Fossil Proteins - Planet Earth Online
Roy - What we're looking at now is a very, very small, probably juvenile reptile from the green river formation, that's about 50 million years old and about 5 centimetres long. It's only part of an organism and we think this poor unfortunate little critter probably got bitten in half and that's why it's ended up in the fossil record.
Richard - If we look at it, there's almost a long tail and two legs, I guess, almost like frog's legs but probably about half the length of my finger imbedded in this quite thin, sandy, almost like a slate [material].
Roy - That's right. You can see a long central tail and then you can see where the legs join in, where the pelvic region is and then the organism is truncated. Mostly what you can see is the skin. And if you look at it very, very closely you can actually see that there is some of the patterning left in the skin.
Richard - It is mottled isn't it?
Roy - Yes that's right, and that's the scale pattern. And that's why we thought this would be a tremendous specimen to look for the residue and patterning of proteins.
Richard - You're actually looking for remnants of proteins of the molecules that made up the skin?
Roy - Some remnants of the original chemistry.
Richard - After 50 million years.
Roy - That's exactly right. It's the chemical fossil. Now that seems like an outrageous thing to propose doesn't it? Yet we have absolutely no problem thinking about organic molecules being preserved as long as we don't think about what species they've come from or from exactly where they're from. We just put them in our gas tanks or petrol tank and burn them. This is a chance, using some of these very, very sophisticated techniques to track back and find some of these very, very robust organic molecules and trace them back to the their source and indeed, we were able to do that.
Richard - So what did you do? It's a very different process to the sorts of things palaeontologists normally get up to.
Roy - And that's why I describe myself as a geochemist. Usually, palaeontologists look at bone and then they look at structures. What we wanted to get to was using chemical techniques and we had this idea of using a different part of the electromagnetic spectrum. It's a very, very simple thing that we did: we just used infrared light rather than visible light. Now, infrared light gives you an idea about the presence of organic molecules because an awful lot of the infrared spectrum will cause vibrations in the organic components. And by that, what that means is that we can identify specific parts of organic molecules and the specific parts of the organic molecules that are present within this fossilised lizard skin are extremely similar to the organic molecular fragments that are present in beta carotene from existing lizard skin.
And so, we did a comparison of the distribution and types of these organic - we'll call them functional groups. We mapped these organic functional groups and compared them from this fossilized skin to skin taken from a present day gecko and the distribution patterns map very, very nicely.
Richard - So what can you conclude then?
Roy - What that showed us is that the protein residue derived from the original skin still has some of the character of the original proteins and the distribution of it is controlled by the original biological structure. It can and it will have a big, big impact on understanding evolution because we can get down to these protein sequence levels. Preservation of DNA, that's just not going to back into deep geological time, but the preservation of some of these proteins from these soft tissues does.
Richard - And this has applications beyond just understanding evolution.
Roy - One of the things I'm very interested in, in fact the other side of my research has to do with radioactive waste disposal and how we can safely sequester radioactive waste. Now, the safety cases, for most countries, have to demonstrate containment for between 100,000 and a million years. Well this is a 50-million year experiment between trace metal contaminants and organic compounds that tells us one way that nature has been able to sequester organic compounds and trace metals in place and that's very, very useful information for us.