Chemistry World Podcast -November 2010
00:12- Introduction
01:20- Non-stick chewing gum hits the market
03:33- Graphene scoops the physics Nobel
07:18- University of Bristol's Richard Evershed explains how isotope ratios in bone collagen can give away the diet habits of ancient populations
14:40- Muscling in on toxic seafood
18:15- Peptide balls prove stiffer than steel
20:00- Nobel laureate Ei-ichi Negishi on exploring the periodic table, cross coupling reactions and the future of organic chemistry
25:55- Twist and shine - stretchy LED tattoos
28:55- Weightlifting crystals
(00:12 - Introduction)
(Promo)
Brought to you by the Royal Society of Chemistry, this is the Chemistry World Podcast.
(End Promo)
Interviewer - Chris Smith
Hello, welcome to the November 2010 episode of Chemistry World with Bibiana Campos-Seijo, Phillip Broadwith andLaura Howes. This month dissolving chewing gum, two Nobel Prizes and plantable LED tattoos and a way to workout what Fred Flintstone might have been having for dinner.
Interviewee - Richard Evershed
The whole idea is based upon the fact that different food groups contain different stable isotope ratios, so therefore if you're consuming a food of one particular isotope ratio, that will be recorded in your skeletal collagen, things like cereals for instance, you will be recording the carbon and nitrogen isotope values of the cereals, whereas if you consume say marine food, you'll record the stable isotope value of the marine food. So by looking at ancient skeletal remains, knowing what we know about the isotope values of the modern materials, we can start to build up pictures of what people were eating in the past.
Interviewer - Chris Smith
Richard Evershed, he'll be with us shortly. I'm Chris Smith and this is Chemistry World.
(Promo)
The Chemistry World Podcast is brought to you by the Royal Society of Chemistry. Look us up online at chemistryworld dot org.
(End Promo)
(01:20 - Non-stick chewing gum hits the market)
Interviewer - Chris Smith
First up, something to get your teeth into, Bibi
Interviewee - Bibiana Campos-Seijo
Yes, in 2007, Terence Cosgrove and his colleagues at the University of Bristol in the UK had been working with a spin-out company called Revolymer and they actually announced at the time that they had created a new gum, which could be removed very easily from most surfaces and also that they're water dispersible. Since then they have been working on the formulation so that they can finally turn this product into a commercial product that is comparable to the available chewing gums in the market that has, you know, we're hoping to get something that had the same taste and consistency.
Interviewer - Chris Smith
It's a dream that mothers and people who have to do washing of their kid's clothes have had for years, isn't it? Chewing gum you can actually get out of something. I presume it isn't worth the hair but tell us about the chemistry. How does it actually work chemically?
Interviewee - Bibiana Campos-Seijo
Traditional chewing gum uses one of two polymers as a gum-based material. It could be polystyrene called butadiene or polyethylene called vinyl acetate. What these guys have done is that they have added an amphiPhillipic copolymer to this gum base and they have achieved the desired effect, which is the great ability and then you know making it washable pretty much.
Interviewer - Chris Smith
So what is this amphiPhillipic polymer or copolymer do, how does it work? How does it change the chemistry of the gum so that you can wash it away?
Interviewee - Bibiana Campos-Seijo
Well it has two components. It has polyisoprene backbone and then it has grafts of polyethylene oxide. So the polyethylene oxide or PEO tends to form complexes with many surfactants, which are very common in normal detergents and soaps like sodium dodecyl sulfate and then obviously any mild detergent will be able to remove the gum from hair like you were saying before or clothes and carpets even. But all said well, the hydroPhillipic nature of the PEO means that it's able to retain enough water, which then is essential for the degradation of the gum, basically it breaks down into small bits of polymer that can be washed away with water.
Interviewer - Chris Smith
You could say a hard act to swallow. Thank you, Bibi.
(03:33 - Graphene scoops the physics Nobel)
Interviewer - Chris Smith
Now Philliplip, tell us about another I reckon the gum-sugared Nobel Prize, but it hasn't that graphene has, so tell us about graphene and why this is important.
Interviewee - Phillip Broadwith
Well Chris, graphene, as anyone who listens to our podcast on a regular basis will know because we keep going on about it is singe layers of atomically thin carbon. It's like one layer out of a sheet of graphite and it has a massive array of really interesting properties. It's a molecule but it's also a crystal and it's completely two-dimensional, so you have very interesting effects of confining electrons in that two-dimensional structure, so from the physics and from the chemistry, it's very interesting thing to study.
Interviewer - Chris Smith
It is but what's also interesting is I actually was fortunate to interview Andre Geim, he's one of the people who got that prize wasn't it, this month just gone. And what I found fascinating was the way he makes it and he just said to me, quite a matter of fact, frankly, well, I will just have to put a bit of sticky tape on a bit of graphite and rip it off and the graphene stuck to the stick tape.
Interviewee - Phillip Broadwith
Yes Chris, that's absolutely right and that's one of the things that have been recognised with this Nobel Prize is the fact that Geim's group has a reputation for doing slightly off the wall projects which he calls Friday afternoon things.
Interviewer - Chris Smith
It levitated a frog.
Interviewee - Phillip Broadwith
Indeed that's right Chris. He stuck a frog in a very high magnetic field and the diamagnetic interactions of the stuff inside the frog held it levitated in the magnetic field. It's crazy but true.
Interviewer - Chris Smith
But this was another Friday afternoon project then.
Interviewee Phillip Broadwith
Yeah, absolutely. So, Kostya Novoselov who's worked in Andre Geim's group for a while took the idea that graphite is made of layers and thought well, how do we get one of those off, we'll stick something to the top and peel it off.
Interviewer - Chris Smith
Sounds great, but what do you think we can actually do with it, why is this such a monumental thing? You've said there's some interesting properties, but what sorts of things is graphene going to useful?
Interviewee - Phillip Broadwith
Okay. So because it has very interesting electronic properties, you can use it in things like displays; we've seen a few months ago there was a Korean group who made a very large sheet of graphene, sort of 30 inch diameter sheet of graphene and they made a working touch screen display out of it,. It's much better in some respects than other materials for that because it's very tough at the same. It's possibly better than lot of other materials for same thing because it's transparent and very tough and very, very thin.
Interviewer - Chris Smith
There was a great paper in Nature a few years back and they were doing imaging of molecules as in really imaging molecules. It was scanning tunnelling electron microscopy and one of the big problems was actually imaging molecular species is they keep moving around all over the place, but if you get a sheet of graphene, these researchers found you can drop molecules on to it. They stick where they're supposed to be and you can physically see them and because the graphene is such a regular structure, the honeycomb shape, you can easily subtract it digitally from the pictures you get and see physical molecules. I was just gobsmacked to see a molecule of butane having this lovely wiggly pattern, just like we used to draw in the chemistry lab. So I can see why graphene is important in some applications, what about commercially though?
Interviewee - Phillip Broadwith
Well that's the next step and that's actually where the chemistry comes in because it's all very well to get a sheet of sticky tape and peel off a tiny crystal of graphene. If you want to make devices you got to make it on large scale and to do that you need chemistry. Most of the large scale stuff is made by chemical vapour deposition, so you get methane gas or some other source of carbon and heat it very hot and lay it down on the surface and hopefully you get crystals of graphene and they're getting better and better, making it bigger and bigger crystals and single layers or just two layers and controlling how that goes down. So I think very soon we're going to start seeing some commercial technology.
Interviewer - Chris Smith
Phillip Broadwith on graphene, the stuff that won Andrew Geim a Nobel Prize this year. And we'll meet another 2010 Nobel laureate in the form of Ei-ichi Negishi this time in person a bit later on in the program.
(07:18 - University of Bristol's Richard Evershed explains how isotope ratios in bone collagen can give away the diet habits of ancient populations)
Interviewer - Chris Smith
But before that how do you work out what someone who's been dead for thousands of years actually ate. Richard Evershed.
Interviewee - Richard Evershed
Earlier dietary reconstruction is the area that we're interested in exploring, trying to understand what people actually ate in the past.
Interviewer - Chris Smith
How easy is that? I mean when you say in the past, we're not just talking tens of years, in some cases it's thousands, isn't it?
Interviewee - Richard Evershed
That's right thousands of years ago, so we're trying to put together what diet was thousands of years ago. Often times before agriculture but also then often looking at what people were eating at the time when agriculture was being introduced by say Neolithic societies.
Interviewer - Chris Smith
In recent weeks, we've seen a group including Anna Revedin who published a paper in the Journal PNAS from Italy looking at what people 30,000 years ago were preparing by way of plant matter and she was analysing starch grains that were embedded into stone tools. Such luxuries aren't always available to archaeologists though are they?
Interviewee - Richard Evershed
No that sort of evidence is quite rare, but we do have other evidence which is much more common such as the organic molecules that are preserved in skeletal remains which are very widely distributed to archaeological sites.
Interviewer - Chris Smith
So, this is actually physically looking at the bone and taking the adage, you are what you eat, and so what goes in ends up turning into you and there's a chemical signature of that.
Interviewee - Richard Evershed
That's exactly it. You are what you eat principle is exactly the one that we exploit through these stable isotope techniques.
Interviewer - Chris Smith
So tell us about that then. If someone gives you a piece of ancient bone how do you then go about processing it and understanding where that bone came from, who it belonged to, where they've been and what they did and what they ate?
Interviewee - Richard Evershed
The first thing you do is demineralise the bone because the things we're focussing on are the biochemical constituents, the organic constituents. And we get rid of the mineral phase, which is most of what you see when you look a bone and we then set about recovering the biochemical and we focussed on a number of different ones over the years, Lipids are one that we've looked at, but the main one which is studied and which we've been giving a lot of, directing a lot of effort to is collagen, the structural protein that is present in all our bones, which is obviously a biopolymer made up of amino acids.
Interviewer - Chris Smith
So how would you look at the collagen, what are you actually looking for when you say stable isotopes, what is that and what can that tell you?
Interviewee - Richard Evershed
Being a protein, it's obviously made up of amino acids which contain carbon, nitrogen, hydrogen, oxygen and some sulphur. The carbon and nitrogen are of particular interest as they have stable isotopes which are atoms of elements which contain additional neutrons in the nucleus, so they're physically different from the most abundant isotopes, so carbon for instance exists in two stable forms, carbon 12 as we call it and carbon 13 is its stable isotope and nitrogen has two major stable isotopes, which is nitrogen 14 which is the most common one and nitrogen 15 which is the one that has the extra neutron.
Interviewer - Chris Smith
How do you actually by comparing the levels of those things get meaningful information out?
Interviewee - Richard Evershed
The whole idea is based upon the fact that different food groups are molecules that are coming through different biochemical pathways contain different stable isotope ratios. So, therefore if you're consuming a food of one particular isotope ratio that will be recorded in your skeletal collagen, if you're consuming another type of food, you'll record its isotope value, so for instance if you're recording things like cereals for instance, you will be recording the carbon and nitrogen isotope values of cereals, whereas if you consume say marine food, you'll record the stable isotope value of the marine food, So by looking at ancient skeletal remains knowing what we know about the isotope values of the modern materials we can start to build up pictures of what people were eating in the past.
Interviewer - Chris Smith
Can you think of any examples in which this has really helped to clinch things recently?
Interviewee - Richard Evershed
Well the direction which our work has gone in is very much one of trying to add a more fundamental basis to this whole stabilised approach, the technique that was originally developed and that which people have used most commonly currently is to basically extract the whole collagen from the skeletal remains. They then combust it to carbon dioxide and nitrogen in order , you can then determine the nitrogen and carbon isotope values in an isotope ratio mass spectrometer. But what we've been doing is taking a part of the collagen at the amino acid level. Collagen is a complex molecule containing a range of amino acids which have different origins, potentially in the diets because you have, for instance, essential and non-essential amino acids. And so what we've been doing is pulling a part of collagen at that level in order to hopefully provide it with a better resolution and one thing that we have discovered through doing this is that if you start to recall the carbon isotope values of the different amino acids you can start to be much more specific about what people were eating. And one example of this and what we did on humans from South Africa where the bulk collagen made it very difficult to distinguish what the prehistoric humans were eating there, that was basically an environment way you had C3, C4 and marine foods as potential dietary resources, but by looking at the individual amino acids, we managed to quite unambiguously resolve the individuals were consuming high amounts of marine protein via by novel amino acid based proxy and that is an area which we are now developing and there's now a lot of interest around the world now and pulling apart this collagen at the amino acid level, because it is now realised that there is much more information if you start to explore at its fundamental level.
Interviewer - Chris Smith
So to make sure you got this correct, what you're saying is that by dismantling the protein by amino acid, separating those amino acids and then analysing them individually you can pick apart much more carefully and accurately what the different things and different components of that diet must have been?
Interviewee - Richard Evershed
That's the idea, yeah, so for the moment we're still doing the picking apart and testing exactly how far we can go with this resolution but we have hints that we can go much further than the then by just using the bulk signal as we call it, And then of course we've also got the nitrogen isotope value which you can start to look at and the thing we hope to do in the long run is to perhaps be able to provide a better sort of quantification of the amount of different foods people were actually consuming, because at the moment based on the whole collagen you can't really quantify to any degree the major sort of macronutrients that were in people's diet in the past. So this is the sort of Holy Grail as to trying to get to this quantification and then that's providing with real information on the sort of choices people were making in selecting components of their diet.
Interviewer - Chris Smith
Richard Evershed, and he is doing that pioneering work at the University of Bristol.
Jingle
End jingle
Interviewer - Chris Smith
This is Chemistry World, with me Chris Smith, still to come new proteins that are stiffer than steel and the LED tattoo.
(14:40 - Muscling in on toxic seafood)
Interviewer - Chris Smith
Now that sounds worrying but, no half so scary as a dose of food poisoning that you might pick up from the sea food platter; thankfully, scientists might have a solution, Laura.
Interviewee - Laura Howes
As everyone knows seafood has a slightly dodgy reputation and if you get a bad you know mussel or bad oyster it can really reveal in the next few days.
Interviewer: Chris Smith:
And what can we do about it?
Interviewee - Laura Howes
Currently not so much but hopefully with the work from some guys in California we might be able to shed some light on to it. there are these small sort of microorganisms that obviously affect seafood, seafood is a filter feeder, it takes in water and so anything that takes in it tends to get magnified in amount in its digestive system, that's why and they're so bad at picking up gruesome things that make you ill. So Michael Burkart and colleagues at the University of California have made a fluorescence dye with a tag at the end, which will bind on to one of the chemicals that's made by these gruesome, horrible sorts of microorganisms and will then be able to fluoresce so if you shine a light on it you'll get a light response back.
Interviewer: Chris Smith:
And this gives you an index of suspicion that ones dodgy is glowing green, but some seafood grown near nuclear power station might do it anyway. How does it work, first tell me?
Interviewee - Laura Howes
Well actually, the technique the way has quite a good acronym in itself that uses Fluorescent In Situ Hybridisation, FISH, which I could, is a good one, it's a good one but basically fluorescence obviously when you shine a light on it, it shines back by making the dyes a little stick on to the actual horrible chemicals that are produced, you get an instant vision of where these toxins are in the body of in your mussel and this tends to obviously focus in the digestive tract. So what Burkart and his colleagues have done is taken the digestive tract out of seafood, wash them in the bit of this dye and then shine a light on, they get a glowing sign, but also the detection is much better than previously used techniques, so immunological ones where they take the bacteria and they see whether there is an immunological response; you have to go away get it to grow and there's a certain problem in this one and it's a lot more responsive and it's immediate, so you can literally take up your mussel that you're growing and pull out one to check and you aren't going to eat them if you have a glowing response.
Interviewer - Chris Smith
I was going to say because there is a problem with this, which is that people don't just eat one mussel, so someone has come along, taking the digestive tract down and said yep that's fine, they are going to take a bowl of mussels and someone is not going to be able to painstakingly examine every single one of them so again you're still going to have the problem that your technique will work on one, it will act as a kind of an indicator for the group but there might be another dodgy one in there still or there might be a whole different pathogen, you know Nora virus or something might be lurking in there and this wont pick that up.
Interviewee - Laura Howes
Sure, and I think that's a fair problem that I think first of all there's the point that if you're picking up one in a sample and you're picking up as soon as it is being infected then you can immediately take out that group of mussels and not to send them to the restaurant and there's also the point that you could probably change the little binding chemical so that it attaches, Nora virus attaches to Nora virus so although this has been a proof of principle for one particular pathogen many others could probably be detected by the same way.
Interviewer -Chris Smith
Terrific. thank you certainly food for thought. Maybe I will keep on shooing the mussels in the meantime, thank you Laura.
(18:15 - Peptide balls prove stiffer than steel)
Interviewer - Chris Smith
Bibi peptide bonds that are stiffer than steel, I'm intrigued.
Interviewee - Bibiana Campos-Seijo
Yes they are indeed, a group of scientists based in Israel in particular at the Weizmann Institute of Science in Rehovot and also at the Tel Aviv University , they have prepared transparent nanospheres, self assembled from a simple protected dipeptide molecule and they measured their mechanical properties and to their surprise they surpassed those of steel and Kevlar.
Interviewer - Chris Smith
So what are the chemicals and how did they actually do this, how did they make it happen?
Interviewee - Bibiana Campos-Seijo
Yes, they produced these spheres using a protected version of diphenylalanine in particular the protecting group N-tert-butoxycarbonyl. Initially they had been working and trying to produce nanotubes, self-assembled nanotubes with this material, they measured the mechanical properties, they saw they were very good; then they took the process a little bit changed the assembly conditions and they were able to produce spheres which showed higher strength. They measured a magnitude called young modulus which is a measure of the material's stiffness and it actually was one order of magnitude higher for these spheres than it was for the nanotubes.
Interviewer - Chris Smith
What sorts of things could we do with this though?
Interviewee - Bibiana Campos-Seijo
Well, the idea at the moment is to use these spheres to strengthen composites, so potential use would be for the reinforcement of materials such as those used for medical implants but further than that we do not know yet.
Interviewer - Chris Smith
A tough material and some equally tough choices about what we do with it, thank you Bibi.
(20:00 - Nobel laureate Ei-ichi Negishi on exploring the periodic table, cross coupling reactions and the future of organic chemistry)
Interviewer - Chris Smith
Synthesising complicated substances usually by joining molecules together is what synthetic chemists frequently do, but sometimes the reactions involved are so long winded that it is almost unviable to do the work which is what makes the contribution of three men who won this year's Nobel Prize for chemistry so important. Two of those scientists were Richard Heck and Akira Suzuki who each independently discovered how to use palladium as a catalyst to link the previously un-linkable quickly, simply and under considerably more mild reacting conditions. The third player in this chemical breakthrough was Ei-ichi Negishi.
Interviewee - Ei-ichi Negishi
When I was a PhD student at the University of Pennsylvania, I started running a series of organic reactions some of which I thought was so roundabout and difficult to run, so I thought of somehow simplifying, you know, I started dreaming. And then one thought I came up with was what I would call Lego game approach to organic synthesis in which we just prepare first of all R1M, R being any sort of carbon group attached to the metal and then R2X, R2 is another carbon group and in principle somewhat dynamically they should react in the form R1R2 which we want plus Mx, Mx is a very stable salt so that should go but in reality these reactions don't go and then I started dealing with oxygen organoboron in Professor Brown's group and started thinking about catalysing organoboron., organoboron being R1M, M is a Boron in this case and after a series of failures, well actually I started using a copper salt as potential catalyst, but copper salts were evidently so impure, hardly anything was working so we decided to screen nickel, so called nickel triad, in the periodic table you see nickel, palladium and platinum lined up. At that time no palladium catalyst cross coupling was known. But when we screened nickel, palladium, and platinum, palladium emerged as very highly satisfactory element as catalyst and then what we did was to screen all sort of conceivable metals that can serve as M part of R1M. We found Boron to work, aluminium to work and then we found zinc, zirconium and so on.
Interviewer - Chris Smith
And at what point did you realise how much of an impact these reactions were going to have at the time and subsequently?
Interviewee - Ei-ichi Negishi
In 1976-77, 78, those three years, we were able to cover sort of a 3 x 3 matrix in my 10 x 10 or so chart, I felt that this principal concept must be applicable beyond 3x3 matrix that we were covering and I began sensing that this could be a reaction method of a very wide scope.
Interviewer - Chris Smith
And how did you then take off from there, when did it dawn on you that you had actually made the important discovery that was going to change the face of chemistry?
Interviewee - Ei-ichi Negishi
Definitely by 1985, I began feeling that this is how organic chemists should try to make molecules, you know, especially complex molecules.
Interviewer - Chris Smith
How does it feel to have been awarded the world's most prestigious science prize for doing that work?
Interviewee - Ei-ichi Negishi
I feel that if this prize recognises palladium catalysed cross-coupling as I define, then I think Suzuki's winning and my winning together, both of us are reasonably proud of what we or I have done.
Interviewer - Chris Smith
What about now though because, forgive me, in your 70's, aren't you still working what you're going to work on next?
Interviewee - Ei-ichi Negishi
Well, our work and my work on this palladium catalyst cross coupling, I consider to be a little more than half-way through and I have been continuously exploring along this line which I definitely would like to do as long as I can. I have not done anything in concrete way, that is to use transition metal catalysis for artificial photosynthesis, converting the mixture of carbon dioxide which is, you know, hated by the world, so chemically converting CO2 and water into useful things. I hope to be able to contribute in my own way to the advancement of this part of chemistry.
Interviewer - Chris Smith
And if he can come up with an artificial form of photosynthesis to lock up CO2 and who knows perhaps you will win another Nobel Prize. That was one of this year's Nobel laureates Ei-ichi Negishi from Purdue University.
(25:55 - Twist and shine - stretchy LED tattoos)
Interviewer - Chris Smith
Now, as if some people's skin decorations aren't bad enough already, scientists have come up with LEDs that you can implant which is making me very wary, Laura.
Interviewee - Laura Howes
You could be wary, you could have them tattooed on to your skin, who knows what you'll be doing with them. This is an interesting paper that's come out of Illinois in the States and a guy called John Rogers who does quite a lot of fun stuff with making fun circuits and doing things and he has basically combined sort of various work that he has done to make
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