April 22, 2013
Over the past few decades, researchers have developed biofuels derived from an remarkable variety of organisms—soybeans, corn, algae, rice and even fungi. Whether synthesized into ethanol or biodiesel, though, all of these fuels suffer from the same limitation: They have to be refined and blended with heavy amounts of conventional, petroleum-based fuels to run in existing engines.
Though this is far from the only current problem with biofuels, a new approach by researchers from the University of Exeter in the UK appears to solve at least this particular issue with one fell swoop. As they write today in an article in Proceedings of the National Academy of Sciences, the team has genetically engineered E. coli bacteria to produce molecules that are interchangeable to the ones in diesel fuels already sold commercially. The products of this bacteria, if generated on a large-scale, could theoretically go directly into the millions of car and truck engines currently running on diesel worldwide—without the need to be blended with petroleum-based diesel.
The group, led by John Love, accomplished the feat by mixing and matching genes from several different bacteria species and inserting them into the E. coli used in the experiment. These genes each code for particular enzymes, so when the genes are inserted into the E. coli, the bacteria gains the ability to synthesize these enzymes. As a result, it also gains the ability to perform the same metabolic reactions that those enzymes perform in each of the donor bacteria species.
By carefully selecting and combining metabolic reactions, the researchers built an artificial chemical pathway piece-by-piece. Through this pathway, the genetically modified E. coli growing and reproducing in a petri dish filled with a high-fat broth were able to absorb fat molecules, convert them into hydrocarbons and excrete them as a waste product.
Hydrocarbons are the basis for all petroleum-based fuels, and the particular molecules they engineered the E. coli to produce are the same ones present in commercial diesel fuels. So far, they’ve only produced tiny quantities of this bacterial biodiesel, but if they were able to grow these bacteria on a massive scale and extract their hydrocarbon products, they’d have a ready-made diesel fuel. Of course, it remains to be seen whether fuel produced in this way will be able to compete in terms of cost with conventional diesel.
Additionally, energy never comes from thin air—and the energy contained within this bacterial fuel mostly originates in the broth of fatty acids that the bacteria are grown on. As a result, depending on the source of these fatty acids, this new fuel could be subject to some of the same criticisms leveled at biofuels currently in production.
For one, there’s the argument that converting food (whether corn, soybeans or other crops) into fuel causes ripple effects in global food market, increasing the volatility of food prices, as a UN study from last year found. Additionally, if the goal of developing new fuels is to fight climate change, many biofuels fall dramatically short, despite their environmentally-friendly image. Using ethanol made from corn (the most widely used biofuel in the U.S.), for example, is likely no better than burning conventional gasoline in terms of carbon emissions, and maybe actually be worse, due to all the energy that goes into growing the crop and processing it info fuel.
Whether this new bacteria-derived diesel suffers from these same problems largely depends upon what sort of fatty acid source is eventually used to grow the bacteria on a commercial scale—whether it would by synthesized from a potential food crop (say, corn or soy oil), or whether it could come from a presently-overlooked energy source. But the new approach already has one major advantage: Just the steps needed to refine other biofuels so they can be used in engines use energy and generate carbon emissions. By skipping these steps, the new bacterial biodiesel could be an energy efficient fuel choice from the start.
April 15, 2013
If you take just a sip of beer, and moments later—before you’ve had close to enough alcohol to get intoxicated, perhaps even before the beer has hit your stomach—feel a distinctly pleasurable sensation, it might not be strictly due to subtle aromas that result from the beverage’s blend of malt, hops and yeast. The cause of your pleasure might be due to tangible changes in your brain chemistry—specifically, a surge in levels of the neurotransmitter dopamine.
Scientists have long known that part of the reason alcohol induces pleasure is that intoxication leads to the release of dopamine, which is associated with the use of other drugs (as well as sleep and sex) and acts as a reward for the brain. But new research suggests that, for some people, intoxication isn’t necessary: Simply the taste of beer alone can provoke a release of the neurotransmitter within minutes.
A group of researchers led by David Kareken of Indiana University came to the finding, published today in the journal Neuropsychopharmacology, by giving tiny amounts of beer to 49 adult men and tracking changes in their brain chemistry with a positron emission tomography (PET) scanner, which measures levels of various molecules in the brain. They chose participants with varying levels of typical alcohol consumption—from heavy drinkers to near-teetotalers—and even tested them with the beer they reported that they drank most frequently. Because they used an automated system to spray just 15 milliliters (about half an ounce) of beer on each participant’s tongue over the course of 15 minutes, they could be sure that any changes in brain chemistry wouldn’t be due to intoxication.
The effect was significant. When the men tasted the beer, their brains released much higher levels of dopamine within minutes, compared to when the same test was conducted on the subjects at other times with both water and Gatorade. They were also asked to rate how much they “craved” a beer at several points during the experiment, and perhaps less surprisingly, their cravings were generally much higher after tasting beer than Gatorade or water.
Interestingly, the amount of dopamine release per person wasn’t random. People who had a family history of alcoholism (as reported on a survey) showed notably higher dopamine levels after tasting beer as compared to others. But participants who were heavy drinkers but didn’t have the family history had merely average dopamine levels.
The researchers believe this could be a clue as to why some people are predisposed towards alcoholism—and why it’s more difficult for them stay on the wagon if they’re trying to quit. The immediate release of dopamine from just a taste of beer would likely serve as a powerful mechanism that drives their cravings, and a tendency towards experiencing this burst of pleasure might be genetically inheritable. This could be part of the reason that people with a family history of alcoholism are twice as likely to experience alcoholism themselves.
Previous work has shown that in people with alcoholic tendencies, stimuli that are merely associated with drinking (such as the smell and sight of a alcoholic drinks or a bar) can trigger dopamine release in the brain. This work shows that for an unlucky group predisposed to suffering from alcoholism, bursts of dopamine can occur even if they’re not heavy drinkers—and it only takes a sip for the pattern to start.
April 8, 2013
If you suffered from a medical ailment in the year 1900, your treatment options were varied: You could take everything from Dr. Tutt’s Liver Pills to Hollister’s Golden Nugget Tablets, Dr. Sawen’s Magic Nerving Pills or Dr. Comfort’s Candy-Covered Cathartic Compound.
Of course, their titles notwithstanding, the creators of these pills weren’t always doctors, and the medicines certainly hadn’t gone through the controlled randomized trials we have today to ensure safety—they could contain ingredients that were ineffective, or worse, toxic. In many cases, their proprietors might not have known what they were even putting in these so-called “snake oil” medicines (a term that likely stemmed from the sale of actual snake oil to supposedly treat joint pain).
But now, at least, we do. Mark Benvenuto, a chemist at University of Detroit Mercy, recently led a research group that chemically analyzed several dozen patent medicines dating to the late 1800s and early 1900s from the Henry Ford Museum‘s collections. Their findings, which they presented yesterday at the annual meeting of the American Chemical Society in Atlanta, were that many of the pills, powders and ointments tested had beneficial ingredients like calcium and zinc—but that others had toxins such as lead, mercury and arsenic.
“Back in the day, this was a very trial-and-error kind of field,” Benvenuto said in an interview. “The stuff that we think of as dangerous now, though it was dangerous, was as cutting-edge as they had at the time.”
The researchers figured out what was in the historical medicines via a pair of methods. For the solid pills and powders, they used X-ray fluorescence, in which a substance is bombarded with X-rays and the particles emitted as a result indicate the material’s composition. For the liquid ointments, they used nuclear magnetic resonance testing, which relies on the electromagnetic emissions of a material’s nuclei when placed in a magnetic field.
The findings, Benvenuto says, will provide extra context for visitors to the Ford Museum, helping them better understand this era of medical quackery. “You can look at Dr. J.J. Gallop’s Vegetable Family Pills and find out what’s supposed to be in them from the box, and what they cost from some old newspaper that’s archived, but you can’t tell what’s really in them without testing,” he said.
Though some medicines intentionally misled customers about their contents and made outlandish claims, the presence of mercury in, say, Dr. F. G. Johnson’s French Female Pills doesn’t necessarily indicate that Mr. Johnson was a quack, Benvenuto said. Mercury was long used as the primary treatment for syphilis, as it kills the spirochete bacteria that cause the disease, though it can also harm the patient. (Lewis and Clark, among others, used mercury to treat the sexually-transmitted infection, and archaeologists have even pinpointed some of the camping spots of their Corps of Discovery Expedition by finding traces of mercury in the soil.)
In an era before rigorously controlled trials, putting a what was commonly believed to be a safe cure into a medicine and simply selling it to people was considered normal practice, and may have indeed led to progress in medicine. “Nowadays, we start by seeing if a drug can kill certain kinds of cells, then we’ll try it in mice, then dogs, then humans,” Benvenuto said. “Obviously, we have a better system now, but I think this type of medicine was the first step in the road to where we are now. Compared to folk cures, it was a first step at being logical.”
April 4, 2013
What can’t a 3D printer build? The number of possible answers to this question has shrunk exponentially in recent years, as the high-tech machines continue to churn out solid object after object from computer designs.
The last few months alone saw countless new products and prototypes spanning an array of industries, from football cleats and pens to steel rocket parts and guns. Last month, the technology helped replace 75 percent of a person’s damaged skull, and this week it restored a man’s face after he lost half of it to cancer four years ago.
Today, a new study suggests 3D-printed material could one day mimic the behavior of cells in human tissue. Graduate student Gabriel Villar and his colleagues at the University of Oxford developed tiny solids that behave as biological tissue would. The delicate material physically resembles brain and fat tissue, and has the consistency of soft rubber.
To create this material, a specially designed 3D printing machine followed a computer programmed diagram and ejected tens of thousands of individual
droplets according to a specified three-dimensional network. As seen in the video above, its nozzles moved in various angles to establish the position of each tiny bead. Each droplet weighs in at about one picoliter—that’s one trillionth of a liter—a unit used to measure the size of droplets of inkjet printers, whose nozzle technology works much the same way to consolidate tiny dots of liquid into complete images and words on paper.
The droplets of liquid contained biochemicals found in tissue cells. Coated in lipids—fats and oils—the tiny aqueous compartments stuck together, forming a cohesive and self-supporting shape, with each bead partitioned by a thin, single membrane similar to the lipid bilayers that protect our cells.
The shapes that the printed droplets formed remained stable for several weeks. If researchers shook the material slightly, droplets could become displaced, but only temporarily. The engineered tissue quickly sprung back into its original shape, a level of elasticity the researchers say is comparable to soft tissue cells in humans. The intricate latticework of a network’s lipid bilayers appeared to hold the “cells” together.
In some of the droplet networks, the 3D printer built pores into the lipid membrane. The holes mimicked protein channels inside the barriers that protect real cells, filtering molecules important for cell function in and out. The researchers injected into the pores a type of molecule important for cell-to-cell communication, one that delivers signals to numerous cells so that they function
together as a group. While the 3D-printed material couldn’t exactly replicate how cells propagate signals, researchers say the movement of the molecule through defined pathways resembled the electrical communication of neurons in brain tissue
Water readily permeated the network’s membranes, even when pores were not built into its structure. The droplets swelled and shrank by the process of osmosis, trying to establish equilibrium between the amount of water they contained and the amount surrounding them on the outside. The movement of water was enough to lift the droplets against gravity, pulling and folding them, imitating muscle-like activity in human tissue.
The researchers hope that these droplet networks could be programmed to release drugs following a physiological signal. Printed cells could someday also be integrated into damaged or failing tissue, providing extra scaffolding or even replacing malfunctioning cells, perhaps even supplanting some of the 1.5 million tissue transplants that take place in the United States each year. The potential seems greatest for brain tissue transplants, as medical engineers are currently trying to grow brain cells in the lab to treat progressive diseases like Huntington’s disease, which slowly destroys nerve cells.
Whether it’s growing human tissue or entire ears, 3D printing technology is in full swing in the field of medicine, and countless researchers will no doubt jump on the bandwagon in the coming years.
April 2, 2013
Step outside after the first storm after a dry spell and it invariably hits you: the sweet, fresh, powerfully evocative smell of fresh rain.
If you’ve ever noticed this mysterious scent and wondered what’s responsible for it, you’re not alone.
Back in 1964, a pair of Australian scientists (Isabel Joy Bear and R. G. Thomas) began the scientific study of rain’s aroma in earnest with an article in Nature titled “Nature of Agrillaceous Odor.” In it, they coined the term petrichor to help explain the phenomenon, combining a pair of Greek roots: petra (stone) and ichor (the blood of gods in ancient myth).
In that study and subsequent research, they determined that one of the main causes of this distinctive smell is a blend of oils secreted by some plants during arid periods. When a rainstorm comes after a drought, compounds from the oils—which accumulate over time in dry rocks and soil—are mixed and released into the air. The duo also observed that the oils inhibit seed germination, and speculated that plants produce them to limit competition for scarce water supplies during dry times.
These airborne oils combine with other compounds to produce the smell. In moist, forested areas in particular, a common substance is geosmin, a chemical produced by a soil-dwelling bacteria known as actinomycetes. The bacteria secrete the compound when they produce spores, then the force of rain landing on the ground sends these spores up into the air, and the moist air conveys the chemical into our noses.
“It’s a very pleasant aroma, sort of a musky smell,” soil specialist Bill Ypsilantis told NPR during an interview on the topic. “You’ll also smell that when you are in your garden and you’re turning over your soil.”
Because these bacteria thrive in wet conditions and produce spores during dry spells, the smell of geosmin is often most pronounced when it rains for the first time in a while, because the largest supply of spores has collected in the soil. Studies have revealed that the human nose is extremely sensitive to geosmin in particular—some people can detect it at concentrations as low as 5 parts per trillion. (Coincidentally, it’s also responsible for the distinctively earthy taste in beets.)
Ozone—O3, the molecule made up of three oxygen atoms bonded together—also plays a role in the smell, especially after thunderstorms. A lightning bolt’s electrical charge can split oxygen and nitrogen molecules in the atmosphere, and they often recombine into nitric oxide (NO), which then interacts with other chemicals in the atmosphere to produce ozone. Sometimes, you can even smell ozone in the air (it has a sharp scent reminiscent of chlorine) before a storm arrives because it can be carried over long distances from high altitudes.
But apart from the specific chemicals responsible, there’s also the deeper question of why we find the smell of rain pleasant in the first place. Some scientists have speculated that it’s a product of evolution.
Anthropologist Diana Young of the University of Queensland in Australia, for example, who studied the culture of Western Australia’s Pitjantjatjara people, has observed that they associate the smell of rain with the color green, hinting at the deep-seated link between a season’s first rain and the expectation of growth and associated game animals, both crucial for their diet. She calls this “cultural synesthesia”—the blending of different sensory experiences on a society-wide scale due to evolutionary history.
It’s not a major leap to imagine how other cultures might similarly have positive associations of rain embedded in their collective consciousness—humans around the world, after all, require either plants or animals to eat, and both are more plentiful in rainy times than during drought. If this hypothesis is correct, then the next time you relish the scent of fresh rain, think of it as a cultural imprint, derived from your ancestors.