Chemistry World Podcast - February 2010
00:12- Introduction
01:58-- Molecular walker takes a stroll
05:18-- Why ancient Egyptians put lead in their eye make-up
07:30-- Mike Edwards explains what's bugging the bees
14:20 -- A copper catalyst to grab CO2 from the air
17:00-- A two-faced catalyst to turn biomass to useful oil
19:14-- Anne Young on new materials for tooth fillings
25:05 -- Clicking molecules onto proteins
28:32-- Using zebrafish to screen psychoactive drugs
31:22-- NEW - Chemistry joke of the month. Can you do better than the CW team? Send us your favourite chemistry jokes
(Promo)
Brought to you by the Royal Society of Chemistry, this is the Chemistry World Podcast.
(End Promo)
(00:12 -- Introduction)
Interviewer - Chris Smith
Hello welcome to February's Chemistry World podcast this month by Phil Broadwidth, Nina Notman, and Bibiana Campos-Seijo. Coming up, how Egyptian eye makeup loaded with lead, as it was, could have had some hidden beneficial effects. We'll also hear the latest on the bee phenomenon, colony collapse disorder, just where do those bees go and with a new way to make better bio-diesel, it's a clever new catalyst that likes water just as much as it likes oil. Plus what causes teeth to fall apart and why do fillings often need replacing, well scientists now know and they've come up with a way around the problem.
Interviewee- Ann Young
There are proteins under the tooth that will start to destroy the dentin and these proteins work once the bacteria have removed the inorganic part of the teeth, so the antibacterial agents that we can release will prevent both these proteins from acting to destroy the tooth structure and also the bacteria.
Interviewer - Chris Smith
So good news for anyone with an aversion to dentists. And talking of teeth, we have drilled out our Chemistry World conundrum and we filled the gap with a brand new feature.
Interviewee-Phil Broadwidth
Well Chris we though we'd take things up a notch and go with chemical joke of the month. What we want people to do is send in their favourite chemistry jokes and the more terrible the better really!
Would you like to get to start it?
Interviewee-Phil Broadwidth
Okay so here's one to start everybody off. What do you call a tooth in a glass of water?
Interviewer - Chris Smith
The answer's on the way and believe me it will set your teeth on edge. Hello 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)
(01:58 -- Molecular walker takes a stroll)
Interviewer - Chris Smith
First this month, to an incredible bit of chemistry and how researchers are making molecules march along. Tell us about this Phil.
Interviewee - Phil Broadwidth
Okay Chris. Well, there's a lot of research at the moment about molecular machines, trying to get molecules to do lots of things that we've seen machines do on the microscopic scale. There's lots of work that actually robots can do, but with molecules it is even more difficult. What David Leigh's team at Edinburgh University are trying to do is work on a molecule that can mimic the actin proteins in our cells, which are little proteins that turns a little along tracks taking various cargoes of protein or whatever to where they need to be in the cell.
Interviewer - Chris Smith
So tell us a little bit first of all about what the problem is they're trying to solve. So if you had a cell in front of you, for example, we know that cells have microtubules and things that connect as railway tracks for cargoes to go along. Scientists are trying to recreate the trains that pull those cargoes basically and that's what these groups are trying to do.
Interviewee - Phil Broadwidth
Yes Chris, that's exactly right. So, first there are two problems here. First of all, you need a track and you need a molecule to work along the track. Then the second problem is getting the walking molecule to fix itself to the track and move along it at the same time. The third problem is to get it to move along in a specific direction.
Interviewer - Chris Smith
And what have they've done to try and achieve that?
Interviewee - Phil Broadwidth
Okay, so the first phase of David Leigh's work was to make a molecule little walk along the track. They took a small track, which had four individual foot holds and a molecule with two legs. The two feet on the end of the legs are different chemical groups, one is a hydrazide and the other is a sulphide and on the track you've then got an aldehyde which reacts with the hydrazide group to make a hydrazone and another sulphide which reacts with the other sulphide on the walker to make a disulfide bridge.
Interviewer - Chris Smith
So you have got a right foot and a left foot and the right foot goes in the right foot hold and the left foot in the in the left hold, so it's already a polarized system.
Interviewee - Phil Broadwidth
Yeah that's exactly right Chris, what they did in the first phase was to cycle the conditions between acidic and basic when you are under acid conditions the hydrazone foot will detach itself so you're stuck on by the disulfide foot and the hydrazone foot can move about and it can go to either of the two aldehyde foot holds and that's an equilibrium process and you get a random selection of things and you cycle the conditions through to basic and the hydrazone foot is stuck and the disulfide foot can switch between its two foot holds in equilibrium.
Interviewer - Chris Smith
So that should step forward, the problems is what stops it going backwards as well as forwards?
Interviewee - Phil Broadwidth
Exactly, the problem there is we've got a completely random thermodynamically driven equilibrium process so what they then did is to introduce a bias on one of those feet, disulfides can not only be broken and made in base they are also susceptible to oxidation so instead of using a base , if you then reduce the disulfide, you lift-off the disulphide foot, then if you add an oxygen you reattach the foot, but that's an irreversible process, you lock the foot in position straight-away and that is enough to give you a slight bias towards moving in one direction rather than the other.
(05:18 -- Why ancient Egyptians put lead in their eye make-up)
Interviewer - Chris Smith
That's a whole new spin on take a walk on the wild side, doesn't it? Thank you Phil and now Nina, let's move back from the present to several thousand and probably about 5000 years back in time to ancient Egypt, fascinating study on that very gaudy gothic, if you want a better term eye makeup the many ancient Egyptians used to wear what's it all about?
Interviewee - Nina Notman
That's right so it is in ancient Egyptian literature that eye makeup was an essential remedy for treating eye infections and skin ailments, but there had not been any recent studies into why this might be.
Interviewer - Chris Smith
So it's in the writing, but no proof basically, scientifically till now.
Interviewee -Nina Notman
Until now, so Philippe Walter's group had been looking at what the makeup actually consists of, so they have been using partly looking at ancient recipes and partly using samples of makeup that was found in tombs and using scanning electromicroscopy and quantitative x-ray diffraction, they've been looking at the samples from a tomb and they found that there is a number of lead compounds in there.
Interviewer - Chris Smith
But lead is awfully bad for you, isn't it?
Interviewee - Nina Notman
It turns out it might not be if you put it on your skin; so they found in the makeup that there is four different lead compounds, lead sulphide which gives them the glossy black colour and three other white lead compounds, now couple of these white compounds are not naturally available so they must have been synthesizing them and they must have been doing that for a reason, so this is where the second group come in so Christian Amatore's group have been proposing that good lead is quite similar to calcium in its charge and radius, etc and calcium is known to trigger the body's immune defences during traumatic times and, may be Lead was doing the same thing and they've been using electrochemistry to study this and looking at the biochemical interaction between lead and cells and they have indeed found that when skin is exposed to the lead 2+ ion it gives off nitric oxide, now nitric oxide is a molecule known to stimulate immune defences. So therefore it seems that the Egyptians did have a reason for doing this.
Interviewer - Chris Smith
Pretty wild though to think you put eye makeup on to make yourself better from bacterial and other potential infections but was it therefore that the women wore the eye makeup and were healthier than the men, or was this very unisex?
Interviewee- Nina Notman
I am no historian, so I don't know, but if you take a look on the Chemistry World web site you'll see a suspiciously cross dresser looking Egyptian.
(07:30 -- Mike Edwards explains what's bugging the bees)
Interviewer - Chris Smith
Want to keep an eye on it I think, thank you Nina. Now where are all the bees going? Mike Edwards.
Interviewee - Mike Edwards
There is a lot of stories about collapse of bee colonies and how pollination is going to be affected disastrously, probably coming out are the story from the United States where there are alomond orchards that produces well over half the world's almonds are reliant on the honey bees which are moved from one end of the United States to the other to pollinate the crop, the collapse as far as they're concerned has been very real but it is not necessarily a collapse of all bees, it is to do with one managed pollinator.
Interviewer - Chris Smith
And when people say colony collapse is that a bit of an over exaggeration or do you literally see a bee colony that has been previously fit and well just vanishing.
Interviewee - Mike Edwards
Absolutely this is what is so odd about, the workers don't seem to come back to the hive they just die off outside, now actually, we know that's what happens with loss of bees; to digress life in honeybees in bumblebees are affected by a fly who jumps from their back and inserts it's egg into its abdomen, now the bumblebee once it has got an egg in its abdomen, its response is actually to stay away from the colony, it's not a hive in terms of managed hives with frames and nets, it's still a colony of insects, and it stays away the object being, if it make the fly larva cold, the fly larva can't grow faster, the bee can still work and take it's pollen back in to the hive but it spends the night out in the cold, so the flight goes on unless probably something like that when the honey bee don't of to it, they don't go back in the hive, if you go back in, you take whatever you've got with you.
Interviewer - Chris Smith
It sounds to me like you're suspecting not so much a chemical culprit but a parasitic or perhaps some other kind of infestationary type manifestation going on here.
Interviewee - Mike Edwards
Most definitely, there's lots and lots of work done trying to tie it down to chemicals, the overall feeling in honeybee hives is that there are more chemicals in the hive which are due to treatments to Varroa, another parasitic mite than the bees are bringing in from the country side.
Interviewer - Chris Smith
Because people have tried to tie various chemical usages to, infestations, to manifestations of colony collapse disorder in various countries, sometimes they tie up, sometimes they don't, in some cases compensation has been paid which argues that perhaps manufacturers of chemical do acknowledge that they could be having at least a part to play in this.
Interviewee - Mike Edwards
That all stresses, we get our food, because we persuade or kill a vast number of insects out there not to live on this plant we actually make sure they can't and in that way honeybees are no different and no other bees is any different; it visits this plant because they want something from the plants, there is a rather a sort of soft feeling about pollination what actually the bees are robbing the plants and the plants are trying to make the robbery to its best advantage.
Interviewer - Chris Smith
Some people have said though if you look at the practices that go on in the US because you brought up the question of the almond trees in California, hundreds of miles of them, isn't it, it's really quite striking, mass agriculture, they way in which those trees get pollinated is because farmers drive bees, billions of bees many, many miles dumped them near these trees at the right time of year, get them working like dervishes to pollinate all the trees and then they steal all of the honey the bees have made and feed the bees back, some fairly weak sugar solutions that can come for it and some people have suggested that this is leading to a progressive and evolving lack of fitness amongst the bees.
Interviewee - Mike Edwards
Yeah, if you know about rickets in humans which is a vitamin deficiency, exactly the same features in bees at present, then you're not putting any of the micronutrients which the bees collect from the plants and that includes pollen as well, but as well if I force you to live on something you could say, actually live on let's say bland flour, you wont be very sick either and this is something that intrigues me with bee keeping and pollination, some of these flower are not very attractive to the honey bees, they don't actually want to go to them and the answer is being to remove all the wild flowers all the else that might distract them, so they've got to go, but that in itself produces stresses on the managed bees.
Interviewer - Chris Smith
Would you say the situation we are seeing at the moment with the bee could be a sort of bee perfect storm where we have had ill-treatment of bees, for want of better phrase for a while, which has led to an evolved and perhaps inbred weakness, they are also not very well able to defend themselves because we keep robbing them of the micronutrients in their honey, this has perhaps culminated in surges in infestation with parasites of some sort, this all comes together and is contributing to this phenomenon, colony collapse disorder, but if you go looking for a single cause you're not going to find it.
Interviewee - Mike Edwards
Yeah, that is what the study cites, it's a bit of everything and depending where you are, the point is the colony collapse disorder, it gets labelled to anything that happens unexpected.
Interviewer - Chris Smith
What do you think we should do? How should we approach the problem and solve it?
Interviewee - Mike Edwards
In the UK it is much easier than it is in the States, because you have don't have the huge movements of to a single flower restriction, just go and visit royal and do nothing else, but we do have a lots of floral diversity in the countryside, now I am a little bit unhappy about paying government money spent for conservation providing forage just for honeybees which are really unmanaged pollinator help, however it is quite good because if you make good flowery margins in the field then the chances are that a lot many other bees will visit those as well, provided you make the flowers a sort of things which all nurture bees and the too fittest species wants to visit, we've done some work on that, we've done some projects and the result is certainly for bumblebees where this possibility has been extremely good with consistent year on year increase with the number of bees and that seems to translate to increase in the population. Providing a better diet is a good idea throughout the countryside, providing that sticking a honeybee colony it I think negates the conservation of them completely because you are swinging it completely so the honeybees get the best diet but I am quite happy to have the honeybees as a part of the whole spectrum on pollination.
Interviewer - Chris Smith
Mike Edwards on what we think underlies bee CCD, colony collapse disorder, Mike is an independent ecological consultant and he specializes in entomology.
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Interviewer - Chris Smith
This is Chemistry World with me Chris Smith still to come a new catalyst to beef up bio-diesel production, how fish larvae are helping scientists to find superior antidepressant and new fillings for teeth that won't fall out hopefully, But first Bibi the element copper seems to be coming to the rescue in the field of carbon capture. Tell us more
(14:20 -- A copper catalyst to grab CO2 from the air)
Interviewee- Bibiana Campos-Seijo
Yes. The team of researchers at Leiden University have developed a selective copper complex that can trap carbon dioxide selectively from atmospheric gases. Basically, the complex is simple and that it has two binding sides and each of the binding sides has a copper atom with an oxidation state 1 and they make it into a solution, bubble carbon dioxide through the solution and the two oxygen atoms of the carbon dioxide molecule bind to each of the copper atoms.
Interviewer - Chris Smith
So the CO2 goes into the solution, interacts with the copper in the 1+ state, it locks onto the oxygen, then what happens to the carbon?
Interviewee- Bibiana Campos-Seijo
Then the carbon atoms of two of the molecules bind together creating an oxalate bridge that binds two halves, if you like, of the molecule, so we end up having a tetranuclear system that contains four molecules of carbon dioxide as oxalate bridges between the two halves of the molecule.
Interviewer - Chris Smith
Oh! Well said you have actually got the carbons bonding together.
Interviewee- Bibiana Campos-Seijo
Yes.
Interviewer - Chris Smith
So how do you think get that molecule off of the copper again?
Interviewee- Bibiana Campos-Seijo
Well, they use lithium salts to extract the oxalate, which then can be used for making oxalic acid for example which is used in household cleaning products or methane or formaldehyde and once they have removed the carbon dioxide, which was present as an oxalate then they need to return the copper from an oxidation state 2 to an oxidation state 1 and they do that by electrochemical reduction. They have to apply a very small voltage of -0.03 relative to the normal hydrogen electrode.
Interviewer - Chris Smith
I see, you just pass more current through the solution it will reset itself and you can start again.
Interviewee- Bibiana Campos-Seijo
Yes and they have proved that it is reusable. They did over a course of seven hours, six rounds of carbon dioxide removal and it worked very well. The only thing to take into consideration is that you can get a build up of the lithium oxalate over the electrodes, but that's something that can be solved pretty easily.
Interviewer - Chris Smith
So, they think this is energetically and also economically viable and it s also scalable, so you could wide this up to a big source of CO2 not just a test tube in the lab.
Interviewee- Bibiana Campos-Seijo
Yes. They are looking to hopefully develop some industrial applications, but at the moment they are quite far away from that.
(17:00 -- A two-faced catalyst to turn biomass to useful oil)
Interviewer - Chris Smith
Still very exciting, thank you Bibi. Now Nina sticking with sort of similar theme, lots of people are very interested in the idea of biomass and producing bio-ethanol from biomass and therefore producing more environmentally friendly fuel. It had been difficult to do it effectively and efficiently but you might have some answers.
Interviewee- Nina Notman
Yes, in a form of catalyst that works as the oil-water interface and it can be easily removed from a solution. So as you just mentioned the biomass, which we get from farming or domestic waste or from an paper industry, once you heat it you get bio-oil, but this need to refined to be useful and by the time we may need to be deoxygenated and also all the molecules and they need to be roughly the same size. So this new catalyst is a combination of metal nanoparticles and carbon nanotubes. One of the problems with the bio-oil is the fact that the oil likely tend to be an emulsion of water and oil with the water containing the smaller molecule and the oil containing the longer molecules.
Interviewer - Chris Smith
And you obviously want to get a deficient all the small stuff to turn into big stuff in the oil, which is the trick.
Interviewee- Nina Notman
Indeed we do and that what the catalysts can do. So the catalyst itself has a hydrophobic area, the carbon nanotube and a hydrophilic are the metal oxide nanoparticles. When the catalyst is put into a solution of bio-oil, it sits itself within the interface and on the water side, the magnesium oxide nanoparticles causes the molecules to polymerize to become longer molecule and once they become a certain length they then will switch over the oil side and on the oil side where you got the carbon nanotubes, there is also some palladium nanoparticles embedded within these and the palladium nanoparticles do the deoxygenation process at the longer molecule. So eventually you end up with all of your molecule that you want within the oil phase so then you can separate out your water and you can also sieve out your catalyst because this is a solid-based catalyst.
Interviewer - Chris Smith
Is this again scalable? Can we get this up to a level where you could produce appreciable amounts of fuel via this route?
Interviewee- Nina Notman
I think there is some tweaking that need to be done but that's certainly what are researchers aiming for?
(19:14 -- Anne Young on new materials for tooth fillings)
Interviewer - Chris Smith
So something of a yin-yan catalyst that likes both oil and water. Thank you Nina. Now here's something to get your teeth into better fillings, Anne Young.
Interviewee- Anne Young
What we are interested in are adhesive methacrylates to repair tooth and bone, material that can go from liquid to solid with just a few seconds of exposure to blue light.
Interviewer - Chris Smith
Methacrylates have been used for very long, we have had the ability to fill teeth for a very long time. So what is the problem with that?
Interviewee - Anne Young
The major problem is bacteria getting down underneath the tooth restoration or you get when the material sets in the tooth, as you get micro gaps and bacteria penetrate down between these micro gaps and cause re-infection.
Interviewer - Chris Smith
Why do you get these micro gaps, what is actually happening chemically to open up these spaces?
Interviewee - Anne Young
The material is methacrylates and when they go from liquid to solid, the chemical reaction causes a small shrinkage. We can do things to try and reduce that shrinkage by adding in lots of inorganic filler particles but you would still have these micro gaps. You also tend to generate them with time when you are eating or chewing, you put forces onto the restoration. When you eat heat or cold things, the material shrinks or expands to a different extent to the surrounding tooth. If you get these cracks developing and then you get your bacteria going down underneath the restoration.
Interviewer - Chris Smith
So that pretty much means almost any tooth filling we have is destined to fight eventually.
Interviewee- Anne Young
It is the major cause of tooth restoration especially with the white composite material because they are not anti bacterial; they have no way of preventing the growth of bacteria underneath the tooth.
Interviewer - Chris Smith
Presumably that is the way around that then?
Interviewee- Anne Young
The way we are looking at is to release antibacterial agents. These not only kill the bacteria that is underneath the tooth but they can also prevent the tooth starting to degrade itself. There are proteins under the tooth that will start to destroy the collagen of the dentine and these proteins work once the bacteria have removed the inorganic part of the tooth. So the antibacterial agents that we can release will prevent both these proteins from acting to destroy the tooth structure and also the bacteria.
Interviewer - Chris Smith
So that is clever. You are talking about putting the chemicals that will protect the tooth into the filler or repair material itself so that the thing does not just fill the gap it also protects the tooth into the long term.
Interviewee- Anne Young
Yes. We are also releasing other calcium phosphate component that can help re-mineralize the tooth. If the tooth has lost its calcium and phosphate species, we release low levels of these from the tooth restoration material and that can also help to close up those gaps that form with time.
Interviewer - Chris Smith
Could you take it a step further and try to get teeth to actually repair themselves because you mentioned that you can get the teeth tissue coming back into the restoration. Could you come up with some way of making a material that either had cells in it that were capable of slowly eroding away the restoration material and replacing it with native tooth material or some kind of restoration material that would encourage cells to come out of the healthy tooth tissue and form a tight interface with the restoration and then slowly through the way to replace it with tooth again.
Interviewee- Anne Young
That's difficult to do with tooth because of the limited number of cells. We actually can do that with bone. Bone itself will actually re-grow if you could get a space to do so. One thing we are doing is we have been modifying these materials so that they are degradable. They will stick the bone together to stop it, but then degrade slowly because of the action of the cells. We can then have the cells use calcium phosphate components we have within the material to help regenerate the bones that's being damaged by disease.
Interviewer - Chris Smith
So are you still at the stage where you are just putting effectively glue with a few chemical tricks into teeth or is that the potential to put bigger stuff, or cells or may be even big molecules, DNA nucleic acids that kind of thing in there that might have therapeutic potential.
Interviewee- Anne Young
We can do that with some of the new materials we are developing that are degradable. We can put DNA inside nanoparticles, which can target cells. These cells will make the degradable adhesive degrade with time and release the DNA within these nanoparticles and then we can get slow transection of cells in surrounding the adhesive.
Interviewer - Chris Smith
And what sort of jobs would that DNA do.
Interviewee- Anne Young
At the moment biologist are developing a number of methods of identifying genetic problems that parts of a gene is wrong. So if we can put the part of the gene that is wrong into the cells we can cure a wide range of different diseases. The problem at the moment is we use viruses to transect cells, but there are a lot of toxicological concerns with the use of viruses. Potentially the sort of material that we are developing will be a lot safer.
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