On 24th of June, Amber Ahark (Y11), who has written an article about poisonous frogs during the COVID-19 lockdown, did a virtual Café Sci talk about her research. She told us how poison frogs are able to hold a neurotoxin within their skin, called batrachotoxin (BTX), which is capable of killing 20,000 mice or the equivalent of 10 grown men. A rare breed of frog called Phyllobates terribilis which originates from Colombia and are bright yellow in colour. Their sizes vary from 1.5 to 6cm. These poisonous frogs secrete the venom from their skin, as the BTX toxin is stored in glands beneath their skin; they absorb the toxins and chemicals from prey such as mice and ants. Once the toxin is injected into an animal, then the toxin disrupts the nervous system by tearing open sodium channels and interferes with the body’s ability to transmit electrical signals. This then leads to hypertension, fibrillation, heart failure or in more severe cases, a seizure. The toxin BTX belongs to the alkaloid group[1] and this was isolated from the bodies of the frogs in Colombia to shoot poison at enemies using blow darts. It is argued that BTX could be used in the future to formulate pain killers, as it has been synthesized and reproduced in laboratories using cis-decalone. The structure of BTX includes a steroid skeleton and an oxazapane ring and the activity of BTX depends on temperature, reaching its maximum at 37 degrees Celsius. However, poisonous frogs are not the only creatures to contain traces of BTX. It was found that Choresine beetles also had high concentrations of the neurotoxin and this leads to speculation that these beetles could be a staple part of the frogs’ diets, as they sequester the toxin from their prey. Essentially, BTX poisons the body by interfering with nerve signals. Within our cells, we have a high concentration of sodium ions outside our cells while the potassium ions are more concentrated within our cells. The movement of these ions are controlled by channels (sodium and potassium channels), and the sodium channels are closed. However, when BTX enters the body, it rapidly opens these sodium channels and it binds to the threshold voltage. BTX inhibits nerve impulses, by binding to the gates of the sodium channels and it becomes irreversible- so the sodium channels cannot be closed. Ultimately, this suggests that the survival rate against BTX is incredibly slim. However, how do poisonous frogs manage to store the neurotoxin within their bodies?
A 2014 study from John Carroll University discovered that the mother frogs give the tadpoles poison, which they absorb to become poisonous themselves. As tadpoles, their mother feeds them her own unfertilised eggs, which contain BTX. Although, these poisonous dart frogs were never poisonous, they evolved to become poisonous and store toxins because of a mutation. This was a very small mutation, where three of the 2,500 amino acids in a receptor changed. This mutation prevented BTX from damaging their own receptors and destroying their nervous system, making them resistant. The mutation that makes the frogs resistance to the toxin occurs in the parts of the receptor that are close to but don't touch the toxin (epibatidine). The amino acids are never in contact with the neurotoxin, yet they can still change the receptor. The receptor's key function was maintained by additional amino acid replacements allowing them to resist their own toxins, while still maintaining the normal function of their target neurotransmitters. Furthermore, some poison frogs managed to retune a neurotransmitter receptor so that it also became insensitive to another toxin, called epibatidine. Overall, despite these poisonous frogs being lethal and capable of killing humans due to the neurotoxin BTZ, they don’t produce it themselves, but sequester the toxin from feeding off their mother’s unfertilised embryos and their prey. Additionally, due to a mutation, their receptors are resistant to the toxin because of a change in their amino acid sequence within their receptors.
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Professor Harrison began by explaining the origins of particle physics and how ancient Greek philosophers questioned what happens when you keep slicing something up – if you eventually reach an elementary level at which further cutting of it would fundamentally change the substance or whether it just gets infinitely smaller. Leucippus and Democritus proposed that the substance would not get infinitely smaller but that you would eventually reach an ‘atom’, meaning ‘indivisible’. 2000 years on we now know much more about what happens when we cut an object into continually smaller objects. Bulk matter is anything greater than 10-9m, atoms and molecules are between 10-8m and 10-10m. Within an atom’s inner structure there is a nucleus of size 10-14m which contains nucleons (protons and neutrons) that are 10-15m containing quarks which are 10-20. Quarks are a type of elementary particle – a particle which has no known structure but makes up larger things. There are different types of elementary particles: quarks, leptons, gauge bosons and scalar bosons. Within these categories there are different types of elementary particles, for example up, down, charm, strange, top and bottom are all types of quark. Professor Harrison then went on to explain how there are 4 guiding principles of Particle Physics – these are: Simplicity, Composition, Unification and Symmetry. With Simplicity Ockham’s Razor is used and this is a philosophical principle that if there are multiple explanations for something then the simplest one is best. Unification is used when trying to explain different physical phenomena using a single idea or law of nature, for example with Coulomb’s Law of electric field around a charge, Amperes Law of Magnetism and Faraday’s Law of Induction, Maxwell was able to show that these were all linked by ‘fixing’ one – allowing him to predict electromagnetic waves. With Symmetry, Noether’s Theorem (1915) is used, ‘Every symmetry of the laws of Nature implies an associated Conservation law’. Next Professor Harrison spoke about the tools of Particle Physics, both theoretical – Quantum Mechanics, Einstein’s Theory of Special Relativity – and things like the Large Hadron Collider and ATLAS. He finished by mentioning some of the unanswered questions such as, ‘Is the discovered Higgs boson the only Higgs boson?’, ‘Why is the Higgs boson mass stable?’, ‘Is the dark matter of the Universe really a new undiscovered particle?’, ‘Is there a way to unify the strong interaction with the weak and electromagnetic?’ and ‘Why do the masses of the elementary particles take the values they do?’.
Overall, this was a really interesting talk on a fascinating area of Physics that clearly has much more research yet to be carried out. This talk was given by Dr J Harrison on Wednesday, 4th March. Dr Harrison spoke about how mitosis is the process allowing one cell to divide and form an entire body of cells. The diagram below shows how mitosis normally takes place: However, sometimes there can be errors in this process with the potential to cause cancer: Which in real life would look like this: The green colour shows the movement of the chromosomes with the orange spots representing the centromeres. As can be seen from the diagram, one chromosome has failed to separate and has lagged behind as the others move to the poles of the cell. These cell division errors can be modelled using mathematics, but this is challenging due to the rarity of these events. He explained that what is different about these error events when compared with the normal behavior of chromosomes in cell division is the decreased distance between sister chromatids. The tension in the protein spring which connects chromatids is one of the key triggers controlling this process. He then went on to speak about the modelling of the COVID-19 epidemic (at the time of the talk we were not yet in lockdown and the virus had only recently started to spread beyond China although there were more cases outside of China than inside). He discussed how infectious diseases can also be modelled using mathematics which allows researchers to compare how effective the different strategies of managing a disease are – for example closing schools and imposing travel restrictions. Many of us have been able to see through the news how mathematical modelling has been used in this way and the importance of the Reproduction number (R0) in how the disease is managed. The diagram below shows the effect of imposing travel restrictions and how this worked in Wuhan to reduce the reproduction number. The red line on each graph is the point at which travel restrictions were introduced. It was really interesting to hear about how Maths can be used in Biology and how it is now of particular significance in the modelling of the current pandemic. Especially as the R0 number is now being used to determine when and how lockdown is eased and to predict the possibility of a second wave.
Over the duration of 3 weeks, groups of Year 6 students from Warwick Prep came to the Science department at King's to give them an insight of what its like to study science at secondary school. Many of them will be joining King's in September, so it was nice for them to get familiar with their surroundings. During their visit, we went over the pH scale and examples of substances with different pH's that they would know, from car batteries to toothpaste. Afterwards we did a lab demonstration where we tested the pH's of 6 different colourless solutions with Universal Indicator and matched them up with correct pH value via the pH scale. We also spoke a little about lab safety, you'll see the safety goggles in the pictures. Additionally, the science technicians helped us make a rainbow in a burette, which was extremely exciting! We did this by placing a small volume of strong acid in the burette with some Universal Indicator, which went red, then via a funnel, adding some strong base. The 2 solutions reacted and produced a vertical rainbow, shown due to the Universal Indicator present. We got some great photos of their visit... On the 29th of January we were fortunate to have Charlotte Fletcher, from Warwick University, give a talk on Superparamagnetic Iron Oxide Nanoparticles, she began by explaining what a nanoparticle was and giving us a concept of the size through comparative examples, including a nanoscale.
A nanoparticle is between 1 and 100 nm in diameter, and their properties depend on their size. As they are so small, they have a large surface area to volume ratio. For nanoparticles to be useful in a biological application, they need to be biocompatible, they need to have a controllable size, and the ability to be functionalised. There are many uses for nanoparticles:
She discussed the reasoning behind the SPIONs having an iron oxide core with a silica (silicon dioxide) coating. Without the silica coating, the iron oxide nanoparticles would be cytotoxic, cause cell elongation and an increase in cell death. You can functionalise SPIONs by attaching things onto their surface, such as amine groups, other functional groups, fluorescent dye, PEGylation (polyethylene glycol polymer chains), and polymers. SPIONS can be inserted into cells using a micropipette. This means we can use nanoparticles to target biomolecules in a cell. We were shown a video where nanoparticles had been attached onto strands of DNA on a microscope slide, and due to the magnetic properties of the nanoparticles, the DNA stands moved when exposed to a magnetic force.
Mrs Fletcher is currently researching the long-term effects of nanoparticles on cells, the ability to target specific regions of cells, and the addition of functional polymers that are both MRI contrast agents (that increase visibility of internal body structures) and provide drug delivery. Thank you to everyone that attended this talk, and to Mrs Fletcher for coming to speak to us. The talk was incredibly interesting, and we all enjoyed it. (The information and images in this blog post come from a presentation that Mrs Fletcher used.) On 4th December 2019, dentist, Dr Rima Hassan came to do a talk about the Science Behind Dentistry. The talk included her passing round a series of materials and instruments used in the dental profession and explanations of their properties and uses. As her talk was more of a free discussion and she didn't use a presentation, here is what she spoke about:
The scientific approach begins for dentistry from A level foundation subjects of biology, physics, chemistry and maths. These subjects are integral to understanding how the human body works. Dr Hassan trained at the Royal London Hospital and graduated in 2000. One of the topics studied during the dental course is Dental Materials. This involves the study of the many different restorative and impression taking materials which are used on a day to day within the job. The main materials dentists use can be divided in to 2 groups:
During the talk, Dr Hassan brought in a few materials, and described their uses. She talked about alginate impression material used for more general impressions, and silicone materials for more high detail, less distortable impressions. Restorations vary from those placed in the mouth, direct restorations, and those constructed out of the mouth and fitted into the mouth - indirect restorations. Direct restorations: mainly involve fillings, amalgam (a metal alloy including mercury to allow it to be mouldable into the cavity in a tooth), glass ionomer cement (used for temporary fillings or to patch up a chipped tooth) and composite (a plastic resin which is mouldable and polishable so has better durability and aesthetic results). The benefit of composite is that it can be shaped into the form required and then set with the UV light, as she demonstrated in the session. Indirect restorations: include dentures or removable prostheses, which are normally made of acrylic plastics or a metal framework. These are needed to replace missing teeth, either partially or completely. The material needs to be comfortable to wear in the mouth and have retention so it doesn’t always fall out while the patient is talking or eating. It also needs to be easily cleaned and maintained by the patient to prevent development of fungal infections etc. Crowns/Bridges are used to cover a heavily restored tooth which would not be strong enough to support a simple filling. They are also used to improve a patient’s cosmetic appearance and to fill missing teeth gaps when required. Biology is important in Dentistry as during the first couple of years in the course, the main topics all involve anatomy and learning about the structure of the human body and all the main systems. A dentist needs to know their way around a human head after all. Even though dentistry may seem to be only about teeth, but in fact, when you go to the dentist, they're actually checking your whole head to make sure everything is healthy, though mostly it's inside your mouth that they're really interested in. Anatomy is also important for dentistry as many of the medications prescribed alongside some treatments need to take into consideration any additional medications (and any side effects) that the patient is taking - this pharmaceutical side incorporates Chemistry as well. Radiology is vital to their practice, to enable dentists to get a clearer diagnosis, particularly for diseases they can't see directly in the mouth. So, physics plays a big role in their ability to do their jobs properly. Teeth are made of a very hard material which luckily shows up very clearly on x-rays. They can then diagnose if there is a cavity due to decay or a deficiency in the bone levels around the teeth i.e. a dark shadow where normally there wouldn’t be would indicate a softer material, decay, rather than hard enamel or dentine. Cysts or tumours are also usually fluid or less dense and can also be similarly diagnosed from an x-ray. The final, and possibly most important, science dentists use every day in their work is Psychology. Fear is a big deterrent for a lot of people for visiting dentists in the first place. As dentists, they learn to manage a patient’s psychological issues in a very skilled way. Even the most confident, able person can be nervous of the vulnerability one feels when you have someone messing around in your mouth and the potential for pain is real. Getting a patient to trust their clinician and allow them to do what is needed is a vital part of the job and can be quite challenging at times. However, it is so rewarding when it works and is a big part of why she enjoys her job. Dentistry is a subject which has such a vast overlap of many scientific foundations, possibly more so than medicine in a lot of cases. However, it also allows artistry and vocational skills to be used as well, which is not always possible in other scientific careers. Dr Hassan feels privileged that it's a job in which she genuinely feels she can make a difference to people’s lives every day, not just to treat disease and remove pain, but to provide a safe and trusting relationship with the patient to help empower them and improve their confidence and working with her local community over the years. This talk from 13th November 2019 by Annabel Husband, a Lower Sixth student, is based on the BBC documentary “Poisoning America: the devil as we know it”. C8 is a chemical found in non-stick frying pans, and other non-stick surfaces.
It was originally discovered in the early 1950s by a manufacturing company called 3M. C8 was produced in West Virginia, USA by DuPont. C8 is useful due to its many desirable properties: a hydrophilic and a hydrophobic end, lipophobic, reacts strongly with polar groups (specifically water), is very stable. These properties also mean it’s very difficult and costly to destroy it. Production of C8 in West Virginia caused contamination of water supplies (small amounts of C8 are in global water supplies) leading to child deformities (e.g. Bucky Bailey) and cancers, which DuPont denied was due to C8. DuPont and 3M both knew about the side effects due to lab testing on rats yet continued to produce it. DuPont was eventually sued after locals from West Virginia filed a lawsuit against them. After being sued, DuPont stopped production of C8, paid a fine of $16.5 million and helped to clean the water in West Virginia. However, DuPont now produce 2 new chemicals: C6 and C7, with virtually the same properties and believed to have the same side effects. Really, though, this talk isn’t a story about C8, but a story about all the untested chemicals which humans have created that may have the same damaging effects that we don’t regulate or monitor but come into contact with, every day of our lives. This talk was given by Mrs Sims on 25th September, 2019.
Altruism is the behaviour of an animal which benefits another at its own expense. It can be seen in human society through actions such as saving someone from drowning – an action which would save another’s life but put your own at risk. Altruism can also be seen in nature, such as in Vampire Bats. When a bat has not managed to find a meal of blood during the night, other bats may regurgitate blood in order to feed these bats. This can be explained due to the bats being closely related and it is expected that they can detect this by chemical signals which they smell and due to usually roosting in family groups. Evolution favours traits which allow the individual to reproduce more often and pass on their genes. Hamilton Kin’s selection theory presents the idea that as related animals will often pass on the same genes, by ensuring another bat survives, they increase the likelihood that their genes will be passed on to offspring. Hamilton stated that altruism will be favoured if: Relatedness x benefit in predicted offspring to recipient > cost in predicted offspring to donor As bats are usually closely related and will normally reproduce once a year, in this example altruism will be favoured by evolution even if the donor was unable to reproduce that year. Another idea behind altruism is Trivers’ Reciprocal Altruism Theory that altruism is selected for in animals if it will benefit the animal by similar altruism in the future. This applies in animals which live in social groups – such as bats – and does not require relatedness. This has been demonstrated by experiments of captive bats as meal-sharing has increased over time so bats will meal-share with those they have been living in close contact with for a long time. What do you think? Are human acts of altruism any different from those of animals or do we act only in the interest of passing on our genes? Here are the references used in the talk, take a look for further information:
Hi all! This academic year, Cafe Scientifique is being lead by myself (Isha), Fiona and Rebecca, 3 Lower Sixth students with a passion for science. We all take Biology and Chemistry at A level and are hoping to continue studying science at University. This year, we plan to organise talks from a range of external, and some internal, speakers within different fields of science, from altruistic behaviour in animals to nanoparticles. Continue reading to find out more, and feel free to comment...
In our first Café Scientifique meeting of the academic year, we debated the controversial question: which science is the most important?
Our views differed at the beginning of the debate; some felt physics was the most important due its help in explaining what we don’t understand. Physics plays a critical role in mechanics and energy production as well as many other daily essentials. Some thought biology was incredibly important as it is the only science which studies living things and is vital to medicine. Others thought chemistry was the most important because of its pharmaceutical applications and the valid point that “we can’t cure diseases with biology alone”. Whilst we debated the question, we soon noticed an interesting trend: biology is applied chemistry, chemistry is applied physics and physics is applied maths. This shows that all sciences are reliant on one another. It also demonstrates that maths is crucial to the formation of the 3 sciences. Having established this trend, we continued our debate and concluded that the three sciences are all integral and our society would collapse without any one of them but that physics was the most important science due to its theory and practical applications to almost everything. Chemistry came second and biology last as we felt it wasn't as necessary as the others. Overall, it was an extremely thought-provoking debate and it was great to hear so many opinions and ideas. |
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