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Why are blacklights used to show proteins and bacteria? Is it related to their ability to make white colors glow? Don't black lights just radiate in the ultraviolet/purple range?

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Scorpions fluoresce in UV also. That's one way of finding them. –  Optionparty Jun 11 '13 at 6:44
@Optionparty I'd rather not know they were there - just wear strong boots and pretend they're not. Do they also carry cyalume tubes and go to rave parties? –  WetSavannaAnimal aka Rod Vance Oct 18 '13 at 6:13

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As you well know, our eyes can only see the visible spectrum (lets say from red to violet). Now, if you turn on a black light in a dark room you can only see a purplish glow. You are "blind" to the ultraviolet light that the bulb is also producing. The things you see under a black light (when illuminating a fluorescent poster, a brand new white t-shirt, etc) are called phosphors. The phosphors is a substance that absorbs the UV light and emits it as visible light. The same general principle holds with bacteria and proteins. Some bacteria contains plasmind, which in turn contains a certain gene, which codes for the Green Flourescent Protein. So you can put the plasmid in the bacteria, the plasmid starts making that protein in the bacteria and the result is a glowing pile of goo. (try a google search on the matter, there are tons of articles, etc. )

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Is this the main protein that fluoresces? Puff adders track prey after having bitten it by seeing in UV because the prey invariably wets itself on being stricken and the urine holds a protein which fluorescences in sunlight at very short wavelength –  WetSavannaAnimal aka Rod Vance Oct 18 '13 at 6:23

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