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Natolx OP t1_j81cnjx wrote

Reply to comment by RebelWithoutAClue in Can the Radiation from a Sample of Depleted Uranium Sterilize? by Natolx

No worries about the denaturing, fluorescent proteins are notoriously stable structures. They are even resistant to Proteinase K... which is ridiculous.

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[deleted] t1_j81maix wrote

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Natolx OP t1_j81vyay wrote

>Without being replenished by new protein, the GFP would photobleach pretty quickly anyways, so I don't think the necklace is worth trying to sterilize. While GFP is stable to protease digestion, it doesn't really remain fluorescent in a purified solution for more than a few days if you just leave it our like you would with normal jewelry. Plus, killing the bacteria probably won't improve the appearance, as they likely broke down a lot of your GFP for food and their corpses will keep making the solution cloudy even if they're no longer alive. Honestly, it's probably easier to write this one off and make a new one.

I think you underestimate how much fluorescent protein we are talking about... This is milligrams. This is many orders of magnitude more protein than you are seeing photobleached in an immunofluorescence assay.

To put this in perspective, this liquid containing fluorescent protein entirely absorbs a 473nm laser I have. None of it makes it out the other side.

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Camilo543 t1_j81z2fz wrote

Would this make UV sterilization impossible?

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Tiny_Rat t1_j822bd1 wrote

UV sterilization would definitely photobleach GFP in the time it took to kill the bacteria.

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Natolx OP t1_j822zcg wrote

>Would this make UV sterilization impossible?

Yes, unfortunately the fluorescent protein would absorb the UV and protect the bacteria! Although there is a small chance UVC might work.... That is well outside of the absorption spectra of the protein

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[deleted] t1_j820ohg wrote

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Natolx OP t1_j822m5l wrote

> Regardless, even large quantities of purified GFP need to be stored at -20C in the dark to remain fluorescent long-term, and raising that temperature to even 4C will dramatically shorten storage time. The rate of photobleaching and degradation at RT isn't going to be affected by the concentration of the protein, it just might take slightly longer to see a difference by eye. This is still a very temporary piece of jewelry, so sterilizing it at this point isn't going to extend its lifespan by much.

I'm sorry but this is simply incorrect. Photobleaching is by definition caused by light being absorbed. A high concentration of protein on the "shell" of the solution is going to "protect' all of the protein on the inside of that shell from from excitatory light. Again, I don't think you can conceptualize how much protein this is compared to "normal" amounts seen in laboratory experiments.

If I left it out in the sun, sure, it's going to bleach for in a week, but the photobleaching power of incidental lighting is just not enough to photobleach this amount of fluorescent protein any time soon.

I have tubes of nonsterile fluorescent protein that have been kept at room temperature for a year now that are cloudy (with contamination) but still fluorescent. Only my sample kept in the sun lost fluorescence.

Additional Note: this is mNeon, not GFP so it is definitely a "better" generation of fluorescent protein. But even GFP at this concentration is going to resist photobleaching for an absurdly long time.

>The "absorbtion" you see with your laser beam probably has more to do with scattering of the laser rather than pure absorption. Any high-density protein solution will behave similarly.

There is no blue light being "scattered" (I have used a blue filter I scavenged to check) , it is not scattering. You can also clearly see the beam go in, stay a beam but just fade into nothing.

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