Researchers Discover 'Green' Pesticide Effective Against Citrus Pests
Friday, January 20, 2012

University of Florida researchers have discovered a key amino acid essential for human nutrition is also an effective insecticide against caterpillars that threaten the citrus industry.

The Lime Swallowtail, or Citrus Swallowtail, is a well-known agricultural pest from southern Asia discovered in the Caribbean in 2006, and researchers say its potential impact on the U.S. citrus industry is cause for serious concern.

“Everything that’s in the Caribbean eventually gets to Florida – Florida is an invasive magnet,” said UF lepidopterist Delano Lewis, lead author of the study published in the current issue of the Journal of Economic Entomology. “That’s why we’re trying to make the first strike to see how to stop it.”

Experiments conducted on the UF campus at the Florida Museum of Natural History’s McGuire Center for Lepidoptera and Biodiversity and the College of Medicine show when methionine is sprayed on leaves it is 100 percent effective in killing larvae related to the Lime Swallowtail caterpillars within two to three days. If not controlled, the caterpillars can completely defoliate young wild lime plants.

Because the Lime Swallowtail, Princeps (Papilio) demoleus, is invasive and cannot be legally brought into the U.S., researchers experimented using a genetically related surrogate with a similar life history and appetite for citrus, the Giant Swallowtail, Heraclides (Papilio) cresphontes. Because these pest caterpillars have the same body structure and biology, researchers are confident methionine will also control the Lime Swallowtail, Lewis said.

“Its effectiveness is based on the biochemistry of the insect gut, so although this work was done on a surrogate, the methionine will block the ion channel in the same way,” Lewis said.

Methionine is needed in the human diet for many reasons, including protein-building and metabolism. It is environmentally safe and harmless to citrus plants, mammals and birds.

“It’s a very curious phenomenon to have this nutrient amino acid that humans can’t live without, yet at the concentrations we put on the leaves, it is toxic to crop-destructive caterpillars,” said study co-author Bruce Stevens, professor of physiology and functional genomics in the UF College of Medicine. “It’s a completely different class of pesticides that has not been seen before – most are toxic to not only the pest, but to people and animals, too.”

Stevens first discovered the pesticide properties of methionine while cloning genes that regulate amino acid metabolism in 1998. Working with co-author James Cuda of UF’s department of entomology and nematology, Stevens later found this amino acid to be effective against yellow fever mosquito larvae, tomato hornworm and Colorado potato beetle.

Methionine disrupts an ion channel that controls nutrient absorption in larvae with an alkaline intestine, such as in caterpillars of the Citrus Swallowtail. In 2004 and 2007, Stevens obtained two patents for the use of methionine as a pesticide, through the UF Office of Technology Licensing.

“The methionine is sprayed on the leaves, and when the caterpillars begin to eat the leaves, they ingest the compound – it’s not in the plant itself,” Lewis said. “Once they take those first few bites, they don’t feed again and remain stationary until they die.”

Methionine is low-cost and serves as fertilizer if it reaches the ground because it’s a biodegradable nitrogen source, Stevens said. The amino acid is mass produced and has been used as a nutritional supplement in outdoor livestock feed since the 1960s. The U.S. Department of Agriculture recently approved the use of methionine for organic poultry production.

“This is a neat idea and I’m hoping that more work will be done on this in the future because there’s a lot of potential there,” said John Ruberson, a professor in the entomology department at the University of Georgia, who was not involved in the study. “The one challenge I can see from a grower’s perspective is that it tends to work kind of slowly. Typically, it takes two to three days to kill the insect, but they do show that [insect] feeding is reduced, which is a good thing.”

Patent rights for the use of methionine to control turf and ornamental pests have been licensed to Phoenix Environmental Care LLC, which is developing a pest control product.

While researchers are unsure how the Lime Swallowtail reached the Caribbean, its proximity poses a potential threat to Central and South American citrus industries, as well.

“We suspect someone could have brought them to release the adult butterflies in weddings, or perhaps they arrived with imported citrus stock,” Lewis said. “Regardless, it’s in the Caribbean and it’s a very strong flyer.”

New clue in the battle against Australian Hendra virus
Friday, January 13, 2012

A new study on African bats provides a vital clue for unraveling the mysteries in Australia’s battle with the deadly Hendra virus.

The study focused on an isolated colony of straw-colored fruit bats on islands off the west coast of central Africa. By capturing the bats and collecting blood samples, scientists discovered these animals have antibodies that can neutralize deadly viruses known in Australia and Asia.

The paper is published today, 12 January, in the journal PLoS ONE, and is a collaboration of the Department of Veterinary Medicine at the University of Cambridge, the Zoological Society of London and the CSIRO Australian Animal Health Laboratory.

Hendra virus in Australia and Nipah virus in Asia are carried by fruit bats and sporadically “spill over” into people with tragic consequences. The findings of the new study are significant as they yield valuable insights for our understanding of how these viruses persist in bat populations.

Cambridge PhD student Alison Peel explains, “Hendra and Nipah viruses cause fatal infections in humans, but we currently understand very little about how the viruses are transmitted from bats to other animals or people. To understand what the risk factors for these ‘spill-overs’ are, it is crucial to understand how viruses are maintained in bat populations. The ability to study these viruses within an isolated bat colony has given us new insight into these processes.”

It was previously believed that these viruses were maintained in large interconnected populations of bats, so that if the virus dies out in one colony, it would be reintroduced when bats from different colonies interact. The new study indicates that a closely related virus is able to persist in a very small and isolated population of bats. This is the first time this has been documented in a natural wild population, casting doubt on current theories.

Peel added, “Although Hendra and Nipah viruses are relatively new to science, it appears that bats have lived and evolved with them over a very long time. We hope that by gaining a better understanding of this relationship, we may then be able to understand why it is only within the last 20 years that spill-over to humans has occurred.”

Honeybee Deaths Linked to Seed Insecticide Exposure

Wednesday, January 11, 2012

Honeybee populations have been in serious decline for years, and Purdue University scientists may have identified one of the factors that cause bee deaths around agricultural fields.

Analyses of bees found dead in and around hives from several apiaries over two years in Indiana showed the presence of neonicotinoid insecticides, which are commonly used to coat corn and soybean seeds before planting. The research showed that those insecticides were present at high concentrations in waste talc that is exhausted from farm machinery during planting.

The insecticides clothianidin and thiamethoxam were also consistently found at low levels in soil - up to two years after treated seed was planted - on nearby dandelion flowers and in corn pollen gathered by the bees, according to the findings released in the journal PLoS One this month.

"We know that these insecticides are highly toxic to bees; we found them in each sample of dead and dying bees," said Christian Krupke, associate professor of entomology and a co-author of the findings.

The United States is losing about one-third of its honeybee hives each year, according to Greg Hunt, a Purdue professor of behavioral genetics, honeybee specialist and co-author of the findings. Hunt said no one factor is to blame, though scientists believe that others such as mites and insecticides are all working against the bees, which are important for pollinating food crops and wild plants.

"It’s like death by a thousand cuts for these bees," Hunt said.

Krupke and Hunt received reports that bee deaths in 2010 and 2011 were occurring at planting time in hives near agricultural fields. Toxicological screenings performed by Brian Eitzer, a co-author of the study from the Connecticut Agricultural Experiment Station, for an array of pesticides showed that the neonicotinoids used to treat corn and soybean seed were present in each sample of affected bees. Krupke said other bees at those hives exhibited tremors, uncoordinated movement and convulsions, all signs of insecticide poisoning.

Seeds of most annual crops are coated in neonicotinoid insecticides for protection after planting. All corn seed and about half of all soybean seed is treated. The coatings are sticky, and in order to keep seeds flowing freely in the vacuum systems used in planters, they are mixed with talc. Excess talc used in the process is released during planting and routine planter cleaning procedures.

"Given the rates of corn planting and talc usage, we are blowing large amounts of contaminated talc into the environment. The dust is quite light and appears to be quite mobile," Krupke said.

Krupke said the corn pollen that bees were bringing back to hives later in the year tested positive for neonicotinoids at levels roughly below 100 parts per billion.

"That's enough to kill bees if sufficient amounts are consumed, but it is not acutely toxic," he said.

On the other hand, the exhausted talc showed extremely high levels of the insecticides - up to about 700,000 times the lethal contact dose for a bee.

"Whatever was on the seed was being exhausted into the environment," Krupke said. "This material is so concentrated that even small amounts landing on flowering plants around a field can kill foragers or be transported to the hive in contaminated pollen. This might be why we found these insecticides in pollen that the bees had collected and brought back to their hives."

Krupke suggested that efforts could be made to limit or eliminate talc emissions during planting.

"That's the first target for corrective action," he said. "It stands out as being an enormous source of potential environmental contamination, not just for honeybees, but for any insects living in or near these fields. The fact that these compounds can persist for months or years means that plants growing in these soils can take up these compounds in leaf tissue or pollen."

Although corn and soybean production does not require insect pollinators, that is not the case for most plants that provide food. Krupke said protecting bees benefits agriculture since most fruit, nut and vegetable crop plants depend upon honeybees for pollination. The U.S. Department of Agriculture estimates the value of honeybees to commercial agriculture at $15 billion to $20 billion annually.

Hunt said he would continue to study the sublethal effects of neonicotinoids. He said for bees that do not die from the insecticide there could be other effects, such as loss of homing ability or less resistance to disease or mites.

"I think we need to stop and try to understand the risks associated with these insecticides," Hunt said.

The North American Pollinator Protection Campaign and the USDA's Agriculture and Food Research Initiative funded the research.

Under Embargo Till: 16:00 UTC March 24, 2010
Posted: 16:00 UTC 03/24/2010

Emotions Key To Judging Others

Wednesday, March 24, 2010

A new study from MIT neuroscientists suggests that our ability to respond appropriately to intended harms — that is, with outrage toward the perpetrator — is seated in a brain region associated with regulating emotions.

Patients with damage to this brain area, known as the ventromedial prefrontal cortex (VMPC), are unable to conjure a normal emotional response to hypothetical situations in which a person tries, but fails, to kill another person. Therefore, they judge the situation based only on the outcome, and do not hold the attempted murderer morally responsible.

The finding offers a new piece to the puzzle of how the human brain constructs morality, says Liane Young, a postdoctoral associate in MIT’s Department of Brain and Cognitive Sciences and lead author of a paper describing the findings in the March 25 issue of the journal Neuron.

“We’re slowly chipping away at the structure of morality,” says Young. “We’re not the first to show that emotions matter for morality, but this is a more precise look at how emotions matter.”

Working with researchers at the University of Southern California, led by Antonio Damasio, Young studied a group of nine patients with damage (caused by aneurisms or tumors) to the VMPC, a plum-sized area located a few inches behind the eyes.

Such patients have difficulty processing social emotions such as empathy or embarrassment, but “they have a perfectly intact capacity for reasoning and other cognitive functions,” says Young.

The researchers gave the subjects a series of 24 hypothetical scenarios and asked for their reactions. The scenarios of most interest to the researchers were ones featuring a mismatch between the person’s intention and the outcome — either failed attempts to harm or accidental harms.

When confronted with failed attempts to harm, the patients had no problems understanding the perpetrator’s intentions, but they failed to hold them morally responsible. The patients even judged attempted harms as more permissible than accidental harms (such as accidentally poisoning someone) — a reversal of the pattern seen in normal adults.

“They can process what people are thinking and their intentions, but they just don’t respond emotionally to that information,” says Young. “They can read about a murder attempt and judge it as morally permissible because no harm was done.”

This supports the idea that making moral judgments requires at least two processes — a logical assessment of the intention, and an emotional reaction to it. The study also supports the theory that the emotional component is seated in the VMPC.

Young hopes to study patients who incurred damage to the VMPC when they were younger, to see if they have the same impaired judgment. She also plans to study patient reactions to situations where the harmful attempts may be directed at the patient and therefore are more personal.

Funded by the National Science Foundation, National Institute of Neurological Disorders and Stroke, National Institute on Drug Abuse, gifts from J. Epstein and S. Shuman.

Fruit flies and test tubes open new window on Alzheimer’s disease

Tuesday, March 16, 2010

A team of scientists from Cambridge and Sweden have discovered a molecule that can prevent a toxic protein involved Alzheimer’s disease from building up in the brain. They found that in test tube studies the molecule not only prevents the protein from forming clumps but can also reverse this process. Then, using fruit flies with Alzheimer’s disease, they showed that the same molecule effectively “cures” the insects of the disease.

Alzheimer's disease is the most common neurodegenerative disorder and is linked to the misfolding and aggregation of a small protein known as the amyloid β (Aβ) peptide. Previous studies in animal models have shown that aggregation of Aβ damages neurones (brain cells) causing memory impairment and cognitive deficits similar to those seen in patients with Alzheimer's disease. The mechanisms underlying this damage are, however, still not understood.

The new molecule - designed by scientists in Sweden - is a small protein known as an Affibody (an engineered binding protein). In this new study, researchers at the University of Cambridge and the Swedish University of Agricultural Sciences found that in test-tube experiments this protein binds to the Aβ peptide, preventing it from forming clumps and breaking up any clumps already present.

In a second experiment, they studied the effect of this Affibody in a Drosophila (fruit fly) model of Alzheimer's disease previously developed at Cambridge.

Working with fruit flies that develop the fly equivalent of Alzheimer's because they have been genetically engineered to produce the Aβ protein, they crossed these flies with a second line of flies genetically engineered to produce the Affibody.

They found that offspring - despite producing the Aβ protein - did not develop the symptoms of Alzheimer's disease.

According to lead author Dr Leila Luheshi of the Department of Genetics at University of Cambridge: "When we examined these flies we found that the Affibody not only prevented and reversed the formation of Aβ clumps, it also promoted clearance of the toxic Aβ clumps from the flies' brains."

"Finding a way of preventing these clumps from forming in the brain, and being able to get rid of them, is a promising strategy for preventing Alzheimer's disease. Affibody proteins give us a window into the Alzheimer's brain: by helping us understand how these clumps damage brain cells, they should help us unravel the Alzheimer's disease process."

According to Professor Torleif Härd of the Swedish University of Agricultural Sciences and one of the senior authors of the study: "Our work shows that protein engineering could open up new possibilities in Alzheimer's therapy development."

Under Embargo Till: 18:00 UTC March 14, 2010
Posted: 18:00 UTC 03/14/2010

New analysis of the structure of silks explains paradox of super-strength

Sunday, March 14, 2010

Spiders and silkworms are masters of materials science, but scientists are finally catching up. Silks are among the toughest materials known, stronger and less brittle, pound for pound, than steel. Now scientists at MIT have unraveled some of their deepest secrets in research that could lead the way to the creation of synthetic materials that duplicate, or even exceed, the extraordinary properties of natural silk.

Markus Buehler, the Esther and Harold E. Edgerton Associate Professor in MIT’s Department of Civil and Environmental Engineering, and his team study fundamental properties of materials and how those materials fail. With silk, that meant using computer models that can simulate not just the structures of the molecules but exactly how they move and interact in relation to each other. The models helped the researchers determine the molecular and atomic mechanisms responsible for the material’s remarkable mechanical properties.

Silk’s combination of strength and ductility — its ability to bend or stretch without breaking — results from an unusual arrangement of atomic bonds that are inherently very weak, Buehler and his team found. Doctoral student Sinan Keten, postdoctoral associate Zhiping Xu and undergraduate student Britni Ihle are co-authors of a paper on the research to be published on March 14 in the journal Nature Materials.

Silks are made from proteins, including some that form thin, planar crystals called beta-sheets. These sheets are connected to each other through hydrogen bonds — among the weakest types of chemical bonds, unlike, for example, the much stronger covalent bonds found in most organic molecules. Buehler’s team carried out a series of atomic-level computer simulations that investigated the molecular failure mechanisms in silk. “Small yet rigid crystals showed the ability to quickly re-form their broken bonds, and as a result fail ‘gracefully’ — that is, gradually rather than suddenly,” graduate student Keten explains.

“In most engineered materials” — ceramics, for instance — “high strength comes with brittleness,” Buehler says. “Once ductility is introduced, materials become weak.” But not silk, which has high strength despite being built from inherently weak building blocks. It turns out that’s because these building blocks — the tiny beta-sheet crystals, as well as filaments that join them — are arranged in a structure that resembles a tall stack of pancakes, but with the crystal structures within each pancake alternating in their orientation. This particular geometry of tiny silk nanocrystals allows hydrogen bonds to work cooperatively, reinforcing adjacent chains against external forces, which leads to the outstanding extensibility and strength of spider silk.

One surprising finding from the new work is that there is a critical dependence of the properties of silk on the exact size of these beta-sheet crystals within the fibers. When the crystal size is about three nanometers (billionths of a meter), the material has its ultra-strong and ductile characteristics. But let those crystals grow just beyond to five nanometers, and the material becomes weak and brittle.

Buehler says the work has implications far beyond just understanding silk. He notes that the findings could be applied to a broader class of biological materials, such as wood or plant fibers, and bio-inspired materials, such as novel fibers, yarns and fabrics or tissue replacement materials, to produce a variety of useful materials out of simple, commonplace elements. For example, he and his team are looking at the possibility of synthesizing materials that have a similar structure to silk, but using molecules that have inherently greater strength, such as carbon nanotubes.

The long-term impact of this research, Buehler says, will be the development of a new material design paradigm that enables the creation of highly functional materials out of abundant, inexpensive materials. This would be a departure from the current approach, where strong bonds, expensive constituents, and energy intensive processing (at high temperatures) are used to obtain high-performance materials.

Peter Fratzl, professor in the department of biomaterials in the Max Planck Institute of Colloids and Interfaces in Potsdam, Germany, who was not involved in this work, says that “the strength of this team is their pioneering multi-scale theoretical approach” to analyzing natural materials. He adds that this is “the first evidence from theoretical modeling of how hydrogen bonds, as weak as they might be, can provide high strength and toughness if arranged in a suitable way within the material.”

Professor of biomaterials Thomas Scheibel of the University of Bayreuth, Germany, who was also not involved in this work, says Buehler’s work is of the “highest caliber,” and will stimulate much further research. The MIT team’s approach, he says, “will provide a basis for better understanding of certain biological phenomena so far not understood.”

Funding for this work was supported by the Office of Naval Research, with additional funding from the National Science Foundation, the Army Research Office, the MIT Energy Initiative, and MIT’s UROP and MISTI-Germany programs.

Under Embargo Till: 18:00 UTC March 14, 2010
Posted: 18:00 UTC 03/14/2010

New microscopy technique offers close-up, real-time view of cellular phenomena

Sunday, March 14, 2010

For two decades, scientists have been pursuing a potential new way to treat bacterial infections, using naturally occurring proteins known as antimicrobial peptides (AMPs). Now, MIT scientists have recorded the first microscopic images showing the deadly effects of AMPs, most of which kill by poking holes in bacterial cell membranes.

Researchers in the laboratory of MIT Professor Angela Belcher modified an existing, extremely sensitive technique known as high-speed atomic force microscopy (AFM) to allow them to image the bacteria in real time. Their method, described in this Sunday’s online edition of Nature Nanotechnology, represents the first way to study living cells using high-resolution images recorded in rapid succession.

Using this type of high-speed AFM could allow scientists to study how cells respond to other drugs and to viral infection, says Belcher, the Germeshausen Professor of Materials Science and Engineering and Biological Engineering. The new work could also help researchers understand how some bacteria can become resistant to AMPs (none of which have been approved as drugs yet).

Atomic force microscopy, invented in 1986, is widely used to image nanoscale materials. Its resolution is similar to that of electron microscopy, but unlike electron microscopy, it does not require a vacuum and thus can be used with living samples. However, traditional AFM requires several minutes to produce one image, so it cannot record a sequence of rapidly occurring events.

In recent years, scientists have developed high-speed AFM techniques, but haven’t optimized them for living cells. That’s what the MIT team set out to do, building on the experience of lead author Georg Fantner, a postdoctoral associate in Belcher’s lab who had worked on high-speed AFM at the University of California at Santa Barbara.

How they did it: Atomic force microscopy makes use of a cantilever equipped with a probe tip that “feels” the surface of a sample. Forces between the tip and the sample can be measured as the probe moves across the sample, revealing the shape of the surface. The MIT team used a cantilever about 1,000 times smaller than those normally used for AFM, which enabled them to increase the imaging speed without harming the bacteria.

With the new setup, the team was able to take images every 13 seconds over a period of several minutes. They found that AMP-induced cell death appears to be a two-step process: a short incubation period followed by a rapid “execution.” They were surprised to see that the onset of the incubation period varied from 13 to 80 seconds.

“Not all of the cells started dying at the exact same time, even though they were genetically identical and were exposed to the peptide at the same time,” says Roberto Barbero, a graduate student in biological engineering and an author of the paper.

In the future, Belcher hopes to use atomic force microscopy to study other cellular phenomena, including the assembly of viruses in infected cells, and the effects of traditional antibiotics on bacterial cells. The technique may also prove useful in studying mammalian cells.

Funding provided by Erwin-Schrodinger Fellowship, National Institutes of Health, Army Research Office, Austrian Research Promotion Agency.

Scavenging energy waste to turn water into hydrogen fuel

Thursday, March 11, 2010

Materials scientists at the University of Wisconsin-Madison have designed a way to harvest small amounts of waste energy and harness them to turn water into usable hydrogen fuel.

The process is simple, efficient and recycles otherwise-wasted energy into a useable form.

"This study provides a simple and cost-effective technology for direct water splitting that may generate hydrogen fuels by scavenging energy wastes such as noise or stray vibrations from the environment," the authors write in a new paper, published March 2 in the Journal of Physical Chemistry Letters. "This new discovery may have potential implications in solving the challenging energy and environmental issues that we are facing today and in the future."

The researchers, led by UW-Madison geologist and crystal specialist Huifang Xu, grew nanocrystals of two common crystals, zinc oxide and barium titanate, and placed them in water. When pulsed with ultrasonic vibrations, the nanofibers flexed and catalyzed a chemical reaction to split the water molecules into hydrogen and oxygen.

When the fibers bend, asymmetries in their crystal structures generate positive and negative charges and create an electrical potential. This phenomenon, called the piezoelectric effect, has been well known in certain crystals for more than a century and is the driving force behind quartz clocks and other applications.

Xu and his colleagues applied the same idea to the nanocrystal fibers. "The bulk materials are brittle, but at the nanoscale they are flexible," he says, like the difference between fiberglass and a pane of glass.

Smaller fibers bend more easily than larger crystals and therefore also produce electric charges easily. So far, the researchers have achieved an impressive 18 percent efficiency with the nanocrystals, higher than most experimental energy sources.

In addition, Xu says, "because we can tune the fiber and plate sizes, we can use even small amounts of [mechanical] noise — like a vibration or water flowing — to bend the fibers and plates. With this kind of technology, we can scavenge energy waste and convert it into useful chemical energy."

Rather than harvest this electrical energy directly, the scientists took a novel approach and used the energy to break the chemical bonds in water and produce oxygen and hydrogen gas.

"This is a new phenomenon, converting mechanical energy directly to chemical energy," Xu says, calling it a piezoelectrochemical (PZEC) effect.

The chemical energy of hydrogen fuel is more stable than the electric charge, he explains. It is relatively easy to store and will not lose potency over time.

With the right technology, Xu envisions this method being useful for generating small amounts of power from a multitude of small sources — for example, walking could charge a cell phone or music player and breezes could power streetlights.

"We have limited areas to collect large energy differences, like a waterfall or a big dam," he says. "But we have lots of places with small energies. If we can harvest that energy, it would be tremendous."

The new paper is co-authored by graduate student Kuang-Sheng Hong, research scientist Hiromi Konishi and mechanical engineering professor Xiaochun Li, all at UW-Madison. Xu's research is supported by grants from the UW-Madison Graduate School, National Science Foundation, NASA Astrobiology Institute and the U.S. Department of Energy.

Scientists Transplant Mosquito's Nose, Advance Fight Against Malaria

Tuesday, February 16, 2010

Scientists at Vanderbilt and Yale universities have successfully transplanted most of the “nose” of the mosquito that spreads malaria into frog eggs and fruit flies and are employing these surrogates to combat the spread of the deadly and debilitating disease that afflicts 500 million people.

The research is described in two complimentary papers, one published this week in the early online edition of the Proceedings of the National Academy of Sciences and the other which appeared online Feb. 3 in the journal Nature.

The mosquito’s “nose” is centered in its antennae, which are filled with nerve cells covered with special “odorant receptors” that react to different chemical compounds. The insect ORs are comparable to analogous receptors in the human nose and taste buds on the tongue.

“We’ve successfully expressed about 80 percent of the Anopheles mosquito’s odorant receptors in frog’s eggs and in the fruit fly antennae,” says Laurence Zwiebel, professor of biological sciences at Vanderbilt, whose lab performed the frog egg transplantation. The fruit-fly (Drosophila melanogaster) work was done in the laboratory of John Carlson, Eugene Higgins Professor of Molecular, Cellular and Developmental Biology at Yale.

Both accomplishments are part of a five-year project supported by the Grand Challenges in Global Health Initiative funded by the Foundation for NIH through a grant from the Bill & Melinda Gates Foundation with the goal of producing novel ways to inhibit the spread of malaria. Scientists from the Wageningen University in the Netherlands, the African Insect Science for Food and Health Institute in Kenya, Ifakara Health Institute in Tanzania and the Medical Research Council Laboratories in the Gambia are also participating in the project.

Previously, scientists have used frog eggs to study the olfactory receptors of moths, honeybees and fruit flies. DNA that encodes insect receptors are injected into a frog egg and given sufficient time to produce and localize proteins. As a result, the surface of the egg is covered with the mosquito odorant receptors. An engineered egg is placed in a voltage clamp system and an odorant is dissolved in the buffer solution in which the egg is floating. If the mosquito receptors react to the compound, the electrical properties of the egg change in a measurable fashion.

“The frog egg system is relatively rapid, highly sensitive and allows us to do very precise measurements of odorant response,” says Guirong Wang, a senior research associate in the Zwiebel lab who was the lead author on the PNAS study and carried out several thousand egg/odorant recordings. “However, we call this a medium throughput system because, while it is relatively quick to set up, we have to make the odorant solutions by hand, which goes relatively slowly.”

By comparison, Yale’s Drosophila system is a somewhat lower throughput system because it takes about three months to engineer a fruit fly with a mosquito odorant receptor in its antennae. The system, originally developed in the Carlson lab, uses mutant flies that are missing an odor receptor. Allison Carey, a graduate student in the Yale lab, systematically inserted mosquito genes into fruit flies one at a time so that a mosquito odorant receptor was expressed in place of the missing receptor. Although the method is slightly slower than the frog egg approach, it has some distinct advantages: Most notably it responds to volatilized odorants so it works with compounds that don’t dissolve readily in water. It is also effective in detecting chemicals that inhibit receptors rather than exciting them.

“Both teams used the same set of 72 Anopheles odorant receptors and tested them using the same panel of 110 odorants,” says Wang. The Vanderbilt team got responses from 37 of the odorant receptors in the frog eggs while testing 6,300 odorant-receptor combinations. “The results of the two systems were quite similar. There were only a few small differences.”

Both studies found that most mosquito receptors are “generalists” that react to a number of different odors while a few are “specialists” that respond to a single or small number of odors. In some cases, the researchers found that a single odorant triggers several receptors while in other cases receptors are specifically tuned to unique compounds. In particular, they found 27 Anopheles receptors that respond strongly to compounds in human sweat.

“We’re now screening for compounds that interact with these receptors. We call those that do BDOCs (behaviorally disruptive olfactory compounds),” Zwiebel says. “Compounds that excite some of these receptors could help lure mosquitoes into traps or repel them away from people while others that block receptor activity may help mask people. Ultimately we are looking for cocktails of multiple compounds that demonstrate activity in the field.”

The project has already developed and patented a blend of BDOCs that is more attractive to mosquitoes than humans and has also identified several repellant BDOCs. It is currently in product development discussions with several private sector companies.

Researchers Discover a Way to Strengthen Proteins

Thursday, December 10, 2009

Proteins, which perform such vital roles in our bodies as building and maintaining tissues and regulating cellular processes, are a finicky lot. In order to work properly, they must be folded just so, yet many proteins readily collapse into useless tangles when exposed to temperatures just a few degrees above normal body temperature.

This precarious stability leaves proteins and the living beings that depend upon them on the edge of a precipice, where a single destabilizing change in a key protein can lead to disease or death. It also greatly complicates the manufacture and use of proteins in research and medicine.

Finding a way to stabilize proteins could help prevent such dire consequences, reduce the very high cost of protein drugs and perhaps also help scientists understand why proteins are often so unstable in the first place. In a paper published in the Dec. 11 issue of the journal Molecular Cell, researchers at the University of Michigan and the University of Leeds describe a new strategy for stabilizing specific proteins by directly linking their stability to the antibiotic resistance of bacteria.

"The method we developed should provide an easy way to strengthen many proteins and by doing so increase their practical utility," said James Bardwell, a Howard Hughes Medical Institute investigator and professor of molecular, cellular and developmental biology at U-M.

In the new approach, the researchers found that when a protein is inserted into the middle of an antibiotic resistance marker, bacterial antibiotic resistance becomes dependent upon how stable the inserted protein is. This enabled the scientists to easily select for stabilizing mutations in proteins by using a simple life-or-death test for bacterial growth on antibiotics. The mutations the scientists identified rendered proteins more resistant to unfolding.

"This method also has allowed us to catch a glimpse of why proteins may need to be just barely stable," said Linda Foit, the graduate student at U-M who initiated the work. "The mutations that we found to enhance the stability of our model protein are mostly in key areas related to the protein's function, suggesting that this protein may need to be flexible and therefore marginally stable in order to work. It may be that, over the course of evolution, natural selection acts to optimize, rather than maximize protein stability."

The work was conducted in the laboratories of Bardwell at U-M and Sheena Radford at the University of Leeds and spearheaded by Foit in Bardwell's lab and postdoctoral fellow Gareth Morgan in the Radford lab. In addition to these researchers, the paper's authors are U-M undergraduate students Maximilian Kern, Lenz Steimer and Anne Kathrin von Hacht and Leeds technician James Titchmarsh and senior lecturer Stuart Warriner. The research was funded in part by the Howard Hughes Medical Institute, the National Institutes of Health, the Wellcome Trust and the University of Leeds.

Flying Dinosaur Controversy Resolved

Thursday, December 10, 2009

New research appears to have ended a scientific debate that has vexed palaeontologists for almost 100 years.

Flying reptiles called pterosaurs ruled the Earth’s skies for over 130 million years and died out 65 million years ago.

The aerodynamics of the membrane stretched over the huge 12-meter wing span would have influenced the way these animals could fly, but scientists have not been able to agree on the orientation of a particular wing-bone that controlled the shape of this membrane.

Since 1914, there have been two theories on the positioning of the pteriod, a unique wing-bone at the front of the pterosaur wing. One argues that it must have been positioned sideways, while the other suggests that it pointed forwards.

Using biomechanical analysis and testing aerodynamic efficiency, new findings by researchers from the University of Bristol, UK, and University College Dublin, Ireland, suggest that the only conceivable positioning of the wing bone is a sideways orientation.

“Based on existing fossil evidence, pterosaurs are believed to have had a wing span of up to 12 meters and a weight of between 80 and 250 kilograms,” says Colin Palmer from the University of Bristol and lead author on the paper.

“In our analysis we show that a forward pointing pteriod would not have been able to withstand the stresses and strains involved in the take off and flight of such a large animal.”

“The structure of the pterosaur wing must have afforded a high safety margin above what was required to support flight in such a massive animal, in order to prevent against any possible breakage or damage which would be catastrophic for the animal. And a forward pointing pteriod would not afford such a safety margin,” explains Palmer.

“We were working to reconstruct how these enormous reptiles flew - how they took to the air, how they landed, and how they made their living in flight,” says Dr Gareth Dyke from University College Dublin, the papers co-author.

“The direction of the pteriod bone has a major impact on the aerodynamics and performance of the pterosaur wing. A sideways orientation implies a faster flyer.”

“It affects the speed at which they could fly, which could tell you about the type of life they led, where they lived, and possibly even what they ate. They are the biggest animals ever take to the skies,” says Dyke.

The research is published online this week in the Proceedings of The Royal Society B.

H1N1 Influenza Adopted Novel Strategy to Move from Birds to Humans

Wednesday, December 9, 2009

The 2009 H1N1 influenza virus used a new strategy to cross from birds into humans, a warning that it has more than one trick up its sleeve to jump the species barrier and become virulent.

In a report in this week's early online edition of the journal Proceedings of the National Academy of Sciences, University of California, Berkeley, researchers show that the H1N1, or swine flu, virus adopted a new mutation in one of its genes distinct from the mutations found in previous flu viruses, including those responsible for the Spanish influenza pandemic of 1918, the "Asian" flu pandemic in 1957 and the "Hong Kong" pandemic of 1968.

Previous influenza strains that crossed from birds into people had a specific point mutation in the bird virus's polymerase gene that allowed the protein to operate efficiently inside humans as well. The polymerase transcribes the virus's RNA, allowing the host to express viral genes, and also copies the viral genome, needed to make new viruses.

The 2009 H1N1 virus retains the bird version of the polymerase, but has a second mutation that seems to suppress the ability of human cells to prevent the bird polymerase from working.

“We were quite shocked when we looked at the swine flu virus, which was clearly replicating in people and other mammalian systems, yet had a polymerase that looked like it was derived from a bird virus, which should not function too well in a human cell type,” said UC Berkeley post-doctoral fellow Andrew Mehle of the Department of Molecular and Cell Biology. “The other mutation within the polymerase seems to compensate and allow the enzyme to function.”

The researchers also discovered another strategy – one not yet adopted by any known flu virus – by which influenza virus can increase its virulence even more. When a particular human subunit is substituted for one of the three protein subunits that make up the bird polymerase, the new combination makes the polymerase more efficient in human cells.

“This is an extremely rare mutation and a rare combination, which suggests that there may be other ways that haven’t emerged yet that these viruses are going to continue to evolve,” said Jennifer Doudna, UC Berkeley professor of molecular and cell biology and an investigator in the Howard Hughes Medical Institute.

“As mechanistic biologists, we are hoping that by understanding how the virus works at the molecular level, we will be able to predict with more accuracy how it will evolve.”

She suggested that those monitoring influenza outbreaks around the world in search of new variants be on the lookout for this recombination of polymerase subunits, which could herald an uptick in swine flu virulence. The findings also could help scientists develop better antiviral treatments, Mehle and Doudna said.

“The more we can understand the biochemistry and the particular structure of these polymerase complexes, the better we can make rational decisions about drug development,” Mehle said.

H1N1, which appeared on the scene earlier this year, was dubbed swine flu because it emerged from pigs, in which human, bird and pig influenza viruses mixed, swapped genes and gave rise to a variant that could infect human cells and reproduce.

While mutations in the surface protein hemagglutinin – indicated by the H in H1N1 – are key to allowing the virus to enter human cells, mutations in the polymerase enzyme are key to the virus's ability to replicate inside human cells. All previous flu strains that entered and were transmitted in humans had a single mutation in the second subunit of the bird polymerase gene, which apparently allowed the enzyme to operate in human cells.

Last year, Mehle and Doudna showed that human cells apparently prevent the three subunits of bird virus polymerases from assembling into a functioning enzyme. A single amino acid switch at position 627 on the second subunit of the polymerase overcomes that inhibition and allows the virus to replicate. Apparently, Mehle said, when the amino acid glutamic acid – typical of most bird virus polymerases – is changed to a lysine, typical of human polymerases, the surface charge of the subunit changes from acidic (negatively charged) to basic (positively charged) and allows assembly of the subunits. Previous studies in mammals have shown that a lysine in that position enhances polymerase activity, increases viral replication and transmission, and in some cases, is associated with increased pathogenicity and death.

In their new study, Mehle and Doudna found that H1N1 has two rare mutations in the second subunit: a serine at position 590 and an arginine at position 591. This combination, which is most common in pigs, apparently has the same effect on surface charge as the mutation at position 627, allowing the polymerase complex to form and function in human cells.

Mehle noted that, in addition to such point mutations, flu viruses also mix and match the three subunits. Both the 1957 and 1968 viruses had polymerases composed of a first subunit from a bird and the other two subunits from humans. H1N1 has a human-like first subunit, while the second and third are bird-like – hence the need for a mutation in the second subunit to make it more human-like.

To see which other combinations might make H1N1 more virulent, they mixed human, avian and pig subunits in culture, replicating the pig "mixing vessel," Mehle said. Several combinations with a human third subunit increased the activity of the polymerase enzyme when other mutations were not present in the second subunit. Viruses with this alteration are now being tested in human cell culture to see if they are more virulent.

"In addition to having individual amino acid changes affecting the ability of the virus to transmit across species and be more pathogenic, we need to think about these entire gene segments being exchanged back and forth," said Doudna, who also is a faculty affiliate of the California Institute for Quantitative Biosciences (QB3). "Those will affect the outcome of disease."

"We are very hopeful that the kind of basic science that we are doing here will have an impact on human health, either at the level of diagnostics or thinking forward to development of antiviral therapeutics," she added.

Mehle and Doudna continue to explore the polymerase to discover what in human cells prevents the assembly of the bird polymerase, and to determine the three-dimensional structure of the enzyme and its three subunits.

The work was supported by the National Institute of General Medical Sciences of the National Institutes of Health.

New molecule identified in DNA damage response

Tuesday, December 8, 2009

In the harsh judgment of natural selection, the ultimate measure of success is reproduction. So it’s no surprise that life spends lavish resources on this feat, whether in the courtship behavior of birds and bees or replicating the cells that keep them alive. Now research has identified a new piece in an elaborate system to help guarantee fidelity in the reproduction of cells, preventing potentially lethal mutations in the process.

In experiments to be published in the December 18 issue of the Journal of Biological Chemistry, researchers at The Rockefeller University identified the molecule SMARCAL1 as part of cells’ damage control response to malfunctioning

DNA replication. In typical cell division, many different molecules have roles in guaranteeing the daughter strands of DNA are as identical as possible to their parent. Some molecules check for errors or ‘proofread’ the offspring for typos, for instance; others, when alerted to a problem, arrest the replication process and conduct repairs.

Lisa Postow, a postdoctoral fellow in Hironori Funabiki’s Laboratory of Chromosome and Cell Biology, used mass spectroscopy to identify SMARCAL1 as involved in this intricate quality control process. Working with Brian T. Chait’s Laboratory of Mass Spectrometry and Gaseous Ion Chemistry, Postow found the protein in a proteomics screen for molecules that were drawn to a dangerous DNA repair problem called a double-strand break.

In both human cells and in cells from African clawed frog egg extract, Postow found that at double-strand breaks, SMARCAL1 gathered with another molecule called RPA, which is known to coat broken strands of DNA and protect them while damage is repaired. SMARCAL1 had an added interest, too: A mutation in the gene that produces it is involved in a rare but lethal disease called Schimke immuno-osseous dysplasia, a disorder that causes wide-ranging problems including kidney malfunction, immunodeficiency and growth inhibition.

To Postow’s surprise, she found that removing SMARCAL1 had little effect on double-strand break repair. However, it did facilitate a different aspect of the DNA damage response called replication fork stabilization, a process that holds steady the junction between parental and daughter strands — the replication fork — when replication is stalled because a problem has been detected. “For a mutation that causes such wide-ranging and severe physiological effects, it is surprising that the protein has such a relatively small effect at the cellular level,” Postow says.

Postow’s findings were largely corroborated by independent new research into SMARCAL1, which was published this fall in four back-to-back papers in Genes & Development. The work reveals another piece of the complex safeguards the body has in place to protect against dangerous mutations.

“This study also proves that the proteomic approach that Lisa has developed with Dr. Chait can efficiently identify proteins involving the DNA-damage recognition and repair process,” says Funabiki. “Many more excitements are ahead of us.”