Sunday, October 30, 2011

Colorful leaves: New chlorophyll decomposition product found in Norway maple

 Autumn is right around the corner in the northern hemisphere and the leaves are beginning to change color. The cause of this wonderful display of reds, yellows, and oranges is the decomposition of the compound that makes leaves green: chlorophyll.

Bernhard Kräutler and a team at the University of Innsbruck (Austria) have now published a report in the journal Angewandte Chemie about the discovery of a previously unknown product in the leaves of Norway maples. The different spatial arrangement of its atoms is indicative of a different decomposition pathway than those of other deciduous trees.

During the summer months, green leaves carry out photosynthesis: chlorophyll converts sunlight into chemical energy. In the fall, deciduous trees reabsorb critical nutrients, such as nitrogen and minerals, from their leaves. This releases the chlorophyll from the proteins that normally bind it. However, chlorophyll is phototoxic in this free from, and can damage the tree when exposed to light. It must therefore be “detoxified” by decomposition.

“Essential pieces of the puzzle of this biological phenomenon have been solved only within the last two decades,” reports Kräutler. Various colorless tetrapyrroles, molecules with a framework of four nitrogen-containing five-membered carbon rings, accumulate in the dying leaves of higher plants, and have been classified as decomposition products of chlorophyll. These are called “nonfluorescent” chlorophyll catabolytes (NCCs). Says Kräutler, “ they are considered to be the final breakdown products of a well-controlled, “linear” and widely common decomposition pathway.” This premise is beginning to get a little shaky.

Kräutler and his co-workers have studied the decomposition of chlorophyll in the Norway maple, a tree native to Eurasia. “We found none of the typical breakdown products in yellow-green or yellow Norway maple leaves,” says Kräuter. “Instead, the main product we found was a dioxobilane, which resembles a chlorophyll breakdown product found in barley leaves.”

However, there are small but important differences in the spatial arrangements of the atoms relative to each other. There is no plausible decomposition pathway that starts with the NCCs and leads to this new decomposition product. “There is clearly a chlorophyll breakdown pathway occurring in Norway maple leaves that differs from those previously known.”

The structure of this newly discovered dioxobilane is reminiscent of bile pigments, which are products of the breakdown of heme, and thus are important constituents of mammalian metabolisms as well as acting as light sensors in plants. “This supports the idea that chlorophyll breakdown is not only a detoxification process; the resulting decomposition products can also play a physiological role,” states Kräuter. “Chlorophyll breakdown products can act as antioxidants in the peel of ripening fruits, making the fruits less perishable. What role they play in leaves is not yet clear.”

More information: A Dioxobilane as Product of a Divergent Path of Chlorophyll Breakdown in Norway Maple, Angewandte Chemie International Edition, … ie.201103934

Provided by Wiley (news : web)

Nuclear receptors battle it out during metamorphosis in new fruit fly model

Growing up just got more complicated. Thomas Jefferson University biochemistry researchers have shown for the first time that the receptor for a major insect molting hormone doesn't activate and repress genes as once thought. In fact, it only activates genes, and it is out-competed by a heme-binding receptor to repress the same genes during the larval to pupal transition in the fruit fly.

For the last 20 years, the known as EcR/Usp was thought to solely control depending on the presence or absence of the hormone ecdysone, respectively. But it appears, researchers found, that E75A, a heme-binding receptor that represses genes, replaces EcR/Usp during when ecdysone is absent.

The findings, which could shed light on new ways to better understand and treat hormone-dependent diseases, such as cancer, were published in the online October 6 issue of Molecular Cell.

"This is the first time we've shown that a steroid hormone receptor and heme-binding nuclear receptor are even interacting with each other," said Danika M. Johnston, Ph.D. "We didn't really think the two were competing against each other to bind to the same sequence of DNA and regulate the same genes."

More specifically, in the absence of ecdysone, both ecdysone receptor subunits localize to the , and the heme-binding nuclear receptor E75A replaces EcR/Usp at common target sequences in several genes. During the larval-pupal transition, a switch from gene activation by EcR/Usp to by E75A is triggered by a decrease in ecdysone concentration and by direct repression of the EcR gene by E75A.

An important nuance of this system is that the heme-binder E75A is sensitive to the amount of nitric oxide in the cell, and it cannot completely fulfill its repressive potential at high levels of this important molecule. Thus, the uncovered system uses changing amounts of two , a steroid hormone and a gas, to regulate transcription during development.

"These were quite unexpected findings, given the longstanding thoughts of this process," said Dr. Johnston, "but we just didn't have the tools in the past to figure out what was going on mechanistically. We're painting a clearer picture now."

Knowing how nuclear receptors regulate gene expression in animal models can provide useful information in the development of drugs. Today, the molecular targets of roughly 13 percent of U.S. Food and Drug Administration approved drugs are nuclear receptors.

"It's very possible that similar situations exist in the mammalian system. That could ultimately lead to different treatments that regulate hormone levels in hormone-dependent diseases, such as cancer," said Dr. Johnston.

Provided by Thomas Jefferson University (news : web)

Israeli wins chemistry Nobel for quasicrystals (Update 3)


Israeli scientist Dan Shechtman was awarded the Nobel Prize in chemistry on Wednesday for a discovery that faced skepticism and mockery, even prompting his expulsion from his U.S. research team, before it won widespread acceptance as a fundamental breakthrough.

When Israeli scientist Dan Shechtman claimed to have stumbled upon a new crystalline chemical structure that seemed to violate the laws of nature, colleagues mocked him, insulted him and exiled him from his research group.

After years in the scientific wilderness, though, he was proved right. And on Wednesday, he received the ultimate vindication: the Nobel Prize in chemistry.

The lesson?

"A good scientist is a humble and listening scientist and not one that is sure 100 percent in what he read in the textbooks," Shechtman said.

The shy, 70-year-old Shechtman said he never doubted his findings and considered himself merely the latest in a long line of scientists who advanced their fields by challenging the conventional wisdom and were shunned by the establishment because of it.

In 1982, Shechtman discovered what are now called "quasicrystals" - atoms arranged in patterns that seemed forbidden by nature.

"I was thrown out of my research group. They said I brought shame on them with what I was saying," he recalled. "I never took it personally. I knew I was right and they were wrong."

The discovery "fundamentally altered how chemists conceive of solid matter," the Royal Swedish Academy of Sciences said in awarding the $1.5 million prize.

Since his discovery, quasicrystals have been produced in laboratories, and a Swedish company found them in one of the most durable kinds of steel, which is now used in products such as razor blades and thin needles made specifically for eye surgery, the academy said. Quasicrystals are also being studied for use in new materials that convert heat to electricity.

Shechtman is a professor at the Technion-Israel Institute of Technology in Haifa, Israel. He is the 10th Israeli Nobel winner, a great source of pride in a nation of just 7.8 million people. Shechtman fielded congratulatory calls from Israeli President Shimon Peres, who shared the Nobel Peace Prize in 1994, and Prime Minister Benjamin Netanyahu.

"Every citizen of Israel is happy today and every Jew in the world is proud," Netanyahu said.

Staffan Normark, permanent secretary of the Royal Swedish Academy, said Shechtman's discovery was one of the few Nobel Prize-winning achievements that can be dated to a single day.

On April 8, 1982, while on sabbatical at the National Bureau of Standards in Washington - now called the National Institute of Standards and Technology - Shechtman first observed crystals with a shape most scientists considered impossible.

The discovery had to do with the idea that a crystal shape can be rotated a certain amount and still look the same. A square contains four-fold symmetry, for example: If you turn it by 90 degrees, a quarter-turn, it still looks the same. For crystals, only certain degrees of such symmetry were thought possible. Shechtman had found a crystal that could be rotated one-fifth of a full turn and still look the same.

"I told everyone who was ready to listen that I had material with pentagonal symmetry. People just laughed at me," he said in an account released by his university.

He was asked to leave his research group, and moved to another one within the National Bureau of Standards, Shechtman said. He eventually returned to Israel, where he found one colleague prepared to work with him on an article describing the phenomenon. The article was at first rejected but was finally published in November 1984 to an uproar in the scientific world.

In 1987, friends in France and Japan succeeded in growing crystals large enough for X-rays to verify what he had discovered with the electron microscope.

"The moment I presented that, the community said, `OK, Danny, now you are talking. Now we understand you. Now we accept what you have found,'" Shechtman told reporters.

Shechtman, who also teaches at Iowa State University in Ames, Iowa, said he never wavered even in the face of stiff criticism from double Nobel winner Linus Pauling, who never accepted Shechtman's findings.

"He would stand on those platforms and declare, 'Danny Shechtman is talking nonsense. There is no such thing as quasicrystals, only quasi-scientists.'" Shechtman said. "He really was a great scientist, but he was wrong. It's not the first time he was wrong."

Shechtman's battle "eventually forced scientists to reconsider their conception of the very nature of matter," the academy said.

Nancy B. Jackson, president of the American Chemical Society, called Shechtman's breakthrough "one of these great scientific discoveries that go against the rules." Only later did some scientists go back to some of their own inexplicable findings and realize they had seen quasicrystals without understanding what were looking at, Jackson said.

"Anytime you have a discovery that changes the conventional wisdom that's 200 years old, that's something that's really remarkable," said Princeton University physicist Paul J. Steinhardt, who coined the term "quasicrystals" and had been doing theoretical work on them before Shechtman reported finding the real thing.

Steinhardt recalled the day a fellow scientist showed him Shechtman's paper in 1984: "I sort of leapt in the air."

More information: http://www.nobelpr … reates/2011/

For advanced information: http://www.nobelpr … ack_2011.pdf

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 has fundamentally altered how chemists conceive of solid matter.

On the morning of 8 April 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.

When scientists describe Shechtman's quasicrystals, they use a concept that comes from mathematics and art: the golden ratio. This number had already caught the interest of mathematicians in Ancient Greece, as it often appeared in geometry. In quasicrystals, for instance, the ratio of various distances between atoms is related to the golden mean.

Following Shechtman's discovery, scientists have produced other kinds of quasicrystals in the lab and discovered naturally occurring quasicrystals in mineral samples from a Russian river. A Swedish company has also found quasicrystals in a certain form of steel, where the crystals reinforce the material like armor. Scientists are currently experimenting with using quasicrystals in different products such as frying pans and diesel engines.

?2011 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

'Perfect plastic' created

Researchers at the University of Leeds and Durham University have solved a long-standing problem that could revolutionize the way new plastics are developed.

The breakthrough will allow experts to create the 'perfect plastic' with specific uses and properties by using a high-tech 'recipe book.' It will also increase our ability to recycle . The research paper is published in the prestigious journal Science on Thursday.

The paper's authors form part of the Microscale Polymer Processing project, a collaboration between academics and industry experts which has spent 10 years exploring how to better build giant 'macromolecules.' These long tangled molecules are the basic components of plastics and dictate their properties during the melting, flowing and forming processes in plastics production.

Low-density polyethylenes (LDPEs) are used in trays and containers, lightweight car parts, recyclable packaging and . Up until now, industry developed a plastic then found a use for it, or tried hundreds of different "recipes" to see which worked. This method could save the manufacturing industry time, energy and money.

The mathematical models used put together two pieces of . The first predicts how polymers will flow based on the connections between the string-like molecules they are made from. A second piece of code predicts the shapes that these molecules will take when they are created at a chemical level. These models were enhanced by experiments on carefully synthesised 'perfect polymers' created in labs of the Microscale Polymer Processing project.

Dr. Daniel Read, from the School of Mathematics, University of Leeds, who led the research, said, "Plastics are used by everybody, every day, but until now their production has been effectively guesswork. This breakthrough means that new plastics can be created more efficiently and with a specific use in mind, with benefits to industry and the environment."

Professor Tom McLeish, formerly of the University of Leeds, now Pro-Vice Chancellor for Research at Durham University leads the Microscale Polymer Processing project. He said, "After years of trying different chemical recipes and finding only a very few provide useable products, this new science provides industry with a toolkit to bring new materials to market faster and more efficiently."

Professor McLeish added that as plastics production moves from oil-based materials to sustainable and renewable materials, the "trial and error" phase in developing new plastics could now be by-passed. He said, "By changing two or three numbers in the computer code, we can adapt all the predictions for new bio-polymer sources."

"This is a wonderful outcome of years of work by this extraordinary team. It's a testimony to the strong collaborative ethos of the UK research groups and global companies involved," he added.

Dr. Ian Robinson of Lucite International, one of the industrial participants in the wider project said, "The insights offered by this approach are comparable to cracking a plastics 'DNA.'"

The model was developed by Dr. Daniel Read, School of Mathematics, University of Leeds, Dr. Chinmay Das of the School of Physics & Astronomy, University of Leeds and Professor Tom McLeish, Department of Physics, Durham University. Their predictions were compared to the results of polymer analysis by Dr. Dietmar Auhl, at the time a physicist at Leeds.

Provided by University of Leeds (news : web)