Chemistry World Podcast - April 2008
00.10 Introduction
02.05 How ants tell friend from foe with chemistry
04.48 Your hair knows where you've been
06.53 The battle against malaria; Joe Cohen from GlaxoSmithKline Biologicals and Tom McLean from the Liverpool School of Tropical Medicine explain how industry has joined the fight against a global killer
13.15 Splitting water with sunlight on an industrial scale - a glimpse into our carbon free future?
16.35 Building an enzyme from scratch
19.40 Interview: Former FBI chemist Ed Bartick explains how to avert a terrorist threat with lasers
24.30 Bisphenol A and the baby bottle debate
27.02 Why are daffodils yellow? And why do drinkers owe a debt of gratitude to the scientist who brought us the first version of the now ubiquitous periodic table of the elements
(Promo)
Brought to you by the Royal Society of Chemistry, this is the Chemistry World Podcast.
(End Promo)
(00.10 -- Introduction)
Interviewer - Chris Smith
Hello welcome to this month's Chemistry World podcast with James Mitchell Crow, Richard Van Noorden, Ananyo Bhattacharya and I'm Chris Smith. Coming up, formication chemistry, scientists have worked out how ants tell friend from foe.
Interviewee - Ananyo Bhattacharya
The team treated an ant from one of the colonies with hexane and that dissolves the alkene-based scent that all ants have. When they coated it with a different alkene that was made in the lab and reintroduced it to the colony, it was immediately attacked by its former friends.
Interviewer - Chris Smith
Perhaps that poor ant should have resorted to some antiperspirant. Also on the way, while the future is bright for hydrogen.
Interviewee - Richard Van Noorden
On March 31st, a power plant that makes hydrogen by splitting water with concentrated sunlight launched in Almeria, Spain and this is really a glimpse into a possible carbon-free future where we use solar-driven chemical reactions to produce hydrogen.
Interviewer - Chris Smith
On fighting terror noninvasively, we will be talking to an ex-FBI man to find out how the next generation of chemical-sensing scanners can pick up potential bombers.
Interviewee - Edward G. Bartick
The Raman instruments also are designed that they can actually take measurements through containers like glass containers and plastic containers, particularly ones that are translucent, we call this noninvasive analysis. We find a suspect sample which you could just point and shoot.
Interviewer - Chris Smith
And also this month, new strategies to fight malaria and also the solution to last month's springtime chemical conundrum.
Interviewee - Victoria Gill
We want to know, what is the pigment that makes daffodils yellow.
Interviewer - Chris Smith
The answer is on the way, together with the list of lucky winners. So keep listening to find out if you're one of them.
(Promo)
The Chemistry World podcast is brought to you by the Royal Society of Chemistry. Look us up online
(End Promo)
(02.05 --How ants tell friend from foe with chemistry)
Interviewer - Chris Smith
When I was at school, one of the things we did to amuse ourselves at break times, was to find a red ant's nest and then drop in a few black ants from a different nest to see what would happen, well it would be delightful. Well the result was that the outnumbered foreigners were usually rapidly dismembered, but the question is how does simple creatures like ants know who should be in their nest and who shouldn't. Well now scientists have come up with the answer, Ananyo.
Interviewee - Ananyo Bhattacharya
Yeah, that's right Chris. Chemists have helped to crack the century old mystery of how the ants tell their friends from their enemies by their smells. So, ants have long been known to exude a complex mix of chemicals. Stephen Martin's team from the University of Sheffield looked at one specific ant, the Formica exsecta ant and they managed to unravel the problem because this particular ant has a very simple mix of alkanes that's the saturated hydrocarbons and alkenes which are unsaturated hydrocarbons and to do that they first, sort of, examine the chemical signature of each ant colony using mass spectrometry and that showed that ants from the same colony produced an almost identical mix of alkenes, but the alkanes they produced were very different and that suggested to them that the ants were likely using only the alkenes to spot intruders. So, the team treated an ant from one of the colonies with hexane and that dissolves the alkene-based scent that all ants have.
Interviewer - Chris Smith
This is like giving an ant a bath, basically.
Interviewee - Ananyo Bhattacharya
Yeah, a very unpleasant bath, I would think, but yeah. And then what they did was they took the ant and coated it with a different alkene that was made in the lab and reintroduced it to the colony, It was immediately attacked by its former friends. So, for their last experiment, they used glass beads as dummy ants, copied the chemical profiles of two different ant colonies and coated the beads with the two different odours. So, when they took a bead with the colony's odour and they introduced it to the ants nest, the ants ignored it, but then finally when they coated the bead with the foreign colony's odour and they placed that inside the nest, the ants attacked it and tried to remove it.
Interviewer - Chris Smith
Using this as a way of tracking different relationships between ant colonies I suppose you could understand how they spread and spread out into the wild then?
Interviewee - Ananyo Bhattacharya
Yeah, that's right and they also hope to find out how the ants are making these chemicals, because they don't that completely yet and also they think that the chemicals themselves make up an indication as to why some ants are more aggressive than others.
Interviewer - Chris Smith
Thanks Ananyo. Well from working out where an ant comes from and perhaps where it's been to, actually doing the same thing with hair on a human. James.
(04.48 -- Your hair knows where you've been)
Interviewee - James Mitchell Crow
Yep, that's right. From a single strand of hair, scientists can now tell where a person has been recently living and police in the US are already using this technique to investigate unsolved murder cases.
Interviewer - Chris Smith
So when you say where a person has been living, this is being put into the hair when the person is growing the hair, is it?
Interviewee - James Mitchell Crow
Yeah, that's right. So, its heavy isotopes of hydrogen and oxygen from tap water. When you drink water, those isotopes eventually get incorporated into the amino acids that make up your hair and the precise isotope ratio depends on where exactly in the world do you live.
Interviewer - Chris Smith
Now I know that in London, the tap water is pretty ropy, but everywhere else around the world, it's said to be okay. So, does water vary that much then?
Interviewee - James Mitchell Crow
Well, it varies enough that you can draw up a general map of a country and assess region by region where exactly a person might come from. So it's not exact enough to pinpoint a specific city yet, but you can tell a rough region and the reason for that is the isotopes in the tap water vary because climate varies in different regions; the heavier isotopes tend to fall as rain more readily than the lighter isotopes do. So, areas where that you tend to get heavier rainfall, you get more of these heavier isotopes, and what this team have done at the University of Utah, they have the pleasant task of sampling a hair from the barber shop floor in 65 cities across the US and then they've correlated that with tap water isotopes and drawn up this map. They can pinpoint roughly where a person has recently been living by looking at the hair and comparing it with this map.
Interviewer - Chris Smith
So, you can see the forensic applications of this straight way, James where that will be useful. Are there are any other possible uses?
Interviewee - James Mitchell Crow
Yep, there are. These guys suggest doctors might actually find it useful as well. The fact that you are laying down these markers within your hair based on what you are taking into your body, perhaps dietary illness could be indicated or also archaeologists looking at samples of ancient peoples could possibly tell what they ate?
Interviewer - Chris Smith
So now when a criminal goes missing, the police can say, "Hair today, gone tomorrow." Thanks James.
(06.53 The battle against malaria; Joe Cohen from GlaxoSmithKline Biologicals and Tom McLean from the Liverpool School of Tropical Medicine explain how industry has joined the fight against a global killer)
Interviewer - Chris Smith
There's something we would certainly like to see gone tomorrow is malaria, which affects about 300 million people every year and kills about 3 million of them. Well now there's hope that that might actually happen because GlaxoSmithKline have been developing an affordable vaccine, which is about to enter large-scale trials. Meera Senthilingam spoke to Joe Cohen who is from GSK in Belgium to find out how it works.
Interviewee - Joe D. Cohen
The basis behind GSK's malaria vaccine on which we started working in 1987 is a specific antigen that's a protein that sits on the surface of one of the forms of the early form of the pathogen when it infects man, and this antigen is called the circumsporozoite protein or CSP and the second very important, actually critical component, is the adjuvant system -- chemical molecules that have an immunostimulating effect. They tend to increase the immune response and focus it toward the kind of response that we want to get. And this vaccine works by targeting the very early stage of the life cycle of the parasite in man, just after the mosquito has injected, has bitten the person and injected the parasite into their blood stream. The vaccine works by using very high levels of antibodies and very strong cell-mediated immune response and these two kinds of immune response either prevent the parasite from infecting its first host system in the body, the liver, or the cell-mediated immunity and then destroy the liver cells that had been infected by the parasite.
Interviewer - Meera Senthilingam
A problem with vaccines often is that resistance may develop due to mutations of the proteins, so is that not a problem with this vaccine?
Interviewee - Joe D. Cohen
Well it is not a problem yet. We have not seen and we have looked at that specifically over the various trials that we have run and we have not seen any signs of what we would call escape mutants or protection towards certain strains of parasite and not others, but of course only time will tell if that will be a problem or not.
Interviewer - Meera Senthilingam
The first positive result you had with this adjuvant system was back in '96; that was over 10 years ago, so what's been happening since then?
Interviewee - Joe D. Cohen
It takes a long time to develop a vaccine. We would need to go through a number of clinical evaluation stages, especially if the final targets are children and infants, they are the most susceptible segment of the population.
Interviewer - Meera Senthilingam
How far away do you think we are from this vaccine being readily available?
Interviewee - Joe D. Cohen
We plan on starting the large registration trial, a so called phase III trial at the end of 2008, this will be a trial that will involve 16,000 children and infants in Africa and the study will take about 2 years and hopefully then as soon as regulatory view is done, we hope that the vaccine would be implemented soon after.
Interviewer - Meera Senthilingam
Well whilst that looks promising both medically and financially, a vaccine alone isn't going to solve the problem of malaria. So, further work being done to defeat malaria comes in the form of insecticides. Tom McLean is from the Innovative Vector Control Consortium, the IVCC. So, Tom you are developing a new insecticide system to help defeat the problem. What is the IVCC's strategy?
Interviewee - Tom McLean
We see vector control as one of the key legs in a strategy for malaria control or eventually elimination alongside drugs and in the future vaccines as well and if you look at the history of malaria control, in Europe where malaria was completely eradicated from southern Europe and similarly in the southern states of America, vector control played an absolutely crucial part of that process.
Interviewer - Meera Senthilingam
And so how did the insecticides actually work for killing the mosquitoes?
Interviewee - Tom McLean
The kind of insecticides that we're interested in are all contact insecticides which persist for a long time in the place that you put them, so that you don't have to keep reapplying them and these might be either as treatments to insecticide treated nets where people sleep under the nets and then the mosquitoes land on the nets and are killed by the insecticide or as sprays to spray on walls so that the mosquitoes when they come into the house and rest on the wall are killed by the insecticide before they bite people living there.
Interviewer - Meera Senthilingam
The main problem with insecticides and also with malaria vaccines, as we discussed earlier is that it's quite easy for the mosquitoes to develop resistance to them. How do you plan on overcoming that problem?
Interviewee - Tom McLean
It's certainly true that resistance is a major issue. So, our intention is to develop a suite of new insecticides that can be used in rotation on mosaic patterns and it has already been demonstrated that if you keep rotating the insecticides or use them in rotating mosaics, so that the mosquito population rather is not exposed continuously to the same insecticide, then you can avoid the build-up of resistance in those populations. A key part of our program is to develop the information tools to understand exactly what you should be spraying on any particular population of mosquitoes. So we are providing diagnostic kits to tell people what their local mosquitoes are resistant to and also information systems that will track the flow of resistant populations from one area to another as part of a long-term vector management process.
Interviewer - Chris Smith
Meera Senthilingam talking with Tom McLean from the Liverpool School of Tropical Medicine and before him Joe Cohen from GSK. They are both looking for ways to solve the malaria problem
(Music)
Interviewer - Chris Smith
This is the Chemistry World podcast with me Chris Smith. Coming up DIY enzymes - how scientists have built their very own enzyme from scratch and also the latest way to catch terrorists with a burst of light from a laser. First though, exciting news for the hydrogen economy, Richard.
(13.15 Splitting water with sunlight on an industrial scale - a glimpse into our carbon free future?)
Interviewee - Richard Van Noorden
Hopefully on March 31st, a power plant that makes hydrogen by splitting water with concentrated sunlight launched in Almeria, Spain and this is really a glimpse into our possible carbon-free future, where we use solar-driven chemical reactions to produce hydrogen. Now this reactor is the largest pilot-scale project of its kind. There have been hundreds of thermochemical water splitting schemes sketched out on paper, tested in laboratories, but this system will take in half a litre of water a minute and produce 3 kilograms of hydrogen an hour, which is really small fry compared to the tons of hydrogen you get from reforming natural gas everyday, but of course it doesn't use up fossil fuels.
Interviewer - Chris Smith
So how does it actually work, belt and braces stuff? What does it do?
Interviewee - Richard Van Noorden
Well, at the core of the reactor, you've got two honeycomb-like chambers and they are coated with oxygen-deficient ferrite structures with zinc and nickel, so that's iron, zinc and nickel and a little bit of oxygen. Now at high enough temperatures they strip water of its oxygen leaving hydrogen gas to bubble away. Now then these oxidized materials must be recycled. They drive off their collected oxygen as gas in a separate reaction step and the clever thing is that mirrors focus sunlight onto these chambers and the reaction that produces hydrogen, the water splitting, takes place in one chamber, next we have the recycling step. Now when the metal oxides have finished, the chambers functions swap over, so it is as if hydrogen is produced continuously rather than in batches. That's how you get 3 kilograms a day.
Interviewer - Chris Smith
It sounds like something from a James Bond movie -- may be an early days James Bond movie, but it certainly sounds like that with the idea of focussing the sun using these mirrors, I mean, will this really work?
Interviewee - Richard Van Noorden
Well focussing sunlight with parabolic mirrors is very well known technology and it is used to heat water now with solar power, so that's not really the problem. The problem of whether its going to work really is whether the materials are going to be able to withstand lots and lots of cycling and also whether this is ever going to be able to produce hydrogen as cheaply, as well, hydrogen reformed from natural gas.
Interviewer - Chris Smith
And what are their predictions. Do they think it's able to do that?
Interviewee - Richard Van Noorden
Well, Athanasios Konstandopoulos, who is headlining this project and works for the Chemical Process Engineering Research Institute in Greece, he has teamed up with German and Spanish teams and with Johnson Matthey in Stobbe Tech Ceramics, the industry and R&D partners here, he says they are making a capacitor within a decade, they are going to produce energy via hydrogen at 6 Euro cents a kilowatt hour which will be he says, the price of hydrogen from steam reforming of natural gas if you include the expected taxes on carbon dioxide production. So, he is optimistic. He points out that electrolysis of hydrogen is less efficient, so there's an alternative clean route, but he doesn't think that's going to work and using a catalyst, means you have to make extra steps to separate hydrogen and oxygen gases, which you will remember, are made in separate chambers in this idea. So he reckons thermochemical methods are the way to go and there are plenty other cycles to consider, but this is the largest scale yet.
Interviewer - Chris Smith
They want to make price not an issue; they just need to involve Gordon Brown who is doing wonders for petrol prices here in the UK.
(16.35 Building an enzyme from scratch)
Interviewer - Chris Smith
Now turning to the very, very small now, James, scientists have actually managed to build their very own bespoke enzyme from scratch.
Interviewee - James Mitchell Crow
Yep. That's right. This team of scientists at the University of Washington in the US have designed and then built this working enzyme completely from scratch. Enzymes are what nature uses to catalyze its reactions and they are honed through an evolution to work incredibly efficiently. Basically how they work, they are protein structures and they have an active site cavity which is a perfect fit for the substrate molecule and then the enzyme tweaks the structure, does the reaction, and off it goes.
Interviewer - Chris Smith
So have this team actually done this because it sounds pretty tricky to achieve that kind of design elegance and functionality, but to do it entirely artificially.
Interviewee - James Mitchell Crow
What they've done is they've taken this particular chemical reaction called the retro-aldol reaction, which breaks a carbon-carbon bond and they've modelled that using a computer and then they've worked out what the enzyme structure would have to be to basically fit the substrate perfectly inside the active site like a nature substrate would fit into a natural enzyme and then for this artificial enzyme to trigger that reaction.
Interviewer - Chris Smith
So does it break open something that's naturally found in nature, so in other words, can you compare it against a biological version, so a natural enzyme that does the same job or is this an entirely synthetic molecule that they can clip and chop with this enzyme.
Interviewee - James Mitchell Crow
Natural enzymes do do the equivalent kind of reaction, but not with this specific substrate. They had 72 designs that the computer has said should work and of those, those two did work, the best one the reaction went 10,000 times faster than the un-catalyzed reaction, but that's still a lot slower than a natural enzyme would catalyze the reaction.
Interviewer - Chris Smith
Could you say, take a computer program that does the equivalent of evolves things and apply it to these enzyme, the artificial enzymes, to see if it would evolve an enzyme that would become equivalent to what nature has provided us with.
Interviewee - James Mitchell Crow
I'll tell you probably could do that, but what these guys have actually gone on and done after their initial study, they've used an evolutionary process themselves and so what they've done is they've taken their best guess of the enzyme and then they've randomly mutated points in this enzyme structure, to see if any of those mutations give you a better enzyme, then they've taken the best enzyme and done the same thing again and so they call this, a sort of, directed evolution approach and so after each round of mutation, you take the best one and mutate again, and so you hope to iteratively reach the best structure.
Interviewer - Chris Smith
How do they see its actually being used though, how would you put this into the market place? What would you do with it?
Interviewee - James Mitchell Crow
Well, the types of reactions that these guys are looking at are typically used to make things like pharmaceuticals, agro-chemicals, so there's definitely a demand for better catalysts to make that kind of molecule and so I'm sure that that's what they're ultimately hoping it will be used for.
Interviewer - Chris Smith
And you never know, perhaps one day they'll even manage to make an enzyme capable of digesting my wife's cooking. Thanks, James.
(19.40 Interview: Former FBI chemist Ed Bartick explains how to avert a terrorist threat with lasers)
Interviewer - Chris Smith
Now if you keep an eye on the news, you'll probably have seen the carnage that heralded the opening of Heathrow's new Terminal 5. Part of the problem is ensuring security, especially as terrorists are becoming cleverer and more daring. Well, thankfully science is fighting back and at the forefront is a series of hand-held gadgets that use Raman spectroscopy to find felons. They can even see through sealed containers and the way they work is to bounce laser light off a material and then study the way the light scatters on its way back. Each individual material produces a specific fingerprint scatter pattern that gives its identity away. Ed Bartick now teaches forensic chemistry at Suffolk University, but until recently he worked for the FBI.
Interviewee - Edward G. Bartick
I've been working with Raman spectrometers which are hand-held instruments that weigh in the order of about 4 pounds. These instruments are very ruggedized, they can be submersed in water; they can be completely cleaned and decontaminated if necessary. There's a computer within it, they can be operated by hazardous materials. Response people who have special gear that has the cumbersome gloves and so forth - they can still operate this by big buttons that are on there and basically there's two ways of obtaining a spectrum with the instrument. There is the vial mode in which you can open a cover and put a small vial in the instrument and it goes into the beam of the laser of the spectrometer or you can do it in the point and shoot mode where the beam of the laser goes outside the instrument and so you just put the instrument close to the samples, which you want to measure and scan the sample. The Raman instruments are also designed that they can actually take measurements through containers like glass containers and plastic containers, particularly ones that are translucent. We call this non-invasive analysis, we find the suspect sample, which you could just point and shoot.
Interviewer - Chris Smith
So how does the Raman spectrometer actually work to spot those chemicals and tell you that they're there?
Interviewee - Edward G. Bartick
Okay, the material is excited by a laser and the light from the laser is scattered and reflected back through the optics to the spectrometer and the spectrometer like any other spectrometer has a monochromator in it, so that you get a spectrum based on intensity versus the wavelength or the frequency and with that it is spectrum that is specific to particular materials every time you do this. And now for the sake of using this in the field the spectra are stored in the computer and then compared to a library and they are used to identify what the explosive actually is composed of.
Interviewer - Chris Smith
How much you are going to detect because you don't need very much of some of these chemicals to make quite a Big Bang?
Interviewee - Edward G. Bartick
All it needs is a few milligrams, it's focussed down to like 2 or 3 milligrams max.
Interviewer - Chris Smith
Surely with that kind of sensitivity though, because that's pretty sensitive, do you not get quite a few false positives, because there must be these molecules floating around in the environment and they could land on things and you could accuse some one of being a bomber, and they're not?
Interviewee - Edward G. Bartick
Absolutely. The way the software had been designed, that is the particular problem. The software traditionally has been designed so that it gives you a best-fit match. If the particular material that you are looking for is not in the library, it still gives you the best fit, which might be wrong -- it could be a false positive or a false negative. I recommended that they design the software that if it doesn't come up with a good match or good fit it tells the user, no match found.
Interviewer - Chris Smith
Is there any way that people who have nefarious intent could come up with molecules that they know would deceive a Raman's spectrometer or conversely can they make something nasty, look like something innocuous to again deceive the spectrometer?
Interviewee - Edward G. Bartick
That's always possible. Some work is being done by some researchers at University of Rhode Island. They're working on understanding this, particularly the peroxide-based explosives, and what are the possibilities that could be done and if so, what type of wavelengths, what type of responses would be obtained.
Interviewer - Chris Smith
Now obviously you are not in the FBI anymore, but I have to ask you this as we finish, which is that were you suit sunglasses and the curly tube in the ear man?
Interviewee - Edward G. Bartick
As a researcher I was upfront, I was not undercover and I was a pretty, sort of, open, sort of, person.
Interviewer - Chris Smith
So with just one handkerchief the ex-FBI man, Ed Bartick.
(24.30 Bisphenol A and the baby bottle debate)
Interviewer - Chris Smith
Something else apart from terrorism that's got people worried is chemicals leaching into our bodies from man-made materials, and that can include baby bottles. So when people say breast is best, they're not wrong, Richard.
Interviewee - Richard Van Noorden
Well this is a really old debate that's flared up yet again on Bisphenol A, a monomer used to make polycarbonates and epoxy resins, 3 million tons a year of this stuff goes into CDs, plastic bottles, glues, paints and its actually known to disrupt hormone signalling; it has been for 70 years, but of course the dose makes the poison and according to the American Chemistry Council this is a problem only at levels far greater than the days we had ingested, so they say 50 micrograms per kilogram body weight today is a safe level, you and I are taking this in at may be 1.5 micrograms from bottles, children may be 11-12 micrograms. Now an August 2007 review suggested that Bisphenol A in the womb could cause cancer in rats, I should stress, but this was at levels close to what we would ingest everyday, nanograms per kilograms of body weight. Now the US National Toxicology Program has done its own review of the literature and it says I have some concern about the effects on pregnant women and children, so there's a bit of a problem there.
Interviewer - Chris Smith
But a rat is not a human, is it?
Interviewee - Richard Van Noorden
A rat is not a human, exactly, but the problem is, how do you test for the effects of Bisphenol A on a human in a controlled clinical trial?
Interviewer - Chris Smith
Well, there must be some situations where there have been humans who have been exposed to this stuff of varying concentrations over varying amounts of time and you could put the amount of exposure you were saying given how ubiquitous this is in industry and in nature. There must be enough exposure data now to be able to get some conclusion, isn't it?
Interviewee -
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