Fringe S2E14 (2010) Part II - "This is Our Toxin"

Spoiler Level – Low (series); moderate (episode)

The Show – An FBI agent and a pair of scientists attempt to solve crimes that cannot be explained by mainstream science.

I've said before that I really like the characters on this show, and I mean that. It's particularly true for the lead, FBI agent Olivia Dunham (Anna Torv). As the only non-scientist of the three main characters, she's needs to serve as a proxy for the audience when the show's "science" is being explained. Too often that sort of character comes across as being dumb, at least compared to the scientists. But this isn't the case with Agent Dunham. She's every bit as smart as scientist Peter Bishop; she just doesn't know as much about the topics being discussed because she chose law enforcement instead of science. I think that's a nice quality for the audience proxy. Audiences need to realize that they're smart enough to understand science if they have the interest.

Of course the show goes and ruins most of that by also presenting scientist Walter Bishop as an unrealistic super genius that no one in the audience (or in reality at all) could hope to compare to. And the science the show presents usually doesn't make at sense at all. This confuses the audience, and makes them think that they're just not smart enough to understand it, which just isn't the case. So let's get back to correcting the inaccuracies.

The Scene – A Nazi scientist attempts to create the master race using a toxin that only kills people with certain genetic traits he finds undesirable. While this is beyond current science, I suggested that it's possible. The toxin kills its victims by inactivating the hemoglobin in the blood, rendering it impossible to get oxygen to their cells. I also said that this is a reasonable action for a toxin. So what's the problem?

The Science – So while I'm okay with a toxin that targets certain genetic groups and a toxin that affects hemoglobin's ability to carry oxygen, I'm not really on board with one toxin that can do both those things.

If we have a toxin that recognizes differences in DNA, the toxin first must reach the DNA. This is not a simple task. Our cells are surrounded by membranes specifically for keeping out foreign molecules. Across the outer or plasma membrane, the interior of the cell is called the cytoplasm. Our DNA is in a second membrane-bound structure called the nucleus.

Approximately 1/10,000,000,000,000th of your body (give or take a zero). From Wikimedia Commons.

Getting from the cytoplasm to the nucleus isn't a big deal. Cells constantly need to send things in and out of the nucleus, and you can hijack the existing system just by adding a short signal called a nuclear localization sequence to the toxin.

Getting across the plasma membrane is a bigger deal. This is actually another area of study that I've personally investigated. Many bacterial toxins need to cross our plasma membranes, and they've evolved quite a number of methods to accomplish this. Some are complicated needle-like structures that help move a toxin directly from the bacteria's cytoplasm to ours. But the simplest ones require only the addition of a single extra protein or domain. These extra parts can also target the toxin to specific cell types, such as nerve cells or immune cells.

So what's the big deal if the show just neglected to mention that the toxin also needed a couple extra parts to reach the nucleus? Well, the problem is that hemoglobin is in red blood cells and a red blood cell doesn't have a nucleus. For a toxin to target the hemoglobin of people with certain genetic traits, it would need to cross a total of five membranes. It has to cross the plasma and nuclear membranes of one cell to recognize the DNA and activate. Then it would have to pass through the same membranes again to exit. And finally, it must cross plasma membrane of a red blood cell to reach the hemoglobin it's targeting.

Fixing the Scene – There's no real need for the show to explicitly state that the toxin has extra parts for crossing membranes. But there is a scene when they discuss the parts of the toxin, and it would be easy to mention it then. When a show can toss in a nice little science fact like that without breaking the flow of the scene, I think it should. Mostly they just need to change the toxin's method of activity. Since it has to reach the nucleus for DNA recognition, it might as well act there. And there are a lot of ways to mess up a cell from the nucleus. The toxin could just chop up the DNA. It could launch a program that tells the cell to kill itself. There are a number of possibilities that would work and be easier than inhibiting hemoglobin.

Next Week – There's one more topic that I'd really like to cover using this episode: how we know the structures of large molecules.