Nature Podcast 22 March 2007

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Chris Smith: This week, why brute force is sometimes not only necessary but can also be a good thing, at least where chemists are concerned.

Jeffrey Moore: Force is going to be a completely new option for the chemists to employ and it's very possible that this will enable reactions that were not possible beforehand.

Chris Smith: More from Jeff Moore shortly on how force looks at to revolutionize chemical reactions. Also, from hard science to homeotherapy and how it can earn you a Bachelor of Science degree at university, but not everyone is choked at the idea.

David Colquhoun: Even if sticking needles in yourself does cause beneficial effects, much pretty dubious, what's objectionable from the point of view of university is the mumbo-jumbo that goes with it. They talk about chi and meridians and energy, and so on. There's not the slightest reason to think that means anything.

Chris Smith: Find out in a few moments what an investigation by Nature turned up on how the subject is being taught in UK universities. Also, we will be hearing how scientists have given the Earth a thorough probing to find out how tectonic plates move.

Douglas Toomey: We do something that is very similar to a CAT scan in the medical sciences. We put down receivers on the sea floor and then we set off explosions. You can mathematically use those to reconstruct the three-dimensional seismic velocity structure of the Earth.

Chris Smith: And have scientists shattered a massive chemical myth?

Phil Baran: Like death and taxes, protecting groups are an inherent part of synthetic organic chemistry, which we will never elude.

Chris Smith: Now, Phil Baran thinks it's just not true and we will be hearing why later. Hello, I am Chris Smith and this is the Nature Podcast. First this week: How chemists have learnt to wrestle the molecules into reacting the right way. Jeff Moore uses ultrasound to stretch molecular groups called mechanophores and this can affect what they turn into. Nature 446, 423–427 (22 March 2007) .

Jeffrey Moore: We discovered that we could change the way that chemical reaction takes place by applying force to what we call a mechanophore, or, in other words, the molecule that is mechanically sensitive.

Chris Smith: But how do you actually apply force to a molecule, I mean, obviously one can compress things and pressure makes reactions go more quickly, but how have you done it?

Jeffrey Moore: Right, so we wanted to apply a tensile force, or, in other words, we wanted to pull atoms apart and that was one of the tricks that we had to overcome, and the way we did that was by attaching long polymer chains to our mechanophore. The mechanophore was right in the centre of this polymer chain and, as the ends of that polymer stretched out, it applied force and tension and pulled apart the atoms that we were trying to pull apart.

Chris Smith: This sounds incredibly tricky, because obviously you are playing around with fairly large polymers, but how do you actually a) know that happened, and b) know the mechanics of how the force was making it happen more effectively?

Jeffrey Moore: Right, so we used ultrasound and the way that that works is it generates tiny bubbles that collapse very rapidly; and a polymer molecule that just happens to be in the vicinity of one of these collapsing bubbles is subjected to a very strong flow field, which causes the molecule to stretch out and, as it stretches out, there really is no other alternative than to put a tension in the centre of the polymer chain.

Chris Smith: How did you prove that you were genuinely demonstrating that this force, when applied via the ultrasound, was affecting the outcome?

Jeffrey Moore: Right, the main experimental proof of that was to start with two different mechanophores, which were isomers of one another. They were identical chemical composition, but the atoms differed in their arrangement and space. Just by heating these molecules up, they were predicted and observed to give two different products. The cis isomer would give one product and the trans isomer would give another. What we surmise is that a force could be applied to both of those isomers, the cis and trans would give the same product, and that is indeed what we observed.

Chris Smith: And how efficient is the effect of the force in that if you add up the products that you get from the reaction, do you find that everything goes down that alternative pathway when you apply the force, or do you end up with a mixture and then still have to separate things out?

Jeffrey Moore: Within the limits of our detection that we applied in this experiment, we saw only one product for both the cis isomer and the trans isomer.

Chris Smith: So, you are going to now try this trick with some other polymers and see how generalizable the rule is?

Jeffrey Moore: Exactly, we have all of organic chemistry to think about in terms of what reactions might be sensitive to force, and we have many ideas on what could be tested; and we think that the method that we came up with would be quite suitable for surveying which reactions are force-sensitive.

Chris Smith: And are there any commercially sensitive compounds that immediately you could think, "Well, this could actually make a big difference"?

Jeffrey Moore: We do think that there are some implications that may be even broader than just what kinds of chemical reactions one can do. For example, we can think about using mechanical forces to transform the properties of polymers. For example, if we could find a reaction that would induce crosslinking or induce a colour change, we could have in the crosslinking case, modified mechanical properties. In the case of a colour change, we might have a means of detecting that force has been applied, perhaps force that would even be of a threshold level or damage threshold level.

Chris Smith: Jeff Moore from University of Illinois with a discovery that force can be used to guide the outcomes of chemical reactions, and you can see video footage of that work on the Nature website. It's at Well, from serious science to a potentially serious problem and that's the teaching of homeotherapy in UK universities. It's a subject of a special report in the News section of Nature this week by Jim Giles and also of a Commentary by David Colquhoun, both of whom joined Mike Hopkin earlier this week to discuss the issue. Nature 446, 352–353 (22 March 2007) ; Nature 446, 373–374 (22 March 2007) .

Michael Hopkin: Homeopathy, is it harmless superstition or dangerous pseudoscience? And if it's the latter, why is it being taught as real science in universities? This is the question Nature has set out to answer this week, and with me here in the studio are David Colquhoun, who has written a Commentary on this subject in this week's issue, and Nature's very own Jim Giles, who has put together a special news report on homeopathic teaching. David and Jim, welcome to the show. Jim, if I could turn to you first, could you explain very briefly what homeopathy involves and why it's widely regarded as not real science?

Jim Giles: Sure, well homeopathy is an alternative therapy, which is based on the idea that drugs that cause symptoms of a disease can also help cure that disease. It's the idea of like for like and it's also distinguished by the fact that it's a very personalized treatment. So, a visit to a homeopath is likely to involve quite an intensive series of questions. A homeopath will enquire as to your emotional state, whether you are stressed, whether you are feeling unhappy, things like that, and also the remedy which they tell a few at the end will then be diluted, extremely diluted— so much so, that it's possible that the amount of active ingredient in the liquid that you are prescribed might actually be zero and it may just be water.

Michael Hopkin: So, it is seen as not much different from a placebo then?

Jim Giles: Now, well, the remaining people who report having benefited from homeopathic treatments, but actually when you combine all the scientific studies together and especially when you focus on the more rigorous scientific studies, you find that it's basically indistinguishable from placebo.

Michael Hopkin: So, you have your special report, what did you actually do and what did you find out?

Jim Giles: Well, we were curious about the fact that homeopathy was being taught in British universities. It's a B.Sc., it's a Bachelor of Science degree, especially since it's a scientific establishment and basically the thing is that it is not science. So, we took a broad look at what was happening in Europe and North America and we found, first up with the situation in the UK was fairly unique. In France, in Germany, in the United States, there is some homeopathy in universities, but it's basically taught as a component of a medical degree, and a very small component usually in passing of a complementary medicine section of that degree, but in the UK things are really different. There are sort of six or seven universities that offer full-time B.Sc. in homeopathy, which result in trained homeopaths and they also include sections on research and they look at the literature, and they teach students to critique the studies around their own homeopathy.

Michael Hopkin: David, given that homeopathy is just one of the range of complementary therapies, some of which seem to have some scientific backing for the idea that they do function above placebo, I am thinking particularly of acupuncture here as probably the best example of that, do you think that justifies their teaching as scientific subjects and should we give homeopathy the chance to try and yield that sort of information as well?

David Colquhoun: Lots of things are being taught, aromatherapy, acupuncture, traditional Chinese medicine, herbal medicine and reflexology, so-called osteopathy, and so on. There's really quite a range of them and even if sticking needles in yourself does cause some beneficial effect on some sorts of pain, and that's really is pretty dubious, but even if it does, what's objectionable from the point of view of university is the mumbo-jumbo that goes with it. They talk about chi and meridians and energy, and so on. There's not the slightest reason to think that means anything. You really can't have universities teaching about energy in one sense of the word in the physics department and in some other alternative sense in a different department. It's just nonsense and to teach that is, to my mind, absolutely unacceptable.

Michael Hopkin: Jim, this idea that Britain is the only place where homeopathy is taught as a specific degree and elsewhere it appears to be a component of medical studies in general, what sort of attitudes did you find outside Britain in terms of how complementary medicine fits alongside traditional Western medicine?

Jim Giles: I mean, I think the similar views inside and outside Britain among some people and the medical establishment, and that is basically if patients report benefits from homeopathy then they are quite happy for those patients to be given homeopathy treatments. And so we had, for example, a doctor from France who teaches homeopathy. He is a conventional doctor, but he teaches homeopathy, and he says homeopathy is almost entirely down to placebos, no evidence that there's anything else in it, but patients want it, they report benefits because it somehow maximizes the placebo effect, so I am quite happy to prescribe that, and that's actually quite a common view, you know; I had, for example, somehow made the point that I have got some evidence-based medicine and concerns with how homeopathy does in this sort of double-blind randomized clinical trial. Patients and GPs want to say 'is this going to make me better' and if a GP feels that a patient is going to improve having been given treatment, they may not really care that much whether it's passed some kind of gold standard evidence test.

David Colquhoun: That's fair enough. There's nothing wrong with placebo effects. They can be good enough. Quite often their apparent effect is simply just spontaneous remission, you know, if you take echinacea your cold gets better in seven days when otherwise it would have taken a week, but that's not to underestimate placebo effects. There is a distressing number of conditions in medicine that not much can be done about, and if someone is happy with a placebo that's just fine, but you've got to be honest about it. What it a real dilemma here, because if somebody is gullible they perhaps get the best placebo effect if you lie, and kept surrounded by lot of mumbo-jumbo, and that's effectively contrary to what the trend has been in medicine recently, which is to be as honest as you can.

Jim Giles: Yeah, I think what you have done is just quite describe the difference between the actual that we have seen in UK and actual we are seeing elsewhere. In the UK, homeopathy is a scientific subject. So, people aren't willing to accept this placebo and they do want to have it without the evidence, whereas in France, in Germany and in United States, we weren't really picking up the same signals, I think because homeopathy in those places is a small component in medical degrees, not more than that.

Michael Hopkin: So, do you think that it's fine for medical practitioners to carry on spouting their 'mumbo-jumbo', as you call it, and really what is more worth worrying about is, is it being taught as a science in universities?

David Colquhoun: Whatever a doctor chooses to do, and I think it's basically okay if they can't do anything else to prescribe a placebo with as little dishonesty as possible. What you cannot have is universities teaching absurd ideas about 'energy' and meridians and all this sort of stuff as though it was science.

Jim Giles: Yes, an interesting point about what the university should be teaching. Homeopathy obviously goes some way to maximizing the benefit that you can get from placebo, because we have different sorts of interaction and there seems to be something about the interaction between a homeopath and a patient which does bring the most out of a placebo; and what is interesting is, we could instead be asking, "well now, what's going on here, what's the psychology, how can we maximize that so that we get the most out of that interaction?"

Michael Hopkin: So, this idea about maximizing the placebo effect, if you will, is it possible that comparing science degrees in homeopathy on people might help with that, because your average gullible patient might have the placebo effect boosted by seeing a certificate on the wall that raises their confidence in the method, and it enrages us intellectuals sitting here and talking about how it's not real science, but what's the harm?

David Colquhoun: I think the harm is that if universities become corrupted, if they teach things that aren't true, then rather than spending money on that, what people should spend money on is ways of maximizing the placebo effect in ways that don't involve dishonesty.

Chris Smith: So, do you agree? It's just pseudoscience and shouldn't be taught in the university setting, or is David Colquhoun just being unfair? Well, you can put your point across at


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Chris Smith: On the way, how predators and immigrants affect the emergence of new species, and how chemists are doing it without protection (making new compounds that is); but first, how giving the Earth a geological equivalent of a CAT scan has led to new insights into how tectonic plates move and how the sea floor forms. Here's Doug Toomey. Nature 446, 409–414 (22 March 2007) .

Douglas Toomey: What we have discovered is the pattern that magma has delivered from the Earth's interior up to crustal magma bodies and in the deep ocean. People have been studying segmentation of mid-ocean ridges, many people know about the black smoker, hydrothermal-vent fields on sea floors, and one of the questions that we have been asked in our community is simply why is one section of the volcanically active mid-ocean ridge hosting a hydrothermal vent field, and another section is not erupting magma frequently or not hosting a hydrothermal vent field.

Chris Smith: So, how do you try to get to the bottom of that?

Douglas Toomey: Well, to get to the bottom of that, we tried to map the magma plumbing system between the Earth's mantle, where the magma is generated, and the crust so we could see what the relationship was between the crustal magma bodies and the mantle plumbing system.

Chris Smith: How do you follow it around, because you have got the challenge of lots of water on top, and of course you have got rocks that you can't see through, so how are you able to dissect out where this magma is going?

Douglas Toomey: Well absolutely, but we do something that is very similar to a CAT scan in the medical sciences. We put down receivers on the sea floor. These are ocean-bottom seismometers or ocean-bottom hydrophones. We deployed approximately 50 of those over a distance of two- to three hundred kilometres along the ridge, and then we set off man-made sources in the water column, air guns that make man-made explosions. That seismic energy or acoustic energy travels down through the water and then to the Earth, and we record minute variations in the travel time that it takes for energy to go from point A to point B. You can mathematically use those to reconstruct the three-dimensional seismic velocity structure of the Earth.

Chris Smith: Because I think most people believe that magma comes up at a mid-ocean ridge and then you get spreading in both directions, it's kind of equal and opposite, don't you, as new sea floors generated, so how does your finding rewrite that model then?

Douglas Toomey: Well, what was expected for the previous couple of decades of study is that flow in the mantle is simply a response to the plate motion above. So, what that means is, if you know which way the plates are moving away from the ridge, that the mantle simply ought to be following suit and moving along with it. What we found, in fact, is quite bizarre. The mantle floor is rotated with respect to the plate boundary, and not only is it rotated with respect to the plate boundary or the direction as the plates are moving, the mantle was actually ahead or in the direction of the recent changes in motion of the plate itself.

Chris Smith: So, in the future what's going to happen is that the spreading of the sea floor is going to adjust to reflect the underlying mantle at the moment?

Douglas Toomey: Exactly, this skew of mantle flow is one of the driving forces that is reorganizing the plate boundary and the plate boundary is just trying to catch up with the change that has already been made.

Chris Smith: And what are the implications of that, because that's a pretty dramatic finding, because it totally turns on its head what we used to think — what's going on?

Douglas Toomey: Well, I think that's a big question that many of us will try and pursue both through experiments and modelling, but one of the things that has me intrigued is that since people discovered plate tectonics they have talked about various forces that moved plates and some of those are the push of the ridges, the gravitational sliding of the ridges downhill, the pool of seduction zones, and there has always been this elusive force in plate tectonics called basal drag, the traction between the moving plate on a surface and a mantle below, and it has been elusive because sometimes it's pushing, sometimes it's resisting, sometimes it's not there, and it has been something that's very difficult to measure; and what I find ironic is that in the supposed passive flow environment of a ridge, it actually gives us a window into measuring basal tractions beneath plates, and I think that could have some broad-reaching implications for what are the forces that cause changes in plate motion.

Chris Smith: The University of Oregon's Doug Toomey. He has turned tectonics on its head by showing tha,t rather than the mantle following the behaviour of the plates, it's actually the other way around. To evolution now, how new species and subspecies emerge to take advantage of different environmental niches. This is known as 'adaptive radiation', and Justin Meyer has been looking at how predators alter this equation. He has done it by growing Pseudomonas bacteria in culture and then introducing something that eats them. He can then compare how they specialize both in the presence or absence of the predator. Nature 446, 432–435 (22 March 2007) .

Justin Meyer: I study a model system. It's a lab adaptive radiation where Pseudomonas fluorescens, which is a bacterium, diversifies to specialize on different resources and different environments within a very small microcosm. During one of our experiments, mutations arise, and there is one type to create other types; and previous work has shown that underlying this process is frequency-dependent selection, so these different types arise and are maintained and the diversity is maintained through some frequency-dependent selection. This type of selection is a type of natural selection that gives rise to multiple kinds of species or genotypes and drives diversification.

Chris Smith: So, in other words, you have got these things growing in culture, there are multiple niches in that culture and therefore the original starting bacterium changes in order to produce different types of bacteria that are going to exploit those niches?

Justin Meyer: Exactly.

Chris Smith: So, what happens if you put something in there that's a predator for the Pseudomonas?

Justin Meyer: Okay, so the predator is a protist predator, it's Tetrahymena thermophila, and when you add the predator to the system, it obviously eats the prey, so it eats the bacteria and it reduces the population densities of the bacteria — and the effect that this has on the adaptive radiation is that resource competition doesn't occur as strongly anymore and resource competition is what drove the adaptive radiation without the predator. So, the radiation still occurs, but it occurs much slower.

Chris Smith: So, what are the implications of finding that the predator actually has a bad effect on diversity when you apply that to, say, the real world? Because lots of people have previously suggested that large numbers of predators drive species to become more specialized and better adapted to cope with the presence of the predator.

Justin Meyer: So, there are two parts of the paper and one part goes over how the adaptive radiation is influenced by the predator when the prey live in environment where they would naturally diversify (that's what I just talked to you about), and then the second part of the paper is how the predator would influence the prey and influence diversification if the prey are living in an environment where there aren't these open niches for the prey to specialize to, and in that second part of the paper we found that the predator actually does drive diversification in the prey and the new types that arise aren't specialized on different resources or environments, but they are specialized on the fact that they can avoid being eaten by the predator.

Chris Smith: So, in one respect it does drive more diversity, but these are bacteria. Do you think the same principles apply to much bigger animals and much, much more specialized species than these prokaryotes you have looked at?

Justin Meyer: That's a very good question. The ecology that drives this diversification is similar to ecology that other species that have diversified in the wild experience, and I do believe that the system does have something to say for other adaptive radiations and especially in more natural conditions. To get to the bottom of this, within the lab system we will be altering the environment to which the bacteria grow, and modulating the strength of competition and predation. In this experiment, we just added competition or added the presence of the predator and just made these changes. So, to really test what we have shown today, we are going to modulate the different strength of the predator and competition in this system and see how that shapes the diversification.

Chris Smith: Justin Meyer from the University of Ottawa, studying how predators shape the form of an adaptive radiation. So, that's predators, but what about immigrants? Tad Fukami has done something very similar, but instead of introducing a predator, he has introduced some more specialist competitors. These were added at various time points and, as it turned out, that timing was critical. If the immigrants were added early on, they had a profound effect on the how the founding population subsequently evolved. Added later though, they made virtually no difference, and Tad thinks that the same is probably true for other organisms, including possibly humans. Nature 446, 436–439 (22 March 2007)

Tadashi Fukami: The question we wanted to ask is whether what we call immigration history affects the diversity that you get in your biological community. To answer that question, what we did was we introduced two different types of bacteria in different timings between six hours later and four days later, and we were counting different types that grow in these test tubes.

Chris Smith: So, in other words, these introduced bacteria, as they grow they sub-specialize, they kind of mutate and turn into subspecialties of the founding bacteria?

Tadashi Fukami: That's right. In addition to these founding populations through mutational processes, you get new bacterial types and those new types also start to grow. So, now you have up to six types of bacteria co-existing in this small microcosm.

Chris Smith: And when you look at it, when you add the immigrant, how does that change the different types that you eventually get, if it does at all?

Tadashi Fukami: It did affect the types of bacteria you get eventually. Sometimes you get multiple similar types of bacteria co-existing using resources in a very similar way, but sometimes not and that depended on immigration timings that I just described.

Chris Smith: So, do you know why the immigrant bacteria have this sort of guiding effect and manipulate what the outcomes are for the subsequent types of bacteria that develop in this way?

Tadashi Fukami: Yes, the keyword is resource competition. So, these different kinds of bacteria need nutrients and oxygen for them to grow, but if you have immigrants introduced very early, by the time the other ones that are trying to mutate, they wouldn't be able to grow because the other one is already there and they are limiting the resources.

Chris Smith: This is very simple system though, Tad, isn't it? So, how would you, say, comparing with the real-life environments, not just two bacteria in a tube but many, many bacteria in a whole ecosystem, or not just bacteria, say, humans in a new land mass. How does it compare and can it be scored off in that way?

Tadashi Fukami: Yes, that's a good question and we think that the kind of things that we are observing with bacteria are applicable to other kinds of organism, maybe large organisms like plants, insects, birds and maybe perhaps even humans in natural ecosystems. The reason for that is the mechanism that we found with the bacteria, such as resource competition. This is known to be reasonably general enough that that happens with a variety of other organisms that I just described.

Chris Smith: Tadashi Fukami from the University of Hawaii, who has found that the effects of immigration on how bacterial populations evolve are all down to the timing. Early immigrants could be quite detrimental, but later arrivals seem to be able to be absorbed without any problem.JingleEnd Jingle

Chris Smith: Finally this week, to a man who wants to rewrite the chemistry textbooks to do away with so-called protecting groups. These are chemicals which are added to a reaction to shield certain functional parts of a molecule as the chemist tweaks other parts. That's fine, but in practice then you have to get rid of them again to purify the product or to manipulate the thing that they were designed to protect in the first place, and this can enormously complicate synthesis and also cut down the chemical yield. To get around the problem, Phil Baran has come up with a series of chemical guidelines, which he says should enable chemists to throw away the rule book. Nature 446, 404–408 (22 March 2007) .

Phil Baran: Since the beginning of organic chemistry we have been unable to control the issue of chemo-selectivity, meaning we are unable to control how different functional groups relate to each other; and the way that we have normally approached this problem historically is to introduce something called the protecting group, and what this is doing in essence is shielding one of the reactive functionalities, so that you can do what you want to do, and then removing it at the end after your desired operation is done; and in essence what this has done is increase the number of steps required to make organic molecules and ironically, although these groups were introduced to control issues of chemo-selectivity, they have added an additional layer of chemo-selectivity considerations and often that can be a detrimental part to a synthesis.

Chris Smith: Because you have got to get rid of them once the reaction is over to clean up your product, haven't you?

Phil Baran: Exactly, and so it just contributes to the perception that complex molecules are way too complex to make in any meaningful quantity. What this Article does, it introduces a proof principle and shows how it's possible to make compounds which previously were made in 20 to 30 steps and in small quantities, like milligram quantities, and in this way, we were able to make it in a way that even rivals nature itself. So, we can make large quantities of the compounds, we can do so in 7 to 10 steps, and we can do so giving only one optical isomer, that is the naturally occurring isomer, and we start from very cheap materials and the procedures are so simple that an undergraduate— or perhaps even a well-trained high-school student— could go through from beginning to end.

Chris Smith: You are probably being a bit optimistic about some of our high-school students, but is there sort of rule book that you can follow in the synthesis that says that if you apply this same set of rules to any synthesis you could do it via the method that you have come up with?

Phil Baran: Yes, so in this Article is delineated several general concepts and principles, which should be applied during the retrosynthetic analysis process, and applying the principles that are put forth here, one should be able to remove many, if not all, of the protecting groups involved, and the approach definitely requires some creativity and imagination, but it also fosters a discovery of new chemical reactivity.

Chris Smith: So, have people just been following dogmatically this pathway of adding these protecting groups because they thought that's what we have always done, that's the only way to do it, so we will carry on doing that, and it's just because you have taken a step back that you have seen this alternative approach and managed to make it work?

Phil Baran: In essence, that's the case. There are many textbooks out there on protecting groups and some famous ones even go as far as to say that, like death and taxes, protecting groups are an inherent part of synthetic organic chemistry, which we will never elude. So, I think when you are a student and you are trained with that philosophy of, if there is a functionality which is free we have got to protect it. This kind of dogma becomes ingrained within a tapestry of your algorithmic logic and how you solve problems. The first thing you think is to protect rather than to embrace natural functionality.

Chris Smith: So, are there any chemical reactions, which are just sort of dangling tantalizingly out there, which you haven't yet been able to make in large amounts, which in applying this approach could really transform the field, or I am thinking of these rare molecules that people are finding in the sea, for example, which they are saying could be the next cure for cancer?

Phil Baran: There are many 'holy grails' within the field of complex-molecule total synthesis and a lot of them come from marine life and, as you mentioned, marine life often provides us with very exciting targets for anticancer research and antibacterial research, so, yeah, we are targeting a number of those, and indeed we have completed synthesis of several members of the class, that's coming on very soon, and those compounds have 10 nitrogen atoms, or even more complex than the molecules reported in this paper, and it has quite remarkable bioactivity including anticancer, antiviral, antibacterial, and so those compounds do make very interesting targets and we have been able to make grand quantities of them by using the principles and concepts delineated in this Nature paper and so its not something that's limited to only one class of natural products, that is a generalizable set of principles.

Chris Smith: Phil Baran from the Scripps Research Institute with an exciting new way to make chemicals more easily. Well, that's it for this week, and next time we will be exploring how supplementing soils is actually a very fertile way to destroy diversity. If you have enjoyed this edition of the program, then please do drop us a line at and tell us. This week's programme was produced and presented by me, Chris Smith, and the, with additional production by Sabina Michnowicz. Until next time, good bye.


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