Chemical Curiosities

The Hollywood Zombie FallacyThe October twilight paints the sky with an eerie glow. You’re a survivor scavenging an abandoned office building. Devastation is all around you. The office windows are smashed. The front doors look as though someone forced them open. Empty cars sit in the parking lot, some turned over. Not a living soul in sight. You slip through the entrance and into the gloom within. As your flashlight beam cuts through the dust and darkness, sweeping across ransacked desks and overturned tables, you search for anything useful. Maybe there are batteries or, better yet, unopened bottles of water.It’s quiet. You pause. You listen again. All you hear are the faint sounds of settling dust and the hollow drip of a corroded pipe echoing somewhere in the building.This place is a dead end. As you turn on your heel back toward the exit, you hear movement behind the reception desk. Before you can even shine your light, a gray, decaying hand shoots out from the shadows and grabs your coat! A rotting, sunken face lunges directly into your flashlight beam, yellow teeth snapping just inches away from your throat. Unbeknownst to you, one of the undead was nearby the entire time!Love the intersection of nature, history, and chemistry? Subscribe for free to join me as I unpack the molecules shaping our world from beehive security to the smell of the ocean.But wait. Something’s wrong with this scene. It has the sound and visuals, but there’s no smell.Unless you were surrounded by the dead all the time, the stench of that walking corpse would have hit you the second you entered through the front door. It would be almost impossible to ignore!Your nose would have detected an invisible, noxious mix of chemicals so potent and revolting that your stomach would have knotted up, your eyes would have watered, and your survival instincts would have sent you fleeing. Hollywood can make it look and sound scary, but it leaves out the single most overwhelming sensory reality of a putrefying corpse walking around: the chemistry of biological decay.When life stops, whether by natural causes or a zombie apocalypse, microorganisms immediately take over, producing a specific cocktail of volatile organic molecules. Two of the star players in that mixture don’t have scientific, high-brow academic names, either. Back in the late 19th century, a German chemist named Ludwig Brieger isolated these compounds and gave them names so brutally honest that horror writers couldn't do better: putrescine and cadaverine. Yes, as in cadavers! Dead bodies!Cadaverine is often described as sickly sweet and like rotting flesh. Putrescine is the pungent scent of decay. Our noses are extremely sensitive to these compounds.Back in the 1800s, chemists lumped these and other deathly compounds into a morbid category called ptomaines, derived from the ancient Greek word for corpse. For decades, people were caught up in the idea of “ptomaine poisonings.” Any mysterious death or illness was blamed on these molecules. Fortunately, we no longer believe in such superstitions. I’m John Knight, and today we’re going to lean into October with a trip into the chemistry of the crypt. We’ll look at how bacteria turn ordinary amino acids into some of the most alarming smells on Earth, why our brains treat that odor like a fire alarm, and why you don’t need dead bodies to find these molecules lurking around. As always, you can check out the full text of this podcast and some chemical structures in my Substack post.So, if you’re in the spirit of the season, grab a hot cider, light a scented candle, and let’s get a little bit into the chemistry of rot.Harmless Building BlocksBefore we talk about what molecules like putrescine and cadaverine are and what they do, we first need to talk about where they come from. They actually have rather ordinary origins. Maybe you remember from school that living things are made of proteins, and those proteins are themselves made of building blocks called amino acids. Every amino acid has the same general features: an acid group (called a carboxyl group, -COOH), an amine group (-NH₂), and a side group that changes. Around 20 amino acids are used to make proteins. Today, though, we will focus on two: lysine and ornithine. Lysine is an essential amino acid that affects muscle growth and healing. The human body can’t produce it, so we must obtain it from our diet. The second amino acid, ornithine, is different. Our bodies can produce it, but it’s not used to make proteins. Instead, it plays an important role in breaking down proteins and getting rid of excess nitrogen atoms in the body. Keep that in mind because nitrogen is really the star element of this whole story. So, these two amino acids are rather important for living things. But we’re not talking about the living today. We’re focused on what happens when life stops. Molecular Shears and RotLet’s imagine someone dies. On the outside, not much changes in the first few minutes after death. At the cellular level, though, things begin to break down quickly. The body’s defenses against the outside world shut down. Internal oxygen levels plummet, and the door is suddenly wide open for anaerobic bacteria to flourish. Surrounded by a rich environment, these microorganisms begin breaking down molecules in the dead body. It’s not malicious. They’re just taking advantage of an opportunity. These bacteria produce specialized enzymes called decarboxylases to break down amino acids into simpler molecules for energy. Decarboxylases act sort of like molecular shears, cutting off the acid group from the amino acid to form an amine. That COOH group becomes carbon dioxide (CO₂) and drifts away. That is where putrescine and cadaverine come from.Lysine gets clipped to produce cadaverine, a linear molecule with five -CH2- groups and two amine groups. Ornithine gets clipped to produce putrescine, a linear molecule with four -CH2- groups and two amine groups.In fact, the only difference between these two molecules is a single -CH2- group in the chain of atoms.Removing the acid group from the amino acid changes everything. That acid group was a strong source of intermolecular interactions, and the resulting amine is not just smaller but also more volatile. It can easily evaporate from decaying flesh.In organic chemistry, an amine group is often described as sharp, pungent, and fishy. Think of household ammonia or bad seafood, and you get the picture. Putrescine and cadaverine don’t have one amine group, though. They have two, and they’re even more likely to trigger a response in the nose.I should take a moment to point out that these aren’t the only molecules associated with death. Sulfur-containing molecules like dimethyl disulfide and dimethyl trisulfide also play a role. Putrescine and cadaverine provide a heavy, nauseating base, while sulfur compounds add a strong, rotten cabbage note that punches you in the face.Electrostatic TrapsSo how do we even smell compounds like putrescine and cadaverine? It turns out that our nasal cavity is lined with special receptors meant to sense amines. These are called Trace Amine-Associated Receptors - or TAARs for short. When you breathe in an amine, its nitrogen atom often becomes positively charged in the mucus in your nose. TAAR receptors have negatively charged pockets where the amine can fit and interact. Think of them as little electrostatic magnets. The positively charged amine is attracted to the negatively charged receptor pocket. Once they interact, your brain receives a signalFor molecules like putrescine and cadaverine, the interaction with TAARs is quite strong. These receptors may even detect them at concentrations so low that we can’t smell them. The Scent o… This is a public episode. If you would like to discuss this with other subscribers or get access to bonus episodes, visit johnknightphd.substack.com

The Myth of Bananas and BeesImagine you’re watching a movie. On the screen, some kids are walking down the sidewalk in a typical American neighborhood. They’re eating bananas, and, like all suburban kids on summer vacation, they’re laughing and having fun. Little do they know that there’s danger! Unfortunately, there’s a large honey bee colony tucked up in a nearby tree cavity. At first the bees are calm, but as soon as the kids walk under the tree with half-eaten bananas in their hands, things quickly change. The bees become agitated. Something makes them angry. Suddenly, one of the kids hears a buzz and a sudden sharp pain in an arm. Before the children can even react, bees are swarming all around them. The stings come in quick succession. Panicked screams fill the air. From across the street, a kind, elderly lady hears the commotion and comes outside to see what’s going on. Her face is at first confused, but it quickly turns to absolute fear when she sees what’s happened. Her loud cry is all you hear as the scene fades to black. It sounds like something right out of a horror movie.You might think it’s crazy, but there’s a popular myth about bananas and bees. Supposedly, if you eat or hold a ripe banana near a beehive, chemicals in the bananas will drive the bees into an aggressive frenzy. A local beekeeper might even give you a warning to never eat bananas around honey bees! Of course, it’s not really accurate. But there is a kernel of truth. I’m John Knight, by the way, and this is where I dig into the chemistry hiding in ordinary things. As always, full transcript and visuals are in the full post on my Substack.The molecule behind it all is called isoamyl acetate. It’s found in ripening fruits and special styles of beer. It even plays a role in how honey bees spread the alarm. Holding a banana near a beehive won’t switch the colony into “Attack!” mode, though. Bees are too sophisticated to rely on a single molecular trigger common in nature. Instead, they respond to context, just like we do!Love the intersection of nature, history, and chemistry? Subscribe for free to join me as I unpack the molecules shaping our world from beehive security to the smell of the ocean.Enter Isoamyl Acetate Before I continue, let’s take a moment to explain what isoamyl acetate is. First, it’s an ester, and it belongs to the family of organic molecules famous for providing rich, fruity, and floral aromas. Without esters, the world would be a pretty boring place!Like all esters, isoamyl acetate is made from two components: a five-carbon molecule called isoamyl alcohol and acetic acid - that’s the acid found in vinegar, by the way. In its pure form, this volatile ester smells remarkably like banana candy and, to some people, like ripe pears. It’s found throughout nature, too. The human nose can even detect it at tiny concentrations in the parts-per-million (ppm) range. I included a chemical structure in the full post on Substack if you’re interested.So, sure, it smells nice, but what does this molecule have to do with bees? To answer that question, we first need to talk about the time of year when bees are the most sensitive to their environment. The Late Summer DearthThat time is late summer and early fall. Depending on your location, August or September, for example. At this point, the honey bee colony is at peak population. Their comb is filled with honey for the winter season. But now food is scarce. The blooms of spring and summer are long gone. Depending on the area, there might be nothing to bring into the hive until March or April. This is called the late summer dearth. To survive, the colony needs to prioritize. The population begins declining. The queen lays eggs for winter bees. Instead of being bred for work in the warm season and living 4 to 6 weeks, these bees will be bred for endurance, surviving up to six months thanks to their higher stores of fat and protein. They will be the bees that take the colony into the new year with the queen. Those summer workers? They won’t make it past the fall.Until winter arrives, though, the colony fiercely protects its honey.Suddenly, what was acceptable earlier in the year is now prohibited. Everything is scrutinized. In the spring, a drifting bee might find its way into another hive without issue. Now, the guards shut her out. Things might even get physical. Protecting the colony and its honey is a matter of survival. And the threats have never been greater: robber bees, wasps/hornets, and honey-hungry animals can easily destroy a smaller or weaker colony before winter even arrives. Not surprisingly, this is a common time of year for bee stings. The bees are on high alert, and even beekeepers notice the change. A colony that was calm and easy to manage in the spring is now aggravated and temperamental. These environmental changes also change how bees respond to the chemical signals they receive. A 40-Compound Battle CryImagine there’s a colony of bees in a tree, except this time, a group of foreign bees shows up at the entrance. These are called robber bees. They aren’t there to pay a visit or say hello. They are there to ransack the place. The specialized guard bees instantly respond, blocking their path. Wings and hair are pulled. Physical fights break out. As a guard bee drives her stinger into an intruder, a chemical flare goes off. Honey bees have a special gland near the base of their stinger called the Koschevnikov gland. When a bee stings, this organ releases a complex cocktail of over forty compounds into the air. Isoamyl acetate is one of the most abundant and most active of these chemicals. It creates a sort of beacon, invisible to the eye, but easily detected by other bees, marking the victim for the rest of the colony’s guards. What this mixture does to the bee’s brain, though, is where things get really interesting. When other guard bees sense this defensive concoction, the chemistry in their brain begins to change. Neurotransmitters like dopamine and serotonin spike, driving up aggression and lowering the threshold for attack. At the same time, a kind of endogenous opioid response occurs - that’s just a fancy way of saying the bee’s body produces its own natural painkiller. By dulling any sensations of pain, the guard has an advantage in a fight to the death to protect the hive. And the mixture is important. The bees don’t respond to just isoamyl acetate. They respond to a mixture containing isoamyl acetate. The context is important!As a side note, anything that blocks these chemical signals will help keep the bees calm. Beekeepers often use smoke when inspecting their colonies, and this smoke effectively prevents them from “hearing” any alarm.It Used to Smell Like PearsAt this point, I think it’s important to mention that scientists only discovered the role of isoamyl acetate and other honey bee alarm pheromones in 1962. We’ve known about the ester for significantly longer, though. In fact, chemists have been synthesizing it for various purposes since the mid-19th century, back when it was all but impossible to isolate it from nature. They did this by reacting acetic acid with fusel oil - the unpleasant, toxic leftover from alcohol distillation. What they created was distinctly sweet and fruity. And that brings us to the other thing that isoamyl acetate is so strongly linked to: bananas. The connection between the fruit and the isoamyl acetate is ingrained in our modern minds. I’m willing to bet that if I had a vial of pure isoamyl acetate and removed the cap, you’d immediately think of bananas or banana-flavored candy upon sm… This is a public episode. If you would like to discuss this with other subscribers or get access to bonus episodes, visit johnknightphd.substack.com

Two Experiences, One MoleculePicture this. You’re sitting at a picnic table on a hot summer’s day. Your friend hands you a cold beer - something light and refreshing. The perfect “lawnmower beer.” You pop the cap, bring it to your mouth, and your nose is immediately hit with the smell of malted grain and a hint of sweet corn. It’s a great combination!Next, imagine you’re standing in a friend’s kitchen. There’s a pot of cabbage on the stove. Unfortunately, your friend has overcooked the greens. Perhaps they got distracted; now the kitchen is filled with an unpleasant, pungent aroma that reminds you of, well, really bad cabbage. Two different experiences. Two different scents. But both come from the same molecule!That molecule is dimethyl sulfide (or DMS). It’s the same molecule I featured in my recent post about the smell of the ocean. DMS goes way beyond the sea, however. Once you start looking for it, you can’t stop finding it! I’m John Knight, by the way, and this is where I dig into the chemistry hiding in ordinary things. As always, full transcript and visuals are on my Substack.Like what you’re reading? Subscribe to learn more about the chemistry and science in ordinary, everyday things!Culinary ChemistryHere’s a fun fact. You’ve probably smelled DMS today. You almost certainly have eaten it this week. Multiple times, in fact. And I bet that you had no idea!Here’s the basic mechanism: a lot of vegetables and fruits - beets, tomatoes, corn, asparagus, and berries - carry a special molecule, something called S-methylmethionine (or SMM). We don’t really know for sure why many plants produce it. On its own, this molecule is colorless and odorless. If you heat it, though, or let it sit too long, it breaks down into DMS. Milk and cheese do something similar, too. It’s what happened in that pot of overcooked cabbage we mentioned earlier. By cooking that cabbage too long, we’ve liberated the very same molecule that helps give the ocean its smell. Some foods get their DMS differently, however. If you read my article about the smell of the sea, you’ll remember where it comes from: phytoplankton make a protective compound, they die, and bacteria break that compound down. You might have an idea of where this is going. This whole process isn’t just limited to phytoplankton and bacteria, though. It happens in the sea creatures that live and feast on the plankton, too. Those lovely oysters you ate over the weekend? They probably had a sweet, briny aroma and taste that comes from trace amounts of DMS. In fact, a little DMS is one of the things people love about seafood. Things can go a bit too far, though. If you don’t store that seafood properly or let bacteria have their way, too much DMS will be formed, and you’ll be sending that seafood back to the kitchen.Oh, and for those of you who are into expensive delicacies, consider the truffle. No, I don’t mean the chocolate. I mean the rare, intensely earthy fungus that commands a high price. If you like the way they taste and smell, you can thank DMS! In fact, truffles owe their highly prized aroma to DMS, and truffle-hunting animals likely use DMS to help search for the fungus.That’s it for the kitchen! Remember that beer from the beginning, though? The one that seemed so perfect on a hot summer’s day? It turns out that DMS isn’t just something that sneaks into your food. Sometimes, it’s exactly what you’re paying for. The Brewer and Winemaker’s DilemmaDMS, it turns out, is a big deal in beer brewing. This really isn’t surprising considering that beer is made from malted grain, which also contains SMM - just like those fruits and vegetables I mentioned earlier! For most beer styles, however, the presence of DMS is considered a flaw. Imagine if your beer had an unusual sweet aroma mixed with cooked cabbage and may even spoiled onions. Doesn’t sound too appealing, does it? DMS is especially an issue for beers made with lightly kilned malts that contain higher amounts of SMM. Brewers make an effort to remove it by boiling the unfermented wort to drive away any DMS and by controlling fermentation conditions. There are a few exceptions, however. Some of you have probably had a cream ale or a German-style pale lager that had a hint of sweet corn. That was no accident! In these styles, a little DMS is a positive thing. Brewers of these styles typically have to adjust their brewing technique to keep just the right amount of DMS in the finished beer.Beer isn’t the only alcoholic drink where the amount of DMS can make or break the experience. Winemakers also have to worry about it. The difference for wine, however, is that most of this DMS is produced slowly over time. Just as before, a tiny amount of DMS can enhance the fruitiness and complexity of a wine. It keeps developing over time, though, even inside a sealed bottle. Store that bottle the wrong way or let the wine age too long, and you’ll probably end up thinking the winemakers kept their socks on before they stomped on the grapes. So far, everything we’ve talked about is related to smell and taste - things that we humans try to manage like brewers boiling off DMS or winemakers hoping you store that bottle correctly. We’re not the only species that notice this molecule, however. For some animals, DMS is a matter of finding food or being fooled into doing something. The Marine Scent TrailIf you’ve been near or on the ocean, you’ve seen it before: seabirds circling above the waves as if searching for something. They seem to know the best spots for foraging, as though they have some kind of hidden sight. It turns out they don’t - they just know how to use DMS as a cue! DMS levels tend to be higher in areas where zooplankton are actively grazing on phytoplankton, which also happen to be the best feeding grounds for some seabirds. And birds like the albatross and petrel are exceptionally good at detecting DMS.In a way, nature has developed an elegant system: just follow the scent trail to dinner!This ability does have a downside in our modern world, though. Remember how I mentioned earlier that DMS in the ocean is formed by phytoplankton, bacteria, and algae living their lives? They especially like to do this on floating plastic, creating a biofilm on the debris that also produces higher levels of DMS. Seabirds, in turn, are drawn to these areas to forage. Inevitably, they end up eating smaller pieces of plastic, which to them smell exactly like their normal food. This is a major driver of plastic consumption in animal species that hunt by smell, and it’s largely something we humans have caused. Bringing It All TogetherHere’s the interesting part, though. A seabird’s nose can’t tell the difference between the krill it normally eats and a floating piece of plastic that smells like that krill. We humans are no different. Our noses aren’t just sensitive to the presence of DMS. They’re sensitive to the concentration of DMS. Depending on what that concentration is, the signal we get could be a delicious dinner or something dangerous. We’ve evolved to associate high levels of DMS with danger because it’s a chemical marker for death, decay, and maybe toxicity. In tiny amounts, however, it can come across as a good thing!Think about everything we’ve covered. A little DMS in a cream ale is refreshing. Too … This is a public episode. If you would like to discuss this with other subscribers or get access to bonus episodes, visit johnknightphd.substack.com

Full post can be read at: https://johnknightphd.substack.com/IntroImagine a beautiful spring morning. The trees are stunning with new, bright green growth and colorful blossoms. Songbirds fill the air with their melodies. Above, small white clouds drift by across the blue sky.Now imagine feeling the warmth of a mug in your hands as you take in this scene. What’s in the cup? For some, it might be a nice cup of coffee. Others might prefer something herbal or fruity. Still others would drink tea - green tea perhaps!And what if that green tea actually tasted like cherry blossoms?Hello everyone! My name is John Knight. As a chemist and writer, my goal for these audio posts is to peel back the curtain on the chemistry of our modern world. Whether it’s the latest lab breakthrough or the hidden science in our daily lives, I’m here to help break down the science so that it’s clear without getting bogged down in a bunch of lab notes.Before I tell you about a very special kind of tea, just a quick reminder: if you’re listening to the audio-only version, be sure to check out the full post on my Substack. There, you’ll find a transcript of everything I’m saying and important visuals, some of which can help you “see” the chemistry I will discuss.And now, let’s talk about a tea that was rejected by the industrial tea world of Japan, although it tastes like one of the most Japanese things of all…The Fleeting Scent of SpringCherry blossoms, or sakura in Japanese, are deeply connected to the spring season. The trees are prized for their beautiful flowers that come in shades of white or pink. For many, they are a symbol of renewal and the end of winter. Tourists will often flock to areas with many cherry blossom trees. Just ask anyone who has traveled to Japan or Washington, D.C. at the beginning of spring!These trees are also a symbol of impermanence. Because they only bloom for one or two weeks on average, their beauty is but temporary, much like spring itself.In Japan, sakura are more than just ornamental flowers, however. They actually have a long history of being used in confectionery and seasonal food. Flavor-wise, they are often described as a combination of floral, vanilla, almond, and light cherry notes.This might be confusing to some who have stood close to a cherry blossom tree. If you put your nose right up to a flower, you will probably smell nothing. They are perfectly edible, but you probably won’t taste anything, either. Instead, the flavor is locked up in the flower, and a little chemistry is required to release it.So how does this work? The flowers are traditionally cured through a kind of pickling process. First, the flowers are washed, dried, and mixed with sea salt to remove moisture. This is followed by a thorough soaking in a vinegar made from plums. This not only preserves the flowers and gives them a vibrant pink color but also changes their flavor.Sunlight and SugarMany plants produce compounds called glycosides, sugar-containing molecules that also contain a non-sugar component. In addition to regulating plant growth and stabilizing pigment molecules, glycosides are also used to store potentially toxic or unstable molecules meant to protect the plant. Plants also produce special enzymes that can break down these glycosides into their individual components when needed.For cherry blossoms, one important glycoside is o-coumaric acid glucoside. That name might sound scary, but bear with me for a moment. Think of this glycoside as a large storage molecule with an important component safely secured inside. On the tree, this glycoside and its unlocking enzyme are never stored in the same place. After harvesting, washing, and curing, however, many of the cells in the flower are broken, allowing the enzyme and glycoside to interact. The enzyme then breaks the glycoside into two molecules: o-coumaric acid and glucose. From there, the rest of the chemistry can happen relatively quickly. That coumaric acid is a rigid, elongated molecule containing what chemists call a trans double bond. Normally, this would be stable, but in this case, it’s not. Add just the right amount of energy into that double bond, and it can be converted into a cis double bond, bending the molecule toward itself. It turns out that ultraviolet light (UV) from the Sun provides the necessary energy to do this. Once the geometry changes, the molecule essentially folds in on itself, placing the atoms in the right position to react and form an important molecule called coumarin.It’s coumarin that is primarily responsible for that sweet, vanilla-almond flavor and scent of sakura.But what does all of this have to do with green tea? That’s a completely different type of plant! And traditional green tea doesn’t contain fermented flower petals…It turns out that this process of making coumarin also occurs during tea production, albeit in very small amounts. For one particular variety, however, this isn’t the case.Japanese Green TeaMany people have a basic understanding of where tea comes from, though they may not be aware of the exact details. Most of the tea consumed in the world is made from the leaves of the tea tree (Camellia sinensis). That’s right - the tea tree is in the same family as all of those glossy, evergreen shrubs that produce bright, showy flowers from fall to spring every year. The processing of the leaves varies considerably from country to country and even region to region. For every producer that uses modern methods of harvesting and processing, it’s not difficult to find some who make tea using more traditional methods and maybe even entirely by hand.Although China is the biggest producer of green tea in the world, Japan also produces its share. It’s also very distinct. When making green tea, it’s important to stop oxidation by enzymes in the leaves. Otherwise, you’ll end up making black tea or oolong tea. In many green tea-producing countries, this is done by pan-frying or even roasting the leaves on a hot surface. In Japan, the leaves are steamed. This gives a completely different flavor profile.Where green teas from China might have mellow, nutty, floral, or even toasty notes, Japanese green teas are more vegetal, grassy, and full of umami flavor. Some producers intentionally shade the trees before harvest, which forces them to produce more flavorful compounds. Japanese producers also love to use machines. In fact, the entire process is mechanical. This is in stark contrast to other countries, where you can still find people harvesting and processing by hand.Japanese Tea CultivarsNow, I mentioned that most tea comes from a single type of tree, but there are many varieties of tea trees worldwide. These are often called cultivars. Think of them as the tea tree equivalent of wine grape varietals. In Japan, there are hundreds of cultivars, and the government has an official registry that recognizes over 130 of them.Despite the large number of cultivars, however, most of the green tea in Japan - roughly 75% - comes from a single cultivar called Yabukita. It’s a mainstay known for its high yields, strong umami flavor, and, perhaps most importantly, its ability to be easily processed using machines. Resilience? It’s got that in spades! Yabukita grows in almost every tea-producing region of Japan, with only the warmest and coldest areas of the country limiting its reach. If you ever drink Japanese green tea, there’s a good chance it’s prepared from Yabukita.Other cultivars exist with their own special characteristics. Saemidori trees mature early and produce a tea with lower bitterness. Okumidori, in contrast, grows better in colder parts of the country. Gokou is kind of like an umami bomb that is used to produce high-grade matcha and shaded teas. Many other cultivars are used to prepare relatively small amounts of tea.The tea that I’m focused on today, though, was mostly forgotten about outside its home region. Instead, it’s a misfit. It was considered unsuitable for large-scale production with a flavor profile that didn’t fit the standard palate of the 20th century. This cultivar is Shizu-7132, and its tea has the flavor of cherry blossoms.Shizu-7132Back in the 1960s, researchers were trying to find a new cultivar that would supplant Yabukita as the go-to cultivar in tea production. They wanted more umami flavor, stronger aroma, and greater resistance to cold and disease. They didn’t rely on artificial breeding programs, though. Instead, they harvested seeds from Yabukita trees in local tea fields and planted them. Although several interesting varieties were found over the years, many had characteristics that made them less desirable in Japan’s highly mechanical tea production system.Shizu-7132 was one of those experimental cultivars. Its strong, cherry blossom-like aroma and flavor were unique, but its leaves also proved problematic during production. Typically, steamed tea leaves are shaped into needles using rolling machines. This step helps break down the leaves and release more flavor compounds. The thicker stems of Shizu-7132 didn’t play well with rolling machines designed for standard cultivars like Yabukita.The cultivar does have its mother’s strong resistance to frost and certain diseases, though. Researchers are uncertain what the father plant is. Some even speculate that the father was a foreign variety used to make black tea. This might explain where the “un-Japanese” flavor profile comes from.Despite all its positive characteristics, Shizu-7132 was never officially registered. It didn’t fit the mold of what was considered desirable at the time. Sidelined, it was mostly relegated to local tea fields in Shizuoka. We owe its continued existence to the work of local tea farmers in that region.What Makes it SpecialTeas made from Shizu-7132 contain coumarin just like fermented cherry blossoms. In fact, the coumarin is produced in a very similar set of reactions during the tea-making process. The cultivar doesn’t just contain higher amounts of coumarin, though. It also contains other chemical compounds that make its tea special. First, Japanese green tea is famous for its umami flavor, and Shizu-7132 is no different here. It contains a relatively high amount of free amino acids, such as L-theanine and L-glutamic acid, that provide the savory, brothy flavor. They also help to balance the natural sweetness of the cherry blossom flavor and other components of the tea.Shizu-7132 also contains relatively higher amounts of compounds that are common in other plants, such as linalool and benzyl acetate. If you’re a fan of lavender or basil, you’ve definitely experienced linalool before. Benzyl acetate, easily found in jasmine flowers, is common in soaps and cosmetics. Both of these compounds contribute distinct floral notes to the tea, giving it a stronger springtime vibe. They won’t make the tea smell like jasmine or a bouquet, but they do add some complexity.When combined, all of these compounds make for a unique cup of tea!The Taste of a CupNow, anyone who really knows me can tell you how much I love tea and particularly Japanese green tea. I had heard about this sakura-like tea variety in the past, but it’s not something you’re going to find available in the United States or even in some tea shops in Japan. The tea is just not that common! This year, though, I had the chance to buy some directly from a Japanese tea maker. I quickly snagged one before it sold out. This tea is probably one of the most expensive I’ve bought ever, but the excitement of trying an unusual tea was too difficult to resist.Japanese-style brewing is rather different than standard Western-style brewing. The leaf-to-water ratio is much higher, and the water temperatures are much lower. Shorter, multiple infusions are the norm. The goal is to extract the savory, umami-rich flavor and sweet notes with minimal bitterness.For the tea I bought, I placed 5 g of leaves in a teapot and poured in 150 mL of water at 150 ℉ (that’s around 65 ℃). After one minute, I poured the tea into a cup. This first steeping was a little on the astringent side, but it wasn’t bitter. The cherry blossom flavor was present but on the light side. Overall, the tea was smooth and a bit mild.The second steeping is where the sakura notes begin to shine. Usually, the second steeping is more intense than the first. The leaves are fully hydrated, and extraction can occur even in a short amount of time. In this case, another 150 mL of water at 150 ℉ didn’t disappoint. Where the first steeping had a lighter, more subtle cherry blossom flavor and aroma, the second was more like a punch in the face. Amazingly, it achieves this without artificial flavors or flower petals. It also has endurance. After four steepings, the sakura flavor is still there.Overall, it was a unique tea to drink. It’s not something I would drink every day, but it was enjoyable!ClosingShizu-7132 is all the more interesting because it comes from a place that traditionally has valued consistency and efficiency. Compared with tea-producing regions around the world, Japanese green tea is definitely more standardized. And yet, here is a tea that is anything but consistent. Today, the consumption of traditional loose-leaf green tea in Japan is declining. As producers adapt and look for new markets outside of the country, atypical teas like Shizu-7132 are getting more attention. At times, it seems like foreigners know more about it than people living in Japan!Thanks for joining me today to hear about the interesting history and chemistry of Shizu-7132. If you enjoyed listening to or reading this, please consider sharing it with those you know or subscribing to my Substack for future content. If you want to learn more about the chemistry of tea, feel free to leave a comment and let me know! Thanks for listening! This is a public episode. If you would like to discuss this with other subscribers or get access to bonus episodes, visit johnknightphd.substack.com

The Battery ParadoxWe live in a world of batteries. They are in our smartphones, laptops, wearables, tablets, and speakers - all the devices we surround ourselves with every day. But it’s not just the things we use or wear that have batteries. They are increasingly being found in things that help us move, too. In 2025, for example, 25% of all new cars sold globally were electric vehicles, powered by rather large lithium-ion batteries. Batteries, though, are just complex chemical reactions that are neatly packaged. They can be fire and safety hazards. Making them isn’t exactly “green,” either. And what do we do with them when they no longer work? That depends on the battery type! Although lead-based batteries are recycled at nearly a 100% rate, the global recycling rate of lithium-ion batteries is significantly lower. It’s just too expensive to do. In many cases, the components are worth less than the cost of recycling. If we are going to live in a world of more and more batteries, we will need to figure out new ways to repurpose and reuse them. Recently, researchers have developed a new way to tease apart two common battery components that have proven difficult to remove from battery waste. They didn’t do this with new machines or some novel scientific theory. Instead, they did it with something you can find in a wine bottle. Hello everyone! My name is John Knight. As a chemist and writer, my goal for these audio posts is to peel back the curtain on the chemistry of our modern world. Whether it’s the latest lab breakthrough or the hidden science in our daily lives, I’m here to break things down without getting bogged down in the technical details.Before we dive deeper into today’s topic, just a quick reminder: if you’re listening to the audio-only version, be sure to check out the full post on my Substack. There, you’ll find a transcript of what I’m saying and some visuals that help you “see” some of the chemistry we're about to discuss.Now, let’s get back to the surprising solution to a long-standing problem in battery waste recycling…Chemical TwinsBefore I go into what the recent breakthrough is, we need to look at two specific battery components: cobalt and nickel. Next to lithium, these are workhorses in the battery world. If you drive a long rangeTesla, there’s probably a battery containing lithium nickel cobalt aluminum oxide (NCA for short). Other common batteries use a combination of nickel, manganese, and cobalt, known as NMC. What do these two metals do? Well, nickel acts as a kind of energy booster, increasing the energy density of a battery and enabling faster charging rates. Cobalt is more of a stabilizer. It’s used to extend the lifespan of a battery and improve its stability.When it’s time to recycle these batteries, however, there’s a big problem. Before these metals can be reused, they need to be separated. Colbalt and nickel, though, don’t separate very easily. They’re right next to each other on the periodic table and are almost chemical twins. Many people would have trouble telling the two pure metals apart!Normally, we can separate metals using a process called electrowinning. Here, you take a liquid solution of the metals and apply a specific voltage to it. By changing the voltage value, you can pull each metal out of the solution. Cobalt and nickel, though, are two elemental peas in a pod. In other words, they come out of the solution at the same specific voltage. If you try to remove cobalt from the solution, the nickel comes right along with it. Currently, cobalt and nickel are separated using something called solvent extraction. It can get the job done, but it’s rather expensive. It also uses a lot of chemicals - think of giant vats or tanks of hazardous chemicals and specialized, toxic molecules. The process isn’t universal, either. What works for one type of battery waste may not work for another. Researchers have been on the hunt for cleaner, cheaper ways to separate these two important metals for years. Recently, they found a molecule that helps tease them apart: tartaric acid. Tartaric AcidBelieve it or not, you’ve probably seen tartaric acid before, even if the name sounds alien. It’s a natural organic acid found in grapes and many other fruits. If you’ve ever used cream of tartar to make baking powder or stabilize egg whites, you’ve used a derivative of this acid. It also plays an important role in the fermentation process, contributing to the acidity and flavor of wine in particular.If any wine lovers are listening, you might recognize tartaric acid as the source of so-called wine diamonds. These are small crystals of potassium bitartrate, a salt of tartaric acid that tends to form over time at the bottom of wine bottles or on the cork. They can also form in wine barrels during storage. Some who see them for the first time think there’s broken glass in their wine, but there’s nothing to fear. These crystals are pretty harmless!Tartaric acid is actually a bit of a celebrity in organic chemistry. The famous scientist Louis Pasteur used this molecule in 1841 to discover chirality - the idea that molecules can have "handedness” and can exist as mirror images of each other. In other words, it’s the stereotype of chirality. So, it’s pretty interesting that a molecule found in everything from your morning muffin to a bottle of Merlot may also be used to solve the problem of separating cobalt and nickel. How It WorksHow did researchers use tartaric acid to separate cobalt and nickel? Well, it turns out that researchers have been trying for years to find molecules that can effectively wrap themselves around one of the metals and change its properties. Think of it as a kind of chemical hug that traps one metal so you can easily remove the other. Concentrated chloride salts showed some promise in the past, but they’re a bit harsh and require large quantities to work.To find something that will make a perfect chemical hug, researchers at John Hopkins University examined 13 different organic acids from nature, which they call bioacids. Among these acids was citric acid, the acid found in lemons, oranges, and other fruits, and lactic acid from yogurt. Of all the acids, though, tartaric acid proved uniquely suited for this role. What makes tartaric acid special is its molecular architecture. When you add tartaric acid to a solution of cobalt and nickel, two of these acid molecules work together to trap two ions of cobalt or two ions of nickel. You might be thinking, “Don’t cobalt and nickel basically act the same?” In many cases, that can be true. Conveniently, tartaric acid actually has a strong preference for nickel over cobalt. It effectively traps the nickel.By binding to nickel ions so strongly, tartaric acid makes separating the two metals using electrowinning much easier. Their voltage potentials are no longer the same because one metal has another molecule wrapped tightly around it!No expensive chemicals required. No hazardous waste or flammable solvents. Just add a bypr… This is a public episode. If you would like to discuss this with other subscribers or get access to bonus episodes, visit johnknightphd.substack.com

A DreamHas there ever been something that you've spent your whole life trying to prove - something that’s lived in the back of your mind for decades? Although Hollywood might want us to think otherwise, many chemists don’t spend their lives staring at flasks or holding beakers of colorful liquids. Their goals are the same as those of other people: get that degree, start a career, publish, and make a name for themselves along the way. Some chemists, though, really do have chemical goals in mind. For Saarland University’s Dr. David Scheschkewitz, that goal was making a single molecule, one predicted to exist years ago but seemingly impossible to make in the lab. He had been chasing it for nearly thirty years, and most of the students who joined his research group took a crack at synthesizing it - only to fail. And suddenly out of nowhere, one of his students serendipitously succeeded! That molecule isn’t just something with a lot of atoms and a long, scary name, either. It challenges ideas of how atoms form bonds, and its very core contains an element that most organic chemists never get to play with directly: silicon. Hello, everyone! My name is John Knight, and my goal for this audio post on my Substack is to share a recent breakthrough in chemistry without getting bogged down in all the lab details. Before I continue, let me just say that if you’re listening to just the audio, check out the full post on Substack. You’ll not only find a transcript of everything I’m saying but also see some nice visuals of the “impossible” chemistry I’m going to describe.Interested in more content about chemistry and science? Subscribe below!Carbon vs. SiliconSo, let’s start with a very fundamental question: why is carbon so special, and why does nature prefer carbon over silicon even though they are so close to each other on the periodic table?In many ways, carbon is the perfect element for building complex molecules. It can form multiple bond types: single, double, and triple. It easily bonds to itself and elements like hydrogen, nitrogen, and oxygen, creating the stable chains and rings that make up life. The proteins, fats, and carbohydrates in our bodies are all built on a framework of carbon atoms. But what about silicon, the second-most abundant element in the Earth’s crust? It’s right below carbon on the periodic table. It should behave similarly! In reality, it doesn’t. We don’t really find any silicon versions of organic molecules in nature. Silicon is a bigger atom, and that makes all the difference. Its bonds are longer and, in many cases, weaker compared to carbon’s. In fact, it would rather form a rigid network of single bonds with elements such as oxygen, the kind of structure you find in sand or computer chips. It generally dislikes forming double or triple bonds, too. Carbon atoms can also do something quite special. If the right number of carbons form a flat ring with the right number of bonding electrons, they can share some of those electrons across all the carbons in the ring. Chemists call this aromaticity, and it makes the molecule significantly more stable than you would expect. Ever heard of benzene, the molecule that looks like a hexagon with three lines in the middle? That’s the poster child of aromaticity! Aromaticity shows up throughout organic chemistry and biochemistry. For example, four of the amino acids that make up proteins have aromatic rings, and the fundamental building blocks of DNA - nucleotides - are also aromatic. Many compounds with strong, pleasant aromas are aromatic, as well.Forcing silicon to form stable, aromatic rings has long been a kind of holy grail of research for decades. And that’s where Dr. David Scheschkewitz’s work comes into play. A Eureka MomentSo, what exactly is this “impossible” molecule that the lab was trying to make for years? It’s not the silicon version of benzene - that was actually achieved back in 2010. No, the “impossible” molecule in this case is an all-silicon version of a molecule named cyclopentadienide. To keep things simple, imagine five atoms bonded in the shape of a pentagon with two double bonds and a negative charge. If the atoms are carbon, then you have a classic, stable arrangement that every organic chemistry student learns about. Silicon usually doesn’t like this arrangement, though. For decades, creating an all-silicon version of this classic organic molecule seemed an “impossible” hurdle to clear. Then, something different happened. You might call it a ‘eureka’ moment. Apparently, a grad student in Dr. Scheschkewitz’s lab was trying to prepare a completely different molecule when he obtained an unexpected result. The data said it contained a unique arrangement of silicon atoms that was relatively stable.Now, chemists have a few tricks to determine just what a molecule looks like. One tool they have is something called X-ray crystallography. The basic idea is simple. First, you grow a small crystal of the molecule you’re interested in. Next, you shoot X-rays at it. Why X-rays? It turns out that X-rays bounce off atoms when they hit them. If you record the pattern the X-rays make after bouncing off atoms, you can construct a 3D model of the molecule. In other words, it’s almost like a photo of how the atoms are arranged. That’s exactly what Scheschkewitz’s student did with his unexpected product. Scheschkewitz apparently almost fainted when his grad student showed him the result. What they obtained was, in fact, a unique silicon compound, and it looked very similar to cyclopentadienide: five silicon atoms in the shape of a pentagon, flat, and decidedly aromatic. The silicon atoms are all bonded to large groups of carbon atoms that help protect the central ring from unwanted reactions. It was a dream molecule come true. If you want to see what this crystal structure looked like, I’ve included the image in the text of this post!A Remarkable CoincidenceUp to this point, I’ve actually only told half of the story. If the work of the Scheschkewitz lab had been all there was, it would still be quite an achievement. In a remarkable twist, however, a Japanese research group at Tohoku University was independently chasing the same dream!While the German lab’s synthesis was serendipitous, the work of Dr. Takeazi Iwamoto’s lab took a methodical, stepwise journey to build the target molecule over several steps. Where one group made it unintentionally, the other group made it intentionally, using decades of previous attempts as a guide. Both groups agreed to mutually publish their findings side by side in the journal Science earlier this month.Interestingly, there were a couple of… This is a public episode. If you would like to discuss this with other subscribers or get access to bonus episodes, visit johnknightphd.substack.com

IntroRecently on Substack, I wrote about one of the world’s favorite indulgences: chocolate. Humans have been eating chocolate for at least four thousand years. From the moment it was introduced to the world outside Mesoamerica, it embarked on a journey where it not only became popular but also changed form. Today, chocolate is everywhere. At the store, it’s in the candy section, the baking section, the frozen food section, and even the health food section.Despite all this time spent with chocolate, we’re still surrounded by myths and misinformation about what it does to us. Is it stronger than your cup of coffee? Will it make your sex life better? Can it get you high? Can a ‘chocolate’ not even be real chocolate?Over the next few minutes, I’m gonna focus on some chemistry myths about chocolate - myths associated with a particular chemical or component found in chocolate. Let’s start with the buzz you might think you’re getting from that morning piece of chocolate. Chocolate Contains a Massive Amount of CaffeineYou might have heard someone say that eating dark chocolate is like drinking a shot of espresso. It’s an old myth about chocolate that doesn’t seem to go away. Personally, I think this particular myth comes from confusion about theobromine, which I wrote about in my last post here on Substack. Theobromine is a stimulant, too, but it just doesn’t affect the body in quite the same way as caffeine. Caffeine hits you fast with an immediate energy boost that can fade in a short time. Theobromine is milder, longer-lasting, and more focused on your heart and circulatory system.While it’s true that chocolate does contain small amounts of caffeine, it’s relatively low. Even a full bar of dark chocolate contains less caffeine than a cup of poorly prepared coffee! So, no, your hot chocolate or candy bar doesn’t contain as much caffeine as a double espresso. But will it make you fall in love?Chocolate Will Turn You Into CasnovaOne of the most common myths associated with chocolate is that it’s an aphrodisiac. In other words, it increases sexual desire, pleasure, and feelings of love. At some point, you’ve probably heard of the legendary Venetian adventurer and libertine Giacomo Casanova and his love of chocolate. He famously claimed that chocolate was not only an aphrodisiac but also second best only to champagne. He supposedly drank a special mixture of hot chocolate and spices - cinnamon, cloves, black pepper, and vanilla, among others - every day and before his romantic encounters. Even today, people sometimes drink a “Casanova-style” hot chocolate that mimics what the Venetians supposedly drink.There’s also the legend of the Aztec Emperor Montezuma, who supposedly drank 50 golden cups of chocolate per day (and maybe more). Most people today probably wouldn’t recognize Montezuma’s chocolate beverage. Modern chocolate drinks are often warm, sweet, and inviting. The chocolate drink consumed by the Aztecs was thick, cool, earthy, frothy, and even spicy. This was no smooth drink, either. Cacao powder, as we know it, didn’t exist yet! By consuming all this savory and unapologetic chocolate, Montezuma was apparently guaranteed stamina and vigor before his physical encounters.But is there any truth to this idea?Well, chocolate does contain chemicals that affect your body. The stimulant theobromine certainly increases your heart rate and boosts your energy levels, and darker chocolate can have a lot of it. When it comes to feelings of love, though, one chemical is frequently cited when it comes to chocolate: phenylethylamine - let’s call it PEA for short. PEA acts like a stimulant in our central nervous system, and it probably influences the levels of neurotransmitters such as dopamine and norepinephrine in the brain. Chocolate does have some PEA, so the thinking is that the PEA in chocolate will cause chemical changes in the brain that promote feelings of love and pleasure. Unfortunately, chocolate doesn’t have much PEA. Furthermore, your body doesn’t actually want chemicals from your food to easily influence your brain chemistry. Most of the PEA you consume from chocolate is quickly broken down before it even has a chance of reaching your brain. In fact, the association of PEA, chocolate, and love or arousal may even be based on pure speculation.So, chocolate isn’t a miracle love potion. Maybe you’ve heard, however, about how it can make you high?Chocolate Will Get You HighWhen I first heard this myth, the explanation was that chocolate contains a special chemical that reacts in the brain the same way THC from cannabis does. The person who told me this didn’t actually know the name of this chemical, but it was pretty obvious from his enthusiasm that he believed every word anyway.To talk more about this myth, I have to introduce a molecule with a rather ‘zen’ name: anandamide. This is a fatty acid derivative that targets the same brain receptors as the active ingredient in cannabis. By doing this, anandamide influences everything from our mood to even memory.Now, chocolate does contain anandamide, and high levels of this molecule are associated with reduced anxiety and improved mood. Chocolate also contains related compounds that inhibit the normal breakdown of anandamide in the brain, keeping levels elevated for longer. Sounds like this myth could be true! As with many things, though, quantity matters.On average, one finds only very small quantities of anandamide in chocolate - as much as 50 micrograms in a standard bar of dark chocolate. Put another way, if you could separate all the anandamide from the dark chocolate, it would look more like a speck or two of dust. According to some estimates, you would have to consume over 25 lbs (11 kg) of chocolate to experience any sort of high. Good luck doing that! Even if you did get high from all that effort, I don’t think you would exactly feel comfortable!So, it isn’t quite coffee. Not quite viagra or marijuana, either. That’s a lot of things that chocolate isn’t! Now let’s finish this discussion with the controversy surrounding the “black sheep” of the chocolate family, which ironically is white. I’m talking about white chocolate. White Chocolate Isn’t Real ChocolateSome people love white chocolate, and the market for it is expanding. In fact, it seems to be most popular among Millennials in the United States right now. It’s still far behind dark chocolate and milk chocolate, however. Despite its growing popularity, there’s a problem - to some chocolate purists, white chocolate is just a big lie.For devoted chocolate lovers, chocolate isn’t chocolate without the nonfat components of the cacao bean that contribute to its color and flavor. White chocolate doesn’t have any of that. Instead, confectioners usually mix up cocoa butter, milk, sugar, and maybe vanilla to produce it. Even stimulants like theobromine are mostly missing without the cacao solids.So, in the eyes of purists, white chocolate is really just sweetened, flavored cacao fat.One could argue that white chocolate is still a product of cacao beans, though. Legally, the government considers it to be chocolate and even has a strict definition for what qualifies. At worst, it’s like a cousin of normal chocolate. It even has that melt-in-your-mouth texture of chocolate thanks to the cocoa butter. If you like white chocolate, don’t let anyone shame you for it. Just tell one of those purists that you're really a botanical fat enthu… This is a public episode. If you would like to discuss this with other subscribers or get access to bonus episodes, visit johnknightphd.substack.com

The Storm that Trended AwayOn Sunday, January 18th, 2026, social media accounts in the United States began to chatter about an upcoming weather event for the following weekend. Along with intense arctic air coming down from Canada, a storm system seemed poised to develop and track across the southern United States. There was a high chance of a significant snow and ice event in areas not accustomed to severe winter weather. By Monday, computer model guidance maps were being shared across platforms such as YouTube, Facebook, and TikTok - some with scary language describing the weather as “going off the rails” or being unprecedented. The spread was so significant that even people who don’t nerd out about the weather heard of the impending storm. My neighbor even commented to me that day about how we were going to get an inch of freezing rain that weekend!To some extent, the reaction from people was a bit predictable. The storm itself did develop, but it tracked significantly farther north than some computer models showed earlier in the week. People argued about trends and which model was better or worse. Expert forecasters even found their forecasts challenged by people armed with nothing more than gut feelings or an attachment to a particular model or outcome. Others panicked, with some stores in my local area running low on certain common items before the weekend, despite the official weather forecast calling for mostly rain. If you wanted to buy some bread here, you may have been forced to buy the healthy stuff that people apparently don’t like during an emergency.Today, people can easily obtain information that was once available only to experts (if at all). For $20 a month (or even free in some cases), you can buy access to the latest weather model guidance, whether you really understand it or not. Information and data have become increasingly democratized in our world.Personally, I’ve tended to think of this as a good thing. Is there a point, however, where all of this easily accessible information becomes more noise than something useful? Have we as a society traded not knowing about something for knowing enough to be wrong? And how are the people who should know better acting? The Danger of a Little InfoAccess to information can be a good thing. News can spread more quickly. Knowledge that used to be located only in hard-to-find books can now be easily obtained on the internet. We can even access raw data, such as the information that a chemist used to characterize newly synthesized molecules. This can create issues when people don’t really understand what they are reading or seeing, though. Misformation, as we all know, can spread just as easily as information.In the late 2010s, health and wellness influencers began talking about serotonin, an important neurotransmitter and hormone in the human body that regulates everything from mood to sleep quality. Serotonin, it was argued, is mostly made in your gut, and your gut health, therefore, significantly impacts your mood and emotional well-being. Some claimed that your poor mood could be quickly reversed with special supplements or by consuming fermented foods. So-called “psychobiotics” were marketed as a kind of biohack or biological upgrade. And what do you know? People loved to hear it! Unfortunately, the fact that serotonin produced in your gut can’t cross the blood-brain barrier never became widespread knowledge on social media. Today, millions of people have submitted DNA samples to services that promise information about their ancestry and health. It’s not uncommon for people to discover that they have a genetic variant that may or may not be consequential. For example, many learn that they have a genetic variation in the MTHFR (Methyltetrahydrofolate reductase) gene. Variations in this gene can impair the body’s ability to process folate (Vitamin B9). Folate is an essential molecule for important biological processes such as cell growth or DNA synthesis. Claims have been made on social media linking these genetic variants to everything from infertility to cancer. Some have even claimed that the consumption of folate itself could be lethal to certain people. The gene was “broken,” and expensive and unproven supplements were necessary to “fix” the problem. Ironically, these genetic variants are quite common, with 50-60% of people having one of them. There is no evidence that they prevent the human body from processing folate completely. Nonetheless, mere knowledge of their existence proved problematic. Information can also make people feel like they are the experts. As crime investigation shows such as Law & Order or CSI became more popular in the 1990s and 2000s, viewers became acquainted with forensic science. Legal observers noticed over time that jurors in criminal trials began developing unrealistic expectations of forensic evidence, possibly because of these shows. A lack of definitive evidence, such as DNA and high-tech test results, could increasingly be viewed with suspicion. Why was there no DNA? Why are there no good fingerprints on the weapon? After an acquittal in the famous Casey Anthony trial, some argued that this so-called “CSI Effect” led the jury to hold the prosecution’s evidence to an impossible standard.The Expertise CrisisWhile information has become more democratized, expertise has been experiencing a crisis of its own. Where experts in the past could expect gravitas and authority to make people listen to them, now they find themselves challenged and viewed with increasing skepticism. Part of this, I think, is due to a growing trend towards anti-authority in our world. People are increasingly distrustful of governments and institutions. Society is more and more divided. Conspiracy theories spread rapidly online. More and more, people are encouraged to “do their own research” and come to their own conclusions. I also think, however, that experts collectively have done themselves no favors. Some seem to view expertise as a status to be brandished rather than something that should be demonstrated. You might even see posts on social media that go something like: “As someone who has worked many years in [X], here’s why you’re wrong about [Y]…” Sometimes, their expertise or degree is only distantly related to whatever they are talking about. The assertion of authority is what’s more important, though. For others, expertise seems to depend on absolute certainty. Saying things like, “I don’t know” or “The data is evolving” may feel more like a weakness that might cost them influence or a seat at the table. Admitting uncertainty might feel like giving the “other side” a victory. This attitude can be especially problematic when experts project certainty that later falls apart.What Can We Do As a Society?So, how do we deal with this world we find ourselves in? Some might love to go back to a time when gatekeepers controlled more information and people deferred to expertise without questioning it. We aren’t going back, though. We will never have less information available than we do today. Much like with AI, the genie can’t be put back in the bottle, so to speak. In fact, it’s still coming out! I don’t pretend to have a perfect answer to this… This is a public episode. If you would like to discuss this with other subscribers or get access to bonus episodes, visit johnknightphd.substack.com

Note from author: This is one of my shorter, more audio-focused posts that I make between my long-form articles. If you’re interested in my most recent audio post on Hangxiety, click the link below!Did you know that when you’re working out at the gym, your breath is changing the air chemistry of the room for everyone else?…You walk into the gym for the first time in the new year. Perhaps you made a New Year’s resolution, and this is your first visit - hopefully, the first of many. Or maybe you’re a regular who has been working out for years. Regardless, the scene that greets you is familiar to many.The gym is packed, full of New Year warriors ready to get fit or lose weight. It’s loud. The gym music can barely be heard above the sounds of voices and overhead TVs. Weights are dropped on the floor. People count loudly or grunt. And then there’s the air: heavy and warm with perhaps a rubbery smell…something slightly sweet, or maybe a hint of citrus or pool water.It turns out that your gym membership came with an unadvertised perk - you get to breathe in a cocktail of chemicals while you work out! Congratulations!So, what is it that you’re breathing in, and what, if anything, is it doing to you? Let’s find out!What’s In the Air…First off, let’s “clear the air,” so to speak, about chemicals. The word is often used menacingly. We live in a world where people try to limit their exposure to “chemicals,” looking for “chemical-free” solutions to problems. Social media is full of content warning about the dangers of common chemicals. It’s all part of the greater trend of people being more and more concerned about their health and what they are exposed to. The thing is, though, chemicals are everywhere. They don’t have to be artificial or unhealthy, either. The air in your house is full of chemicals. The street cafe you like to drink lattes at has its own chemicals. Even that beautiful mountain meadow in spring, with its colorful flowers and “fresh air,” is a biochemical factory.Ironically, people obsess over air quality at home or outside, but they seem to think nothing of the air quality in their gym. It’s a temple to health improvement, after all! It has to be okay!The truth is that the air in your gym, especially when it’s crowded, can have more sources of chemicals than people realize. Some are expected, while others may sound scary. Here are some of the top chemicals and particles you can find in a typical gym:* Carbon dioxide (CO2)CO2 is breathed out by humans as part of normal respiration. If more people are working out, there is significantly more CO2 in the air. This can make the air feel “heavy” and “stale.”* Fine particulate matter (PM2.5)The dust and particles are generated by movement, friction on machines, and stuff kicked up from the floors. These are 2.5 micrometers or smaller - about 30 times smaller than a human hair. - and are small enough to bypass your lungs’ natural filters.* Metabolic organic moleculesThese are molecules generated by the human body during workouts. Someone exercising can emit significantly more chemicals than a person at rest. One of these is acetone, which your body releases when you’re low on carbs and burning fat even for short periods of time. Then there’s human sweat, which has its own chemical cocktail. When molecules such as these make it into the air (and they do), they can react to create entirely new compounds.* Cleaning productsThese are kind of special to the gym environment because of how often they are used. Cleaning products usually contain a mixture of chemicals, including chlorine-based disinfectants. We might apply them to benches and surfaces at the gym, but just like a person’s sweat on a bench, they don’t stay there. Some of these chemicals can also react with those metabolic molecules mentioned previously.Cleaning products can also release a lot of scent molecules, such as limonene, which has a citrus-like smell.On a special note, some cleaning product chemicals can react to form a special class of molecules called N-chloramines and N-chloraldimines. Essentially, these molecules react with things like acetone in your breath or amino acids in sweat to produce new compounds with nitrogen-chlorine (N-Cl) bonds. Anyone who has spent a lot of time around a swimming pool knows exactly what they smell like.* Infrastructure organicsThis is just a way of saying the floors, walls, and building are giving off chemicals. You breathe in things like benzothiazole from the rubber flooring. Paint and adhesives can contain solvents called BTEX chemicals that are slowly released into the air. That vinyl mat you lie on while working out? It might release small amounts of phthalates every time you adjust your position.How Crowds Can Make It Worse…All of these molecules exist in the air of a gym, but the levels in crowded gyms might surprise people. For example, CO2 levels inside a crowded gym may be over five times that of normal air, and the humidity levels may also be quite high. Gyms often lack the best ventilation, too. There may be no open windows, and the HVAC system may struggle without you even realizing it. Gyms will cut corners to save money, as well. For example, I used to go to a 24-hour gym that would completely turn off the HVAC system at night during the summer - a fact they initially denied when they tried to tell people that gyms are naturally warmer and more humid at night!Can All of This Affect You?Now, the question you may be asking yourself at this point: do any of these things affect me? The answer is that they might. The number one effect of poor air quality at the gym is so-called “gym headaches.” This can be caused by the higher CO2 levels and other volatile organic molecules, some of which can also cause sensitivities and allergic conditions.Most importantly, for those trying to push themselves the hardest at the gym, all of this poor air quality can make your lungs work harder, resulting in a drop in available oxygen. High levels of particulate matter can even cause inflammation in the lungs and eyes. All of this leads to lower performance.These effects can be temporary, especially if they are the result of really crowded time periods or poor ventilation. Of course, working out over long periods of time in these environments can lead to chronic problems.What Can You Do?So, what can you do about your exposure to all of this? Cancel your gym membership? Buy a home gym? There’s no need to go that far! You can lower your exposure in some ways if it concerns you.* Avoiding crowdsPeople are the biggest driver of volatile chemicals in gym air, so it might be a good idea to avoid times when the gym is really crowded. Sign up for classes that aren’t so full. Go at night or in the middle of the day.* Think about where you work outYou may not be able to avoid crowds, but you can try to avoid working out in tight spaces or at a gym that is not well-maintained.* Clean surfaces and machines properlyBelieve it or not, a lot of people think they’re being “extra clean” but dousing equipment and surfaces with cleaning sprays. They’re actually doing the opposite! Those people just fill the air with chemicals. It’s better to just spray directly on the towel you’re going to use to wipe things down.* Practice good hygieneThis is entirely under your control! Do everyone … This is a public episode. If you would like to discuss this with other subscribers or get access to bonus episodes, visit johnknightphd.substack.com

Transcript:If you’ve ever woken up at 4:00 AM after a night out with a racing heart and a sense of embarrassment, you’ve probably experienced ‘hangxiety.’ In the main article I wrote on my Substack about the chemical causes of hangovers, I discussed ethanol and the metabolic crisis it creates as your body tries to remove it. That’s not the only crisis happening, though!Hangxiety is your nervous system struggling to regain balance after being disrupted by ethanol. To understand where this anxiety comes from, we need to look at the two most important neurotransmitters in your head: GABA (gamma-aminobutyric acid) and glutamate. Think of your brain like a seesaw. On one side, you have GABA. This is your ‘inhibitory’ neurotransmitter that promotes relaxation. On the other side, you have glutamate, an excitatory neurotransmitter.When you drink, ethanol acts as a massive weight on the side of GABA. It mimics the effects of GABA, telling your brain to relax and calm down. Your brain doesn’t like this disruption! It tries to balance the seesaw by cranking up its own production of glutamate.Here is the problem: ethanol is a relatively short-term guest. As your liver clears it, that ‘fake’ GABA weight disappears. Your brain can’t respond quickly enough as it’s still trying to produce glutamate. Suddenly, the seesaw slams down on the glutamate side. This puts you into a state of hyperexcitability. That is hangxiety.At the same time, alcohol triggers a massive spike in cortisol, your primary stress hormone. Usually, cortisol levels drop at night to let you rest. Ethanol keeps this from happening, leaving your body in a physical ‘fight or flight’ state long after the party is over.This chemical chaos is made worse because you’ve lost your ‘Emotional Reset’ button. Ethanol also suppresses rapid eye movement (REM) sleep, which is the stage of sleep where your brain processes emotions and files away stress. Without it, the logical part of your brain is weakened.The result is that your hyper-reactive, sleep-deprived brain begins worrying about worst-case scenarios. You aren’t just tired; you are obsessively reviewing every cringeworthy thing you might have said.If you want a mental picture of this, think of your brain like a high-end nightclub.While you were drinking, ethanol acted like a heavy-handed security team that kept everyone quiet and orderly. But when that security team suddenly leaves the building at 4:00 AM, the crowd goes wild. They pump up the volume, start a riot, and break windows. Hangxiety is like that riot. The good news? It’s temporary! Your real ‘security team’ will return as your brain chemistry returns to normal, usually within 24 to 48 hours.How severe this hangxiety is depends on the person. Some people may never experience much anxiety after a night of heavy drinking. Others will suffer considerably and may need to avoid alcohol entirely. The same advice for avoiding hangovers also applies here: * Keep yourself hydrated. * Eat something. * Use breathing exercises to calm down your heart rate. * Avoid caffeine or other stimulants. * Get plenty of restUltimately, the best thing you can do is remind yourself that the sense of doom you feel isn’t real. Your brain is in a chemical imbalance. You’re not a bad person. The world is not ending. And you probably didn’t do anything that no one else hasn’t done before. Thanks for taking the time for this separate audio deep dive. If you found it interesting, let me know in the comments!References This is a public episode. If you would like to discuss this with other subscribers or get access to bonus episodes, visit johnknightphd.substack.com