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News from the Department of Physics.
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    Read more about how clinical researchers, physicists, engineers and social scientists are among those collaborating as part of the Cancer Research UK Early Detection Programme.

    Kate Gross was just 36 years old when she died of cancer. Researchers at Cambridge – including her husband – are trying to ensure that others receive their diagnoses early enough to stop their cancer. 

    Kate Gross

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    One of the fundamental ideas of quantum theory is that quantum objects can exist both as a wave and as a particle, and that they don’t exist as one or the other until they are measured. This is the premise that Erwin Schrödinger was illustrating with his famous thought experiment involving a dead-or-maybe-not-dead cat in a box.

    “This premise, commonly referred to as the wave function, has been used more as a mathematical tool than a representation of actual quantum particles,” said David Arvidsson-Shukur, a PhD student at Cambridge’s Cavendish Laboratory, and the paper’s first author. “That’s why we took on the challenge of creating a way to track the secret movements of quantum particles.”

    Any particle will always interact with its environment, ‘tagging’ it along the way. Arvidsson-Shukur, working with his co-authors Professor Crispin Barnes from the Cavendish Laboratory and Axel Gottfries, a PhD student from the Faculty of Economics, outlined a way for scientists to map these ‘tagging’ interactions without looking at them. The technique would be useful to scientists who make measurements at the end of an experiment but want to follow the movements of particles during the full experiment.

    Some quantum scientists have suggested that information can be transmitted between two people – usually referred to as Alice and Bob – without any particles travelling between them. In a sense, Alice gets the message telepathically. This has been termed counterfactual communication because it goes against the accepted ‘fact’ that for information to be carried between sources, particles must move between them.

    “To measure this phenomenon of counterfactual communication, we need a way to pin down where the particles between Alice and Bob are when we’re not looking,” said Arvidsson-Shukur. “Our ‘tagging’ method can do just that. Additionally, we can verify old predictions of quantum mechanics, for example that particles can exist in different locations at the same time.”

    The founders of modern physics devised formulas to calculate the probabilities of different results from quantum experiments. However, they did not provide any explanations of what a quantum particle is doing when it’s not being observed. Earlier experiments have suggested that the particles might do non-classical things when not observed, like existing in two places at the same time. In their paper, the Cambridge researchers considered the fact that any particle travelling through space will interact with its surroundings. These interactions are what they call the ‘tagging’ of the particle. The interactions encode information in the particles that can then be decoded at the end of an experiment, when the particles are measured.

    The researchers found that this information encoded in the particles is directly related to the wave function that Schrödinger postulated a century ago. Previously the wave function was thought of as an abstract computational tool to predict the outcomes of quantum experiments. “Our result suggests that the wave function is closely related to the actual state of particles,” said Arvidsson-Shukur. “So, we have been able to explore the ‘forbidden domain’ of quantum mechanics: pinning down the path of quantum particles when no one is observing them.”

    Reference
    D. R. M. Arvidsson-Shukur, C. H. W. Barnes, and A. N. O. Gottfries. ‘Evaluation of counterfactuality in counterfactual communication protocols’. Physical Review A (2017). DOI: 10.1103/PhysRevA.96.062316

    Researchers from the University of Cambridge have taken a peek into the secretive domain of quantum mechanics. In a theoretical paper published in the journal Physical Review A, they have shown that the way that particles interact with their environment can be used to track quantum particles when they’re not being observed, which had been thought to be impossible. 

    We can verify old predictions of quantum mechanics, for example that particles can exist in different locations at the same time.
    David Arvidsson-Shukur
    2015-12-22 chemistry

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    As the global population increases, so too does energy demand. The threat of climate change means that there is an urgent need to find cleaner, renewable alternatives to fossil fuels that do not contribute extensive amounts of greenhouse gases with potentially devastating consequences on our ecosystem. Solar power is considered to be a particularly attractive source as on average the Earth receives around 10,000 times more energy from the sun in a given time than is required by human consumption.

    In recent years, in addition to synthetic photovoltaic devices, biophotovoltaics (BPVs, also known as biological solar-cells) have emerged as an environmentally-friendly and low-cost approach to harvesting solar energy and converting it into electrical current. These solar cells utilise the photosynthetic properties of microorganisms such as algae to convert light into electric current that can be used to provide electricity.

    During photosynthesis, algae produce electrons, some of which are exported outside the cell where they can provide electric current to power devices. To date, all the BPVs demonstrated have located charging (light harvesting and electron generation) and power delivery (transfer to the electrical circuit) in a single compartment; the electrons generate current as soon as they have been secreted.

    In a new technique described in the journal Nature Energy, researchers from the departments of Biochemistry, Chemistry and Physics have collaborated to develop a two-chamber BPV system where the two core processes involved in the operation of a solar cell – generation of electrons and their conversion to power – are separated.

    “Charging and power delivery often have conflicting requirements,” explains Kadi Liis Saar, of the Department of Chemistry. “For example, the charging unit needs to be exposed to sunlight to allow efficient charging, whereas the power delivery part does not require exposure to light but should be effective at converting the electrons to current with minimal losses.”

    Building a two-chamber system allowed the researchers to design the two units independently and through this optimise the performance of the processes simultaneously.

    “Separating out charging and power delivery meant we were able to enhance the performance of the power delivery unit through miniaturisation,” explains Professor Tuomas Knowles from the Department of Chemistry and the Cavendish Laboratory. “At miniature scales, fluids behave very differently, enabling us to design cells that are more efficient, with lower internal resistance and decreased electrical losses.”

    The team used algae that had been genetically modified to carry mutations that enable the cells to minimise the amount of electric charge dissipated non-productively during photosynthesis. Together with the new design, this enabled the researchers to build a biophotovoltaic cell with a power density of 0.5 W/m2, five times that of their previous design. While this is still only around a tenth of the power density provided by conventional solar fuel cells, these new BPVs have several attractive features, they say.

    "While conventional silicon-based solar cells are more efficient than algae-powered cells in the fraction of the sun’s energy they turn to electrical energy, there are attractive possibilities with other types of materials," says Professor Christopher Howe from the Department of Biochemistry. “In particular, because algae grow and divide naturally, systems based on them may require less energy investment and can be produced in a decentralised fashion."

    Separating the energy generation and storage components has other advantages, too, say the researchers. The charge can be stored, rather than having to be used immediately – meaning that the charge could be generated during daylight and then used at night-time.

    While algae-powered fuel cells are unlikely to generate enough electricity to power a grid system, they may be particularly useful in areas such as rural Africa, where sunlight is in abundance but there is no existing electric grid system. In addition, whereas semiconductor-based synthetic photovoltaics are usually produced in dedicated facilities away from where they are used, the production of BPVs could be carried out directly by the local community, say the researchers.

    “This a big step forward in the search for alternative, greener fuels,” says Dr Paolo Bombelli, from the Department of Biochemistry. “We believe these developments will bring algal-based systems closer to practical implementation.”

    The research was supported by the Leverhulme Trust, the Engineering and Physical Sciences Research Council and the European Research Council.

    Reference
    Saar, KL et al. Enhancing power density of biophotovoltaics by decoupling storage and power delivery. Nature Energy; 9 Jan 2018; DOI: 10.1038/s41560-017-0073-0

    A new design of algae-powered fuel cells that is five times more efficient than existing plant and algal models, as well as being potentially more cost-effective to produce and practical to use, has been developed by researchers at the University of Cambridge. 

    This a big step forward in the search for alternative, greener fuels
    Paolo Bombelli
    Artist' impression
    Researcher Profile: Dr Paolo Bombelli

    Dr Paolo Bombelli is a post-doctoral researcher in the Department of Biochemistry, where his research looks to utilise the photosynthetic and metabolic activity of plants, algae and bacteria to create biophotovoltaic devices, a sustainable source of renewable current. He describes himself as “a plants, algae and bacteria electrician”.

    “Photosynthesis generates a flow of electrons that keeps plants, algae and other photosynthetic organisms alive,” he explains. “These electrons flow though biological wires and, like the electrical current obtained from a battery and used to power a radio, they are the driving force for any cellular activity.”

    Dr Bombelli’s fascination with this area of research began during his undergraduate studies at the University of Milan.

    “Plants, algae and photosynthetic bacteria are the oldest, most common and effective solar panels on our planet,” he says. “For billions of years they have been harnessing the energy of the sun and using it to provide oxygen, food and materials to support life. With my work I aim to provide new ways to embrace the potential of these fantastic photosynthetic organisms.”

    His work is highly cross-disciplinary, with input from the Departments of Biochemistry, Plant Sciences, Chemistry and Physics, and the Institute for Manufacturing, as well as from researchers at Imperial College London, UCL, the University of Brighton, the Institute for Advanced Architecture of Catalonia in Spain and the University of Cape Town, South Africa.

    “Universities are great places to work and so they attract many people,” he says. “People choose to come to Cambridge because they know the ideas they generate here will go on to change the world.”

    In 2016, Dr Bombelli won a Public Engagement with Research Award by the University of Cambridge for his work engaging audiences at more than 40 public events, including science festivals and design fairs, reaching thousands of people in seven countries. His outreach work included working with Professor Chris Howe to develop a prototype ‘green bus shelter’ where plants, classical solar panels and bio-electrochemical systems operate in synergy in a single structure.

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    An international team led by Dr Renske Smit from the Kavli Institute of Cosmology at the University of Cambridge used the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile to open a new window onto the distant Universe, and have for the first time been able to identify normal star-forming galaxies at a very early stage in cosmic history with this telescope. The results are reported in the journal Nature, and will be presented at the 231st meeting of the American Astronomical Society.

    Light from distant objects takes time to reach Earth, so observing objects that are billions of light years away enables us to look back in time and directly observe the formation of the earliest galaxies. The Universe at that time, however, was filled with an obscuring ‘haze’ of neutral hydrogen gas, which makes it difficult to see the formation of the very first galaxies with optical telescopes.

    Smit and her colleagues used ALMA to observe two small newborn galaxies, as they existed just 800 million years after the Big Bang. By analysing the spectral ‘fingerprint’ of the far-infrared light collected by ALMA, they were able to establish the distance to the galaxies and, for the first time, see the internal motion of the gas that fuelled their growth.

    “Until ALMA, we’ve never been able to see the formation of galaxies in such detail, and we’ve never been able to measure the movement of gas in galaxies so early in the Universe’s history,” said co-author Dr Stefano Carniani, from Cambridge’s Cavendish Laboratory and Kavli Institute of Cosmology.

    The researchers found that the gas in these newborn galaxies swirled and rotated in a whirlpool motion, similar to our own galaxy and other, more mature galaxies much later in the Universe’s history. Despite their relatively small size – about five times smaller than the Milky Way – these galaxies were forming stars at a higher rate than other young galaxies, but the researchers were surprised to discover that the galaxies were not as chaotic as expected.

    “In the early Universe, gravity caused gas to flow rapidly into the galaxies, stirring them up and forming lots of new stars – violent supernova explosions from these stars also made the gas turbulent,” said Smit, who is a Rubicon Fellow at Cambridge, sponsored by the Netherlands Organisation for Scientific Research. “We expected that young galaxies would be dynamically ‘messy’, due to the havoc caused by exploding young stars, but these mini-galaxies show the ability to retain order and appear well regulated. Despite their small size, they are already rapidly growing to become one of the ‘adult’ galaxies like we live in today.”

    The data from this project on small galaxies paves the way for larger studies of galaxies during the first billion years of cosmic time. The research was funded in part by the European Research Council and the UK Science and Technology Facilities Council (STFC).

    Reference:
    Renske Smit et al. ‘Rotation in [C II]-emitting gas in two galaxies at a redshift of 6.8.’ Nature (2018). DOI: 10.1038/nature24631

    Astronomers have looked back to a time soon after the Big Bang, and have discovered swirling gas in some of the earliest galaxies to have formed in the Universe. These ‘newborns’ – observed as they appeared nearly 13 billion years ago – spun like a whirlpool, similar to our own Milky Way. This is the first time that it has been possible to detect movement in galaxies at such an early point in the Universe’s history. 

    We’ve never been able to see the formation of galaxies in such detail, and we’ve never been able to measure the movement of gas in galaxies so early in the Universe’s history.
    Stefano Carniani
    Artist's impression of spinning galaxy
    Researcher profile: Renske Smit

    Dr Renske Smit is a postdoctoral researcher and Rubicon Fellow at the Kavli Institute of Cosmology and is supported by the Netherlands Organisation for Scientific Research. Prior to arriving in Cambridge in 2016, she was a postdoctoral researcher at Durham University and a PhD student at Leiden University in the Netherlands.

    Her research aims to understand how the first sources of light in the Universe came to be. In her daily work, she studies images of deep space, taken by telescopes such as the Hubble Space Telescope. To gather data, she sometimes travels to places such as Chile or Hawaii to work on big telescopes.

    “In Cambridge, I have joined a team working on the James Webb Space Telescope, the most ambitious and expensive telescope ever built,” she says. “With this telescope, we might be able to see the very first stars for the first time. To have this kind of privileged access to world-leading data is truly a dream come true.

    “I would like to contribute to changing the perception of what a science professor looks like. Women in the UK and worldwide are terribly underrepresented in science and engineering and as a result, people may feel women either don’t have the inclination or the talent to do science. I hope that one day I will teach students that don’t feel they represent the professor stereotype and make them believe in their own talent.”

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    An international team of researchers led by the University of Cambridge found that the addition of potassium iodide ‘healed’ the defects and immobilised ion movement, which to date have limited the efficiency of cheap perovskite solar cells. These next-generation solar cells could be used as an efficiency-boosting layer on top of existing silicon-based solar cells, or be made into stand-alone solar cells or coloured LEDs. The results are reported in the journal Nature.

    The solar cells in the study are based on metal halide perovskites – a promising group of ionic semiconductor materials that in just a few short years of development now rival commercial thin film photovoltaic technologies in terms of their efficiency in converting sunlight into electricity. Perovskites are cheap and easy to produce at low temperatures, which makes them attractive for next-generation solar cells and lighting.

    Despite the potential of perovskites, some limitations have hampered their efficiency and consistency. Tiny defects in the crystalline structure of perovskites, called traps, can cause electrons to get ‘stuck’ before their energy can be harnessed. The easier that electrons can move around in a solar cell material, the more efficient that material will be at converting photons, particles of light, into electricity. Another issue is that ions can move around in the solar cell when illuminated, which can cause a change in the bandgap – the colour of light the material absorbs.  

    “So far, we haven’t been able to make these materials stable with the bandgap we need, so we’ve been trying to immobilise the ion movement by tweaking the chemical composition of the perovskite layers,” said Dr Sam Stranks from Cambridge’s Cavendish Laboratory, who led the research. “This would enable perovskites to be used as versatile solar cells or as coloured LEDs, which are essentially solar cells run in reverse.”

    In the study, the researchers altered the chemical composition of the perovskite layers by adding potassium iodide to perovskite inks, which then self-assemble into thin films. The technique is compatible with roll-to-roll processes, which means it is scalable and inexpensive. The potassium iodide formed a ‘decorative’ layer on top of the perovskite which had the effect of ‘healing’ the traps so that the electrons could move more freely, as well as immobilising the ion movement, which makes the material more stable at the desired bandgap.

    The researchers demonstrated promising performance with the perovskite bandgaps ideal for layering on top of a silicon solar cell or with another perovskite layer – so-called tandem solar cells. Silicon tandem solar cells are the most likely first widespread application of perovskites. By adding a perovskite layer, light can be more efficiently harvested from a wider range of the solar spectrum.

    “Potassium stabilises the perovskite bandgaps we want for tandem solar cells and makes them more luminescent, which means more efficient solar cells,” said Stranks, whose research is funded by the European Union and the European Research Council’s Horizon 2020 Programme. “It almost entirely manages the ions and defects in perovskites.”

    “We’ve found that perovskites are very tolerant to additives – you can add new components and they’ll perform better,” said first author Mojtaba Abdi-Jalebi, a PhD candidate at the Cavendish Laboratory who is funded by Nava Technology Limited. “Unlike other photovoltaic technologies, we don’t need to add an additional layer to improve performance, the additive is simply mixed in with the perovskite ink.”

    The perovskite and potassium devices showed good stability in tests, and were 21.5% efficient at converting light into electricity, which is similar to the best perovskite-based solar cells and not far below the practical efficiency limit of silicon-based solar cells, which is (29%). Tandem cells made of two perovskite layers with ideal bandgaps have a theoretical efficiency limit of 45% and a practical limit of 35% - both of which are higher than the current practical efficiency limits for silicon. “You get more power for your money,” said Stranks.

    The research has also been supported in part by the Royal Society and the Engineering and Physical Sciences Research Council. The international team included researchers from Cambridge, Sheffield University, Uppsala University in Sweden and Delft University of Technology in the Netherlands.

    Reference:
    Mojtaba Abdi-Jalebi et al. ‘Maximising and Stabilising Luminescence from Halide Perovskites with Potassium Passivation.’ Nature (2018). DOI: 10.1038/nature25989

    A simple potassium solution could boost the efficiency of next-generation solar cells, by enabling them to convert more sunlight into electricity. 

    Perovskites are very tolerant to additives – you can add new components and they’ll perform better.
    Mojtaba Abdi-Jalebi
    Atomic scale view of perovskite crystal formation

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    Joanna Waldie

    My research focuses on developing devices that can manipulate electrons one at a time. I also happen to have long gaps on my CV that take some creativity to explain in job interviews. This is because I’ve had mental health problems since I was a teenager.  During treatment for this, I’ve been privileged to meet some wonderful people with a variety of mental health conditions and to gain a little insight into their struggles.

    Mental health conditions are often invisible. If I have a broken leg or a sore throat then it doesn’t take much for my colleagues to understand that I need time off work. If my mental health is bad then the onus is on me to explain to other people why I need time off work.

    I worry that people will think I am silly, or oversensitive, or lazy, or skiving. However, the first person you need to convince that it’s OK to have time off is yourself. It feels like a great step forward when you do.

    There are a lot of misconceptions about mental illnesses, not least because their invisibility makes awareness of their prevalence remain low. If I tell someone what mental health conditions I have, I have no idea what this will mean to them, and whether it will match the reality of how I feel. This is particularly the case in the multicultural research environment, where different cultures may have very different understandings of mental health.

    As researchers we have succeeded in our University studies and got our PhDs. We are used to solving problems, achieving highly and getting stuff done.

    When faced with a mental health condition, we feel desperately that we need to understand and solve the problem, and soon. But even after many years I do not fully understand my mental health problems. I cannot fix them or solve them as I would a problem in the lab.

    It has taken me years to learn to spot triggers and recognise warning signs when things are getting bad, and to learn some things that sometimes help. I have learned a huge amount, but there is still much I don’t understand about this illness.

    I have told few colleagues about my health problems, but those I have told have been supportive. I’ve benefited from some fantastic services at the University including the staff counselling and occupational health services. That support – at work and from family and friends – makes a huge difference.

    There are still challenges – my ongoing mental health problems are classed as a disability, and that meant I had to tick a box labelling me as a “disabled person” when I started this job in order to qualify for reasonable adjustments. Not everyone would feel OK about that. These labels can create barriers to people coming forward to seek help.

    Researchers often have to move around a lot to advance their careers, doing a series of short-term contracts in several places. If someone with a mental health condition comes to the UK for an 18-month postdoc job, it might take them a while to understand how to access treatment in the UK. They might wait for months to be seen by a specialist. And treatment in the UK might be very different to what they have known in in their home country.

    I’ve been very lucky in this respect. When I was a PhD student, my College provided me with free accommodation near to the hospital where I was being treated so I didn’t have to move back to live with my parents and start all over again on a waiting list.

    My fellowship is normally only open to people who are moving to Cambridge. But the selection panel took into account that I wanted to stay in Cambridge to continue to access treatment and support at the same clinic.

    The sector needs to do more to help researchers who have moved for a job, uprooting themselves from their support networks.

    Research is challenging. In trying to do things no one has ever done before there are always setbacks. For someone with a mental health condition, you can go from one setback in the lab to deep despair in the time it takes to say ‘Supercalifragilisticexpialidocious’.

    Sometimes I wish having someone beside me to give moral support during difficult experiments counted as a ‘reasonable adjustment’. But I am lucky to have colleagues and a boss who do support me.

    As a researcher you need to believe in your research ideas and your ability to carry them out. You need to be able to sell your research. You need to be excited by your research and be able to convince other people to get excited about it, to publish it, to fund it. This is hard to do if you are feeling depressed, and you don’t even feel like life is worth living. It’s really hard.

    But friends and colleague can make a real difference in helping people with mental health problems to flourish in their research.

    A greater openness about mental health in the research community will surely benefit us all.

    Herchel Smith postdoctoral research fellow in Physics Dr Joanna Waldie shares her personal story to support Mental Health Awareness Week

    When I need time off, I worry that people will think I am silly, or oversensitive, or lazy, or skiving - the first person you need to convince that it’s OK is yourself
    Joanna Waldie

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    The researchers, whose work appears in the journal Science, say their findings could be a “game changer” by allowing the energy from sunlight absorbed in these materials to be captured and used more efficiently. 

    Lightweight semiconducting plastics are now widely used in mass market electronic displays such as those found in phones, tablets and flat-screen televisions.  However, using these materials to convert sunlight into electricity to make solar cells is far more complex. 

    The photo-excited states – when photons of light are absorbed by the semiconducting material – need to move so that they can be “harvested” before they lose their energy.  These excitations typically only travel about 10 nanometres in plastic (or polymeric) semiconductors, so researchers need to build tiny structures patterned at the nanoscale to maximise the “harvest”.

    Dr Xu-Hui Jin and colleagues at the University of Bristol developed a new way to make highly ordered crystalline semiconducting structures using polymers.

    Dr Michael Price of Cambridge's Cavendish Laboratory measured the distance that the photo-exited states travelled, which reached distances of 200 nanometres – 20 times further than was previously possible.

    200 nanometres is especially significant because it is greater than the thickness of material needed to completely absorb ambient light, making these polymers more suitable as “light harvesters” for solar cells and photodetectors.

    “The gain in efficiency would actually be for two reasons: first, because the energetic particles travel further, they are easier to “harvest”, and second, we could now incorporate layers around 100 nanometres thick, which is the minimum thickness needed to absorb all the energy from light – the so-called optical absorption depth,” said co-author Dr George Whittell from the University of Bristol. “Previously, in layers this thick, the particles were unable to travel far enough to reach the surfaces.”

    “The distance that energy can be moved in these materials comes as a big surprise and points to the role of unexpected quantum coherent transport processes,” said co-author Professor Sir Richard Friend from Cambridge's Cavendish Laboratory, and a Fellow of St John's College. 

    The research team now plans to prepare structures thicker than those in the current study and greater than the optical absorption depth, with a view to building prototype solar cells based on this technology.

    They are also preparing other structures capable of using light to perform chemical reactions, such as the splitting of water into hydrogen and oxygen.

    Reference:
    Xu-Hui Jin et al.Long-range exciton transport in conjugated polymer nanofibers prepared by seeded growth.’ Science (2018). DOI: 10.1126/science.aar8104 

    Adapted from a University of Bristol press release. 

    Scientists from the Universities of Cambridge and Bristol have found a way to create plastic semiconductor nanostructures that absorb light and transport its energy 20 times further than has been previously observed, paving the way for more flexible and more efficient solar cells and photodetectors. 

    The distance that energy can be moved in these materials comes as a big surprise.
    Richard Friend
    Image showing light emission from the polymeric nanostructures and schematic of a single nanostructure

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    Researchers at the University of Cambridge and the University of Illinois at Urbana-Champaign say their lipid-scrambling DNA enzyme is the first to outperform naturally occurring enzymes – and does so by three orders of magnitude. Their findings are published in the journal Nature Communications.

    “Cell membranes are lined with a different set of molecules on the inside and outside, and cells devote a lot of resources to maintaining this,” said study leader Aleksei Aksimentiev, a professor of physics at Illinois. “But at some points in a cell’s life, the asymmetry has to be dismantled. Then the markers that were inside become outside, which sends signals for certain processes, such as cell death. There are enzymes in nature that do that called scramblases. However, in some other diseases where scramblases are deficient, this doesn’t happen correctly. Our synthetic scramblase could be an avenue for therapeutics.”

    Aksimentiev’s group came upon DNA’s scramblase activity when looking at DNA structures that form pores and channels in cell membranes. They used the Blue Waters supercomputer at the National Center for Supercomputing Applications at Illinois to model the systems at the atomic level. They saw that when certain DNA structures insert into the membrane – in this case, a bundle of eight strands of DNA with cholesterol at the ends of two of the strands – lipids in the membrane around the DNA begin to shuffle between the inner and outer membrane layers.

    To verify the scramblase activity predicted by the computer models, Aksimentiev’s group at Illinois partnered with Professor Ulrich Keyser’s group at Cambridge. The Cambridge group synthesised the DNA enzyme and tested it in model membrane bubbles, called vesicles, and then in human breast cancer cells.

    “The results show very conclusively that our DNA nanostructure facilitates rapid lipid scrambling,” said co-first author Alexander Ohmann, a PhD student in Keyser’s group in Cambridge’s Cavendish Laboratory. “Most interestingly, the high flipping rate indicated by the molecular dynamics simulations seems to be of the same order of magnitude in experiments: up to a thousand-fold faster than what has previously been shown for natural scramblases.”

    On its own, the DNA scramblase produces cell death indiscriminately, said Aksimentiev. The next step is to couple it with targeting systems that specifically seek out certain cell types, a number of which have already been developed for other DNA agents.

    “We are also working to make these scramblase structures activated by light or some other stimulus, so they can be activated only on demand and can be turned off,” said Aksimentiev.

    “Although we have still a long way to go, this work highlights the enormous potential of synthetic DNA nanostructures with possible applications for personalised drugs and therapeutics for a variety of health conditions in the future,” said Ohmann, who has also written a blog post on their new paper.

    The US National Science Foundation and the National Institutes of Health supported this work.  

    Reference:
    Alexander Ohmann et al. ‘A synthetic enzyme built from DNA flips 107 lipids per second in biological membranes.’ Nature Communications (2018). DOI: 10.1038/s41467-018-04821-5

    ​Adapted from a University of Illinois at Urbana-Champaign press release.

    A new synthetic enzyme, crafted from DNA rather than protein, ‘flips’ lipid molecules within the cell membrane, triggering a signal pathway that could be harnessed to induce cell death in cancer cells.

    This work highlights the enormous potential of synthetic DNA nanostructures for personalised drugs and therapeutics for a variety of health conditions.
    Alexander Ohmann
    DNA scramblase

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  • 07/13/18--02:08: Homeward Bound
  • Earlier this year a team of 78 women from around the world took part in a three-week expedition to Antarctica, a trip that marked the culmination of the year-long Homeward Bound leadership programme for women in Science, Technology, Engineering, Mathematics and Medicine (STEMM). Read more about their adventure here

    Homeward bound expedition

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    The researchers, from the University of Cambridge and the Medical Research Council Laboratory of Molecular Biology (MRC LMB), found that the chances for life to develop on the surface of a rocky planet like Earth are connected to the type and strength of light given off by its host star.

    Their study, published in the journal Science Advances, proposes that stars which give off sufficient ultraviolet (UV) light could kick-start life on their orbiting planets in the same way it likely developed on Earth, where the UV light powers a series of chemical reactions that produce the building blocks of life.

    The researchers have identified a range of planets where the UV light from their host star is sufficient to allow these chemical reactions to take place, and that lie within the habitable range where liquid water can exist on the planet’s surface.

    “This work allows us to narrow down the best places to search for life,” said Dr Paul Rimmer, a postdoctoral researcher with a joint affiliation at Cambridge’s Cavendish Laboratory and the MRC LMB, and the paper’s first author. “It brings us just a little bit closer to addressing the question of whether we are alone in the universe.”

    The new paper is the result of an ongoing collaboration between the Cavendish Laboratory and the MRC LMB, bringing together organic chemistry and exoplanet research. It builds on the work of Professor John Sutherland, a co-author on the current paper, who studies the chemical origin of life on Earth.

    In a paper published in 2015, Professor Sutherland’s group at the MRC LMB proposed that cyanide, although a deadly poison, was in fact a key ingredient in the primordial soup from which all life on Earth originated.

    In this hypothesis, carbon from meteorites that slammed into the young Earth interacted with nitrogen in the atmosphere to form hydrogen cyanide. The hydrogen cyanide rained to the surface, where it interacted with other elements in various ways, powered by the UV light from the sun. The chemicals produced from these interactions generated the building blocks of RNA, the close relative of DNA which most biologists believe was the first molecule of life to carry information.

    In the laboratory, Sutherland’s group recreated these chemical reactions under UV lamps, and generated the precursors to lipids, amino acids and nucleotides, all of which are essential components of living cells.

    “I came across these earlier experiments, and as an astronomer, my first question is always what kind of light are you using, which as chemists they hadn’t really thought about,” said Rimmer. “I started out measuring the number of photons emitted by their lamps, and then realised that comparing this light to the light of different stars was a straightforward next step.”

    The two groups performed a series of laboratory experiments to measure how quickly the building blocks of life can be formed from hydrogen cyanide and hydrogen sulphite ions in water when exposed to UV light. They then performed the same experiment in the absence of light.

    “There is chemistry that happens in the dark: it’s slower than the chemistry that happens in the light, but it’s there,” said senior author Professor Didier Queloz, also from the Cavendish Laboratory. “We wanted to see how much light it would take for the light chemistry to win out over the dark chemistry.”

    The same experiment run in the dark with the hydrogen cyanide and the hydrogen sulphite resulted in an inert compound which could not be used to form the building blocks of life, while the experiment performed under the lights did result in the necessary building blocks.

    The researchers then compared the light chemistry to the dark chemistry against the UV light of different stars. They plotted the amount of UV light available to planets in orbit around these stars to determine where the chemistry could be activated.

    They found that stars around the same temperature as our sun emitted enough light for the building blocks of life to have formed on the surfaces of their planets. Cool stars, on the other hand, do not produce enough light for these building blocks to be formed, except if they have frequent powerful solar flares to jolt the chemistry forward step by step. Planets that both receive enough light to activate the chemistry and could have liquid water on their surfaces reside in what the researchers have called the abiogenesis zone.

    Among the known exoplanets which reside in the abiogenesis zone are several planets detected by the Kepler telescope, including Kepler 452b, a planet that has been nicknamed Earth’s ‘cousin’, although it is too far away to probe with current technology. Next-generation telescopes, such as NASA’s TESS and James Webb Telescopes, will hopefully be able to identify and potentially characterise many more planets that lie within the abiogenesis zone.

    Of course, it is also possible that if there is life on other planets, that it has or will develop in a totally different way than it did on Earth.

    “I’m not sure how contingent life is, but given that we only have one example so far, it makes sense to look for places that are most like us,” said Rimmer. “There’s an important distinction between what is necessary and what is sufficient. The building blocks are necessary, but they may not be sufficient: it’s possible you could mix them for billions of years and nothing happens. But you want to at least look at the places where the necessary things exist.”

    According to recent estimates, there are as many as 700 million trillion terrestrial planets in the observable universe. “Getting some idea of what fraction have been, or might be, primed for life fascinates me,” said Sutherland. “Of course, being primed for life is not everything and we still don’t know how likely the origin of life is, even given favourable circumstances - if it’s really unlikely then we might be alone, but if not, we may have company.”

    The research was funded by the Kavli Foundation and the Simons Foundation.

    Reference:
    Paul B. Rimmer et al. ‘The Origin of RNA Precursors on Exoplanets.’ Science Advances (2018). DOI: 10.1126/sciadv.aar3302

    Inset image: Diagram of confirmed exoplanets within the liquid water habitable zone (as well as Earth). Credit: Paul Rimmer

    Scientists have identified a group of planets outside our solar system where the same chemical conditions that may have led to life on Earth exist. 

    This work brings us just a little bit closer to addressing the question of whether we are alone in the universe.
    Paul Rimmer
    Artist's concept depicting one possible appearance of the planet Kepler-452b

    Creative Commons License
    The text in this work is licensed under a Creative Commons Attribution 4.0 International License. Images, including our videos, are Copyright ©University of Cambridge and licensors/contributors as identified.  All rights reserved. We make our image and video content available in a number of ways – as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

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