OREGON STATE UNIVERSITY

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Groundbreaking investigative effort identifies gonorrhea vaccine candidates

CORVALLIS, Ore. – Researchers at Oregon State University have identified a pair of proteins that show promise as the basis for a gonorrhea vaccine.

The findings are an important step toward a potential new weapon in the fight against a sexually transmitted disease that affects millions of people around the globe, with nearly 80 million new cases estimated each year.

The pathogen that causes the disease, Neisseria gonorrhoeae, is considered a “superbug” because of its resistance to all classes of antibiotics available for treating infections. 

Gonorrhea is highly damaging to reproductive and neonatal health if untreated or improperly treated. It can lead to endometritis, pelvic inflammatory disease, ectopic pregnancy, epididymitis and infertility. Also, babies born to infected mothers are at increased risk of blindness.

More than half of infected women don’t have symptoms, but those asymptomatic cases can still lead to severe consequences for the patient’s reproductive health, including miscarriage or premature delivery, said OSU College of Pharmacy researcher Aleksandra Sikora.

Subjecting N. gonorrhoeae to the phenotypic microarray screening method for the first time, Sikora’s team focused on seven proteins from the bacteria’s cell envelope, which consists of the outer membrane, the cell wall and the inner membrane. 

Phenotypic microarrays are a high-throughput system featuring plates with 96 wells per plate, each well representing a different condition under which to research the phenotypes – the observable characteristics – of the examined mutants.

The goal was to see which if any of the seven proteins would show strong potential as a vaccine antigen – a molecule that sends the immune system into action. Vaccines prevent disease because the antigens they contain trigger an immune response that allows antibodies to recognize and attack pathogens to prevent future infection.

“Proteins in the cell envelope play key roles in cell function and bacterial physiology,” Sikora said. “That and their location make them attractive candidates for developing vaccines. But a lot of them are hypothetical proteins – we know bacteria have them but we don’t know for sure how they function. Learning what they contribute to cell structure, permeability, membrane biogenesis and so on is important in vaccine research because antibodies against protein antigens can disable the protein’s function.”

In all, more than 1,000 conditions were used to study the effects of knocking out each of the seven proteins.

“It’s like a football coach trying to choose the top quarterback among seven candidates by looking at their performance on many different teams during many different games,” Sikora said. “Imagine being able to look at those seven quarterbacks in over a thousand different games simultaneously. Of course, that’s not possible with football, but this is what we are doing here to identify the most promising vaccine candidates.”

Researchers found 91 conditions that had uniquely positive or negative effects on one of the mutants, and a cluster analysis of 37 commonly beneficial compounds and 57 commonly detrimental compounds revealed three separate phenotype groups.

Two of the proteins, NGO1985 and NGO2121, showed extensive sensitivity to antimicrobial compounds and thus emerged as the most promising vaccine candidates. This study serves as a jumping-off point for further characterization of proteins in the cell envelope. 

“Neisseria gonorrhoeae is a difficult bacteria to work with, and it’s very diverse,” Sikora said. “It has great genome plasticity – there are huge variations between strains. Phenotypic screening allows us to see how similar and how different they are.”

The National Institutes of Health supported this research. Findings were recently published in the Journal of Bacteriology.

The study was designed by Sikora and performed by Ph.D. candidate Benjamin Baarda in collaboration with Philip Proteau, a colleague of Sikora in the Department of Pharmaceutical Sciences, and Sarah Emerson in the Statistics Department of the OSU College of Science.

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New assay leads to step toward gene therapy for deaf patients

CORVALLIS, Ore. – Scientists at Oregon State University have taken an important step toward gene therapy for deaf patients by developing a way to better study a large protein essential for hearing and finding a truncated version of it.

Mutations in the protein, otoferlin, are linked to severe congenital hearing loss, a common type of deafness in which patients can hear almost nothing.

The research suggests otoferlin, which is in the cochlea of the inner ear, acts as a calcium-sensitive linker protein. The study also shows that a mutation in otoferlin weakens the binding between the protein and a calcium synapse in the ear, and deficiencies in that interaction might be at the root of hearing loss related to otoferlin.

The size of the otoferlin molecule and its low solubility have made it difficult to study, including how otoferlin works differently than another neuronal calcium sensor in the brain, synaptotagmin.

To combat those challenges, researchers in OSU’s College of Science developed a single-molecule colocalization binding titration assay – smCoBRA – for quantitatively probing otoferlin.

“It’s a one-trick pony of a protein,” said corresponding author Colin Johnson, associate professor of biochemistry and biophysics. “A lot of genes will find various things to do, but otoferlin seems only to have one purpose and that is to encode sound in the sensory hair cells in the inner ear. And small mutations in otoferlin render people profoundly deaf.”

The work by Johnson and collaborators in the Department of Physics and Department of Biochemistry and Biophysics provides a molecular-level explanation for the observation that otoferlin and synaptotagmin don’t have the same functional role.

The research, performed using recombinant protein from cell lysate isolated in vitro, also validates a methodology for characterizing large, multivalent membrane proteins in general.

“The otoferlin gene is really big, and it makes a huge protein,” Johnson said. “The traditional method for making a recombinant protein is using E. coli, but they loathe big proteins. This paper came up with a way of getting around that challenge.

“We were trying to shorten the gene, to find a truncated form that can be used for gene therapy. There is a size limit in terms of what you can package into the gene delivery vehicle, and otoferlin is too large. That’s the holy grail, trying to find a miniature version of otoferlin that that can be packaged into the delivery vehicle and then hopefully the patient can start hearing.”

Otoferlin’s size has precluded rescue experiments in which a modified mRNA for otoferlin is transfected into an animal model to replace a suppressed or knocked-down otoferlin gene causing deafness.

The study by Johnson, doctoral biochemistry student Nicole Hams, former biochemistry doctoral student Murugesh Padmanaryana and biophysicist Weihong Qiu identified a truncated form of otoferlin that can function in the encoding of sound.

The National Institutes of Health supported this study. Results were recently published in the Proceedings of the National Academy of Sciences.

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Colin Johnson

Colin Johnson

Protein transport channel offers new target for thwarting pathogen

CORVALLIS, Ore. – A bacterium that attacks people suffering from chronic lung disease and compromised immune systems could be halted by disrupting the distribution channels the organism uses to access the nutrient-rich cytoplasm of its host cell.

The findings by researchers in Oregon State University’s colleges of science and veterinary medicine are important because they suggest a new therapeutic target for one of the leading causes of bacterial infection in patients with HIV/AIDS.

The bacterium is Mycobacterium avium, the most common pathogen among non-tuberculosis mycobacteria. Highly opportunistic, M. avium invades and proliferates within a variety of human cells; it resides in a cytoplasmic vacuole and survives by remodeling its vacuolar compartment and resisting its host’s antimicrobial mechanisms.

“Most bacteria that grow in phagocytic cells export their effector proteins that impair or redirect macrophage function by using a needle-like apparatus that perforates the vacuole membrane and delivers virulence-associated molecules to the cytoplasm,” said co-corresponding author Luiz Bermudez of OSU’s College of Veterinary Medicine. “But mycobacteria don’t have that, so the question has always been, how do all these proteins get exported, how do they cross the vacuole membrane?”

They likely do so because proteins of the pathogen dock to transport proteins of the phagosome in the host cell in a way that allows for the efficient secretion of effector proteins. Co-corresponding author Lia Danelishvili, also of the College of Veterinary Medicine, identified voltage-dependent anion channels as a possible means of exporting those proteins.

“A VDAC is very small, but it can become larger if several VDAC proteins get together through polymerization,” Bermudez said. “We found that yes, mycobacteria use surface proteins to bind to the VDAC. But although we tried to see if the proteins of the mycobacterium were exported by the VDAC, we couldn’t show that. However, we did show that another component of the cell wall of the mycobacterium, lipids, are exported by that mechanism.”

Next up is determining what specific physical and chemical interactions occur to make effector protein transport possible.

“The idea is to find out the mechanism bacteria use to secrete proteins produced in the cells that have important functions in controlling the phagocytic activity that’s supposed to kill them,” Bermudez said.

Findings were recently published in Scientific Reports. 

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As Tolstoy noted (sort of), all unhappy microbiomes are unhappy in their own way

CORVALLIS, Ore. – The bacterial communities that live inside everyone are quite similar and stable when times are good, but when stress enters the equation, those communities can react very differently from person to person.

A microbiological version of the “Anna Karenina principle,” it’s a new paradigm suggested by scientists at Oregon State University – one that has key implications for a more personalized approach to antibiotic therapy, management of chronic diseases and other aspects of medical care.

The principle gets its name from the opening line of the novel “Anna Karenina” by 19th century Russian author Leo Tolstoy: “All happy families are alike; each unhappy family is unhappy in its own way.”

It turns out that this observation also applies to perturbed microbiotas of humans and animals.

“When microbiologists have looked at how microbiomes change when their hosts are stressed from any number of factors – temperature, smoking, diabetes, for example – they’ve tended to assume directional and predictive changes in the community,” said Rebecca Vega Thurber, corresponding author on the perspective study funded by the National Science Foundation. “After tracking many datasets of our own we never seemed to find this pattern but rather a distinct one where microbiomes actually change in a stochastic, or random, way.”

Findings were published today in Nature Microbiology.

Lead author Jesse Zaneveld of the University of Washington-Bothell collaborated with Vega Thurber and her student, Ryan McMinds, to survey the literature on microbial changes caused by perturbation. Together they found those stochastic changes to be a common occurrence, but one that researchers have tended to discard as “noise” rather than report.

“Thus we present the Anna Karenina principle for microbiomes,” Vega Thurber said. “When microbiomes are happy they are all similar in their composition but during stress or unhappiness they change in a multitude of distinct ways. This piece draws together diverse microbiome research. We think this is an important emerging paradigm for thinking about microbiome data. We present ways of identifying it and distinguishing it from other patterns.”

In addition to the literary reference, Vega Thurber offers a wintry metaphor to explain what she and her collaborators have discovered.

“When healthy our microbiomes look alike, but when stressed each one of us has our own microbial snowflake,” she said. “You or I could be put under the same stress, and our microbiomes will respond in different ways – that’s a very important facet to consider for managing approaches to personalized medicine. Stressors like antibiotics or diabetes can cause different people’s microbiomes to react in very different ways.”

Humans and animals are filled with symbiotic communities of microorganisms that often fill key roles in normal physiological function and also influence susceptibility to disease. Predicting how these communities of organisms respond to perturbations – anything that alters the systems’ function – is one of microbiologists’ essential challenges.

Studies of microbiome dynamics have typically looked for patterns that shift microbiomes from a healthy stable state to a dysbiotic stable state; dysbiosis refers to the microbial communities being out of their natural balance, which can result in the interruption of basic biological functions for the host person or animal.

“The Anna Karenina principle is a complementary alternative,” Vega Thurber said. “The changes induced by many perturbations lead to transitions from stable to unstable community states – dysbiotic individuals vary more in microbial community composition than healthy individuals.”

Scientists found patterns consistent with Anna Karenina effects in a range of systems, from corals exposed to above-average temperatures to the lungs of smokers to patients suffering from HIV/AIDS.

“Our message to researchers is, don’t throw out these observations as noise, but include this principle in the microbiome pipelines and software so that scientists can press a button that gives you the answer to, ‘Do I see the Anna Karenina principle in the dataset,’” Vega Thurber said.

OSU researchers have already given multiple presentations on the principle and it’s been well received in the microbiology community, Vega Thurber said. 

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Study reveals seven complete specimens of new flower, all 100 million years old

CORVALLIS, Ore. – A Triceratops or Tyrannosaurus rex bulling its way through a pine forest likely dislodged flowers that 100 million years later have been identified in their fossilized form as a new species of tree.

George Poinar Jr., professor emeritus in Oregon State University’s College of Science, said it’s the first time seven complete flowers of this age have been reported in a single study. The flowers range from 3.4 to 5 millimeters in diameter, necessitating study under a microscope.

Poinar and collaborator Kenton Chambers, professor emeritus in OSU’s College of Agricultural Sciences, named the discovery Tropidogyne pentaptera based on the flowers’ five firm, spreading sepals; the Greek word for five is “penta,” and “pteron” means wing.

“The amber preserved the floral parts so well that they look like they were just picked from the garden,” Poinar said. “Dinosaurs may have knocked the branches that dropped the flowers into resin deposits on the bark of an araucaria tree, which is thought to have produced the resin that fossilized into the amber. Araucaria trees are related to kauri pines found today in New Zealand and Australia, and kauri pines produce a special resin that resists weathering.”

This study builds on earlier research also involving Burmese amber in which Poinar and Chambers described another species in the same angiosperm genus, Tropidogyne pikei; that species was named for its flower’s discoverer, Ted Pike. Findings were recently published in Paleodiversity.

“The new species has spreading, veiny sepals, a nectar disc, and a ribbed inferior ovary like T. pikei,” Poinar said. “But it’s different in that it’s bicarpellate, with two elongated and slender styles, and the ribs of its inferior ovary don’t have darkly pigmented terminal glands like T. pikei.”

Both species have been placed in the extant family Cunoniaceae, a widespread Southern Hemisphere family of 27 genera.

Poinar said T. pentaptera was probably a rainforest tree.

“In their general shape and venation pattern, the fossil flowers closely resemble those of the genus Ceratopetalum that occur in Australia and Papua-New Guinea,” he said. “One extant species is C. gummiferum, which is known as the New South Wales Christmas bush because its five sepals turn bright reddish pink close to Christmas.”

Another extant species in Australia is the coach wood tree, C. apetalum, which like the new species has no petals, only sepals. The towering coach wood tree grows to heights of greater than 120 feet, can live for centuries and produces lumber for flooring, furniture and cabinetwork.

So what explains the relationship between a mid-Cretaceous Tropidogyne from Myanmar, formerly known as Burma, and an extant Ceratopetalum from Australia, more than 4,000 miles and an ocean away to the southeast?

That’s easy, Poinar said, if you consider the geological history of the regions.

“Probably the amber site in Myanmar was part of Greater India that separated from the southern hemisphere, the supercontinent Gondwanaland, and drifted to southern Asia,” he said. “Malaysia, including Burma, was formed during the Paleozoic and Mesozoic eras by subduction of terranes that successfully separated and then moved northward by continental drift.”

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Tropidogyne pentaptera

Tropidogyne pentaptera

For bacteria that cheat, food is at the forefront

CORVALLIS, Ore. – If you’ve got plenty of burgers and beers on hand and your own stomach is full, an uninvited guest at your neighborhood barbecue won’t put much strain on you.

But if you’re hungry and food and drink supplies are running low when the moocher shows up, it’s a different story.

New research at Oregon State University indicates bacteria know just how you feel.

Microbes that produce important secretions for use in a community suffer a blow to their own fitness for supplying the non-producing “cheater” bacteria – but only when production requires the same nutrients that would otherwise go into growth and biomass.

Findings were published today in Nature Communications.

Bacteria are important organisms for evolutionary biology research because their fast growth allows scientists to study evolution in real time in the lab. The common, rod-shaped bacteria in the study, Pseudomonas aeruginosa, can lead to infections in humans, and cheater strains are often found among the infection-causing organisms.

“The big picture of this research is a better understanding of how cooperation works and how cooperation evolved,” said corresponding author Martin Schuster. “We can use microbes to study social evolution. Essentially every environment is nutrient limited in some way, and our study allows us to make predictions about what types of environments are conducive to cooperation or cheating.”

The study by Schuster and 2017 Ph.D. graduate Joe Sexton involved P. aeruginosa and a peptide siderophore it secretes, pyoverdine, or PVD.

P. aeruginosa uses PVD to scavenge iron, an essential and hard-to-get nutrient; the cheaters don’t produce PVD but have a receptor to collect the iron the siderophore binds with.

“The secretions benefit everyone, and cheating bacteria don’t participate in the production,” said Schuster, associate professor in OSU’s Department of Microbiology in the colleges of Science and Agricultural Sciences. “In general, cooperation is considered costly; therefore, cheaters can exploit the process by saving on the costs of cooperation.”

Building on earlier studies that showed cooperative behavior in P. aeruginosa can be exploited by mutant cheaters, this research demonstrates that the costs of bacterial cooperation are conditional.

“It’s all contextual and depends on the environment, the available nutrients, the bacterial diet,” Schuster said. “Sometimes cooperation is very costly, other times not at all. And if cooperation isn’t costly, it means that cheating doesn’t provide an advantage.”

In the case of PVD secretion, there’s a fitness cost involved for P. aeruginosa when carbon or nitrogen are in limited supply; those are building blocks for PVD and also necessary for producing cellular biomass.

But shortages of other nutrients – iron, phosphorus and sulfur – don’t result in a fitness cost; thus, the cheaters don’t gain an edge in those scenarios.

“Before, fitness cost was thought to be proportional to how much siderophore was being made,” Sexton said. “We showed that under different nutrient conditions the bacteria were still making the same amount, but the fitness costs varied dramatically.”

The researchers experimentally verified their modeling predictions with a chemostat format, an open system in which fresh nutrients flow in at the same rate spent growth medium flows out; cell density and growth rate are kept constant. In this system, the fitness costs of PVD production were apparent as growth differences between cooperators and cheaters in a mixed culture.

“In addition to fundamental questions about the evolution of cooperation, our work is also relevant to natural populations,” Sexton said. “There are siderophore-negative strains in the soil and the ocean and in human infections. Where did they come from? Did they evolve as cheaters, or for some other reason? Our work provides a new piece of the puzzle to consider in real-world contexts.”

The National Science Foundation and the Alexander von Humboldt Fellowship for Experienced Researchers supported this research.

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Siderophore cross-feeding

Bacterial "cheating"

Diatoms have sex after all, and ammonium puts them in the mood

CORVALLIS, Ore. – New research shows a species of diatom, a single-celled algae, thought to be asexual does reproduce sexually, and scientists learned it’s a common compound – ammonium – that puts the ubiquitous organism in the mood.

The findings, published today in PLOS One, may be a key step toward greater understanding of the evolution of sexual behavior and also have important biotechnology implications.

“Our discoveries solve two persistent mysteries that have plagued diatom researchers,” said corresponding author Kimberly Halsey, a microbiologist at Oregon State University. “Yes, they have sex, and yes, we can make them do it.”

Diatoms hold great potential as a bioenergy source and also for biosensing. In addition, their intricate, silica cell walls offer promising nanotechnology applications for materials chemists and drug-delivery researchers.

There are more than 200,000 species of diatoms, and the organisms are abundant nearly everywhere water is found, forming huge blooms in the spring and fall that help drive the marine carbon cycle.

“Diatoms are amazing; their silica frustules are beautiful and exquisite,” Halsey said. “Now that we can control their sexual pathway, that should open the door to being able to make crosses between different diatoms with different characteristics. We should be able to breed them just like we do with corn or rice or strawberries to select for traits that are really desirable.”

Halsey and collaborators in botany and statistics from OSU’s colleges of Science and Agricultural Sciences studied the “centric” Thalassiosira pseudonana species of diatom, a model organism for researchers; it’s one of two diatoms, the other being the “pennate” diatom Phaeodactulum tricornutum, to have had its genome sequenced.

Centric diatoms are radially symmetrical – think of them as shaped like a soup can, Halsey says – and pennate diatoms are bilaterally symmetrical: elongated in the manner of a pea pod.

“Everybody said Thalassiosira pseudonana was asexual, because they’d never seen anything else,” Halsey said. “The general thinking was that it just lost the ability or need to go through sex.”

Other scientists, Halsey notes, had showed T. pseudonana retained genes necessary for meiosis, a type of genetic replication specific to sexual reproduction, and concluded the diatom wasn’t using those genes.

“But we started seeing very different morphologies,” changes in cell structure, Halsey said, in this case related to sexual activity. “We also saw genes expressed that are involved in flagellar structures and assembly, which would only happen with sperm cells.”

Graduate student Eric Moore, lead author on the research, was astonished to learn “these single-celled organisms can differentiate into male and female cells, completely changing their morphologies.”

“In fact, I was convinced my cultures were contaminated before I realized what was actually going on,” he said.

Previous work by other researchers studying different types of centric diatoms showed that growth stress – interruptions of light, changes in salinity, shifts in nutrients – can sometimes, but not reliably, cause cells to become sexual.

“Lab efforts to induce sex in centric diatoms have ranged from sweet talk to torture,” Halsey said.

But manual, microscopic analysis by Halsey’s team found that ammonium, a common compound that’s a metabolic waste product of animals, reliably caused two strains of T. pseudonana and two other centric diatoms to change their cell structures, making eggs and sperm; ammonium caused the diatoms to get ready for sex when at least one other cell growth factor – such as light, phosphorus or silica – was in short supply.

In addition, RNA sequencing showed more than 1,200 diatom genes that changed in activity when ammonium lit the algae’s sexual fires. Halsey suggests that in nature, the protists that graze on the diatom blooms excrete the ammonium that triggers the diatoms’ sexualization.

“The specific collection of environmental factors that make diatoms have sex aren’t yet known,” she said. “But identifying ammonium as a sexuality inducer potentially opens the door to new avenues of research into breeding and genetic modification to control important traits.”

Collaborators also included Brianna Bullington of OSU’s Department of Microbiology, Alexandra Weisberg of the Department of Botany and Plant Pathology, and Yuan Jiang of the Department of Statistics.

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Thalassiosira pseudonana

New approach improves ability to predict metals’ reactions with water

CORVALLIS, Ore. – The wide reach of corrosion, a multitrillion-dollar global problem, may someday be narrowed considerably thanks to a new, better approach to predict how metals react with water.

Researchers at Oregon State University and the University of California, Berkeley, have developed a new computational method that combines two techniques to make predictions faster, less costly and more effective.

The findings, published in Nature Communications, could have a wide range of applications, including in the design of bridges and aircraft engines, both of which are susceptible to corrosion.

Every metal except precious metals like gold and silver reacts with water, said Doug Keszler, distinguished professor of chemistry in Oregon State’s College of Science.

“We’d like to predict the specific reactions of metals and combinations of metals with water and what the products of those reactions are, by computational methods first as opposed to determining them experimentally,” said Keszler, who also serves as director of the Center for Sustainable Materials Chemistry at OSU.

Traditionally, Keszler noted, when looking at metals dissolved in water, the chemical assumption has been that a metal dissolves to form a simple salt. That’s not always what happens, however.

“In many cases, it initially dissolves to form a complex cluster that contains many metal atoms,” he said. “We can now predict the types of clusters that exist in solution, therefore furthering the understanding of metal dissolution from a computational point of view.”

Studying aqueous metal oxide and hydroxide clusters from Group 13 elements – aluminum, gallium, indium and thallium – scientists coupled quantum mechanical calculations with a “group additivity” approach to create Pourbaix diagrams, the gold standard for describing dissolved metal species in water. 

“Applying this new approach, we arrive at a quantitative evaluation of cluster stability as a function of pH and concentration,” said study co-author Paul Ha-Yeon Cheong, associate professor of chemistry at OSU.

Understanding clusters is critical because of the role they play in chemical processes ranging from biomineralization to solution-deposition of thin films for electronics applications. And characterizing corrosion stems from being able to depict metals’ stable phases in water.

“If you’re designing a new steel for a bridge, for example, you’d like to include the potential for corrosion in a computational design process,” Keszler said. “Or if you have a new metal for an aircraft engine, you’d like to be able to determine if it’s going to corrode.”

These examples are not merely hypothetical. Just last summer, a Japanese airline had to refurbish all 100 Rolls-Royce engines on its fleet of Boeing 787 Dreamliners after a series of engine failures caused by the corrosion and cracking of turbine blades. The engines sell for $20 million each.

“Most Pourbaix diagrams do not include these metal clusters and hence our understanding of metal dissolution and reaction with water has been lacking,” said study co-author Kristin A. Persson, professor of materials science at UC Berkeley. “We have now uncovered a fast and accurate formalism for simulating these clusters in the computer, which will transform our abilities to predict how metals react in water.”

The National Science Foundation partially supported this research.

Lindsay Wills, I-Ya Chang and Thomas Mustard of the OSU Department of Chemistry were co-authors of the research, as was Xiaohui Qu of the University of California, Berkeley. 

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Coastal bridge

Alloying materials of different structures offers new tool for controlling properties

CORVALLIS, Ore. – New research into the largely unstudied area of heterostructural alloys could lead to greater materials control and in turn better semiconductors, advances in nanotechnology for pharmaceuticals and improved metallic glasses for industrial applications.

Heterostructural alloys are blends of compounds made from materials that don’t share the same atom arrangement. Conventional alloys are isostructural, meaning the compounds they consist of, known as the end members, have the same crystal structure.

“Alloys are all around us,” said study co-author Janet Tate, a physicist at Oregon State University. “An example of an istostructural alloy is an LED; you have a semiconductor like aluminum gallium arsenide, dope it with a particular material and make it emit light, and change the color of the light by changing the relative concentration of aluminum and gallium.”

Structure and composition are the two means of controlling the behavior of materials, Tate said. Combining materials gives the alloy properties between those that the end members have individually.

“If two materials have different structures, as you mix them together it’s not so clear which structure will win,” said Tate, the Dr. Russ and Dolores Gorman Faculty Scholar in the College of Science. “The two together want to take different structures, and so this is an extra way of tuning an alloy’s properties, a structural way. The transition between different crystal structures provides an additional degree of control.”

Tate and collaborators from around the world, including the National Renewable Energy Laboratory, published their findings in Science Advances.

“This is a very interesting piece of materials science that represents a somewhat uncharted area and it may be the beginning something quite important,” Tate said. “The heterostructural alloy concept had been known before, but it’s different enough that it hadn’t really been explored in a detailed phase diagram – the mapping of exactly how, at what temperature and what concentration, it goes from one structure to another.

“This paper is primarily the NERL’s theoretical work being supported by other collaborators’ experimental work,” Tate said. “Our involvement at OSU was in making one of the kinds of heterostructural alloys used in the research, the combination of tin sulfide and calcium sulfide.”

Tate and graduate student Bethany Matthews have been focusing on the semiconductor application.

“Tin sulfide is a solar cell absorber, and the addition of calcium sulfide changes the structure and therefore the electrical properties necessary for an absorber,” Tate said “Combining tin sulfide with calcium sulfide makes it more isotropic – properties being the same regardless of orientation – and that’s usually a useful thing in devices.”

In this study, thin-film synthesis confirmed the metastable phases of the alloys that had been predicted theoretically.

“Many alloys are metastable, not stable – if you gave them enough time and temperature, they’d eventually separate,” Tate said. “The way we make them, with pulsed laser deposition, we allow the unstable structure to form, then suppress the decomposition pathways that would allow them to separate; we don’t give them enough time to equilibrate.”

Metastable materials – those that are thermodynamically stable provided they are not subjected to large disturbances – are in general understudied, Tate said.

“When theorists predict properties, they tend to work with materials that are stable,” she said. “In general the stable compounds are easier to attack. The idea here with heterostructural alloys is that they give us a new handle, a new knob to turn to change and control materials’ properties.”

In addition to scientists at the National Renewable Energy Laboratory, the collaboration included researchers at the University of Colorado, the Colorado School of Mines, the SLAC National Accelerator Laboratory, and Harvard University.

The U.S. Department of Energy supported this research.

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OSU researcher part of $14 million NSF program for improved genomic tools

CORVALLIS, Ore. – Coral researcher Virginia Weis of Oregon State University is one of eight researchers selected for a new $14 million National Science Foundation program aimed at helping scientists better understand the relationship between gene function and the physical and functional characteristics of organisms.

Weis, head of the Department of Integrative Biology in OSU’s College of Science, will use her $1.875 million EDGE program award to further study the microscale cellular, molecular and genetic mechanisms that underpin the symbiosis between corals and algae.

EDGE stands for Enabling Discovery through Genomic Tools. The NSF’s Biological Sciences Directorate administers the program, which funds projects that seek to develop new tools and teach researchers how to use them.

“It’s a tremendous honor to be selected for this important new program,” Weis said.

Corals are made up of interconnected animal hosts called polyps that house microscopic algae inside their cells, Weis said. The coral-algal symbiosis, or partnership, is the foundation of the entire coral reef ecosystem; the polyps receive food from the algae, and the polyps in turn provide nutrients and protection to the algae.

“Coral reefs are profoundly important, diverse ecosystems that are threatened worldwide by environmental variation and stress,” Weis said. “While a great deal of attention has been focused on the environmental threats to corals, there remains only a partial understanding of the regulation of the symbiosis, and more knowledge will provide a stronger foundation for studies of coral health and coral stress, such as coral bleaching, in which the host polyps lose their symbiotic algae.”

Weis’ project will bring together coral biologists, cell biologists and geneticists from Stanford University, the Carnegie Institution and Florida International University to study a small sea anemone that serves as a proxy for corals. Corals do not survive well in a laboratory setting, are slow growing and are difficult to collect.

The fast-growing, weedy sea anemone Aiptasia will allow researchers to make quick progress on the study of coral symbiosis.

“This award is focused on technique development and swift dissemination of results through online communication platforms to both the scientific community and the public,” Weis said. “A variety of genetic techniques will be developed, including gene editing in both partners, to be able to test hypotheses about the involvement of specific genes in coral health and stress. This award will contribute to the training of scientists and expose school-aged children and others in the general public to coral reef and symbiosis science.”

Oregon Health & Science University, the University of Texas, Massachusetts Institute of Technology, Michigan State University, Penn State, Virginia Tech and Boyce Thompson Institute are the home institutions of the other EDGE award recipients.

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Virginia Weis

Virginia Weis