10 March 2009

Once Burned, Twice Shy

I am surrounded by things that will kill me. I'm not even talking about any of the deadly pathogens we study (this time). The spot of trouble I had was with a fairly mundane experiment.

The other week, I had to perform roughly two hundred gel purifications in preparation for a cloning experiment. First, you load a mixed DNA sample (in my case, the products of a PCR) onto an agarose gel and apply electric current to separate the DNA into bands based on size (a process called gel electrophoresis). Then, if there's a specific piece of DNA that you're interested in manipulating further (for instance, the pieces of DNA I wanted to clone), you can just cut the band of corresponding size out of the gel and extract the DNA from it using a special filter.

It's a straightforward and common practice, but you do have to be a little careful when running an agarose gel. To visualize the DNA, you stain the gel with ethidium bromide (EtBr), a chemical that becomes fluorescent when it binds to DNA. Its proclivity for binding DNA is all well and good for the sake of running the gel, but you don't want it coming in contact with your skin. It can induce DNA mutations, and is therefore suspected to be a carcinogen.

I take care not to get EtBr on my skin. I don't want cancer.

I guess I should have been more careful about the radiation burns, then.

Okay, so that sounds melodramatic, but that's technically what happened. You see, EtBr fluoresces under ultraviolet light. In order to cut all the bands out of my gels, I had to spend a fair deal of time standing over gels lit from below by a UV light box. Before you scold me, I was actually wearing a UV shield and safety glasses over my face. It wasn't until I was washing my face that night, however, that I realized the face shield hadn't given my neck much coverage. So yeah, I wound up with a mild sunburn on my neck (and a bit of color in my face... the shield doesn't give perfect protection). It was a little sore for a few days (I actually got a cold around the same time, so my throat was sore inside and out!), but otherwise no serious harm done. Good for a chuckle at my own expense, and a reminder that I'm a trained professional who deals with some dangerous stuff.

So now I know better than to lounge in front of the UV box without a scarf and/or a turtleneck. Hey, at least I wasn't performing protein electrophoresis. Proteins are run on a polyacrylamide gel instead of agarose. Polyacrylamide is mostly harmless, but non-polymerized acrylamide is a pretty serious neurotoxin.

I love science. Excitement around every corner.


Reginald Selkirk said...

At least you were using the full-face shield. I know someone who was just wearing the goggles, and got a racoon-style makeover.

Aaron Golas said...

Heh, yeah, that would have been worse. I've got to use the UV box again today and tomorrow, I'll have to remember to take care this time. :-P