Tuesday, March 30, 2010
Monday, March 8, 2010
As some people have noticed, I'm not much of a chemist. I would go so far as to say that it's one of my weak points. But this list of "Things I Won't Work With" has to be some of the most interesting and funny reading I've seen in a while. People in my lab tend to freak out about things like acrylamide, ethidium bromide, and beryllium fluoride. I tend to think that as long as you don't ingest anything or get it in your eye, you're probably okay, and shouldn't freak out too much. And, this list really gives you a sense of perspective, e.g.:
You start off by making absolutely pure anhydrous hydrogen azide, which is a proposal that you don't hear very often around the lab, and is the sort of thing that leads to thoughts of career changes...The next step is introduction of the fluorine, and when elemental fluorine is the most easily handled reagent in your scheme, let me tell you, you're in pretty deep
Thursday, March 4, 2010
Looking at Ion Torrent's new technology, they are detecting base addition by the release of a single proton. This seemed a bit far fetched to me. I mean, water is constantly in flux between the protonated and deprotonated state, so how could you detect a single new proton? So, a rough back-of-the-envelope calculation (just to prove I can still do it):
Assume that their nanofab chamber volume is about 1 zeptoliter (10-21L). I got this number from one of Pacific Biosciences' papers, but I'm guessing the scale is quite similar. The concentration of one single hydrogen ion in 1 zL is then:
(1/6 x 1023)/(10-21) ≈ 2 mM. That is actually quite a bit! Thought about another way, though, pure water is at 55M concentration, so there are 55M x 6 x 1023 x 10-21 = 33,000 water molecules in a single reaction volume, so you're trying to detect a single proton against a background of 66,000 possible free protons (two per water molecule.) That makes it sound a bit harder. In any case, it's apparent that it works!