Lee Cronin
speaker
545 appearances
2 recordings
1 series
first heard Dec 2023
last heard Jun 2024
Lee Cronin’s voice in public audio — every appearance, attributed to the second.
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But they were able to find out a lot, right, in looking at verbrates, inverbrates, Cameron explosion, all this stuff. And then came the genomic revolution, and suddenly everyone used gene sequencing. And Craig Venter is a good example. I think he's gone around the world in his yacht just picking up samples, looking for new species, where he's just found new species of life just from sequencing.
It's amazing. So you have taxonomy, you have sequencing, and then you can also do a little bit of molecular archaeology, like measure the samples and form some inference. What we did is we were able to fingerprint we took a load of random samples from all of biology and we use mass spectrometry.
And what we did now is not just look for individual molecules, but we looked for coexisting molecules where they had to look at their joint assembly space and where we were able to cut them apart and undergo recursion in the mass spec and infer some relationships. And we were able to recapitulate the tree of life using mass spectroscopy, no sequencing and no drawing.
So what you do is you take an unknown sample, you pung it into the mass spec. Because this comes from what you're asking, like, what do you see in E. coli? And so in E. coli, you don't just see, it's not that the most sophisticated cells on Earth make the most sophisticated molecules. It is the coexistence of lots of complex molecules above a threshold.
And so what we realize is you could fingerprint different life forms. So fungi make really complicated molecules. Why? Because they can't move. They have to make everything on site. Whereas some animals are lazy. They can just go eat the fungi. They don't need to make very much.
And so what you do is you look at the... So you take, I don't know, the fingerprint, maybe the top number of high molecular weight molecules you find in the sample. You fragment them to get their assembly indices. And then what you can do is you can infer common origins of molecules. You can do a kind of molecular...
when the reverse engineering of the assembly space, you can infer common roots and look at what's called the joint assembly space. But let's translate that into the experiment. Take a sample, bung it in the mass spec, take the top, say, 10 molecules, fragment them, And that gives you one fingerprint. Then you do it for another sample, you get another fingerprint.
Now the question is you say, hey, are these samples the same or different? And that's what we've been able to do. And by basically looking at the assembly space that these molecules create. Without any knowledge of assembly theory, you are unable to do it. With a knowledge of assembly theory, you can reconstruct the tree.
let's go to two leaves on different branches on the tree, right? What you can do by counting the number of differences, you can estimate how far away their origin was. And that's all we do. And it just works. But when we realized you could even use assembly theory to recapitulate the tree of life with no gene sequencing, we were like,
Yeah, absolutely. I would love to get old fossil samples and apply assembly theory mass spec and see if we can find new forms of life that are no longer amenable to gene sequencing because the DNA is all gone. DNA and RNA is quite unstable. But some of the more complex molecules might be there and might give you a hint of something new.
Or wouldn't it be great if you find a sample that's worth really persevering and doing the proper extraction to PCR and so on and then sequence it and then put it together.
Yeah, and it appears that you can do some dating. Now, there are really good techniques. There's radiocarbon dating. There is longer dating, going looking at radioactive minerals and so on. And you can also, in bone... you can look at what happens after something dies. You get what's called racemization, where the chirality in the polymers basically changes and you get decomposition.
The deviation from the pure enantiomer to the mixture you can have a time it gives you a time time scale on it half-life so you can date when it died i want to use assembly theory to see if i can date use it date death and things and and trace the tree of life and also decomposition of molecules do you think it's possible
oh yeah then without a doubt it may not be better than what because like the i was just at a conference where some brilliant people were looking at isotope enrichment and and looking at how life enriches isotopes and they're really sophisticated stuff that they're doing but i think there's some fun to be had there because it gives you another dimension of dating how old is this molecule um in terms of in or more importantly how long ago was this molecule produced by life
The more complex the molecule, the more prospect for decomposition, oxidation, reorganization, loss of chirality, and all that jazz. But what life also does is it enriches. As you get older, the amount of carbon-13 in you goes up. because of the way the bonding is in carbon-13. So it has a slightly different bond strength than you. It's called the kinetic isotope effect.
So you can literally date how old you are or when you stop metabolizing. So you could date someone's death, how old they are, I think. I'm making this up. This might be right. But I think it's roughly right. The amount of carbon-13 you have in you, you can kind of estimate how old you are.
Yeah, yeah, like you could say, oh, this person is 10 years old and this person is 30 years old because they've been metabolizing more carbon and they've accumulated it. That's the basic idea. It's probably completely wrong timescale.
Mm-hmm.
At the moment, we should be able to do this to morphology in cells. So we're looking at cell surfaces and really try and extend further. It's just that, you know, we worked so hard to get this paper published
out and people to start discussing the ideas and i was but but it's kind of funny because i think the peb the the penny is falling on this so yeah so what's that even what what's it mean for a penny i mean no the the pennies dropped right because a lot of people like it's rubbish it's rubbish you've insulted me it's wrong and i'm and then you know i mean the paper got published on the 4th of october it had 2.3 million engagements on twitter
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