tag:theconversation.com,2011:/global/topics/chemical-reactions-5308/articlesChemical reactions – The Conversation2024-02-20T19:57:01Ztag:theconversation.com,2011:article/2172752024-02-20T19:57:01Z2024-02-20T19:57:01ZFire is a chemical reaction. Here’s why Australia is supremely suited to it<p>Over the last 15 million years, Australia has slowly dried out. After humans arrived more than 65,000 years ago, they learned to use fire to their advantage. Today, fire weather is getting more frequent – and <a href="https://www.nature.com/articles/s41467-021-27225-4">fires are following</a> as the world heats up. This month, fires have flared in Victoria, destroying 46 houses, while Western Australia endures a heatwave and braces for <a href="https://www.watoday.com.au/national/western-australia/extreme-fire-danger-conditions-on-tuesday-to-close-wa-schools-dfes-warns-20240219-p5f65r.html">potential fires</a>. </p>
<p>We use controlled fire for food, industry and many other uses. But we fear it when it is uncontrolled. For something so common, it’s not well understood. </p>
<p>Fire is chemistry – a set of reactions known as combustion. Here’s what that means – and why parts of Australia are so well suited to fire. </p>
<h2>What is fire?</h2>
<p>For a fire to start, it needs three things: fuel, an oxidising agent and heat. </p>
<p>In bushfires, the fuel is plant material, the oxidising agent is oxygen in the atmosphere, and the heat could come from lightning or the fire itself once it starts. </p>
<p>First, the heat has to get to the fuel. Plants are mostly comprised of cellulose (a natural carbohydrate polymer we can’t digest) and lignin (a complex aromatic hydrocarbon), alongside other organic molecules. </p>
<p>But big molecules such as cellulose and lignin don’t burn easily, unlike small molecules such as propane or ethanol. It takes an external heat source to get them to burn. This is normally in the form of lightning, the cause of <a href="https://fennerschool.anu.edu.au/news-events/events/which-lightning-strikes-ignite-bushfires-review-fire-neural-network-fnn-high-risk">most large bushfires</a>. But humans have added other sources – a flicked cigarette, angle-grinders, or sparks from a downed powerline. </p>
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<a href="https://images.theconversation.com/files/576640/original/file-20240220-24-1z8zna.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="lightning striking tree" src="https://images.theconversation.com/files/576640/original/file-20240220-24-1z8zna.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/576640/original/file-20240220-24-1z8zna.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=397&fit=crop&dpr=1 600w, https://images.theconversation.com/files/576640/original/file-20240220-24-1z8zna.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=397&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/576640/original/file-20240220-24-1z8zna.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=397&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/576640/original/file-20240220-24-1z8zna.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=499&fit=crop&dpr=1 754w, https://images.theconversation.com/files/576640/original/file-20240220-24-1z8zna.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=499&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/576640/original/file-20240220-24-1z8zna.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=499&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">To start a fire, you need an external heat source such as lightning.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/lightning-oak-tree-625416632">David Wheat/Shutterstock</a></span>
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<p>A little bit of extra heat won’t do it. But when cellulose and lignin are heated to 300°C, pyrolysis begins and the natural polymers begin to break down into small organic molecules, which promptly evaporate and form a gas. </p>
<p>At these temperatures, this gas rapidly reacts with oxygen in the air to produce carbon dioxide, water vapour – and heat. This is combustion. </p>
<p>As it burns, the gas becomes hot enough to glow, as do any solid particles within it. When we gaze at a campfire, that’s what we’re seeing – burning gas, glowing particles. </p>
<p>Many believe it’s the breaking of chemical bonds in the fuel that produces heat. But it’s actually the opposite. When we break any chemical bond, heat is absorbed. It’s making new chemical bonds that releases heat – the creation of water vapour and carbon dioxide. </p>
<p>These newly formed bonds are stronger than the bonds in the hydrocarbon fuel, meaning heat is released overall. So much heat that pyrolysis is sustained, consuming more fuel and spreading the fire. </p>
<h2>What about the water in plants?</h2>
<p>Plant material contains water as well as organic compounds. </p>
<p>There’s a unique bit of chemistry which takes place here. When heat first hits plant material, the water within begins to warm. But water has an extraordinarily high ability to store heat. </p>
<p>As water heats up, it begins to evaporate. Evaporation is endothermic, meaning it absorbs heat. That’s why we use it to stop ourselves overheating – we rely on sweat evaporating off our skin and taking heat with it. </p>
<p>This means you need still more energy to increase the temperature and overcome water’s heat absorbing properties. For pyrolysis to occur at all, the water in the plant matter has to evaporate. If there’s still water in the leaves or bark, it won’t burn. </p>
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Read more:
<a href="https://theconversation.com/how-does-the-stuff-in-a-fire-extinguisher-stop-a-fire-120859">How does the stuff in a fire extinguisher stop a fire?</a>
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<h2>Fire weather and gum trees</h2>
<p>Australia’s forests and bushlands are mostly on the east coast, avoiding the arid interior. But they can’t avoid the extremely hot and dry air the deserts produce, especially over summer. </p>
<p>Hot air can hold a remarkable amount of water. Its ability to soak up water roughly doubles every 10°C. So hot, dry air acts like a sponge. It scours the water from plant matter and soaks it up. </p>
<p>Plant material largely comes from gum trees. Our hundreds of species are famously messy, dropping bark, leaves and limbs on the forest floor. </p>
<p>Eucalyptus leaves often contain large amounts of volatile organic oils. In dry conditions, these leaves act as like natural lighter fluid, or “pre-pyrolysed material”. </p>
<p>This is because eucalypts like fire. Fire wipes out competitor species and can trigger gumnut germination.</p>
<p>When a bushfire begins and starts to spread, it’s usually burning the dead, dry litter and grasses, not large living trees with plenty of water. </p>
<p>Dry fuel is one thing. But a bushfire needs wind to spread. </p>
<p>Hot days in Australia are often windy, due to the temperature difference between hot deserts and cold oceans. If a lightning triggers pyrolysis and starts a fire, wind is what makes it spread. </p>
<p>Wind provides fresh oxygen to the fire front, making it more intense. It also blows hot dry air over fresh fuel ahead of the fire front, drying it out. If there’s no wind, fire spreads much more slowly. </p>
<p>What does it take to end a bushfire? A large fire will naturally burn itself out if there’s no more fuel for it. Heavy rain can douse a fire, though coals can keep smouldering and restart fires if dry, hot air arrives again. </p>
<p>Firefighters make firebreaks to try to starve the fire of its fuel, spray water to wet and cool the fuel or apply chemical agents such as fire-fighting foam to prevent oxygen getting in. </p>
<p>If we add more and more carbon dioxide to the atmosphere it traps more heat, leading to hotter days. More heat means fire weather – hot, dry and windy conditions – is more likely. And that means combustion will be more likely in some places. Under climate change, there’s more fire in our future. </p>
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Read more:
<a href="https://theconversation.com/before-fusion-a-human-history-of-fire-55198">Before fusion: a human history of fire</a>
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<p class="fine-print"><em><span>Jason Dutton receives funding from The Australian Research Council. </span></em></p>We’re all familiar with fire. But do you really know what it is and how it starts? Here’s the chemistry of fire – and why Australia is so prone to going up in flames.Jason Dutton, Professor of Chemistry, La Trobe UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1919952022-10-07T12:18:38Z2022-10-07T12:18:38ZNobel Prize: How click chemistry and bioorthogonal chemistry are transforming the pharmaceutical and material industries<figure><img src="https://images.theconversation.com/files/488596/original/file-20221006-12-btim8w.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C2190%2C1369&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Click chemistry joins molecules together by reacting an azide with a cyclooctyne.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/human-hands-connect-two-circles-royalty-free-image/1360214925">Boris Zhitkov/Moment via Getty Images</a></span></figcaption></figure><p><em>The <a href="https://www.nobelprize.org/prizes/chemistry/2022/press-release/">2022 Nobel Prize in chemistry</a> was awarded to scientists Carolyn R. Bertozzi, Morten Meldal and K. Barry Sharpless for their development of click chemistry and bioorthogonal chemistry.</em> </p>
<p><em>These techniques have been used in a number of sectors, including <a href="https://www.statnews.com/sponsor/2021/12/22/it-takes-two-the-future-of-click-chemistry-therapeutics/">delivering treatments</a> that can kill cancer cells without perturbing healthy cells as well as sustainably and quickly producing large amounts of polymers to build materials. One click chemistry-based drug is currently undergoing <a href="https://clinicaltrials.gov/ct2/show/NCT04106492">phase 2 clinical trials</a>. Bertozzi is a scientific adviser of the company developing the drug.</em></p>
<p><em>We asked chemistry Ph.D. candidate <a href="https://scholar.google.com/citations?user=HaxobcoAAAAJ&hl=en">Heyang (Peter) Zhang</a> of the <a href="http://lin.chem.buffalo.edu">Lin Lab</a> at the University at Buffalo to talk about how these techniques figure in his own research and how they have transformed his field and other industries.</em></p>
<h2>1. How does click and bioorthogonal chemistry work?</h2>
<p><a href="https://doi.org/10.1038/s43586-021-00028-z">Click chemistry</a>, as the name suggests, is a way of building molecules like snapping Lego blocks together. It takes two molecules to click, so researchers refer to each one as click partners. </p>
<p>K. Barry Sharpless and Morten Meldal independently discovered that <a href="https://ehs.stanford.edu/reference/information-azide-compounds">azide</a>, a high-energy molecule with three nitrogens bonded together, and <a href="https://www.angelo.edu/faculty/kboudrea/molecule_gallery/03_alkynes/00_alkynes.htm">alkyne</a>, a relatively inert and naturally rare molecule with two carbons triple-bonded together, are great click partners in the <a href="https://doi.org/10.1021/cr0783479">presence of a copper catalyst</a>. They found that the copper catalyst can bring the two pieces together in an optimal arrangement that snaps them together. Prior to this technique, researchers did not have a way to quickly and precisely make new molecules under accessible conditions, like using water as a solvent at room temperature.</p>
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<a href="https://images.theconversation.com/files/488632/original/file-20221006-26-yu5sd6.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Diagram of click chemistry reaction" src="https://images.theconversation.com/files/488632/original/file-20221006-26-yu5sd6.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/488632/original/file-20221006-26-yu5sd6.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=162&fit=crop&dpr=1 600w, https://images.theconversation.com/files/488632/original/file-20221006-26-yu5sd6.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=162&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/488632/original/file-20221006-26-yu5sd6.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=162&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/488632/original/file-20221006-26-yu5sd6.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=204&fit=crop&dpr=1 754w, https://images.theconversation.com/files/488632/original/file-20221006-26-yu5sd6.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=204&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/488632/original/file-20221006-26-yu5sd6.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=204&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">By combining an azide with a cyclooctyne, bioorthogonal chemistry allows researchers to join molecules quickly together without disturbing the rest of the cell.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Clickscheme.png">Cliu89/Wikimedia Commons</a></span>
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<p>Chemical biologists quickly realized that click reactions can be a fantastic way to probe living systems like cells because they produce little to no toxic byproducts and can happen quickly. However, the copper catalyst is itself toxic to living systems.</p>
<p>Carolyn Bertozzi devised a workaround for this issue by <a href="https://doi.org/10.1021/ja044996f">removing the copper catalyst from the reaction</a>. She did this by placing the alkyne into a ring structure, which drives the reaction forward using the ring strain produced from molecules forced into a cyclical shape. These bioorthogonal reactions, or reactions that happen “parallel” to the chemical environment of the cell, can occur in cells without perturbing their normal chemistry.</p>
<h2>2. How do you use this chemistry in your work?</h2>
<p>In <a href="https://youtu.be/-Ch3VJhIbH4">an interview</a>, Carolyn Bertozzi stated that the next steps for bioorthogonal chemistry are to find new reactions and applications for it. Our lab’s research focuses exactly on that. </p>
<p>My colleagues and I apply this technique to track molecules we are interested in as they naturally behave in a cell. In a living cell, we were able to <a href="https://doi.org/10.1021/jacs.8b00126">add a probe to a receptor</a> that plays a role in a number of cellular processes.</p>
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<figcaption><span class="caption">Carolyn Bertozzi is one of the winners of the 2022 Nobel Prize in chemistry.</span></figcaption>
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<p>To find new reactions, our lab has spent the last 15 years to <a href="https://doi.org/10.1002/cbic.202200175">push how fast bioorthogonal reactions can run</a>. Speed is important because many molecules in living organisms are present in low concentrations, and using too much of the chemicals required for the reaction can be toxic for the cell. The faster the reaction, the fewer the unwanted side reactions.</p>
<p>We pioneered another way to achieve click and bioorthogonal reactions with even faster speed. Instead of using an azide and an alkyne like the Nobel Prize winners did originally, we used two other molecules that join together when a light is shined on them. With this technique, we are able to add molecules to the surface of a live cell in <a href="https://doi.org/10.1021/jacs.1c10354">as little as 15 seconds</a>. We can then observe how a particular structure on a cell functions in its natural environment, or detect how it changes when exposing it to drugs or other substances. Researchers can then more easily test how cells react to potential treatments.</p>
<p>Currently, we are working to develop a new method of triggering these reactions without light. We are actively working on using bioorthogonal chemistry to improve PET imaging to screen and monitor tumors.</p>
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<span class="caption">Bioorthogonal chemistry can be used for ‘click-to-release’ cancer drugs.</span>
<span class="attribution"><a class="source" href="https://doi.org/10.1038/s41467-018-03880-y">Rossin 2018 (Nature Communications)</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
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<h2>3. Why are these techniques so important to your field?</h2>
<p>Prior to click and bioorthogonal chemistry, there was no way of visualizing molecules in living cells in their natural state.</p>
<p>As an analogy, imagine you needed to find a specific dollar bill with the serial number 01234567. That would be a pretty daunting task. It would require you to go through every dollar you can get your hands on and verify whether the serial number is the one you are looking for. </p>
<p>Tracking molecules in our body is just as hard, if not more. Because biological environments are so complex, it was previously impossible to add a probe to just the molecule of interest without accidentally tagging something else, or worse, altering the normal chemistry of the cell. With bioorthogonal reactions, however, researchers can essentially add a GPS tracker to the molecule without affecting the rest of the cell.</p><img src="https://counter.theconversation.com/content/191995/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Heyang (Peter) Zhang works in Lin's lab at the University at Buffalo.</span></em></p>Click and bioorthogonal chemistry has enabled researchers to closely study how molecules work in their natural state in living organisms, with applications that span from cancer treatment to polymers.Heyang (Peter) Zhang, PhD Candidate in Chemistry, University at BuffaloLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1694272021-10-07T00:01:19Z2021-10-07T00:01:19ZMy Ph.D. supervisor just won the Nobel Prize in Chemistry for designing a safer, cheaper and faster way to build molecules and make medicine<figure><img src="https://images.theconversation.com/files/425118/original/file-20211006-15-15z9fbz.jpg?ixlib=rb-1.1.0&rect=125%2C98%2C5748%2C3628&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Many catalysts currently used to make many drugs are expensive and can produce toxic byproducts. </span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/row-of-test-tubes-with-liquid-yellow-background-royalty-free-image/1057217750?adppopup=true"> Westend61 via Getty Images</a></span></figcaption></figure><p>The reason that ibuprofen treats headaches and ice cream tastes sweet is that their chemical components fit perfectly into certain receptors in your body. The better a drug or flavor molecule fits with its matching receptor, the more effective the medicine or tastier the treat.</p>
<p>But an interesting quirk of nature is that many molecules can come in two versions – a right–handed version and left–handed version – and receptors in your body must match the handedness of a molecule to fit correctly. A left–handed glove won’t fit on your right hand. </p>
<p>So how do chemists make the correct version of a molecule so that drugs work as intended?</p>
<p>This is a question <a href="https://scholar.google.com/citations?user=t8h1sWIAAAAJ&hl=en&oi=ao">I as a chemist</a> was deeply fascinated by when I started my Ph.D. studies with <a href="https://www.nobelprize.org/prizes/chemistry/2021/macmillan/facts/">Dave MacMillan</a> at Princeton. And he, along with <a href="https://www.nobelprize.org/prizes/chemistry/2021/list/facts/">Ben List of the Max Planck Institute</a>, have together <a href="https://www.nobelprize.org/uploads/2021/10/press-chemistryprize2021.pdf">won the 2021 Nobel Prize in Chemistry</a> for discovering entirely new ways to make molecules of one orientation or another.</p>
<p>They developed a new simple type of catalyst – called asymmetric organocatalysts. These catalysts are able to efficiently produce molecules with a particular 3-D orientation and have enabled chemists to discover and manufacture safe and effective drugs.</p>
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<span class="caption">All molecules can come in right–handed or left–handed versions that are mirror opposites of each other but not identical.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Chirality_with_hands.svg#/media/File:Chirality_with_hands.svg">πϵρήλιο via WikimediaCommons</a></span>
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<h2>What is an asymmetric catalyst?</h2>
<p>Catalysts are the tools that both nature and chemists <a href="https://www.sciencenewsforstudents.org/article/explainer-catalyst-chemistry">use to build complex molecules</a>. They work by lowering the amount of energy required for a chemical reaction to occur. Chemists use catalysts to produce large amounts of complex molecules that would otherwise be hard to make efficiently, or even at all.</p>
<p>Normally, chemical reactions produce an equal amount of left–handed and right–handed molecules. <a href="https://doi.org/10.1073/pnas.0306715101">Asymmetric catalysts</a> are catalysts that selectively produce molecules with one orientation or the other.</p>
<p>Twenty years ago, the chemists who first invented asymmetric catalysts won the <a href="https://www.nobelprize.org/prizes/chemistry/2001/summary/">2001 Nobel Prize in Chemistry</a>. But the catalysts they invented use <a href="https://doi.org/10.1021/acs.accounts.5b00385">precious metals</a> that can be expensive and toxic. They are also sensitive to air and water. Scientists have been using these metal–based asymmetric catalysts ever since, but a lot of care needs to go into recycling or removing these sometimes toxic metals from the many medicines they are used to create.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/425121/original/file-20211006-15-12o6jdm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A tangled web of spirals and shapes representing and aldolase enzyme." src="https://images.theconversation.com/files/425121/original/file-20211006-15-12o6jdm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/425121/original/file-20211006-15-12o6jdm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=478&fit=crop&dpr=1 600w, https://images.theconversation.com/files/425121/original/file-20211006-15-12o6jdm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=478&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/425121/original/file-20211006-15-12o6jdm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=478&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/425121/original/file-20211006-15-12o6jdm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=601&fit=crop&dpr=1 754w, https://images.theconversation.com/files/425121/original/file-20211006-15-12o6jdm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=601&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/425121/original/file-20211006-15-12o6jdm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=601&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Biology uses incredibly complex molecules, like this model of an enzyme, to produce specific products.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:1qo5.jpg#/media/File:1qo5.jpg">Astrojan via WikimediaCommons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>How does nature make asymmetric molecules?</h2>
<p>Biological receptors – structures on cells that receive chemical signals – often only bind to one version of a molecule. So nature has mastered how to make molecules selectively using large, complex, almost factorylike enzymes. These elaborate enzyme catalysts are often made of thousands of amino acids and assemble chemical building blocks into the correct left or right orientation. This beautiful strategy is the product of millions of years of evolution and works great in living organisms. </p>
<p>The problem when it comes to using enzymes to produce drugs is that they are often 10,000 times larger than the actual target medicine and can take just as long to make. In fact, the 2018 Nobel Prize in Chemistry separately recognized scientists who developed <a href="https://www.nobelprize.org/prizes/chemistry/2018/summary/">a way to make enzyme catalysts more easily</a>. Despite these advances, making these large enzymes is not yet practical for medicinal chemists in the lab. </p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1445694278668152843"}"></div></p>
<h2>Asymmetric organocatalysts: Hand tools doing the job of a factory</h2>
<p>MacMillan and List each developed a type of organic, or carbon–based, catalyst made from a single amino acid that can produce complex molecules of a single handedness. Instead of using toxic metals or entire molecular factories, scientists can now use single amino acids to produce specific drugs.</p>
<p>In early 2000, <a href="https://doi.org/10.1021/ja994280y">List</a> reported that a single amino acid, proline, could effectively mimic an entire enzyme that performs the <a href="https://en.wikipedia.org/wiki/Aldol_reaction">aldol</a> reaction, an essential bond-forming chemical reaction. That same year, <a href="https://pubs.acs.org/doi/abs/10.1021/ja000092s">MacMillan</a> showed that several different modified amino acids could asymmetrically promote the <a href="https://en.wikipedia.org/wiki/Diels%E2%80%93Alder_reaction">Diels-Alder</a> reaction, another important reaction that forms bonds. In this seminal paper, MacMillan coined the term “organocatalyst.”</p>
<p>So how do organocatalysts work?</p>
<p>There are now many different types of asymmetric organocatalysts, but the type that started this field are often circular amino acids that hold chemical building blocks in a particular 3D shape during a chemical reaction. In a choreographed three-part dance, the catalysts first make a strong bond with a building block of the desired end product, orient it for the bond formation and then release it after the chemical reaction has occurred. </p>
<p>The circular shape of the catalysts is often essential. List used the only naturally occurring ring-shaped amino acid, proline, as his catalyst. MacMillan, on the other hand, tied the amino acids back in a ring that forces chemical reactions to only produce molecules with one orientation.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/425123/original/file-20211006-14-jacs9x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A hand holding a pill packet." src="https://images.theconversation.com/files/425123/original/file-20211006-14-jacs9x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/425123/original/file-20211006-14-jacs9x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/425123/original/file-20211006-14-jacs9x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/425123/original/file-20211006-14-jacs9x.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/425123/original/file-20211006-14-jacs9x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/425123/original/file-20211006-14-jacs9x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/425123/original/file-20211006-14-jacs9x.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Asymmetrical organocatalysts are already being used to produce many kinds of drugs.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/female-hand-holds-a-package-of-yellow-pills-royalty-free-image/1272367209">Olena Ruban/Moment via Getty Images</a></span>
</figcaption>
</figure>
<h2>A Nobel-worthy discovery</h2>
<p>The techniques that List and MacMillan discovered have led to the <a href="https://doi.org/10.1038/nature07367">creation of thousands of new catalysts and chemical reactions</a> that can produce drugs more cheaply and efficiently than before.</p>
<p>The ability to build so many molecules with such a simple and effective approach has revolutionized medicinal chemistry. Today, organocatalysts are frequently used to <a href="https://doi.org/10.1039/D0CS00196A">make many types of drugs that treat a wide range of diseases</a>, including cancer, diabetes, HIV and many more.</p>
<p>By the time I joined MacMillan’s lab in 2006, we were building on these discoveries and merging them with new technologies to make <a href="https://doi.org/10.1038/nature10647">entirely new types of medicines</a>. The dozens of fun and creative scientists that I worked with there have shown that it is possible to use MacMillan’s discovery to invent hundreds of new chemical reactions.</p>
<p>I once asked MacMillan why he thought his discovery had made such an impact on medicine. His answer was that amino acids are cheap, sustainable materials and are much more practical to use than air- and water–sensitive metal catalysts. This means that people don’t need big budgets or fancy equipment to employ this technology and manufacture new drugs. Chemists around the world – from poor and rich countries alike – can build on the technology.</p>
<p>I still strongly agree that this is why organocatalysts have been put to such great use so quickly and so widely.</p>
<p>[<em>Get our best science, health and technology stories.</em> <a href="https://theconversation.com/us/newsletters/science-editors-picks-71/?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=science-best">Sign up for The Conversation’s science newsletter</a>.]</p><img src="https://counter.theconversation.com/content/169427/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>David Nagib receives funding from the National Institutes of Health, National Science Foundation, Eli Lilly, and the Sloan Research Foundation. MacMillan was his PhD advisor from 2006-2011.</span></em></p>Dave MacMillon and Ben List both developed simple catalysts that make precise chemical reactions much faster and more efficient.David Nagib, Associate Professor of Chemistry, The Ohio State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/984762018-06-19T14:42:27Z2018-06-19T14:42:27ZSelf-heating drinks cans return – here’s how they work<figure><img src="https://images.theconversation.com/files/223601/original/file-20180618-85863-fkjmvu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">shutterstock</span> </figcaption></figure><p>A US technology firm is hoping to make a very old idea finally work by launching self-heating drinks cans. HeatGenie <a href="https://www.foodbev.com/news/heatgenie-raises-6m-bring-self-heating-drink-cans-market/">recently received</a> US$6m to bring its can design to market in 2018, more than 15 years after Nestle <a href="https://www.campaignlive.co.uk/article/nescafe-discards-self-heating-cans/155450?src_site=marketingmagazine">abandoned a similar idea</a>. Yet the principles behind the technology go back much further – to 1897, when <a href="https://ifood.tv/equipment/self-heating-can/about">Russian engineer Yevgeny Fedorov</a> invented the first self-heating can. So how do these cans work, why has no one has managed to make them a success, and what’s HeatGenie’s new approach? To answer that, we have to go back to World War II.</p>
<p>The imposing cliffs of Pointe de Hoc overlook the Normandy beaches where Allied troops landed on June 6 1944. The assaults marked the beginning of the liberation of German-occupied Europe. And the cliff tops were the perfect spot for artillery pieces capable of devastating any troops who tried to attack the Omaha and Utah beachheads.</p>
<p>The Allied command knew this and so, to shore up the attack, the navy bombarded Pointe de Hoc. Afraid this might not be enough, they also had a backup plan. A team of <a href="https://www.abmc.gov/cemeteries-memorials/europe/pointe-du-hoc-ranger-monument#.WydlXy-ZPMJ">US Rangers scaled the 30-metre cliffs</a> and, after locating the weaponry, deployed grenades, destroying the guns. The key to success was the choice of thermite-based charges. These weren’t the kind of “high explosives” normally found in grenades, but instead used a chemical reaction that produced temperatures hot enough to melt the steel of firing mechanisms.</p>
<p>Surprisingly, <a href="http://www.rsc.org/learn-chemistry/resource/res00000724/the-thermite-reaction?cmpid=CMP00005969">the thermite</a> the Rangers used is incredibly simple. It is just rust (iron oxide) and powdered aluminium. Mixed together they are entirely safe and stable – that is until the mixture is given an energetic kick, typically by lighting a magnesium metal fuse. And then the fireworks start. The aluminium grabs the oxygen from the rust and in the process produces iron and a huge burst of heat. The reaction can easily reach 2,500°C, hot enough to produce molten (liquid) iron.</p>
<p>The following video shows the reaction in slow motion. The bright light at the start is just the magnesium burning. Then, when the fuse burns down to the thermite, things get impressive, leaving a melted tube and a flaming puddle of iron.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/Rfz15v1F8cM?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>Thermite is an extreme example of an exothermic reaction, a chemical reaction that produces energy in the form of light and heat. Fire, typically the result of a reaction involving carbon and oxygen, is probably the exothermic reaction we are most familiar with. But there are plenty more. In fact many of the very same troops who were landing on the Normandy beaches that day had <a href="http://www.bbc.co.uk/history/ww2peopleswar/stories/55/a2319455.shtml">another example in their ration packs</a>, in the form of self-heating cans of soup.</p>
<p>These were essentially <a href="http://www.gmmg.org.uk/our-connected-history/item/tin/">a stove and can rolled into one</a>, with a tube of <a href="https://www.chemistryworld.com/podcasts/cordite/1010201.article">cordite</a> (more typically used as the propellant in small arms ammunition) running through the centre of the can to act as fuel. The cans were quick and easy to use and could be lit with a cigarette, allowing troops to prepare a hot meal in under five minutes. Unfortunately, they also had a <a href="http://www.thejournal.ie/self-heating-soup-cans-1370166-Mar2014/">tendency to explode</a>, showering the assembled squaddies with piping hot soup. </p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/223609/original/file-20180618-85834-jrossy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/223609/original/file-20180618-85834-jrossy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=787&fit=crop&dpr=1 600w, https://images.theconversation.com/files/223609/original/file-20180618-85834-jrossy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=787&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/223609/original/file-20180618-85834-jrossy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=787&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/223609/original/file-20180618-85834-jrossy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=989&fit=crop&dpr=1 754w, https://images.theconversation.com/files/223609/original/file-20180618-85834-jrossy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=989&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/223609/original/file-20180618-85834-jrossy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=989&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Self-heating cocoa.</span>
<span class="attribution"><a class="source" href="https://www.spri.cam.ac.uk/museum/news/object-in-focus/2015/11/10/object-in-focus-self-heating-cocoa-tin/">University of Cambridge</a></span>
</figcaption>
</figure>
<p>Since then, there have been numerous attempts to make self-heating cans into a mainstream product. Most relied on a rather less volatile reaction to provide the heat, although some have <a href="https://www.nytimes.com/2006/05/02/business/02puck.html">still struggled with</a> explosive issues. Quicklime (calcium oxide) heats up rapidly when mixed with water. But it’s not particularly efficient, producing about 60 calories of energy per gram of reactant (one calorie will heat up one millilitre of water by 1°C).</p>
<p>The upshot is that, to heat the drink by 40°C, you need a heating element that takes up nearly half the packaging. That’s just about OK if you want a small drink on a warm day, but in the depths of winter, when you might really want a hot drink, you only end up with a tepid coffee.</p>
<h2>More powerful cans</h2>
<p>What’s needed is a much more efficient reaction. Something, like thermite perhaps? As crazy as packing a can with a reaction capable of disabling an artillery gun may seem, that’s just what HeatGenie is planning. Over the last ten years, the firm has <a href="https://patents.google.com/?q=thermite&assignee=heatgenie&oq=heatgenie++thermite">filed numerous patents</a> describing the use of thermite within self-heating cans. It turns out the reaction used by the US Rangers is still too hot to handle, so they’ve dialled things back a bit by replacing the rust with a less reactive but no less familiar material, silicon dioxide. So the latest generation of heated cans is fuelled on aluminium and ground-up glass.</p>
<p>When this reaction is triggered it still kicks out a whopping 200 calories per gram of reactant and can achieve 1,600°C. Given the troubled history of self-heating packaging, releasing this much energy from the can in your hand might be a bit of a concern, so several of HeatGenie’s patents cover safety issues.</p>
<p>These include a complex arrangement of “<a href="https://patents.google.com/patent/US20140127634A1/en?q=thermite&assignee=heatgenie&oq=heatgenie++thermite">firewalls</a>” that can block the so-called “flamefront” should things get too hot, and <a href="https://patents.google.com/patent/US9500389B2/en?q=thermite&assignee=heatgenie&oq=heatgenie+thermite">energy-absorbing “heatsinks”</a> to ensure the heat is efficiently transmitted around the drink, as well as vents to let off any steam. With all that is place, the company claims just 10% of the packaging is taken up by the heating elements, which can still produce a warm coffee in two minutes (although the exact temperature hasn’t been revealed). </p>
<p>So, well over a century on from Fedorov’s first efforts, has HeatGenie final cracked the self-heating can? Judging from the patents and investments, the firm might have sorted out the technical side, but whether it really has a hot product on its hands is another thing entirely.</p><img src="https://counter.theconversation.com/content/98476/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mark Lorch does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>US firm HeatGenie is hoping to revive a technology that has surprising origins in World War II and beyond.Mark Lorch, Professor of Science Communication and Chemistry, University of HullLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/796102017-07-03T13:54:05Z2017-07-03T13:54:05ZTiny ‘micro drop’ chemical reactors are helping to revolutionise scientific experiments<figure><img src="https://images.theconversation.com/files/176591/original/file-20170703-32638-nzjnlf.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption"></span> <span class="attribution"><span class="license">Author provided</span></span></figcaption></figure><p>Science is getting smaller. From <a href="https://theconversation.com/folding-graphene-like-origami-may-allow-us-to-wear-sensors-in-our-skin-45346?sr=2">two-dimensional new materials</a> <a href="https://theconversation.com/from-living-computers-to-nano-robots-how-were-taking-dna-beyond-genetics-60580?sr=1">to nano-robots</a>, many of the latest advances are being made at scales impossible to see with the human eye. </p>
<p>The latest technique to shake things up at the micro level is a way to trap and study individual living cells to try to understand why they malfunction when diseased. Until now, scientists have done this with <a href="https://www.ncbi.nlm.nih.gov/pubmed/22767244">electrode “microtraps”</a> and <a href="http://science.sciencemag.org/content/sci/288/5463/113.full.pdf?ck=nck">highly complex networks of channels</a> carved into plastic chips.</p>
<p>But now there’s a way to analyse up to millions of cells simultaneously by putting them inside tiny water-in-oil droplets <a href="https://www.ncbi.nlm.nih.gov/pubmed/16511628">not much bigger than the cells themselves</a>. This could massively speed up efforts to identify diseased cells, find new drug molecules or new ways to <a href="https://www.ncbi.nlm.nih.gov/pubmed/18651063">diagnose disease</a>.</p>
<p>The days when scientists carried out experiments by mixing chemicals in large glass flasks are long gone. Nowadays, tests are performed in trays punctuated by a number of “microwell” holes that mean just a few microlitres (millionths of a litre) of each sample is needed. The difficulty with going much smaller is that it’s hard to move liquid around at this scale because really tiny <a href="https://www.ncbi.nlm.nih.gov/pubmed/20559601">drops tend to clump together or evaporate</a>.</p>
<p>Although the potential of encapsulating single cells was identified as <a href="https://www.nature.com/nature/journal/v181/n4620/abs/1811419a0.html">early as the 1950s</a>, the droplet field has really picked up pace with the emergence of fabrication technologies borrowed from the semiconductor industry.</p>
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<p>The microdroplet solution is to separate and protect each picolitre (one trillionth of a litre) drop of water by wrapping it in oil. To do this, you feed the water and oil through tiny tubes in a “microfluidic” device and force them to meet at a cross junction where they combine into individual microdroplets. This can create <a href="https://www.ncbi.nlm.nih.gov/pubmed/23805985">many thousands of identical tiny chemical reactors a second</a>.</p>
<p>Other microfluidic devices can be used to combine, split or sort the droplets, just as a scientist might do at a <a href="https://www.ncbi.nlm.nih.gov/pubmed/28390246">larger scale with a pipette</a> Specially formulated chemicals at the interface between the water and oil keep the droplets <a href="https://www.nature.com/articles/ncomms10392">stable for days at a time</a>.</p>
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<h2>Finding a cellular needle in a haystack</h2>
<p>Droplets are an attractive proposition for tackling needle-in-a-haystack problems, such as isolating very rare cells with a unique mutation or molecular make-up. For example, cells from a tumour can sometimes break off and circulate through the bloodstream, potentially causing cancer elsewhere in the body (metastasis). Finding a way to detect these circulating tumour cells (CTCs) would essentially provide a blood test update on the state of a patient’s cancer. But they are very hard to find because they exist at concentrations as low as <a href="http://www.nature.com/nrc/journal/v14/n9/full/nrc3686.html">one per 10 ml of blood</a>. Using a microdroplet technique could allow doctors to quickly comb through the cells from a patient’s blood sample <a href="https://www.ncbi.nlm.nih.gov/labs/articles/27311775/">to find a CTC</a>.</p>
<p>Microdroplet techniques can even help confine DNA molecules together with the proteins produced by specific genes, such as biocatalysts or enzymes that help enable certain chemical reactions in a living organism. This means we can find rare DNA mutations that result in more efficient biocatalysts, a process called <a href="http://www.pnas.org/content/113/47/E7383.full.pdf">directed evolution</a>. This is helpful because many biocatalysts are responsible for reactions needed for industrial processes, <a href="http://www.sciencedirect.com/science/article/pii/S1367593117300418">from washing using detergent powders to making biofuels</a>.</p>
<p>Today, the process of screening gene libraries with millions of encoded members is becoming more and more routine. Another promising application is to use environmental samples in the search for molecules that could be used as <a href="https://www.nature.com/articles/ncomms10008">antibiotics or anti-cancer agents</a>. Likewise, researchers can assess collections of antibodies with the hope of finding <a href="http://www.pnas.org/content/109/29/11570.long">one that can function as a drug</a>.</p>
<p>Microdroplet techniques do have their limits. For example, small molecules can sometimes diffuse through the oil phase making droplets in effect leaky compartments. Yet there are still many potential advances to be made. For example, one can envision truly <a href="https://theconversation.com/how-science-is-using-the-genetics-of-disease-to-make-drugs-better-30747">personalised medicine</a> where many different drugs are rapidly tested against many different patient cells to find which one is best to prescribe. Microdroplets have had just a decade of use. Think of what they could achieve in the future.</p><img src="https://counter.theconversation.com/content/79610/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Fabrice Gielen is co-founder and director of Drop-Tech Ltd.</span></em></p>Why do one big experiment when you can do millions of tiny ones?Fabrice Gielen, Research Fellow in Microfluidics, University of ExeterLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/316452014-09-16T05:17:39Z2014-09-16T05:17:39ZNow you can turn your inkjet printer into a chemistry lab<figure><img src="https://images.theconversation.com/files/59029/original/2jrg9gvq-1410778261.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Ready, set, print me a reaction.</span> <span class="attribution"><span class="source">Chaikom</span></span></figcaption></figure><p>If you stop and think about it for a moment, you will realise what an astonishing feat of precision engineering your colour printer is. It can take the primary colours – cyan, yellow, magenta and black – and mix them together carefully enough to achieve more than a million different hues and shades. Not only that but the drops of colour are mere nanolitres (billionths of a litre) in volume, each of which is then placed on the paper – assuming its not jammed in the feeder tray – with better than pinpoint accuracy.</p>
<p>Now a group of enterprising chemists from Tsinghua University are exploiting that precision engineering, which normally results in high-resolution colour prints, to screen millions of different chemical reactions. Their results have been published in the journal <a href="http://dx.doi.org/10.1039/c4cc06158f">Chemical Communications</a>.</p>
<p>Yifei Zhang and colleagues have been trying to understand reaction pathways in living things. Every chemical process that goes on in living organisms is controlled by a cascade of reactions. The steps in a cascade are mediated by protein molecules called enzymes. Each enzyme makes a small chemical alteration, like workers on a production line, to a molecule before passing its product onto the next enzyme. In this way, for example, plants build sugars from carbon dioxide and your food gets broken down and then reconstructed into other useful chemicals for your body. </p>
<p>The problem is that to understand these complicated processes by reconstructing them outside of a living cell is difficult. The concentrations of an enzyme relative to the next in the line is key. Get this wrong and bottle necks are formed in the production line, as one enzyme works faster than the next. </p>
<p>To figure out what are the right conditions to replicate a living cell’s workings, chemists must set up and monitor a vast number of reactions. Screening large numbers of reactions like this is often done using “96-well plates”, which are 96 tiny containers with a unique combination of chemicals in each. These reactions might be set up manually or, if the lab is well-funded, by an expensive robot. But even with the best robots available it can still be a slow process.</p>
<p>Colour printers are a lot cheaper than robots. And if the inks are replaced by solutions of enzymes then suddenly you have a device that has the potential to dispense more than a million different reaction mixtures.</p>
<p>That is just want Yifei and colleagues have done. Their printers were loaded with a series of enzymes that, when they work together in the correct ratios, produce coloured reaction products. These were printed directly onto paper where it was immediately obvious, from the intensity of a coloured dot, which reaction mixtures worked best. </p>
<p>In the test cases reactions were deliberately chosen that resulted in colour changes. This made for a nice quick visual indication of whether the system worked well. So for example one test started with glucose and a chemical called ABTS in the magenta cartridge, then the enzymes glucose oxidase (GOx) and horse-radish peroxidase (HRP) in the yellow and cyan cartridges. When they are mixed together the GOx removes a hydrogen from the glucose and adds it to oxygen, producing hydrogen peroxide. Next the HRP reacts this with the ABTS, which results in a green chemical.</p>
<p>The potential applications for these printer-based mixtures extend beyond curiosity-driven research on biological pathways. Yifei and colleagues have already shown that by loading the printer cartridges with the right enzymes they can use the set up to indicate the presence of glucose in a sample. Glucose in urine is a indication of diabetes, so their printer-based chemistry already has the potential to diagnose diabetes. </p>
<p>The result then could be a future where a trip to the doctors results in a printout of, quite literally, your urine and some enzymes alongside, after 30 seconds or so, a diagnosis and the prescription.</p><img src="https://counter.theconversation.com/content/31645/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mark Lorch does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>If you stop and think about it for a moment, you will realise what an astonishing feat of precision engineering your colour printer is. It can take the primary colours – cyan, yellow, magenta and black…Mark Lorch, Senior Lecturer in Biological Chemistry, University of HullLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/187072013-10-15T23:38:05Z2013-10-15T23:38:05ZJelly-making protein could help make cheap fuel cells<figure><img src="https://images.theconversation.com/files/33065/original/hw9dn8wx-1381828749.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Get your fill of energy.</span> <span class="attribution"><span class="source">kfoodaddict</span></span></figcaption></figure><p>New research shows that a catalyst made from gelatin, the same protein used to make jelly desserts, helps fuel cells be more efficient. This may offer a cheap alternative to the expensive metal-based fuel cells.</p>
<p>In a fuel cell, energy released from a chemical reaction (most commonly hydrogen and oxygen combining to form water) is converted into electricity. Many carmakers like Toyota are racing to find a commercially viable fuel cell. If they are able to, cars of the future will spit out only water, instead of the carbon dioxide, water and other pollutants that today’s fossil fuel powered cars do.</p>
<p>Researchers from the UK, Japan and China, led by Zoe Schnepp at the University of Birmingham, reported their new catalyst in the <a href="http://dx.doi.org/10.1039/C3TA12996A">Journal of Materials Chemistry A</a>. To make the catalyst, they mixed salts of magnesium and iron with gelatin to create a foam. Heating this foam to 800 °C in a process called calcination degrades the gelatin and oxidises the metals, producing a sponge which contains metal nanoparticles (which are a million times smaller than a human hair). Any remaining metal is washed off with acid, leaving behind a porous structure made of carbon.</p>
<p>This porous structure is an advantage for the catalyst. The network of pores and bubbles inside the catalyst provides a very large surface area for chemical reactions to occur. The more places there are for hydrogen and oxygen to react to produce water, the more efficient the catalyst is.</p>
<p>The choice of metal salts proved to be important too. The identity of the metals used determined the size of the pores formed, and thus affected how well the reactions occur. The two metals used react differently during calcination: the magnesium is converted to nanoparticles of magnesium oxide, while the iron bunches together into much larger particles of iron carbide. This meant that the ratio of magnesium to iron can be used to tune the pore size.</p>
<p>During heating iron carbide converts the carbon around it to a thin sheet, which happens to be good for a fuel cell reaction. Nitrogen atoms from the gelatin become embedded in this thin sheet of carbon, and previous results have shown this makes the catalyst even more effective. </p>
<p>When Schnepp compared commercial platinum catalysts with her catalyst, she found they did just as well. Crucially, the new catalyst is also as durable as the platinum ones. Platinum is too expensive to be used for commercial fuel cells. In recent years, there have been many efforts to find a cheaper and better alternative. Schnepp’s catalyst needs cheap gelatin and plentiful metal nitrate salts, making it one of the best alternatives yet.</p>
<p>By exploiting the properties of biological polymers, Schnepp and colleagues have found simple route to a structurally complex and useful material. Simplicity, as Steve Jobs would say, is often the first step to a great product.</p><img src="https://counter.theconversation.com/content/18707/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Andrew Bissette does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>New research shows that a catalyst made from gelatin, the same protein used to make jelly desserts, helps fuel cells be more efficient. This may offer a cheap alternative to the expensive metal-based fuel…Andrew Bissette, PhD student, University of OxfordLicensed as Creative Commons – attribution, no derivatives.