November
Chemistry World Podcast - November 2012
1:25- How many molecules are in the smallest possible ice-cube?
4:18- Buildings that sweat may be able to cool themselves without air-conditioning
7:25- 2012 chemistry Nobel laureate Robert Lefkowtiz tells us about the G-protein-coupled receptor
15:38- Water-soluble silicon circuits could be used for medical implants that don't need to be removed later
18:47- How do you identify what type of wood you've just dug up?
21:55- Scott White discusses self-healing materials
29:51- Self-assembling nanotubes respond to temperature and can squeeze together
32:38- TNT can be used to explode decoys to save fighter jets from heat-seeking missiles
35:55- Trivia: What were fireworks like before the addition of metal salts?
(Promo)
Brought to you by the Royal Society of Chemistry, this is the Chemistry World Podcast.
(End Promo)
Interviewer - Chris Smith
This month, how small in terms of the number of molecules is the smallest possible ice cube that can be made. No idea, well you can find out in a moment, because scientists have actually made one and the answer may well surprise you. We'll also take a look at the building material that can sweat in warm weather to cut down aircon costs and is this, the stuff the Nobel prizes are made of?
Interviewee - Robert Lefkowtiz
I describe myself as a reluctant scientist. I had absolutely no interest in research, I mean I went to medical school for one reason and one reason only and that was to become a practicing physician and my first year at the NIH I oddly and completely failed, nothing I did worked, I hated it and I decided that I wanted no part of research.
Interviewer - Chris Smith
Thankfully everything changed for Robert Lefkowtiz who joins us in a moment.
(Promo)
The Chemistry World podcast is brought to you by the Royal Society of Chemistry look us up online at chemistry world dot org.
(End Promo)
Interviewer - Chris Smith
Hello, I am Chris Smith and with us for this the November 2012 edition of Chemistry World are Andrew Turley, Ian Le Guillou and Neil Withers who has been looking at the cold stuff.
(1:25 - How many molecules are in the smallest possible ice-cube?)
Interviewee - Neil Withers
Well how many water molecules do you think it takes to make an ice cube?
Interviewer - Chris Smith
It's obviously going to be a tricky question. I know that you get these hydrates, these little tiny ice cubic things that have watery cages and they are in the region of about 22, so I would go for that simple path.
Interviewee - Neil Withers
Okay that's not a bad guess, but those aren't really proper ice, you know, with the sort of the hexagonal structure of hydrogen bonded water molecules that we all know and love and learn about and put in our gin and tonic, so it turns out that the smallest ice cube that is recognizably ice would have about 275 water molecules in it.
Interviewer - Chris Smith
That's quite a few. How do they know that, and why do you need 275?
Interviewee - Neil Withers
How they found out using Mass spec, this was by Thomas Zeuch and Udo Buck both from various institutions in Germany. They used Mass spec and IR, so they used Mass Spec to look at very small clusters of water molecules only from say 70-80 molecules up to several hundred. So they used Mass spec because then they could pick out the right sizes and then they used IR to look at the structure of what was going on inside those clusters. So all the different bonds have a different characteristic frequency and the solid ice has a very characteristic one whereas the amorphous or the liquid has a different one and when it got to 275, they saw the characteristic solid peak.
Interviewer - Chris Smith
Why that threshold number though, what is going on between 270 water molecules and let's say 275 that means it suddenly starts to form ice, it must come down to energetic or something.
Interviewee - Neil Withers
It's energetics and it's the size of the cluster that's the important thing. So, as we'll know from our gin and tonics and other soft drinks with the ice cubes in the ice floats because ice is less dense than liquid water because it takes more space to make this hydrogen bonded network as a solid than as a liquid. So below a certain size the clusters are too small for this hydrogen bonded network to form. So, it's impossible to get the ice that we know in these lower clusters whereas by 275, in the very centre you start to get some of this kind of crystalline ice.
Interviewer - Chris Smith
What are the implications of us knowing this? I mean it's a nasty story, it's fun, but does it have implications for chemistry or understanding the world around us that you need 275 water molecules to make a miniature ice cube?
Interviewee - Neil Withers
Well, as you say, water is all around us, in the atmosphere there's an awful lot of different size water droplets forming clouds and things like that, so knowing exactly at what point it changes from a liquid to a solid and at what point the different phases are there could be very important for atmospheric chemistry.
(4:18 - Buildings that sweat may be able to cool themselves without air-conditioning)
Interviewer - Chris Smith
Thank you very much Neil. Andrew sticking with the watery theme, what's this about using water to keep buildings cool? Normally it's just the workers in the building who keep cool by getting a drink.
Interviewee - Andrew Turley
Right, so we all cool ourselves down using water, we all sweat and it's water on the surface of our skin that as it evaporates it helps to cool us down. Now it turns that you can do something similar with buildings by controlling water on the surface of the buildings and the reason you might want to do this is because keeping buildings cool is hugely energy intensive.
Interviewer - Chris Smith
Especially, I mean in hot countries, where they're spending a lot of energy just running aircon units to keep the cold in and the hot out.
Interviewee - Andrew Turley
Absolutely, so if you can keep those energy costs down, it all helps towards our emissions targets and the bigger climate change picture.
Interviewer - Chris Smith
But this could be about to change?
Interviewee - Andrew Turley
Perhaps what Wendelin Stark and his colleagues at ETH Zurich in Switzerland have done is developed a kind of gel that will hold water onto the surface of the building and it will in a cyclic nature and it will hold water when it rains, it will grab that water and keep it there and then when it gets too hot when the building gets too hot it will release that water and the building will almost sweat.
Interviewer - Chris Smith
And in the process of doing that you remove energy from the surface of the building in order to turn the water back into water vapour.
Interviewee - Andrew Turley
Yes, you use the energy to energize the water and then as that is removed the building stays cool and they predict that you could save 60% of your emissions, CO2 emissions through using this kind of eco-cooling.
Interviewer - Chris Smith
The fly in the ointment I could see those that if you've got a well insulated building then you're going to have thermal changes on the outside surface but how would you get that to go inside the building.
Interviewee - Andrew Turley
So this would necessarily be for everywhere, really this has been designed for tropical environments, where there's a lot of water and it's raining very regularly and then it gets very hot as well and also these happened to be very poor regions usually where insulation, it's either you can't afford it, or perhaps you won't need it, because it doesn't get that cold.
Interviewer - Chris Smith
Is it easy to retrofit? it is literally a question of you'll slap this stuff with the paint brush or if cost is a problem, if it is really hard to build and apply this stuff that could be an impediment.
Interviewee - Andrew Turley
The basic units for it shouldn't really be that expensive, the thermo-responsive hydrogel is based on a fairly common polymer. What the researchers found is that they can hold 5 mm of water and that's enough to cool a building on a sunny day using these polymers.
Interviewer - Chris Smith
And just out of interest I hear you say a very long name, I am afraid it's got one, what is the polymer.
Interviewee - Andrew Turley
The polymer is, wait for it, poly(N-isopropylacrylamide) which abbreviates very nicely to PNIPAM.
(7:25 - 2012 chemistry Nobel laureate Robert Lefkowtiz tells us about the G-protein-coupled receptor)
Interviewer - Chris Smith
Sounds like it should be an appetizing tropical cocktail, thank you Andrew. And now to somebody who describes himself as initially at least a reluctant scientist but one who has subsequently gone on to radically change the world of biology and pharmacology with his discovery of the workings of G-proteins and G-protein coupled receptors. These are the structures that enables hormones and nerve transmitters to pass signals between cells and now he has been rewarded with the chemistry Nobel Prize.
Interviewee - Robert Lefkowtiz
My name is Dr. Robert G. Lefkowtiz. I am a professor of Medicine and Biochemistry at Duke University Medical Centre in Durham North Carolina in the USA. Receptors are molecules on the surface or within cells of the kind of receptors that I study are on the surface of cells with which drugs and hormones initially interact, circulating in our blood are all manner are biologically active molecules, some of these are hormones or neurotransmitters or substances that we make ourselves and other times they are drugs which are given to us by physicians. The question is how do they exert their actions on the appropriate tissues and how do they do the right thing. And so the job of the receptors to discriminate these different types of molecules, we often use the analogy of a lock and a key. So the key would be a circulating molecule in the blood stream. Let's take adrenaline as an example which might be secreted into your bloodstream if you were experiencing the proverbial fight or flight response. Now, it's got to know to bind to your heart cells for example to make them beat stronger and faster .How does that do that? Well, it finds a molecule on the surface of a heart cell called the beta-adrenergic receptor which is complimentary to the structure of adrenaline. It is a lock into which the key adrenaline is able to fit. Now it's able to turn that lock and stimulate molecules inside the cell they happen to be called G proteins which lead to a whole cascade of events which in this case makes the heart beat stronger and beat faster.
Interviewer - Chris Smith
Before you came along and solved the structure of what they look like and how they work, what did scientists think was going on when you dropped some adrenaline on to a heart cell in a dish and it beat more quickly and more forcibly.
Interviewee - Robert Lefkowtiz
It was really a black box and in fact right up until the early to mid 1970s, there was a great deal of scepticism as to whether structures or molecules which we today know as receptors even existed at all, many of the leading pharmacologists in the world were very, very sceptical.
Interviewer - Chris Smith
So, how did you then approach that and say we have to work out how these cells were interpreting these signals?
Interviewee - Robert Lefkowitz
It was clear in order to do this we would need to develop some new technology, so what allow us to study the receptors directly. Since the core function of a receptor was to bind or interact with a molecule like adrenaline or with a beta blocker if you had that drug, we thought that the most direct way in would be to make a radioactively labelled form of one of these drugs and then see if we could work out the technology for actually sticking it to the curative for alleged receptors in the cell. If we could it would give us a way of tracking the receptors and studying them directly. We were successful in doing that in the early 70s. And we were able to use these techniques as a way of always tagging or finding the receptors and then over the next decade we developed techniques for solubilising the receptors that is removing them from the cell membrane with detergents and then purifying them to what we call homogeneity that is isolating the receptor molecules. This is a very daunting task because there are very few of the receptors in the cell membrane.In fact we had to purify the receptors a hundred-thousand fold from solubilised cell membranes in order to obtain them in isolated form. Once we had them isolated we could chop them up in a variety of ways and get little stretches of the sequence of the protein. And then we could use those stretches of amino acid sequence to design nucleotide probes which allow us to clone the gene for several of these receptors and thereby learn the complete amino acid sequence and when we did that we had a true eureka moment. In the deduced sequence of the beta-adrenergic receptor which was the very first one that we were able to solve, we could see that it had very marked similarity to the structure of a molecule called rhodopsin which is a molecule in the retinal membrane which allows us to perceive light. And as soon as we saw that these two remarkably divergent molecules for sensing our environment, light in one case and adrenaline in the other looked like each other. It immediately dawned on us that maybe all of this big family of receptors would look alike. And in fact over the next several years, we were able to clone the genes for 10 of these different receptors and true they all were very close in their amino acid sequence. And so we knew that this was a general principle of biology that all of these receptors were part of the what we call the same gene family and that they all worked in a similar way.
Interviewer - Chris Smith
It has taken you about 40 years to produce the huge corpus of work that you have and win a Nobel Prize for it, justly. How long would it take you to do the same stuff today armed with the molecular tools we now have, would it be a summer's work or slightly longer.
Interviewee - Robert Lefkowitz
Well, I think it would be slightly longer but I dare say I myself marvel at the progression of techniques since when I was in the laboratory 40 years. I often point out to my trainees that with exception of one or two techniques such as some forms of chromatography, column chromatography, there is virtually no technique that were used routinely in my laboratory that had even been invented when I started in the laboratory a little bit more than 40 years ago.
Interviewer - Chris Smith
I was talking with John Gordon the other day, who is in a lab down the corridor from here and he has on his desk his school report from his science teacher telling him he should forget it and go and do Greek instead of physics, it's exactly what the school said he should do. , Do you have any kind of letter of disparagement or rejection that you refer to, to remind you that you are human as well as being a Nobel laureate.
Interviewee - Robert Lefkowitz
Well, I will tell you this I described myself as a reluctant scientist. I had absolutely no interest in research. I mean I went to medical school for one reason and one reason only and that was to become a practicing physician. In fact I had never failed at anything until I got to the National Institutes of Health in 1968 as a clinical and research associate for two year which is essentially a post doctoral fellowship and my first year at the NIH, I utterly and completely failed; nothing I did worked. I hated it and I decided that I wanted no part of research. During the second year things started to work a bit better and I started to catch the bug. I still went ahead and finished the residency but then I gravitated back into the research but that first year of abject failure was certainly very chastening. Most of research is failure, it is that simple, I mean, 99% of everything you do is doomed to fail and in fact I actually give a tutorial to research fellows here at Duke every year called How to deal with failure and rejection in Science, I think there's some important lessons in there.
(15:38 - Water-soluble silicon circuits could be used for medical implants that don't need to be removed later)
Interviewer - Chris Smith
I think there's a lesson in that for all of us isn't it? That was chemistry Nobel laureate Robert Lefkowitz. Coming up shortly a new breakthrough that means electronic circuit boards could prepare themselves, before that though medical implants and sensors that can dissolve inside the body. Ian.
Interviewee - Ian Le Guillou
So this is the latest development to come out from John Rogers from the University of Illinois where we have electronic circuit that will dissolve over time. Now normally there would be no reason that you want your circuit to dissolve, in this case we could have it using it as an implant for medical purposes say that will last for a prescribed amount of time before eventually dissolving freely into the body and so it allows you to implant a device without ever having to take it back out again, avoiding any long-term effects.
Interviewer - Chris Smith
How did they do that?
Interviewee - Ian Le Guillou
They had previously developed a device that uses the silicon circuit on top of a silk layer and the silk was able to dissolve quite happily but now they've found that if you make the silicon circuit thinner so by 10 times then down to only 20 nanometres thick then it will slowly dissolve away at a rate of about 1 nanometre a day.
Interviewer - Chris Smith
And it's not that sort of thickness actually still used for, can you do stuff with that sort of resolution?
Interviewee - Ian Le Guillou
So, they've been testing out a few different devices that you could attach to something like this. So, they've already developed a 64-pixel camera that you would be able to implant as well as using things as an antenna or as a temperature sensor even a solar cell, they've found, I am not sure why you would want to implant that in someone..
Interviewer - Chris Smith
Solar cell...
Interviewee - Ian Le Guillou
It's there to be tested.
Interviewer - Chris Smith
Energy untapped, the idea being that you could do sort of invasive monitoring which would then not require further invasive surgery to get it back out again.
Interviewee - Ian Le Guillou
Exactly and you would be able to alter the thickness of the silicon layer and make sure that it lasts for only a certain length of time.
Interviewer - Chris Smith
Ingenious, is it safe though?
Interviewee - Ian Le Guillou
It's only appears to be safe; they've tested on mice so far and they can see that within the certain amount at a time all of the device disappears and the silicon and magnesium that makeup the circuit are absorbed by the body and can be easily excreted.
Interviewer - Chris Smith
I suspect probably they come out in your wee I would think, didn't they? Any suggestion that moving this to the clinic now or is this still very much planted in the basic medical sciences, not been translated camp.
Interviewee - Ian Le Guillou
It seems like it has every potential to go into clinical uses. I think it may be just a bit more work on making the device as that you can attach that bit more useful and making it worthwhile using these.
Interviewer - Chris Smith
So, if you had John Rogers sitting in front of you and he offered to make you a some kind of sensor that you could implant what would it be?
Interviewee - Ian Le Guillou
Well that's a tricky one, unless I can have like wireless internet with me everywhere I went.
(18:47 - How do you identify what type of wood you've just dug up?)
Interviewer - Chris Smith
Okay, take it for a while, what would you have Neil?
Interviewee - Neil Withers
Well, having had by health check up recently I would like to monitor my cholesterol, so if I can have an extra bit of cheese or not.
Interviewer - Chris Smith
You better not make the sensor out of cholesterol because it can certainly go up. Tell us about this wood story.
Interviewee - Neil Withers
Okay, so if you dug up an ancient piece of wood from an archaeological dig or maybe from some geological strata you want to know what that type of wood is, like whether it's oak or peach or laurel or whatever and what Pierre Adam and colleagues have done is they found a molecule that is a molecular fossil which means they can identify what type of wood it is.
Interviewer - Chris Smith
Can we not tell different types of wood then? Can we not look under the microscope and say, ah! That structure is oak and that one is peach.
Interviewee - Neil Withers
You can tell relatively young in an archaeological and geological sense but once the wood is so old that it's been, say it's been shipwrecked for thousands of years and it's gone blackened and aged and you can't see any of the structure then you just can't tell by conventional means.
Interviewer - Chris Smith
So, what is their solution? What they have done?
Interviewee - Neil Withers
So, their solution is they found a specific molecule that occurs only in oak and they've sort of traced its evolution over time and they found this molecule, this kind of fingerprinting triterpenoid and they can specifically say that it doesn't occur anywhere else, so if you find this molecule in a piece of old wood that it must have been oak.
Interviewer - Chris Smith
Does this stuff accumulate over time or is it there from the time in which the tree is growing?
Interviewee - Neil Withers
Yes.
Interviewer - Chris Smith
And therefore it doesn't matter how old the piece of wood is, you can still nonetheless say that is oak.
Interviewee - Neil Withers
Yes, so this molecule occurs naturally in wood, the original one and over time it changes from its original form which has two oxygenated groups next to each other and then over time they think by some sort of bacterial effect it becomes slightly different and there's only one oxygenated part and it's in that specific place where it doesn't occur in the natural oak. So they know that it does not come from the new piece of oak you know next door or being contaminated, so they know that it really is old oak.
Interviewer - Chris Smith
Can you therefore workout how old, by titrating the amount or do we not know what rates of accumulation so that wouldn't be possible?
Interviewee - Neil Withers
I don't think they can't work that way, I guess they would use carbon dating for that but this is instead of age it's just to identify it.
Interviewer - Chris Smith
Is that not a danger that there might be a relatively recent piece of wood that doesn't have any of this stuff in because it hasn't been in the ground well enough. So, you would mistake it for something else, or is it pretty clear cut?.
Interviewee - Neil Withers
I think, it's quite clear-cut that there's a very distinct difference between the molecule that occurs in current oak between the kind of the marker the old marker and you wouldn't get any overlap between the two, you would either have the new molecule that occurs in fresh oak if you like or you would have the very much older one, so you would be able to tell that it was old.
Interviewer - Chris Smith
And just oak or?
Interviewee - Neil Withers
At the moment it is just oak, but they hope to find other versions of this molecule that might occur in other types of wood, so that like an archaeological toolkit, molecular fossil toolkit so they can go and analyze difference pieces of wood and say okay so it's got this compound, it must be ash or it must be birch.
(21:55 - Scott White discusses self-healing materials)
Interviewer - Chris Smith
That would be nice, thanks Neil. Now if like me, you've been a victim of other people's poor parking abilities and you come back to your car to find that it's been scratched or dented, then you'll relish the work of this man who is working on ways to equip surfaces including car body work with the ability to repair themselves. He is doing it by embedding or even circulating healing chemicals through the materials in much the same way that our own vascular system delivers clotting factors to a wound.
Interviewee - Scott White
My name is Scott White, I am a professor at the University of Illinois and I work at the Beckman Institute and I lead the research group that is called the Autonomous Material Systems Group and basically we're trying to create materials that have the same kind of function that biological materials have in biological systems. We create materials like these things like they heal themselves, whenever they damage.
Interviewer - Chris Smith
So what sorts of applications are right at the forefront that you could say this is a real priority that we solve this?
Interviewee - Scott White
I am sure in the next maybe a year or so, you'll start to see self-healing coatings being offered in a commercial market put on to materials to protect them from corrosion.
Interviewer - Chris Smith
So, this would be for instance on my car, so as I am driving along and I accidentally scratch it on the side of the garage or something while I am manoeuvring out that scrape could put itself right so I don't then end up with the bare metal going rusty.
Interviewee - Scott White
Precisely.
Interviewer - Chris Smith
But the one problem with this is yes it works on the first occasion what about if I do it again.
Interviewee - Scott White
Right, so what's the likelihood that you're actually going to scratch it in the exact same place the second time, it's pretty low to begin with. So, even as you have a one such healing system, it's going to end up extending the lifetime of these kinds of products. The second aspect is that the original technology which is based on micro capsules that are releasing a healing agent in the material and it gives you an ability to heal one time locally wherever that capsule actually was living in the material and we ask the question well, if all the capsules are broken, we've released the entire supply of healing agents for that materials you can't heal anymore. So, what's beyond that concept in terms of healing that would allow us to do this repeatedly and so that sparked a new line of research on micro vascular materials and now instead of dispersing capsules that contain the healing agents throughout these materials, we actually deploy a vascular network now interconnected micro channels, so that we can circulate healing agents, we have the entire volume of that material and continue to replenish the supply of healing agents.
Interviewer - Chris Smith
What are the chemicals that you're using that are capable of doing these interesting reactions and how do you make sure that it only goes off where it needs to?
Interviewee - Scott White
The way we approach this is we have isolated vascular networks, so it's not just one network that we're working with but at least two and then we isolate the components of that chemistry from each other by putting them into separate networks. So when they're damaged, you know, you penetrate both of these networks equally, the release of fluids from both of those networks then goes to the site of damage, it mixes locally and you get a chemical reaction.
Interviewer - Chris Smith
How easy would it be to have a car that had a vascular system under it's paint work so that the old scratch and dent could prepare itself. I would think this is going to be pretty difficult, isn't it to plumb this in?
Interviewee - Scott White
What we've done is to locate that problem in terms of its manufacturing and make it scalable and cost effective, the way we do that is to create a material that we can remove after all the normal types of processing has occurred to reveal the vascular network that we intended in the first place and the way we do that is we create fibres or particles or sheets of material out of a very special polymer treated such that it will de-polymerize and vaporise into a gas and remove itself from that, the host material system.
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