Chilling Out - The Science of Cryogenics
This week, we're chilling out in the world of cryogenics, the science of the super-cold. We'll find out what happens to living tissue when it freezes, and how we can use low temperatures to keep organs, and maybe even one day whole bodies, in suspended animation. We also talk to the company behind an attractive new design of super-efficient fridge that runs on magnetism. In the news we hear how computer gamers have contributed to a breakthrough in HIV, why humans are programmed for overconfidence, and how the nervous system controls the immune system. Plus, we ask, is modern medicine altering the human gene pool?
In this episode
01:40 - Computers gamers solve protein puzzle
Computers gamers solve protein puzzle
Online computer gaming is sometimes viewed as a mere pastime without much outward benefit, but a new paper published today in the journal Nature Structural and Molecular Biology reveals how gamers playing an online game called Foldit have managed to crack the 3-dimensional structure of an important protein produced by the Mason-Pfizer Monkey virus, which causes a disease similar to AIDS in monkeys.
Figuring out the exact 3-D structures of proteins is really important in order to understand how they work, and also to develop drugs that can target them effectively - regular listeners may remember the paper's lead author Professor David Baker talking about this on the show back in August. There are several lab techniques that can be used to figure out protein structures, but these don't always provide a definite answer, and tend to rely on having a good model with which to intepret the physical data. In the case of the monkey virus protein, scientists had struggled for a long time to come up with a solution with no luck. So the researchers turned to the ingenuity of the Foldit players to try and come up with the 3-D structure.
There is a lot of computing power going into uncovering the 3-D structure of proteins - there's a big server called Rosetta, which also uses distributed computing power - that's the power of people's home computers when they're not in use - to churn through millions of possible protein structures in an automated way to look for the ones that seem most likely. But again, in some cases - such as this monkey virus protein - Rosetta still isn't providing the right answers, and a little bit of human intuition and puzzle-solving is needed.
In this case, the researchers gave the Foldit gamers some basic information about the protein's likely structure, based on data from a technique called NMR spectroscopy. The gamers set to work, and came up with a model, which they then tweaked. The researchers particularly note the contributions of three players - called spvincent, grabhorn and mimi - for making specific breakthroughs in solving the structure.
Once the players had come up with a good model, based on sound biochemical and physical principles, the researchers could then use that model as the basis for interpreting the data from physical analysis of the protein, using a technique called X-ray crystallography. They found that it was a really good match, proving that the Foldit gamers had accurately predicted the structure of the protein.
In the case of the monkey virus protein, the final structure has revealed some interesting regions that could be targeted by specifically-designed drugs. But more importantly, this is the first demonstration of the power and ingenuity of online gamers to solve long-standing scientific problems by combining computing power with the human brain. And this doesn't necessarily need the brains of trained scientists, as most of the Foldit gamers don't have a background in biochemistry. And given that there are many more unsolved protein structures out there, it's likely that the Foldit gamers are going to make a lot more breakthroughs in the future - and it's nice to know that they're making a big contribution to science while sitting at home on the computer.
05:26 - Overconfidence is the human norm
Overconfidence is the human norm
Humans have evolved to develop an over-inflated sense of our own abilities, which ultimately helps us to survive against the odds, scientists have discovered.
It sounds counter-intuitive that a penchant towards over-confidence should be biologically beneficial, but by crafting a mathematical model in which notional "players" compete for limited resources and decide whether to fight or back down based on an assessement of their opponent's apparent strengths, researchers James Fowler from UCSD and Edinburgh University scientist Dominic Johnson have shown that the best strategy is to err on the bullish side.
In other words, the costs of walking away from conflicts you might win are outweighed by the potential gains that come with taking a gamble if the prizes are sufficiently large. This over-egging of human self-belief might explain a lot about our behaviour, such as financial bubbles, wars we cannot win, tendencies to smoke or drive dangerously and even, Johnson points out, complacency about climate change.
Published in the journal Nature, the study also goes some way to explaining why a staggering 94% of University lecturers, when asked, rate their teaching skills as "above average". In fact, the only people who appear to have an accurate view of the world are those suffering from depression who display what's known as "depressive realism". And judging by their experiences, the advantages of pepping up our personal attributes are clear.
"It's this unrealistic view of the world is what gets us through life," says Johnson.
08:38 - X Ray Vision from New Super CT Scanner
X Ray Vision from New Super CT Scanner
with Professor Ian Sinclair, University of Southampton
Chris - A newly launched multimillion pound x-ray imaging facility at the University of Southampton has been providing new insights into a whole host of areas from climate change through to evolution. The combined facilities that they've put into the site not only mean that a lot of things can be scanned very quickly, but also, very large, and I mean seriously large, things can be studied - subjects that they're looking at range from dinosaur remains to bits of aircrafts and even crocodile poo. Jane Reck has been finding out what it's all about.
Jane - Three dimensional x-ray vision is no longer just the domain of fictional characters like Superman. For Professor Ian Sinclair and his team at the University of Southampton, it's all in a day's work. Using something called Computer Tomography (CT), they could find themselves doing anything from gazing within the jaws of an enormous fossilised sea creature to looking at the less appealing intricacies of a landfill site.
Ian - This term tomography means looking at something by slices through it, but the nice thing about computer tomography as we perform it is you don't actually have to cut the thing up to see those slices. And in fact, if you can take many slices of something all at once, you then get a 3D image of what is inside it. The centre offers the single largest high energy, high resolution computer tomography capability in UK universities. The further important thrust of the work is not just scale. It's going to be the numbers of samples that we can put through. In addition to the very large scanning machine, we have another device sitting beside it that will handle smaller objects. In that machine, we can basically scan at a rate that's about ten times faster than what comparable systems around the UK or indeed around the world can typically achieve today. It's not just the scanner. It's the computing hardware and the analysis software that we're integrating together into a complete workflow where the overall productivity, end to end, will just be faster than it is elsewhere.
Jane - The centre is supported by the Engineering and Physical Sciences Research Council. It's being used in an incredible array of projects including examination of the Staffordshire hoard, which is the largest ever find of Anglo-Saxon gold, the structure of plant roots and how they may respond to climate change in the future, and the development of human health and disease. However, even this list doesn't begin to cover everything...
Ian - We have rubbish - real rubbish from landfill sites being pulled up. This is a very important engineering challenge to understand the behaviour of landfill. We are doing innovative, absolutely world-leading work on the performance of composites for structures of a great variety of applications. We use CT to the level that we can look in an airplane wing, and if we really, really need to; find individual carbon fibres. We can understand composite structures, and load them, cause them to fail, understand those failures, and produce new models of a form that will reliably allow engineers to design with these materials in a way that they cannot do at the minute.
Jane - One of the most exciting projects to go behind the 4-ton door of the largest scanner is an enormous fossilised skull of a pliosaur found on the Jurassic coast of England.
Ian - A pliosaur is a fearsome beast, something like 17 metres long. The pieces are large lumps of rock and it is of considerable interest to take the small bits that the skull has become broken down into, scan them, get the exact structure, and then digitally reconstruct it. We can also see the internal structure in considerable fidelity, we can pick out where blood vessels, nerve channels would've lain, where tendons would've been that were holding the whole thing together. There's only a handful that've been found in the world and the skull we have represents one of the most intact and least deformed. It's therefore a very valuable resource to gain information from.
Jane - New insight into the evolution of man is being provided by an unusual find on an archaeological dig in Africa.
Ian - So this is the extremely interesting story of an uninspiring brown lump of rock being brought to the lab with the notion that it may or may not have been a fossilised crocodile poo. This was found in an area of Africa where apes that were ancestors to hominids, humans, were known to live. It was felt to be very important to understand what conditions and what environment they lived in, particularly, was there water, where there lakes around, where there marshes around. The underlying question is, was living in and around water one of the driving forces for apes becoming two-legged and subsequently evolving into human kind as we are now. We imaged it and they came to the conclusion it was a crocodile poo. And this strange small lump of uninspiring nature turns out to be part of a much larger picture of human development and human evolution.
Jane - In the long term, who knows what other uses the centre could be put to? A bit like Superman's powers, it seems the possibilities are endless.
Ian - There are so many opportunities. It seems to be limitless at times. I have used the terminology to people of imagining having Superman's instant 3D x-ray vision. In a way, that's what this gives you - something akin to that can be achieved.
14:27 - Body's defences not immune to brain control
Body's defences not immune to brain control
A neurochemical circuit that enables the brain to control the immune system has been revealed for the first time.
Scientists have known for many years of the powerful connection between the psyche and the functioning of the immune system, although the neurological underpinnings of the relationship have remained shrouded in mystery.
Now a team at the Feinstein Institute for Medical Research in New York and the Karolinska Institute in Stockholm, writing in the journal Science, have unravelled the workings of the communication system linking the nervous system and immunity. And what's really surprising is that immune cells themselves act as go-betweens to transmit chemical messages from nerve cells to other immune signalling cells.
Previous work conducted by Kevin Tracey, the senior author in the present study, had shown that stimulating the Vagus nerve, which runs from the brainstem to supply tissues in many parts of the body, could stop the immune system pumping out inflammatory signals. The signal responsible seemed to be a well-known nerve transmitter chemical called acetyl choline. But the wrinkle in the story was that the Vagus nerve did not appear to be producing it!
Now, by studying the spleens of experimental mice, the team have solved the mystery. White blood cells in the spleen called CD4 lymphocytes, when activated by inflammatory processes, become sensitive to the nerve transmitter chemical noradrenaline, secreted in the spleen by the splenic branch of the Vagus nerve. The CD4 lymphocytes themselves then secrete acetyl choline, which in turn switches off the production of inflammatory chemicals by other nearby cells.
The team proved this by carrying out experiments in mice lacking their own CD4 cells; these animals did not switch off the supply of inflammatory mediators when their Vagus nerves were stimulated. But when activated CD4 cells were transfused into the animals from donor mice, they immediately began to churn out acetyl choline, inhibiting the inflammatory process. Switching off the ChAT gene, which makes acetyl choline in these cells, also prevented any response.
Importantly, as the team point out in their paper, the regulatory system they have discovered is not confined to the spleen because the same sorts of CD4 lymphocytes are present throughout the body, particularly in lymph glands and specialised lymphoid tissue in the intestine called Peyer's Patches. This means that the system almost certainly plays a major role in controlling inflammation throughout the body and manipulating it could hold the key to controlling autoimmune and other related disorders...
16:50 - Planting Vaccines, Detecting Lies and Paternal Men
Planting Vaccines, Detecting Lies and Paternal Men
with Brian Ward, McGill University; Frances Wall, University of Exeter; Prashant Pillai, University of Bradford; Hassan Yugail, University of Bradford; Christopher Kuzawa, Northwestern University.
Meera - Tobacco plants could hold the key to large scale production of flu vaccines in the future.
In research unveiled at the ESWI conference on Influenza in Malta this week, Canadian biotech company Medicago add genes encoding the outer coat of the influenza virus to tobacco plants. These produce immune stimulating particles that resemble the flu virus but are devoid of any infectious content. Professor Brian Ward is Medicago's medical officer...
Brian - The viral protein then migrates to the surface of the plant cell and it auto assembles into this small virus-like particles that look, from the outside, like a virus but have nothing on the inside.
Elemental risk List
Meera - The British Geological survey have published a 'risk list' of 52 chemical elements that could soon be in short supply.
Abundance, location of reserves and political stability of countries mining the elements were taken into account in compiling the list at the top of which were metals like platinum, tungsten, and the rare earth elements. From the university of Exeter, professor of Mineralogy, Frances Wall...
Frances - So things like hybrid cars, wind turbines, mobile phones, they all use a huge number of elements. In a mobile phone, there are something like 66 different chemical elements incorporated into that technology. So we now need to be looking at the availability of elements all across the periodic table.
Eye Movement Controlled wheelchair
Meera - Wheelchair users could soon use their eyes to direct where they go.Dr. Prashant Pillai's team at the University of Bradford have developed a tracking device resembling a pair of glasses that, in combination with an electric wheelchair, uses cameras to track the position of the wearer's eyes.
Prashant - The most important thing about this is to try and give a lot of independence to the disabled. Our final aim is just to try to have a house which you could control just by looking at different appliances. So you can look at the TV and switch it on, look at the radio and switch it on and then get on to the wheelchair, and then look exactly where you want to go and it takes you.
Emotion Detection Scanner
Meera - A camera developed by UK scientists can detect when someone is not telling the truth.
The device looks for tell-tale facial changes, including altered expressions, blood flow and eye movements known to be associated with lying...Inventor Hassian Yugail is at the University of Bradford...
Hassan - Our accuracy rate is 70% which means we can catch 2 out of 3 lies. We hope to go beyond that up to a level of 90%. We see this in police interrogation scenarios, immigration, border-control points, anywhere where interviewing is involved, including potentially job interviews.
Testosterone in Fathers
Meera - And finally, Levels of testosterone in men drop when they become fathers.
A trial of over 600 young men in the Philippines, led by Christopher Kuzawa from Northwestern University, found that single men have higher levels of testosterone than those who have become fathers and amongst those helping with childcare levels fell by up to 34%...
Christopher - Interacting with a child can lower a man's testosterone it seems, but we also know from prior studies that men, during pregnancy of their mate, approaching birth, you see a drop in their testosterone before the child is born. And so, that suggests that there's something psychological perhaps and it also could be the stress of an impending birth. We don't really know, but it seems that there are multiple ways by which having a child can lower a man's testosterone.
The work suggests an evolutionary adaptation, using high levels of testosterone to attract and secure a mate with levels lowering at fatherhood, biologically wiring men to help with parenting.
21:02 - Where do all the salmon go? Planet Earth Online
Where do all the salmon go? Planet Earth Online
with Dr Clive Trueman & Dr Kirsteen MacKenzie, University of Southampton
Kat - Salmon numbers in the UK have been falling since the 1970s. This isn't down to overfishing, so scientists are trying to find out why. However, salmon are pretty tricky to follow. Their life cycle takes them from rivers into the open oceans, and then back again to rivers to breed. Now, a new technique that uses samples of the fish's scales could change all that. Planet Earth podcast presenter Sue Nelson met up with South Hampton University's Clive Trueman and Kirsteen Robinson.
Clive - So here we are in the imaging biominerals lab where we keep the scale archives.
Sue - Now you say scale archives, all I can see so far are a bundle of small white boxes.
Kirsteen - That's the collection from the River Frome archive which contains scales mounted on microscope slides dating from 1971 all the way up to 2002 and in each box...
Sue - Just taking one out there...oh yeah, it's got two tiny translucent scales, probably slightly smaller than my fingernail.
Sue - Clive, what are these scales actually made from?
Clive - Scales are actually related to teeth, evolutionarily, and they're made of a protein and a mineral. The mineral part is apatite, calcium phosphate, and the organic part is collagen. The collagen grows underneath the apatite and it's the collagen part that we're actually using for our analyses.
Sue - Before we get to the analysis, I see that there are a couple of microscopes over there on the other side of the lab, so I suspect this is an ideal opportunity for us to actually look at those fish scales in more detail and find out exactly how you examine them.
Clive - Absolutely.
Sue - Kirsteen, you're just going to pop that slide under the microscope ... I did not expect that. If you hadn't told me that was a fish scale, I would say you've got a cross section of a tree.
Kirsteen - Yes, it does look very much like that and it's because the salmon put down these calcium phosphate, these apatite mineral rings on top of the scale every two to three weeks, sometimes every one week if they're growing rapidly they'll lay down another ring on this scale.
Sue - What are you actually looking for then?
Kirsteen - What we're looking for is the very final season of marine growth at sea and from these salmon scales, very much like on a tree, you can tell how many winters they've had at sea, how many summer's they've had at sea and how many years they've lived in total, including how many years they have spent in fresh water.
Sue - What, purely from counting the rings?
Kirsteen - It's actually simpler than counting the rings. What we do is we use the rings to determine which part we sample and if you look at the scale through a microscope, there are dark bands and light bands. The dark bands are where the rings are very close together because the fish have been growing slowly in the winter and the light bands are where the rings are further apart because the fish have been growing rapidly when there's been lots of food in the summer. So what we do is dissect out the final portion of summer from the scale and then we have that portion of marine collagen that they grew while they were feeding at sea and we can analyse that chemically to find out what was going on with them at sea.
Sue - Now this is where you come in isn't, Clive, as a chemist. How do you do this analysis?
Clive - All marine food chains depend upon phytoplankton, the plants of the ocean at the bottom of the food chain. Now, when those plants grow they fix carbon and there's two forms of carbon, two isotopes, and the proportion of those different isotopes fixed into the phytoplankton cells is dependent upon the environmental conditions at the time those plankton grew and in the place those plankton grew. So, fish feeding on plankton in one particular place at one particular time will inherit an isotopic signal or an isotope ratio that's different from fish feeding in a slightly different place. We try and match up the carbon isotope record that we see in the scales with the record of sea surface temperature that we can get from satellites or from records of ocean temperature, and they also go back for decades.
Sue - Kirsteen, have you found out where Atlantic salmon are spending a certain period of their time?
Kirsteen - We've looked at two populations specifically, the one from the River Frome in Dorset and another one from the north east coast of the UK and what we've found was that the River Frome fish tended to match up between their isotopes and sea surface temperature records around Iceland, whereas the north east coast salmon seemed to be spending their summers in the Norwegian sea with the younger portions of the population spending it further south towards home and the older portions further north. Not only that we've found something very unexpected in that fish from just a few hundred miles apart are doing completely different things in the ocean.
27:02 - Cryoprotectant Molecules - Nature's Anti-freeze
Cryoprotectant Molecules - Nature's Anti-freeze
with Lorna Dougan, University of Leeds
Chris - So how are you approaching this problem?
Lorna - Well Chris, I'm a physicist using experimental techniques to try and understand how cryoprotectant molecules work. Cryprotectant molecules are things like glucose and glycerol, sugars and sugar alcohols, and they're used around the world by people in research labs when people want to store proteins or cells in fridges or freezers at low temperatures for long periods of time. Having the sugar or sugar alcohol there allows you to do that - it allows you to bring those proteins or cells to very low temperatures without them being damaged. So in my research lab, we're trying to figure out how it's possible to do that, and the particular area that we're focused on is proteins. Now proteins have this very unique three-dimensional structure, and that structure is really important for their function. When you heat a protein up or apply a force to it, you unravel it, just like you would unravel a piece of string, so you reduce that three-dimensional structure. What we want to try to figure out is what happens when you add these interesting cryoprotectant molecules to the surroundings of the protein - what do they do to stop the protein unravelling?
Chris - So at the moment, we're using these chemicals because we know they work - but scientifically speaking, we don't really understand very much about how they're working?
Lorna - That's absolutely right. They work, so why do I need to do these experiments? One of the things that's motivating me is some research that's going on here at Leeds where they're using these cryoprotectant molecules to preserve ovarian cell tissue. This is incredibly important for fertility treatment. Now the problem with this is, if you use a molecule like glucose or glycerol to preserve these cells, when you freeze them and then rethaw them at a later date you only recover a certain percentage of the cells. Ideally, we would want to recover as much as possible so that we can use them for later treatment, so we want to go right back to the beginning. We want to understand how these molecules are working, we want to understand how different cryoprotectant molecules work, and then we want to figure out which are the right cryoprotectants to use for particular proteins, cells and tissues. So we really want to get down to the details of how this mechanism works.
Chris - What do we know so far about how it's working? Because we've got lots of natural examples to look at: there are plants that grow in very dry countries that can survive enormous amounts of desiccation, and they stabilise themselves and come back to life as soon as they're wet again. There are other things that can survive temperature extremes in the opposite direction. Are there any chemical processes that unite the two that can give us a clue as to how these organisms are able to resist these extremes?
Lorna - Well one particular school of thought is that the cryoprotectants do something interesting to the water in the environment. So, for example, glycerol can do something to stop the water freezing - when water freezes, it forms this extended hydrogen bonded network, and this can be incredibly damaging for biological cells because it can rupture the membrane of the cell. That's one line of research that we're following - we're trying to look at the details of the water network when it has cryoprotectant molecules in its vicinity, and it's really not that simple, as it destroys the hydrogen bonded network. It's much more detailed than that, so water is still able to form a network, but glycerol for example is very effective at getting in between that hydrogen bonded network. So certainly, it is diminished and in this way, it could stop the water freezing at its normal temperature. If you look at the freezing temperature of water and glycerol, water freezes around zero degrees. Glycerol freezes at about 20 degrees, but if you put them together in a very particular combination, you can get that mixture to freeze at below zero degrees, right down at minus 47 degrees. So there's something really interesting going on when you mix these two hydrogen bonded liquids together.
Chris - It sounds elegantly simple, but I'm sure it's a totally different matter to try to work out the movements of particles which are literally just a couple of atoms glued together. So how are you following these networks of particles, the water molecules, and the glycerol, and seeing how they interact together?
Lorna - We're using two experimental techniques. The first one is neutron diffraction, and we're doing those experiments at the ISIS facility at the Rutherford Appleton Laboratories near Oxford. Neutron diffraction allows you to look at atomistic level detail at liquids and so, it allows us to ask these questions about the hydrogen bonded network. Of course, we're also interested in proteins, and we're using another experimental technique to look at protein stability. We're using an atomic force microscope which you may have heard of before in the show. This instrument was created back in the 1980s, and it actually earned its creators the Nobel Prize in physics. We've built a modified form of the atomic force microscope here in Leeds, and what that allows us to do is pick up a single protein and apply a mechanical force to that protein. That force is enough to unravel its folded 3D structure. It's a very specialist piece of equipment because the forces that we need to apply are actually piconewtons and we're working with molecules that are on a nanometre length scale, but we do this every day in the lab. So we're applying these tiny forces to proteins in the presence of cryoprotectant molecules, and this allows us to look at the details of the kinetics and the dynamics of protein unfolding and folding in these interesting cryoprotecting environments.
Chris - And so, putting it all together for us Lorna, what do you actually think is going on when we mix one of these cryoprotecting chemicals with say, a cell or a set of proteins to protect that protein down at very low temperature?
Lorna - I think that the solution is incredibly important, so the hydrogen bonded network that the water is forming plays a massive impact on the stability of the protein. I think that where the cryoprotectant molecule is interacting with the cell or the protein itself can give it extra stability as well, and the concentration of that solution is key to the temperature at which you can reduce the system without it becoming denatured.
35:16 - Controlling Cooling to Preserve Organs
Controlling Cooling to Preserve Organs
with Barry Fuller, UCL
Kat - One good reason to understand the physical processes involved in freezing is to use them in organ transplants and tissue archiving, a way that freezing tissues and organs could actually keep them healthier for longer so they can be transplanted to people that need them. But at the moment, only very, very simple things like sperm and egg cells can cope with the freezing process. Now we're joined by Barry Fuller. He's Professor in Surgical Sciences at UCL and he's working on this low temperature preservation of cells, tissues, and organs.
So, tell us a little bit at the moment about how we freeze live tissues and what sort of things we can freeze.
Barry - Well the ability to store cells and tissues at low temperatures, as you say, is really very helpful in many areas of medicine and biology, particularly where we need to transfer cells and tissues between different patients and different institutions. It makes things possible where, in the past, it wasn't possible. So for the future, we hope there are many ways that we can build on this little bit of knowledge that we have already and take this forward into new areas of regenerative medicine and stem cell biology for the future.
Kat - Now I actually used to work on very early embryos and I know that you can freeze a little ball of cells, an embryo, for several years even and then thaw it, transplant it into a lady and it will grow into a baby. Why can't we freeze tissues like say a liver or a heart, and bring them back?
Barry - Well you're right. We can freeze embryos but we had a lot of learning to do to be able to do that. We needed to understand a little bit about the anti-freezes, or cryo-protectants, the need to have them inside the cell and around the cell. And also, control the rate of cooling, the way that heat moves in the system, and the way that ice forms. This is because the fundamental problem is the way that water transmits into ice at very low temperatures. So we had to learn how to do that by controlling physical events to make it successful even for small cells. Moving up the scale to large tissues and organs, we haven't yet been able to make the engineering work to have that exquisite control of cooling and warming that we need.
Kat - Is that because it's difficult just to get all the cells in a larger piece of tissue with all the cryoprotectants in them, and cool them all down at the same speed?
Barry - Exactly right, because we've learned to avoid the formation of ice as much as possible. Getting the right anti-freezes and getting the control of cooling, we can get living cells and tissues to very low temperatures with small amounts of ice and then they go to a glassy state. The residual water goes glassy, so we avoid the problems of ice. In small samples of cells and embryos, in something like 100 micro litres you can easily control the cooling and warming exquisitely. If you have something the size of a human liver however, of a kilogram, it becomes really very difficult to have that exquisite control across the whole of the organ.
Kat - So what sort of things are you looking at to try and enable this in larger organs and allow more tissues to be cryo-preserved in the future?
Barry - Well one of the things we're doing is working with engineers to look at varying the rates of temperature change in larger volumes, so that we can induce this glassy state in a more controlled way. In the past, we've tended to simply use a slow linear cooling rate because it was easy to produce. Understanding where the damage areas are in the low temperature scale is helping us focus on different parts of the cooling chain and possibly manipulate those rates of cooling at different parts of the overall cycle, so we're moving away from a linear to a nonlinear profile.
Kat - So that's not just sticking something in the freezer - you're trying to control even different regions of say, a liver, to cool them?
Barry - Different parts of the cooling cycle, having slower or faster regimen so that the size of the tissue or organ won't lose control of temperature change because as you know, if you put a liver into a normal freezer, the outside will freeze very quickly and the centre will stay unfrozen for many hours. So, we need to be able to make sure that everything transmits across the whole of the organ in terms of cooling.
Kat - And just to sort of explain why this is so important, I understand that at the moment say, if you have an organ for transplant, you can only keep it alive outside the body for a couple of days at the most. Why would it be so useful to be able to freeze organs or keep them preserved at lower temperatures for longer?
Barry - Well we can't freeze organs as we just said. We can store them in special liquids just above freezing - about 4 degrees centigrade - making sure that these special solutions are around all the cells in the organ. That helps to prevent some of the injury of the cooling and the fact that the organ is outside the body, it's not receiving oxygen. What we're trying to do now is to reproduce a life support system for the organ at low temperatures which will pump around oxygen and nutrients, and try and keep the organ in a better state at low temperatures. Because our cells and bodies, our organs, can use oxygen and molecules like glucose at low temperatures, very slowly, but they can use them. So we need to be able to resuscitate those organs to keep them in the best possible quality for the patient that's going to receive them.
41:53 - Future Fridges
with Neil Wilson, Camfridge
Neil - The basic challenge with domestic refrigeration is trying to get more and more efficient appliances. An average domestic fridge at home is probably about 10% efficient and the European Union has introduced a new set of legislation, essentially asking fridge manufacturers to go from 10% to 20%. The challenge they have is that they can do this, but they need to do a lot of work in changing the insulation. They need to use vacuum panels, which are fragile and expensive, and also require them to redesign the appliance. Manufacturers are keen not to do this and so they're looking to our technology to allow them to introduce the highest efficiency devices without having to change the way they make and construct an appliance.
Ben - So, your device does the job of the compressor that we would normally see in the back of a fridge?
Neil - Yes. If you look at the back of your fridge, you'll see a big metal black box, and that's the gas compressor. The engine inside compresses the gas which liquefies, and that then gets pumped around, where the gas can evaporate. When it evaporates, it absorbs heat and cools down the milk. At the other side of the cycle, the gas recondenses into liquid and emits heat. So at the back of your fridge, you feel heat coming out - that's the gas recondensing, and inside your fridge of course is cold and that's where the liquid is evaporating.
Ben - How are you seeking to replace it or improve on it?
Neil - We're using a completely different approach to creating a cooling cycle using magnets and special metal alloys. In some sense conceptually, it is a very similar sort of process. In the gas compressor, you rely on the liquid gas transition. In the magnetic solution, we're relying on a very similar change from a ferromagnetic phase where the electrons inside this metal are all nicely organised and aligned. In that state it's attracted to magnets, and by changing the magnetic field, you can make it switch to a paramagnetic phase where the electrons are completely disordered, and no longer attracted to external magnetic fields.
Ben - So how does a change in the magnetic field or the magnetic structure of a metal lead to a change in temperature?
Neil - We're using special materials called magnetocaloric alloys, and these are materials that change temperature when exposed to a magnetic field, and that forms the basis for magnetic cooling. Now this effect has been known about for some time, in fact, I think it was discovered in the late 19th century in iron at several hundred degrees Celsius. All what we're really doing is using this effect, but using it at room temperature in order to exploit the temperature change.
Ben - So what actually is that metal? I can see you have a piece, roughly a square centimetre of it with you here. What's it made of?
Neil - This particular alloy is 95% iron, but it's doped with lanthanum, silicon, and cobalt. This has been designed to have a Curie temperature around room temperature. What I mean by that is when the material is below its Curie temperature, it's attracted to this magnet. As you can see, it's sticking onto the magnet quite happily, but when the material goes above its Curie temperature, it ceases to become magnetic. If I turn on the fan here and just heat it...
Ben - It almost immediately falls off!
Neil - Yes, as soon as it was pushed above its Curie temperature, it fell off the magnet, and it's these magnetic properties that we're exploiting in a magnetic cooling engine and combining that with the magnetocaloric effect, the actual temperature change. You can actually create four sides of a refrigeration cycle and it's those four process - the temperature change, and then the way the material changes its properties when exposed to heat - that you can use to actually pump heat from cold to hot or from hot to cold.
Ben - So how would we then integrate this into the existing design of a fridge?
Neil - In an existing fridge, you have the gas compressor, and the gas compressor absorbs heat from the interior of the fridge and it also emits heat from a hot exchanger at the back of the fridge. In a magnetic cooling system, it's somewhat different because our refrigerant isn't a gas or a liquid that's pumped around, our refrigerant is solid and so it sits inside our device. So in order to couple the refrigerant to the hot and cold exchanger, we use a liquid - but that liquid is nothing special, it's basically water. So in fact, with our magnetic solution, not only have we got rid of the often toxic gases that are used in gas compressors, we have a solid so it cannot leak and at the same time the liquid that we're using to move the heat around is a safe, nontoxic fluid like water.
Ben - So in terms of efficiency, you said the aim with this is to allow a new generation of extremely efficient fridges. How does it compare to what we've already got? How much bang for your buck do you get?
Neil - Roughly speaking, if you take a standard A-plus fridge using a gas compressor, and replace that gas compressor with our magnetic engine, you will double the efficiency of your fridge without having to make any other changes to the appliance. So it's a factor of two improvement.
Ben - What else can we refine to try and make this even better?
Neil - Well, the first area is we can improve the refrigerant materials. The lanthanum, iron, silicon, cobalt I talked about earlier, that's a very nice compound. However, down the road in the next 12 months, there will be a more powerful version of this material, and that will allow us to make the magnetic field smaller, so the device can be even smaller, even lighter, and cost less. The second thing that is key is to be able to run the machine faster. If you run the machine faster, you either create more cooling power or, again, require less material or less magnet. Those two factors combined will allow us to either make the solution for the domestic fridge that's expensive and increasingly competitive or alternatively, it will allows us to make bigger versions in terms of cooling power for the technology that might be applicable for supermarkets or for car air conditioning.
49:59 - Has any living organism ever been recovered back to life after freezing?
Has any living organism ever been recovered back to life after freezing?
Barry - Well, there are some lower vertebrates that have evolved to live in very cold parts of the world, the Arctic Tundra or Canadian Permafrost areas, and it seems that they have developed a system which allows them to make their own anti-freezes as winter turns around the corner. They're seasonally adjusted to make their anti-freezes and then they're able to survive freezing, but only freezing within a very limited temperature range of about minus 15 to minus 20 degrees centigrade. And they take very great care about where the ice forms in their body, so they are very carefully tuned to this process.
51:04 - Can animals that naturally freeze give us some clues for freezing human organs?
Can animals that naturally freeze give us some clues for freezing human organs?
Barry - Well we've learned along the way that some of these organisms actually have what we call anti-freeze proteins which dictate where the ice starts to form in their bodies. So instead of allowing themselves to freeze all over, they localise the ice that does form into parts of their body that are not going to be injured - the areas under the skin, or the abdominal cavity. They try and avoid freezing inside organs. So again, they're evolutionarily tuned to survive this process.Chris - One point that was made to me in relation to these specialist creatures, like the frogs and toads that can survive being frozen solid, is that if ice does form inside their cells, then the ice forms out of pure water and the solution that's left around the ice crystals is more concentrated so it pulls water into the cell by the process of osmosis, making the cells swell a bit, and then more freezing takes place, and leaves more concentrated water, so the cells swell a bit more, and this ruptures cells. So what they actually do is encourage themselves to freeze really well, really quickly. So in fact, they don't have this process happening to rupture all of their cells. I don't know if you have a perspective on that, Lorna.Lorna - Yes, that's absolutely right. So that's known as osmotic pressure or osmotic stress and in fact, that's how a lot of these organisms develop mechanisms to protect themselves. They can change their solvent composition to either increase the amount of cryoprotectant molecules in the vicinity or reduce it. Humans can do this as well, interestingly. We have membrane proteins called aqua- or glycerolporins and they can control the traffic of water or glycerol molecules across the cell membrane. But obviously we can't do it as effectively as some of these other organisms like the frogs or the fish. But perhaps there is potential there for the future.
Can you stop water expanding when it freezes?
Water and glycerol have really fantastic properties. You can freeze water, as we know, at around 0Ã?,°C whereas glycerol, pure glycerol, freezes at a much higher temperature. If you mix the two components together, you can actually reduce the freezing temperature to below 0. I believe at a concentration of 0.3 mole fraction, so 30% glycerol, 70% water, you can get the freezing temperature of that solution, all the way down to -45Ã?,°C. now what's that doing to the actual hydrogen bonded network of water, that's exactly what we're trying to find out, using this neutron diffraction technique.
54:23 - Why don't natural anti-freezes cause problems in animals that use them?
Why don't natural anti-freezes cause problems in animals that use them?
Well in fact, many of the natural anti-freeze cryoprotectants are simply sugars and sugar alcohols which we use every day and which are heavily used in the food industry. The problem comes where we use very high quantities of them at the cellular level, then they can become toxic to the cell. Researchers are doing very detailed studies to find out at what exact concentration these cryoprotectants become atoxic.
Why can some plants resist freezing and others can't?
This is an evolutionary trick as winter comes along in cold environments. These particular plants have learned how to change their chemical metabolism, starting to produce more of the sugars and the alcohols that allows them to survive the overall wintering period. But obviously, not all plants will do that.
Will it ever be possible to revive a cryopreserved human?
Barry - If you're asking a personal opinion, no. I think freezing whole human bodies at the moment is a matter of personal choice and faith. There's no scientific evidence that we will be able to cryo-preserve a whole human body or a whole human person in a way that would allow them to come back sensibly and live their life out in the future.
Kat - So bad news for Walt Disney in his freezer then! Lorna, have you got any ideas on that one?
Lorna - Yeah. I think I'm in agreement with Barry but perhaps the romantic in me would like to believe that in time, anything is possible with science.
Why does food change in the freezer?
Barry - There's a problem, as Lorna said all along, with ice. Domestic freezers only cool steaks down to about -10 to -15°C. There's plenty of mobile water there and the ice will re-crystallise over time, so you get larger ice crystals, and you do get evaporation directly, cold evaporation. So you're left with a freeze-burn effect, which changes the texture and changes the overall flavour value.
Chris - And I guess, also, if your vegetables are frozen and then you cook them, the vegetable tissue is riddled with holes. So the goodies are more likely to float out and they're going to be less good for you than fresh?
Barry - Yes. You get the "mushy strawberry" effect, I think. If anybody could freeze strawberries really well then they could make a fortune!
Chris - Mushy peas are good though! Lorna, anything to add to that?
Lorna - Just a tip: puree your strawberries before you freeze them, and then you don't have the mushy strawberry effect!
57:53 - Is modern medicine affecting the human gene pool?
Is modern medicine affecting the human gene pool?
We put this question to Professor Bill Amos, from the Department of Zoology at Cambridge University...
Bill - This is an interesting question but I'm afraid many of the aspects really are quite unresolved.
Perhaps we could start with the problems with births. Humans of course have been evolving larger and larger brains for a while now which gives them larger skulls and this of course can present problems during the birth process. These days, we can use caesarean section but the key point here is that it's only going to become an increasing problem if those children born by caesarean section are born, grow up and have larger families than on average.
This is a recurrent theme, so for example individuals with spina bifida - this is a rare genetic disease. If they also grow up, again, this is only going to become an increasing problem if they themselves then have larger families, and it's almost certainly not the case that this would happen with most genetic defects.
I think perhaps more interesting is the question of the immune function, that genes that help us fight disease. And here, I think there may be an interesting issue. In developing countries where there's much less access to medical treatment and antibiotics, many children die through infections that are potentially preventable. This, in theory, removes some of those individuals with weaker or poorly attuned immune systems from the population, but in the western culture where more medicine is present, these individuals would grow up. So what happens to them in western culture? My best guess is that these are the people who are likely most prone to asthma and allergies since these are potentially reflections of a poorly tuned immune system and that is what we might predict these have.
Diana - So modern medicine might change who lives and who dies, but as the human population is so large, the overall effect on the gene pool shouldn't be species altering and this is because the number of people either being born by caesarean section or surviving in spite of inherited diseases aren't likely to breed in greater numbers than the rest of the population. Human immune function however may change through time.