MadSci Network: Biochemistry

Re: Green Florescent Protein human retina

Date: Fri Mar 19 11:44:40 2010
Posted By: Karin Crowhurst, Assistant Professor, Biochemistry
Area of science: Biochemistry
ID: 1268516021.Bc

Hi Jennifer,

I am 99.99% certain that the fluorescence seen in some human eyes is NOT from green fluorescent protein. Something very seriously bad would have had to transpire in the food chain in order for that to be in our eyes (or it would have had to be put there on purpose).

As to what it is, I think the most plausible explanation I have been able to find is that there are a series of compounds that exist in our eyes that are fluorophores. The two major types are called:

3-hydroxy kynurenine glucoside (3-OHKG), and
4-(2-amino-3-hydroxyphenyl)-4-oxobutanoic acid O-glucoside (AHBG)

These compounds are believed to act as UV filters, especially in younger people. In a younger person, these compounds are fluorescent, but when that person ages, there is a change in those compounds (possibly due to a reaction between the compound and lens crystallins in the eye) such that the amount of fluorescence produced by these compounds increases (or at the very least the fluorescence produced has a longer lifetime, so you can see it longer). These compounds are caused to fluorescence when you shine light of wavelengths between 295 and 400 nm (within the range you mentioned).

Hope this helps!

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