Venomous Vipers, Artificial Kidneys and LSD

Mark looks at snakes, artificial kidneys and how LSD works.
18 February 2007

Interview with 

Mark Peplow


Chris - Time now to find out about various things, including how toads are having their poison stolen by snakes, how we could be a step closer to making an artificial kidney, and we could possibly be unlocking the secrets of LSD. That's because the editor of Chemistry World, the magazine of the Royal Society of Chemistry, Mark Peplow is with us now. So what's this story about snakes that are robbing toads of their toxins?

Mark - Most animals tend to steer clear of poisonous toads, but scientists have found that there's a species of Japanese snake, the Japanese colubrid snake, that actually seeks out toads because it wants to eat them. This is so it can steal their toxins and use them to kill its prey.

Chris - But why doesn't the snake end up succumbing to the toxin?

Mark - Well that's the interesting thing. Now that the scientists involved have actually found out that it's able to do this, they hope now that they're going to be able to work out why it does this. What they did was analyse two different groups of snake. One of them was fed on these toads and the other one didn't have the toads in its diet. They found that it was only the ones that were able to eat toads that ended up being poisonous.

Chris - So it's not a genetic difference, it's purely a dietary difference.

Mark - That's right. There's a small island off Japan where these snakes don't have access to toads, and they found that if they took snakes from that island and gave them toads, they ultimately became poisonous after a relatively short time. When they looked at exactly what molecules the snake was using, they found that they'd actually changed the molecule slightly. So they'd taken them in in one form from the toads and tweaked them chemically. Now that, the scientists speculate, might be the reason why the snake isn't poisoned by the toads because it can rapidly change their chemistry to stop it doing them damage.

Helen - I also hear that there have been steps towards a new type of membrane that could allow us to create a new type of kidney.

Mark - That's right. Scientists announced this this week. What it is, is a filter for molecules and it's just about 15 nanometres thick - that's 15 billionths of a metre thick. That's at least 1000 times thinner than a piece of human hair. It's like a sieve that you would sieve your pasta with in the kitchen apart from the holes are about a million times smaller. Now this is important for a variety of reasons. In laboratories you need to separate proteins, very big tangled molecules, from smaller biological molecules for analysis. But that's exactly what's going on in a dialysis machine as well. Now given the success scientists have seen with this, they've found that it speeds up the separation of these molecules by at least an order of magnitude. That's at least ten times faster. In the test that they did where they were comparing small fluorescent dye molecule with a big fat protein called bovine serum albumen, they found that what would normally take a couple of hours using a couple of polymer membranes that you see in dialysis machines, they could achieve the same thing in six and a half minutes. Now if you could get this working in a conventional dialysis machine, that potentially speeds up the process immensely. Now they're not there yet, but this is a very promising material and moreover it's really quite tough and relatively easy to manufacture. This mainly because it's made out of silicon, the same stuff that goes in silicon chips in your computer.

Chris - Especially given how much dialysis costs the NHS, because it's a very expensive process to do. But Mark lastly this week, you've got an interesting thing about how unlocking LSD sends us on the trip of a lifetime.

Mark - Yes this is a nice short and sweet little story actually. Brain researchers have always been confused about why LSD has such a different effect in the brain in comparison with other drugs that work in what appears to be quite a similar way. When people take LSD, the molecules hit a receptor in the brain called a serotonin receptor. Normally this is used to recognise this molecular messenger in your brain called serotonin. But if you have a drug like LSD hitting that, why then don't other drugs like sleeping pills, which also hit serotonin receptors, give you hallucinations? The researchers have found that it's basically because it's not a two-stage on-off switch. This receptor can either be 'off', or it can be 'on' by LSD which sends out one chemical cascade of reactions that ultimately gives you hallucinations. Or they compared another drugs that's very similar to LSD in the way that it works in the brain called lysuride, which is an anti-Parkinson's agent. They looked at exactly how that was interacting with the serotonin receptor and they found that it was switching it to a third position, which researchers hadn't known about before. Now ultimately understanding how this serotonin receptor switches is actually quite important for a variety of psychiatric reasons because you can potentially make new drugs that can target these different positions of the serotonin receptor.

Chris - That was Mark Peplow who's the editor of Chemistry World, which is the magazine of the Royal Society of Chemistry. You can find out more about those stories at their website which is


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