Origin of Photosynthesis Revealed

Schematic of Cyanophora paradoxa. (Credit: Courtesy of Bhattacharya Lab.)

Atmospheric oxygen really took off on our planet about 2.4 billion years ago during the Great Oxygenation Event. At this key juncture of our planet’s evolution, species had either to learn to cope with this poison that was produced by photosynthesizing cyanobacteria or they went extinct. It now seems strange to think that the gas that sustains much of modern life had such a distasteful beginning.

So how and when did the ability to produce oxygen by harnessing sunlight enter the eukaryotic domain, that includes humans, plants, and most recognizable, multicellular life forms? One of the fundamental steps in the evolution of our planet was the development of photosynthesis in eukaryotes through the process of endosymbiosis.

This crucial step forward occurred about 1.6 billion years ago when a single-celled protist captured and retained a formerly free-living cyanobacterium. This process, termed primary endosymbiosis, gave rise to the plastid, which is the specialized compartment where photosynthesis takes place in cells. Endosymbiosis is now a well substantiated theory that explains how cells gained their great complexity and was made famous most recently by the work of the late biologist Lynn Margulis, best known for her theory on the origin of eukaryotic organelles.

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New ‘Diamond?’ New Form of Superhard Carbon Is as Strong as a Diamond

Carbon is the fourth-most-abundant element in the universe and takes on a wide variety of forms, called allotropes, including diamond and graphite. Scientists have now discovered a new form of carbon, which is capable of withstanding extreme pressure stresses that were previously observed only in diamond. (Credit: © adimas / Fotolia)

Carbon is the fourth-most-abundant element in the universe and takes on a wide variety of forms, called allotropes, including diamond and graphite. Scientists at Carnegie’s Geophysical Laboratory are part of a team that has discovered a new form of carbon, which is capable of withstanding extreme pressure stresses that were previously observed only in diamond.

his breakthrough discovery will be published in Physical Review Letters.

The team was led by Stanford’s Wendy L. Mao and her graduate student Yu Lin and includes Carnegie’s Ho-kwang (Dave) Mao, Li Zhang, Paul Chow, Yuming Xiao, Maria Baldini, and Jinfu Shu. The experiment started with a form of carbon called glassy carbon, which was first synthesized in the 1950s, and was found to combine desirable properties of glasses and ceramics with those of graphite. The team created the new carbon allotrope by compressing glassy carbon to above 400,000 times normal atmospheric pressure.

This new carbon form was capable of withstanding 1.3 million times normal atmospheric pressure in one direction while confined under a pressure of 600,000 times atmospheric levels in other directions. No substance other than diamond has been observed to withstand this type of pressure stress, indicating that the new carbon allotrope must indeed be very strong.

However, unlike diamond and other crystalline forms of carbon, the structure of this new material is not organized in repeating atomic units. It is an amorphous material, meaning that its structure lacks the long-range order of crystals. This amorphous, superhard carbon allotrope would have a potential advantage over diamond if its hardness turns out to be isotropic — that is, having hardness that is equally strong in all directions. In contrast, diamond’s hardness is highly dependent upon the direction in which the crystal is oriented.

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‘Quasicrystals’ Once Thought Impossible Have Changed Understanding of Solid Matter

Aperiodic mosaics, such as those found in the medieval Islamic mosaics of the Alhambra Palace in Spain (shown above), have helped scientists understand what quasicrystals look like at the atomic level. In those mosaics, as in quasicrystals, the patterns are regular — they follow mathematical rules — but they never repeat themselves. (Credit: © cbomers / Fotolia)

The Royal Swedish Academy of Sciences has decided to award the Nobel Prize in Chemistry for 2011 to Daniel Shechtman of the Technion — Israel Institute of Technology in Haifa, Israel, for the discovery of quasicrystals: non-repeating regular patterns of atoms that were once thought to be impossible.

A remarkable mosaic of atoms

In quasicrystals, we find the fascinating mosaics of the Arabic world reproduced at the level of atoms: regular patterns that never repeat themselves. However, the configuration found in quasicrystals was considered impossible, and Daniel Shechtman had to fight a fierce battle against established science. The Nobel Prize in Chemistry 2011 recognizes a breakthrough that has fundamentally altered how chemists conceive of solid matter.

On the morning of April 8, 1982, an image counter to the laws of nature appeared in Daniel Shechtman’s electron microscope. In all solid matter, atoms were believed to be packed inside crystals in symmetrical patterns that were repeated periodically over and over again. For scientists, this repetition was required in order to obtain a crystal.

Shechtman’s image, however, showed that the atoms in his crystal were packed in a pattern that could not be repeated. Such a pattern was considered just as impossible as creating a football using only six-cornered polygons, when a sphere needs both five- and six-cornered polygons. His discovery was extremely controversial. In the course of defending his findings, he was asked to leave his research group. However, his battle eventually forced scientists to reconsider their conception of the very nature of matter.

Aperiodic mosaics, such as those found in the medieval Islamic mosaics of the Alhambra Palace in Spain and the Darb-i Imam Shrine in Iran, have helped scientists understand what quasicrystals look like at the atomic level. In those mosaics, as in quasicrystals, the patterns are regular — they follow mathematical rules — but they never repeat themselves.

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Making Complex Composite Materials to Order

A sample of a co-continuous polymer composite material produced in the lab by a team including MIT postdoctoral researcher Lifeng Wang. Device in background is used to test the strength of the material. (Credit: Melanie Gonick)

A team of researchers at MIT has found a way to make complex composite materials whose attributes can be fine-tuned to give various desirable combinations of properties such as stiffness, strength, resistance to impacts and energy dissipation.

composites is a “co-continuous” structure of two different materials with very different properties, creating a material combining aspects of both. The co-continuous structure means that the two interleaved materials each form a kind of three-dimensional lattice whose pieces are fully connected to each other from side to side, front to back, and top to bottom.

The research — by postdoc Lifeng Wang, who worked with undergraduate Jacky Lau and professors Mary Boyce and Edwin Thomas — was published in April in the journal Advanced Materials.

The initial objective of the research was to “try to design a material that can absorb energy under extreme loading situations,” Wang explains. Such a material could be used as shielding for trucks or aircraft, he says: “It could be lightweight and efficient, flexible, not just a solid mantle” like most present-day armor.

In most conventional materials — even modern advanced composites — once cracks start to form they tend to propagate through the material, Wang says. But in the new co-continuous materials, crack propagation is limited within the microstructure, he says, making them highly “damage tolerant” even when subjected to many crack-producing events.

Some existing composite materials, such as carbon-carbon composites that use fibers embedded in another material, can have great strength in the direction parallel to the fibers, but not much strength in other directions. Because of the continuous 3-D structure of the new composites, their strength is nearly equal in all dimensions, Wang says.

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Biodegradeable products may be more harmful to the environment

by Emma Woollacott

Think you’re doing the right thing by using biodegradeable products? Think again. Research from North Carolina State University shows that they’re actually doing more harm than good, by releasing a powerful greenhouse gas as they break down.

“Biodegradable materials, such as disposable cups and utensils, are broken down in landfills by microorganisms that then produce methane,” says Dr Morton Barlaz. “Methane can be a valuable energy source when captured, but is a potent greenhouse gas when released into the atmosphere.”

The US Environmental Protection Agency (EPA) estimates that only about a third of municipal solid waste goes to landfills that capture methane for energy use. Another third is captured and burned off-site, and the rest allowed to escape.

“In other words,” Barlaz says, “biodegradable products are not necessarily more environmentally friendly when disposed in landfills.”

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A Car Battery at Half the Price

Battery prototype: Two sludge-like electrode materials are fed into the device shown here. The anode material flows into the top half, and the cathode flows into the bottom. Lithium ions pass from one material to the other, and electrons flow through the black and red leads.  Credit: Yet-Ming Chiang

A startup hopes to commercialize a novel design that features a liquid electrolyte.

Last year, the battery startup A123 Systems spun out another company, called 24M, to develop a new kind of battery meant to make electric vehicles go farther and cost less. Now a research paper published in Advanced Energy Materials reveals the first details about how that battery would work. It also addresses the challenges in bringing the battery to market.

A big problem with the lithium-ion batteries used in electric vehicles and plug-in hybrids is that only about 25 percent of the battery’s volume is taken up by materials that store energy. The rest is made up of inactive materials, such as packaging, conductive foils, and glues, which make the batteries bulky and account for a significant part of the cost.

24M intends to greatly reduce the inactive material in a battery.  According to estimates in the new paper, its batteries could achieve almost twice the energy densities of today’s vehicle battery packs. Batteries with a higher energy density would be smaller and cheaper, which means electric and hybrid cars would be less expensive. The paper estimates that the batteries could cost as little as $250 per kilowatt hour—less than half what they cost now.

A conventional battery pack is made up of hundreds of cells. Each cell contains a stack of many thin, solid electrodes. These electrodes are paired with metal foil current collectors and separated from each other by plastic films. Increasing the energy storagerequires adding more layers of electrode material—which in turn requires more layers of metal foil and plastic film.

24M’s design makes it possible to increase energy storage without the extra metal foil and plastic film. The key difference is that the electrodes are not solid films stacked in a cell, but sludge-like materials stored in tanks—one for the positive electrode material and another for the negative electrode.

The materials are pumped from the tanks into a small device, where they move through channels carved into blocks of metal. As this happens, ions move from one electrode to the other through the same kind of separator material used in a conventional battery. Electrons make their way out of the material to an external circuit. In this design, increasing energy storage is as simple as increasing the size of the storage tanks—the device that allows the electrodes to interact stays the same size. The design also does away with the need to wire together hundreds of cells to achieve adequate energy storage.

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Particle Trap Paves Way for Personalized Medicine

Scientists were able to trap a single particle between four microelectrodes, paving the way for a faster and cheaper way to sequence DNA. (Credit: Weihua Guan and Mark Reed/Yale University)

Sequencing DNA base pairs — the individual molecules that make up DNA — is key for medical researchers working toward personalized medicine. Being able to isolate, study and sequence these DNA molecules would allow scientists to tailor diagnostic testing, therapies and treatments based on each patient’s individual genetic makeup.

But being able to isolate individual molecules like DNA base pairs, which are just two nanometers across — or about 1/50,000th the diameter of a human hair — is incredibly expensive and difficult to control. In addition, devising a way to trap DNA molecules in their natural aqueous environment further complicates things. Scientists have spent the past decade struggling to isolate and trap individual DNA molecules in an aqueous solution by trying to thread it through a tiny hole the size of DNA, called a “nanopore,” which is exceedingly difficult to make and control.

Now a team led by Yale University researchers has proven that isolating individual charged particles, like DNA molecules, is indeed possible using a method called “Paul trapping,” which uses oscillating electric fields to confine the particles to a space only nanometers in size. (The technique is named for Wolfgang Paul, who won the Nobel Prize for the discovery.) Until now, scientists have only been able to use Paul traps for particles in a vacuum, but the Yale team was able to confine a charged test particle — in this case, a polystyrene bead — to an accuracy of just 10 nanometers in aqueous solutions between quadruple microelectrodes that supplied the electric field.

Their device can be contained on a single chip and is simple and inexpensive to manufacture. “The idea would be that doctors could take a tiny drop of blood from patients and be able to run diagnostic tests on it right there in their office, instead of sending it away to a lab where testing can take days and is expensive,” said Weihua Guan, a Yale engineering graduate student who led the project.

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