So today I want to talk to you about a molecule which, when it was first isolated, was called "Very Fast Death Factor". Now this molecule is a really potent toxin, and it's found in pond scum. The green, sort of gloopy algae stuff that you find sometimes on freshwater ponds. It's actually not algae that makes
this, it's called cyanobacteria. And that green, it turns out, is kind of
really important for this molecule. As it turns out, the molecule itself is unstable to light. So nature's clever, it didn't really - it wants a toxic molecule, for some reason, in that cyanobacteria, in that algal bloom, but it
didn't want to spread too much. So as soon as you take the molecule out of that, it becomes destroyed by light. But nonetheless, don't let this fool you. This is a very, very dangerous molecule. So I've got nearly 5 grams in this round bottom flask here. That would be enough to kill around 350 people. This is a seriously toxic molecule. Now luckily, for everyone involved, this is actually in a protected form, this molecule you see here in this flask, this compound. BRADY: What does that mean? So, it's got a safety catch on it. It's got something called a "protecting group". And it completely kills the reactivity of one atom in this molecule, the nitrogen atom. And that atom is a key to the biological response that it will provoke. So if we quickly put that one down... Here is a molecular model of anatoxin-a, which is the "Very Fast Death Factor". It was renamed because that was thought not to be particularly scientific, but I quite like "Very Fast Death Factor", it does what it says on the tin, essentially. So here is that key nitrogen. So it turns out it's the nitrogen and this oxygen over here, and that distance, which is the key to its
biological activity. It fits a certain receptor that one of your natural neurotoxins triggers. So this molecule is a toxin, and what it does and why it's called "Very Fast Death Factor" is that it paralyzes somebody who ingests it, be that an animal, a cow, a rabbit, bird, or whatever that's drinking from the pond, or somebody who drinks or swims in the
pond. And it works really quickly, thus the
name, "Very Fast Death Factor". Turns out that a lot of potent toxins
actually work very slowly. It's an agonizing death. This works very, very quickly, a matter of minutes rather than hours or days. What this does is it stops your brain communicating with your muscles. So nerves have two functions really. One, they tell muscles and your body to move - be that breathe, which is part of - you know, you're on autopilot, you don't think about breathing, but every few seconds, your brain's saying
"breathe in, breathe out, breathe in, breathe out." It does it automatically - or move your
muscles. So if you stop any of those signals, then obviously, your muscles stop. And if you stop breathing, you're gonna die pretty quick. Obviously this compound is a very dangerous compound, so why on earth would we be interested in making this and
analogues of this compound? Well it turns out that it could be a good treatment for Alzheimer's disease. If you imagine a nervous system as a long piece of electrical wire, and every now and again along that wire
you get, just like you do at home, a plug and a socket where two bits of wire join. Now in electricity, the plug and the
socket are made of metal, and the electrons can hop from one to the other, and there's no problem. In nervous transmission there is a little gap in-between the plug and the socket. And there's little molecules called "neurotransmitters" which come out of one end, they swim across the gap, and they trigger the response in the other
end of the "synapse", as it's called. And then the electrical signal goes on again. Now obviously you don't want those electrical signals to be on all the time. So the little molecule comes back out, and there's a Pacman-type molecule which comes and munches those up. To make sure that, you know, the response is gone, we now need to get rid of those and wait for the next signal. Now in certain conditions like Alzheimer's disease, your normal neurological condition degrades some more. They're called "neurodegenerative diseases". The nerves in your brain don't work properly, and the problem is that you get too many of these Pacman molecules taking up too many of those transmitters. And so your nervous system, your
brain isn't working properly. Now it could be that molecules like this,
which are able to disable these Pacman molecules, could be very useful leads for treatment of Alzheimer's disease and other neurodegenerative diseases. So that's why, as chemists, we're interested in these things. We're not interested, obviously, in killing 350 people.
