethidium bromide fluoresces when it is in a hydrophobic environment, such as when its stuck between two base pair stacks in DNA- water quenches its fluorescence.

I also found this article citing the fact that sunlight can break down EtBr but only when a catalyst of iron and titanium dioxide is there to catalyze the reaction.

A lot of the original characterization of EtBr as a stain is very old, so I couldn't access it directly online... It looks like the compound itself is pretty stable, but UV can, somehow interact with it when its bound to DNA to bleach it out.

Good question.

I found this reference in "Molecular Biology: A Project Approach"

A phenomenon called photobleaching occurs when ethidium bromide (EtBr) -stained DNA is illuminated by ultraviolet light.... This decreased fluorescence is presumably due to the dissociation of ethidium bromide from the DNA.

Ethidium bromide fluoresces when it is in a hydrophobic environment, such as when its stuck between two base pair stacks in DNA- water quenches its fluorescence.

I also found this article citing the fact that sunlight can break down EtBr but only when a catalyst of iron and titanium dioxide is there to catalyze the reaction.

A lot of the original characterization of EtBr as a stain is very old, so I couldn't access it directly online... It looks like the compound itself is pretty stable, but UV can, somehow interact with it when its bound to DNA to bleach it out.

Good question.

I found this reference in "Molecular Biology: A Project Approach"

A phenomenon called photobleaching occurs when ethidium bromide (EtBr) -stained DNA is illuminated by ultraviolet light.... This decreased fluorescence is presumably due to the dissociation of ethidium bromide from the DNA.

Ethidium bromide fluoresces when it is in a hydrophobic environment, such as when its stuck between two base pair stacks in DNA- water quenches its fluorescence.

I also found this article citing the fact that sunlight can break down EtBr but only when a catalyst of iron and titanium dioxide is there to catalyze the reaction.

A lot of the original characterizatino of EtBr as a stain is very old, so I couldn't access it directly online... It looks like the compound itself is pretty stable, but UV can, somehow interact with it when its bound to DNA to bleach it out.

Good question.

I found this reference in "Molecular Biology: A Project Approach"

A phenomenon called photobleaching occurs when ethidium bromide (EtBr) -stained DNA is illuminated by ultraviolet light.... This decreased fluorescence is presumably due to the dissociation of ethidium bromide from the DNA.

Ethidium bromide fluoresces when it is in a hydrophobic environment, such as when its stuck between two base pair stacks in DNA- water quenches its fluorescence.

I also found this article citing the fact that sunlight can break down EtBr but only when a catalyst of iron and titanium dioxide is there to catalyze the reaction.

A lot of the original characterization of EtBr as a stain is very old, so I couldn't access it directly online... It looks like the compound itself is pretty stable, but UV can, somehow interact with it when its bound to DNA to bleach it out.