# Struggling to make sense of Km

So I have two substrates for one enzyme and I measured the product formation-> michaelis menten kinetics. The Vmax for both substrates is the same, the Km however is higher on substrate number 2. What can I conclude from this in terms of enzyme-substrate interaction?

The situation you described is entirely normal. $$V_{max}$$ is the same, so when described with a graph of initial reaction rate vs. substrate concentration, both curves will asymptotically approach the same maximum level. $$K_M$$ is higher in one than the other, so the exact shape of the curve as it goes from 0 to $$V_{max}$$ is different. As you may know, you can interpret $$K_M$$ as the substrate concentration that causes the initial reaction rate to be half of $$V_{max}$$. This means the substrate with the higher $$K_M$$ will have a shallower first half of the curve.

You can read more about these parameters and initial enzyme kinetics in Berg biochemistry or at khanacademy.

The problem with problems is that they don't come one at a time. They generally appear in clusters and sometimes they even have puppies. When one is taken care of, another pops up to take its place, and you wonder to yourself, "What did I do to deserve this?"

No, it isn't Karma-you aren't being punished-it's just life. Combine the economic woes that we can't seem to fix, issues that arise in any normal relationship, plus the unexpected upsets that besiege our day, and it's understandable that there will be times when your mood reaches a low point.

There's no quick fix or Pollyanna affirmation that's going to change things. The truth is that you have to trudge forward until you can make them change. Perhaps someone else can help, but chances are they can't take away your troubles.

A lot of people think that there's a magic bullet that could make it all better. Well, it can help you feel good when someone touches your heart, but on the other hand, if you are struggling with personal or professional problems, they can be a burden on a relationship—especially if you refuse to talk about it.

Not wanting to look bad in the eyes of the person you admire may keep you from sharing what's on your mind. Yet, if someone loves you, he or she will help you deal with your dilemmas. Talking about it can help shed light on how to get through a problem. That's also how therapy works.

You may find that brainstorming with another person or even a group will help you find new ideas to help you move forward. When you know someone has your back, that emotional support can make all the difference.

If you have been sitting on your stuff to the point where it's starting to hurt, it's time to let it out. How you choose to do it is up to you, but just keeping your pain inside will eventually lead to some kind of a meltdown.

Learning that it's okay to talk about our problems can feel a bit like a trip to the dentist. You know that the discomfort will stop once you get the tooth fixed, but you don't want to go though the process because it hurts too. And sometimes, with emotional issues, you may be embarrassed to share what's really going on for you. That's why it's so important to talk with someone who is comforting and nonjudgmental.

There will always be problems in our lives, but sometimes we don't have the capacity to handle them all by ourselves. Getting a 360-degree view is impossible when all you can see is what's going wrong. And talking with another person can give you perspective.

Just know that you can minimize your problems by discussing them with those you trust. Give your pain a voice, and let someone listen. You will be amazed at how much weight will be lifted off your shoulders.

## How a Kitty Walked 200 Miles Home: The Science of Your Cat’s Inner Compass

When a battered, skinny tortoiseshell cat wandered into a yard in Florida earlier this year, she could have been any other stray, but she was nothing of the kind. She carried an implanted microchip—one put there by a loving owner—and it revealed an intriguing story: the cat belonged to a local family, had been lost on a trip two months earlier, and had traveled 200 miles (322 km) in that time to arrive back in her hometown. Her journey inspired a spate of articles looking for an explanation for how this one cat, and a few others who’ve made similar trips, managed such impressive feats of navigation. The response from many eminent animal researchers was the same: “No idea.”

Cats’ long-distance travels are relatively rare in the scientific literature, which explains the dearth of answers—at least so far. But that’s not the case for the wanderings of sundry other creatures, especially those that migrate. Such extreme journeys—mapless, compassless, sometimes intercontinental, through places the animals have never seen before—seem nothing short of miraculous. That’s the kind of mystery that gets scientists moving, and move they have, conducting all manner of experiments over the years—locking animals in planetariums, carrying them around in dark boxes, putting them in wading pools wrapped in magnets, and destroying various bits of anatomy to see which piece was the important one. These experiments have yielded fascinating insights into the animal brain and into a world beyond human sensation.

Part of what navigating animals do is not entirely surprising. Planetarium studies reveal that some animals steer by the stars, an approach that’s comfortingly familiar to Homo sapiens but practiced by organisms as distant as the nocturnal dung beetle, which, as one recent study revealed, can roll its precious gob of poo in a straight line only as long as the Milky Way is in view. One of the most accomplished animal navigation researchers of the twentieth century, naturalist Ronald Lockley, found that captured seabirds released far from their homes could make a beeline back so long as either the sun or the stars were visible an overcast sky threw them off so much that many never made it back.

But plenty of other navigating animals are using something most humans regularly forget exists: the Earth’s magnetic field. In illustrations, the field is usually depicted as a series of loops that emerge from the south pole and reenter the planet at the north pole, and extend out to the edges of our atmosphere, sort of like a cosmic whisk. Our compass needles are designed to align with the field, and in the last few decades it’s become clear that numerous animals can find their way by feeling some of its various field.

Sea turtles, for example, don’t use the field simply to tell north from south. According to experiments led by Kenneth Lohmann, a professor of biology at University of North Carolina, Chapel Hill, they are actually born knowing a magnetic map of the ocean. Newly hatched loggerhead turtles in the populations Lohmann studies journey 8,000 miles (12,900 km) from their hatching beaches around the Atlantic Ocean to reach feeding areas, and if they don’t keep right on track, they do not survive. Lohmann learned early on that the turtles could sense the Earth’s magnetism: he found that hatchlings from the Florida coast, which normally swim east in darkness to start their migration, swam the other way when they were put in a magnetic field that reversed north and south. That got Lohmann thinking that the turtles’ long-distance navigation might be linked to their being able to respond to whorls and quirks in the planetary field they encounter along the way.

To study this, he and colleagues collected baby sea turtles a few hours before they would have left the nest on their own and put them in pools surrounded by magnetic coils. The coils were designed to reproduce the Earth’s magnetic field at specific points along the turtles’ migration. Reliably, the young turtles oriented themselves and swam in the direction relative to the magnetic field that, had they been in the open ocean, would have kept them on course. Lohmann has tested this with 8 different locations along their route, and in each case the turtles head in just the direction required to get them to their destination. The turtles may not know where they are in any big-picture way—as Lohmann says, they may not see themselves as blinking spots on a map—but they have inherited a sense that should they feel a particular pull from the magnetic field, well, better take a right.

The list of animals that navigate by magnetism, suspected and confirmed, is long, and includes a few mammals in addition to migrating birds and turtles. But our understanding of the mechanism behind that ability is sketchy: sea turtles tend to be threatened or endangered species, so scientists can study only their behavior, not their brains, and even in animals in which such work is possible, it’s hard to tell what parts of the brain and other physical structures are involved.

Pigeons, one of the most intensively studied animal navigators, show how complex a question this is. One leading theory holds that iron-containing cells in the beak send magnetic information to the brain, since destroying the nerve that carries sensation from beak to brain seems to disrupt pigeons’ navigation. However, last year it emerged that those beak cells are not neurons capable of sending messages, as had been supposed they appear to be immune cells, throwing the beak theory into confusion. Another school of thought suggests that the magnetic field may be affecting chemical reactions in the birds’ eyes, literally changing the way the world looks when they are oriented in a particular direction. And David Dickmann, a professor at the Baylor College of Medicine whose primary work is on a magical ability we humans often forget we have—our ability to sense gravity and constantly adjust our position to keep our balance—has lately published work showing that pigeons may have a magnetic-field sensor in their inner ears. No one knows yet which of these mechanisms, or what combination of them, is at the root of the pigeon’s powers.

And lest we forget, the magnetic field is far from the only thing out there that navigating animals can sense and humans cannot. The heads of sharks are threaded with jelly-filled tubes, called the ampullae of Lorenzini, that allow them to detect extremely faint electric currents and may help them with navigation. Scents in the air, at concentrations far below human perception, are perceivable to numerous creatures that may use them to steer (in fact, pigeons that cannot smell seem oddly lost, even with their magnetic abilities intact). Bees can see patterns in sunlight invisible to the naked human eye and can use them to find their way.

We can see only the outcomes, never the workings, of whatever evolved systems animals use to orient themselves across hundreds or thousands of miles. But that hasn’t stopped us from working to understand the feats of migrating reptiles, homing pigeons, and even lost pets. With reminders like the odyssey of the Florida housecat, how can we stop?

## A Cognitive Limitation

It shouldn’t be too surprising that humans have great difficulty with large numbers. While living and evolving in a so-called state-of-nature, our paleolithic ancestors had no need (i.e. no environmental pressures) to develop such a capacity. Back then, and prior to the advent of a formal numbering system, early humans only really needed to get a basic sense of small batches of quantities, like the number of people in the clan, or how many animals might occupy a certain area.

These days, however, we’re surrounded by large numbers. Like, stupid large numbers. We’re told that there are 7-billion humans on Earth, that there are 300-billion stars in the Milky Way, and that there may be upwards of 70-sextillion stars in the Universe (that’s 10 21 , or a 1 with 21 zeros behind it). Good luck trying to wrap your head around what such a quantity actually means or signifies.

## What does Twist Bioscience do, and what are its strengths?

Twist Bioscience manufactures and sells custom DNA sequences. That in and of itself is a decades-old capability, but churning out very large volumes of DNA sequences with low error rates at low cost is potentially revolutionary. In the first nine months of 2018 the company generated 73% of revenue from R&D services and industrial biotech customers, 25% from academic customers, and 2% from agricultural biotech customers.

The company's technology platform is based on a novel approach that uses a silicon chip with tiny wells carved in it. The chemical building blocks of DNA are combined in the wells, then assembled into precise DNA sequences. Compared to traditional methods routinely used in life sciences labs, Twist Bioscience's approach can reduce the amount of expensive reagents needed by a factor of 1 million, and increase the number of genes that can be synthesized by a factor of up to 9,600.

Simply put, no company is better at writing DNA today than Twist Bioscience. Case in point: The company actually sells synthetic DNA to four of its top competitors.

Image source: Getty Images.

## METHODS

This study was conducted at a research-intensive institution in the Southwest United States. To generate our collection of syllabi, we used the university’s course catalog to identify undergraduate biology courses offered in the spring 2019 semester at the institution. On the course catalog page, instructors have the opportunity to upload a copy of the syllabus for the course they are teaching, which can be accessed by staff and students. Our initial collection of syllabi contained 39 syllabi for in-person undergraduate biology (BIO) courses, which is ∼28% of all biology courses offered at the institution in spring 2019.

To prevent oversampling syllabi from a single instructor, the data set was reviewed to identify instructors teaching multiple courses. If an instructor had more than one syllabus in our data set, one syllabus was selected at random. The final data set consisted of 75 course syllabi from unique instructors. This represents ∼58% of all instructors teaching in-person biology courses during the spring 2019 semester in this department at this institution.

Because the syllabi collected are publicly available data at the institution, Institutional Review Board approval was not necessary for this study. Additionally, before analysis, we de-identified all course instructors to ensure privacy and confidentiality (e.g., replaced instructor name with an ID number). Any quotes that are used have been edited to preserve content while maintaining syllabus anonymity.

## Struggling to make sense of Km - Biology

I have a confession to make. But first, I want you to make a little confession to me. In the past year, I want you to just raise your hand if you've experienced relatively little stress. Anyone?

How about a moderate amount of stress?

Who has experienced a lot of stress? Yeah. Me too.

But that is not my confession. My confession is this: I am a health psychologist, and my mission is to help people be happier and healthier. But I fear that something I've been teaching for the last 10 years is doing more harm than good, and it has to do with stress. For years I've been telling people, stress makes you sick. It increases the risk of everything from the common cold to cardiovascular disease. Basically, I've turned stress into the enemy. But I have changed my mind about stress, and today, I want to change yours.

Let me start with the study that made me rethink my whole approach to stress. This study tracked 30,000 adults in the United States for eight years, and they started by asking people, "How much stress have you experienced in the last year?" They also asked, "Do you believe that stress is harmful for your health?" And then they used public death records to find out who died.

Okay. Some bad news first. People who experienced a lot of stress in the previous year had a 43 percent increased risk of dying. But that was only true for the people who also believed that stress is harmful for your health.

People who experienced a lot of stress but did not view stress as harmful were no more likely to die. In fact, they had the lowest risk of dying of anyone in the study, including people who had relatively little stress.

Now the researchers estimated that over the eight years they were tracking deaths, 182,000 Americans died prematurely, not from stress, but from the belief that stress is bad for you.

That is over 20,000 deaths a year. Now, if that estimate is correct, that would make believing stress is bad for you the 15th largest cause of death in the United States last year, killing more people than skin cancer, HIV/AIDS and homicide.

You can see why this study freaked me out. Here I've been spending so much energy telling people stress is bad for your health.

So this study got me wondering: Can changing how you think about stress make you healthier? And here the science says yes. When you change your mind about stress, you can change your body's response to stress.

Now to explain how this works, I want you all to pretend that you are participants in a study designed to stress you out. It's called the social stress test. You come into the laboratory, and you're told you have to give a five-minute impromptu speech on your personal weaknesses to a panel of expert evaluators sitting right in front of you, and to make sure you feel the pressure, there are bright lights and a camera in your face, kind of like this.

And the evaluators have been trained to give you discouraging, non-verbal feedback, like this.

Now that you're sufficiently demoralized, time for part two: a math test. And unbeknownst to you, the experimenter has been trained to harass you during it. Now we're going to all do this together. It's going to be fun. For me.

I want you all to count backwards from 996 in increments of seven. You're going to do this out loud, as fast as you can, starting with 996. Go!

Go faster. Faster please. You're going too slow.

Stop. Stop, stop, stop. That guy made a mistake. We are going to have to start all over again.

You're not very good at this, are you? Okay, so you get the idea. If you were actually in this study, you'd probably be a little stressed out. Your heart might be pounding, you might be breathing faster, maybe breaking out into a sweat. And normally, we interpret these physical changes as anxiety or signs that we aren't coping very well with the pressure.

But what if you viewed them instead as signs that your body was energized, was preparing you to meet this challenge? Now that is exactly what participants were told in a study conducted at Harvard University. Before they went through the social stress test, they were taught to rethink their stress response as helpful. That pounding heart is preparing you for action. If you're breathing faster, it's no problem. It's getting more oxygen to your brain. And participants who learned to view the stress response as helpful for their performance, well, they were less stressed out, less anxious, more confident, but the most fascinating finding to me was how their physical stress response changed.

Now, in a typical stress response, your heart rate goes up, and your blood vessels constrict like this. And this is one of the reasons that chronic stress is sometimes associated with cardiovascular disease. It's not really healthy to be in this state all the time. But in the study, when participants viewed their stress response as helpful, their blood vessels stayed relaxed like this. Their heart was still pounding, but this is a much healthier cardiovascular profile. It actually looks a lot like what happens in moments of joy and courage. Over a lifetime of stressful experiences, this one biological change could be the difference between a stress-induced heart attack at age 50 and living well into your 90s. And this is really what the new science of stress reveals, that how you think about stress matters.

So my goal as a health psychologist has changed. I no longer want to get rid of your stress. I want to make you better at stress. And we just did a little intervention. If you raised your hand and said you'd had a lot of stress in the last year, we could have saved your life, because hopefully the next time your heart is pounding from stress, you're going to remember this talk and you're going to think to yourself, this is my body helping me rise to this challenge. And when you view stress in that way, your body believes you, and your stress response becomes healthier.

Now I said I have over a decade of demonizing stress to redeem myself from, so we are going to do one more intervention. I want to tell you about one of the most under-appreciated aspects of the stress response, and the idea is this: Stress makes you social.

To understand this side of stress, we need to talk about a hormone, oxytocin, and I know oxytocin has already gotten as much hype as a hormone can get. It even has its own cute nickname, the cuddle hormone, because it's released when you hug someone. But this is a very small part of what oxytocin is involved in.

Okay, so how is knowing this side of stress going to make you healthier? Well, oxytocin doesn't only act on your brain. It also acts on your body, and one of its main roles in your body is to protect your cardiovascular system from the effects of stress. It's a natural anti-inflammatory. It also helps your blood vessels stay relaxed during stress. But my favorite effect on the body is actually on the heart. Your heart has receptors for this hormone, and oxytocin helps heart cells regenerate and heal from any stress-induced damage. This stress hormone strengthens your heart.

And the cool thing is that all of these physical benefits of oxytocin are enhanced by social contact and social support. So when you reach out to others under stress, either to seek support or to help someone else, you release more of this hormone, your stress response becomes healthier, and you actually recover faster from stress. I find this amazing, that your stress response has a built-in mechanism for stress resilience, and that mechanism is human connection.

I want to finish by telling you about one more study. And listen up, because this study could also save a life. This study tracked about 1,000 adults in the United States, and they ranged in age from 34 to 93, and they started the study by asking, "How much stress have you experienced in the last year?" They also asked, "How much time have you spent helping out friends, neighbors, people in your community?" And then they used public records for the next five years to find out who died.

Okay, so the bad news first: For every major stressful life experience, like financial difficulties or family crisis, that increased the risk of dying by 30 percent. But — and I hope you are expecting a "but" by now — but that wasn't true for everyone. People who spent time caring for others showed absolutely no stress-related increase in dying. Zero. Caring created resilience.

And so we see once again that the harmful effects of stress on your health are not inevitable. How you think and how you act can transform your experience of stress. When you choose to view your stress response as helpful, you create the biology of courage. And when you choose to connect with others under stress, you can create resilience. Now I wouldn't necessarily ask for more stressful experiences in my life, but this science has given me a whole new appreciation for stress. Stress gives us access to our hearts. The compassionate heart that finds joy and meaning in connecting with others, and yes, your pounding physical heart, working so hard to give you strength and energy. And when you choose to view stress in this way, you're not just getting better at stress, you're actually making a pretty profound statement. You're saying that you can trust yourself to handle life's challenges. And you're remembering that you don't have to face them alone.

## Arithmetic of compassion

More tragedy doesn’t always elicit more empathy it can counterintuitively bring about apathy. The magnitude of the death toll can cause some people to become less compassionate, says Paul Slovic, a psychologist at the University of Oregon, due to a phenomenon he calls “psychic numbing.”

In a 2014 study that looked at charitable giving, Slovic found that people’s concern for those in distress didn’t increase as the number of needy cases did. “Our feelings are very strong for one person in danger, but they don’t scale up very well,” he says. “If there are two people, you don’t feel twice as bad. Your attention gets divided, and you don’t have as strong an emotional connection.”

Slovic suggests our brains evolved this way as a coping mechanism. Millions of years ago, humans weren’t even aware of distant people’s plagues, conflicts, or disasters, so we naturally focused on protecting ourselves, our families, and our small communities.

In addition, the long duration of the pandemic, combined with the absence of a clear end, can dull people’s sense of shock, other experts say. Simply put, some brains have gotten used to hearing about COVID-19 deaths to the point where higher numbers no longer register emotionally.

If you think about people living in a war zone, the kind of thing that was once appalling
becomes normal.

“The human species is really adaptive,” says Weber, who studies how people make decisions when facing risks and uncertainty. “If you think about people living in a war zone, the kind of thing that was once appalling becomes normal. Our brain neurons fire when something changes, but they stop after a while. If you’re in a room with a bad smell, you eventually stop noticing it.”

This feeling of being in the middle of a crisis has prevented us from mourning and creating the types of memorials that help us connect with victims, such as the inscribed names of loved ones that people can visit and touch the September 11 Memorial in New York City, or the Vietnam Veterans Memorial in Washington, D.C. Those rituals usually are created after an event has occurred or when a crisis has ended, says Yu-Ru Lin, an associate professor at the School of Computing and Information at the University of Pittsburgh in Pennsylvania.

In her research, Lin has documented people’s emotional reactions on social media to “short-term and shocking” events or natural disasters, such as this study about the 2015 terrorist attacks in Paris. She has found that being able to express a surge of emotions after the defined event helped people cope.

Viral memes that often circulate on social media following certain tragedies can also spark emotional responses that resonate, such as how the horrific image of a Syrian refugee toddler who washed ashore on a Turkish beach in 2015 led to record donations to help victims of Syria’s civil war.

Having an actual place to go where the tragedy occurred and perhaps even bring flowers has also been key to processing grief. “When I studied the [2013] Boston Marathon bombing, people had gatherings and ceremonies after the event and would even have an anniversary event to remember these losses,” Lin says.

By contrast, the coronavirus is everywhere, and people don’t have a way to process their amorphous, long-haul grief. No single iconic photo that conveys the gravity of the pandemic has emerged and prompted mass indignation. Due to restrictions on social gatherings, many family members of victims cannot even attend funerals, let alone visit memorials that haven’t been built.

A common stress response to unpleasant thoughts is to deny them or simply shut them out.

There’s also the fact that while the death toll is high, most people in the U.S. haven’t yet experienced the loss of a loved one, and that makes a big and grave number feel more remote.

“These impacted communities are quite invisible to many people, unless you know of someone in your social network,” says Lin. “For others, the loss is more ambiguous,” like the interruptions to normal life or not being able to visit people in the hospital.

Another reason some people are tempted to check out emotionally is that humans struggle with tolerating the uncertainty of whether COVID-19 will surge in the winter or whether and when an effective and safe vaccine will become available. A common stress response to unpleasant thoughts is to deny them or simply shut them out.

“It calms us down,” says Mardi Horowitz, a psychiatrist at the University of California, San Francisco, who studies grief and trauma.

## Biologists create the most lifelike artificial cells yet

No biologist would mistake the microscopic "cells" that chemical biologist Neal Devaraj and colleagues are whipping up at the University of California, San Diego (UCSD), for the real thing. Instead of the lipid membrane that swaddles our cells, these cell mimics wear a coat of plastic—polymerized acrylate. And although they harbor a nucleuslike compartment containing DNA, it lacks a membrane like a real cell's nucleus, and its main ingredients are minerals found in clay.

Yet these mock cells are cutting-edge, "the closest anyone has come to building an actual functioning synthetic eukaryotic cell," says synthetic biologist Kate Adamala of the University of Minnesota in Minneapolis, who was not part of the work. Like real cells, the spheres can send protein signals to their neighbors, triggering communal behavior. And as Devaraj and his team revealed in a preprint recently posted on the bioRxiv site, the "nucleus" talks to the rest of the cell, releasing RNA that sparks the synthesis of proteins. The artificial nuclei can even respond to signals from other cell mimics. "This may be the most important paper in synthetic biology this year," Adamala says.

Synthetic biologists have big dreams for artificial cells. Compared with simpler synthetic structures, such as the liposomes that are already being used to transport certain drugs in the body, they could be more sensitive to their environment and perform a greater variety of jobs. In the future, artificial cells may deliver drugs more precisely to their targets, hunt down cancer cells, detect toxic chemicals, or improve the accuracy of diagnostic testing. Arrays of interacting synthetic cells could form artificial tissues and smart materials that sense and adapt to their surroundings. As scientists struggle to devise cell facsimiles, they may also learn more about how life originated and overcame some of the same engineering challenges.

Performing some functions of a cell, such as manufacturing proteins and duplicating DNA, in isolation won't be enough. "If we are going to develop synthetic materials, we need to have the individual units cooperate," Devaraj says. Researchers had already devised synthetic cells that can communicate with each other by exchanging relatively small molecules such as sugars and hydrogen peroxide. However, Devaraj notes, many of the molecular signals in our bodies, including the hormone insulin and the cytokines that fire up our immune cells, are proteins and are typically much larger.

To make a more cell-like cell mimic, Devaraj and his colleagues stepped away from nature. Their latest pseudocells "look a little bit like natural cells, but they are made of completely artificial materials," says co-author Henrike Niederholtmeyer, a synthetic biologist at UCSD. The researchers used a silicon chip with microscopic fluid-filled channels to extrude tiny droplets that contain raw materials such as DNA, minerals from clay, and individual acrylate molecules. Ultraviolet light and chemical treatment spurred a porous membrane to form around each droplet. At the same time, the minerals and DNA inside the droplet condensed into a gel with the texture of a soft contact lens, creating a version of the nucleus, Devaraj says.

The result was a cell replica with new powers of communication. For some experiments, Devaraj's team equipped the nuclei of the cell mimics with DNA that encodes green fluorescent protein (GFP). They also outfitted some of their creations with a trap, a sticky stretch of DNA that captures GFP molecules. By adding a mixture of enzymes and other necessities for protein synthesis, such as ribosomes, to the fluid surrounding the ersatz cells, the investigators switched them on. This molecular machinery crossed the porous membrane, read the genetic information in the nucleus, and sparked synthesis of GFP.

The scientists then mixed cell mimics designed to produce GFP with receiver cells that couldn't make the marker themselves but did harbor the DNA trap for GFP. After 2 hours, receiver cells that were adjacent to senders were aglow, indicating that they had picked up the GFP message from neighbors. In a similar experiment, the team crafted mimics that released a different protein signal that switches on GFP synthesis in recipients. Like real cells, these cell mimics could communicate with nearby counterparts and stimulate them to produce proteins.

The imitation cells also displayed another lifelike attribute called quorum sensing, in which cells' behavior changes once they become abundant enough. This ability came to light when researchers tested solutions containing different densities of cell mimics, all of which released the activator of GFP synthesis and could make GFP as well when triggered. If a solution contained only a few of the synthetic cells, almost none turned green. After they reached a threshold density, however, nearly all of them lit up. Before they can begin to make GFP, the artificial cells apparently need to absorb a certain minimal amount of the activating protein from their surroundings.

The cell mimics are tough, remaining undamaged after 2 years in a freezer. Their durability may make them good environmental sensors—one of several applications for the structures that the UCSD team is now exploring. And Devaraj and colleagues hope to equip these or other synthetic cells with the ability to grow and divide.

Bioengineer Yuval Elani of Imperial College London is impressed with the design of the cell mimics. "The concept of using these nonbiological components is a powerful one." But the artificial components could also be a drawback for applications, he notes, if they prove incompatible with "natural" components making up artificial cells that other researchers are developing.

## Biohacker: Meet the people 'hacking' their bodies

Biohackers want to make their bodies and brains function better by "hacking" their biology. The BBC's Victoria Derbyshire programme meets the people who are inserting technology under their skin, adopting extreme diets and trying to change their DNA.

Liviu Babitz wants to create new human senses. Touch his chest and you feel his first effort, a vibration every time he faces north. If some animals can already sense direction, why shouldn't we?

He can feel north because of an electronic implant on his chest called the "North Sense". It includes a compass chip, Bluetooth connection and is attached to the skin with two titanium bars like a piercing.

Liviu, 38, is the chief executive of his own company, Cyborgnest, which designed the implant. He sees this as the first step in an entirely in-built navigation system and hopes to end what he calls "generation screen".

"You walk on the street staring at your phone. You want to get somewhere but you have no idea what's happened in the world around you because all you did was stare at the screen on the way," he says.

"Imagine if you didn't need it, you could navigate the world exactly like a bird and you would know exactly where you were all the time - blind people could navigate."

His invention is highly unusual but actually seems tame in comparison with Rich Lee, a 40-year-old cabinet-maker from St George, in the US state of Utah.

Rich is a grinder - a biohacker that does extreme body modification. In his fingers, he has magnets and two near-field communication (NFC) chips that can be programmed to link to websites or open car doors, among other tasks.

He has a biotherm chip in his forearm, which can constantly monitor body temperature (but are usually used in pets), and headphone implants right in his ears.

He has also attempted "Crispr" - probably the most extreme and controversial kind of biohacking, a technique used by scientists to target and edit your genes.

While scientists are still working out the limits and dangers, Rich is experimenting at home and admits if he gets it wrong, he could kill himself.

"We've got all this genetic engineering knowledge and what I'm backing is the concept of being able to change your genes or get genetic modification like you would get a tattoo," he says.

"I want to see a biologically fluid society where people can just augment these things."

This home biohacking can of course go very badly wrong - Rich pulls up his trouser legs to reveal a selection of scars from implanted shin guards that got so swollen they had to be removed, which he did with pliers and no painkillers.

Luke Robert Mason, director of the Virtual Futures organisation, says there is a great deal of excitement around biohacking but "we are a long way from radically altering the human body in the sorts of ways they evangelise".

"What we see today are the first steps by a brave group of pioneers. Today's reality is a lot more experimental (and painful) than is often communicated to the public.

"There is a lot that can be learned from the outcome of their self-experimentation. Some have even argued that biohackers might increasingly be responsible in helping the advancement of wearables and wellness technologies."

There are biohackers working with far less extreme - though still very experimental - methods.

Corina Ingram-Noehr, 33, an American events organiser living in Berlin, has a daily ritual involving technology, diet and more than 20 different vitamin supplements to try to keep in peak physical condition.

Next to a cupboard that resembles a chemist's shop, she also has a Power Plate, which vibrates from 30 to 50 times a second to make her exercise more effective. And while vibrating, she uses an infrared light in an attempt to build collagen in her skin.

Corina can also be found walking the freezing cold streets of Berlin with bare legs. She calls this her cheap biohack version of cryotherapy - or cold therapy - and admits the "cops on her street" think it is hilarious.

She discovered biohacking when recovering from a serious concussion that left struggling to speak. Her boss recommended trying medium chain triglycerides (MCT) oil, which helped her "head turn on" and acted as something of a gateway drug for biohacking.

"It opened the floodgates and I was like, 'If this works, this one little thing works so well - like, what else can I do?'

"Biohacking for me is taking control of your own biology. It's taking shortcuts to get to a place that you want to be - so shortcutting your health. That's kind of how I think of it at least."