Researchers correlate incidences of rheumatoid arthritis and giant cell arteritis with solar cycles (BMJ Open)

Solar storm

Coronal mass ejection hurling plasma from the sun. (Image credit: NASA)

By John Greenwald, Princeton Plasma Physics Laboratory

What began as a chat between husband and wife has evolved into an intriguing scientific discovery. The results, published in May in BMJ (formerly British Medical Journal) Open, show a “highly significant” correlation between periodic solar storms and incidences of rheumatoid arthritis (RA) and giant cell arteritis (GCA), two potentially debilitating autoimmune diseases. The findings by a rare collaboration of physicists and medical researchers suggest a relationship between the solar outbursts and the incidence of these diseases that could lead to preventive measures if a causal link can be established.

RA and GCA are autoimmune conditions in which the body mistakenly attacks its own organs and tissues. RA inflames and swells joints and can cause crippling damage if left untreated. In GCA, the autoimmune disease results in inflammation of the wall of arteries, leading to headaches, jaw pain, vision problems and even blindness in severe cases.

Inspiring this study were conversations between Simon Wing, a Johns Hopkins University physicist and first author of the paper, and his wife, Lisa Rider, deputy unit chief of the Environmental Autoimmunity Group at the National Institute of Environmental Health Sciences in the National Institutes of Health, and a coauthor. Rider spotted data from the Mayo Clinic in Rochester, Minnesota, showing that cases of RA and GCA followed close to 10-year cycles. “That got me curious,” Wing recalled. “Only a few things in nature have a periodicity of about 10-11 years and the solar cycle is one of them.”

Wing teamed with physicist Jay Johnson of the U.S. Department of Energy’s Princeton Plasma Physics Laboratory, a long-time collaborator, to investigate further. When the physicists tracked the incidence of RA and GCA cases compiled by Mayo Clinic researchers, the results suggested “more than a coincidental connection,” said Eric Matteson, chair of the division of rheumatology at the Mayo Clinic, and a coauthor. This work drew upon previous space physics research supported by the DOE Office of Science.

The findings found increased incidents of RA and GCA to be in periodic concert with the cycle of magnetic activity of the sun. During the solar cycle, dramatic changes that can affect space weather near Earth take place in the sun. At the solar maximum, for example, an increased number of outbursts called coronal mass ejections hurl millions of tons of magnetic and electrically charged plasma gas against the Earth’s magnetosphere, the magnetic field that surrounds the planet. This contact whips up geomagnetic disturbances that can disrupt cell phone service, damage satellites and knock out power grids. More importantly, during the declining phase of the solar maximum high-speed streams develop in the solar wind that is made up of plasma that flows from the sun. These streams continuously buffet Earth’s magnetosphere, producing enhanced geomagnetic activity at high Earth latitudes.

The research, which tracked correlations of the diseases with both geomagnetic activity and extreme ultraviolet (EUV) solar radiation, focused on cases recorded in Olmsted County, Minnesota, the home of the Mayo Clinic, over more than five decades. The physicists compared the data with indices of EUV radiation for the years 1950 through 2007 and indices of geomagnetic activity from 1966 through 2007. Included were all 207 cases of GCA and all 1,179 cases of RA occurring in Olmsted County during the periods and collected in a long-term study led by Sherine Gabriel, then of the Mayo Clinic and now dean of the Rutgers Robert Wood Johnson Medical School.

Correlations proved to be strongest between the diseases and geomagnetic activity. GCA incidence — defined as the number of new cases per capita per year in the county — regularly peaked within one year of the most intense geomagnetic activity, while RA incidence fell to a minimum within one year of the least intense activity. Correlations with the EUV indices were seen to be less robust and showed a significantly longer response time.

The findings were consistent with previous studies of the geographic distribution of RA cases in the United States. Such research found a greater incidence of the disease in sections of the country that are more likely to be affected by geomagnetic activity. For example, the heaviest incidence lay along geographic latitudes on the East Coast that were below those on the West Coast. This asymmetry may reflect the fact that high geomagnetic latitudes — areas most subject to geomagnetic activity — swing lower on the East Coast than on the opposite side of the country. While Washington, D.C., lies just 1 degree farther north than San Francisco geographically, for example, the U.S. capital is 7 degrees farther north in terms of geomagnetic latitude.

Although the authors make no claim to a causal explanation for their findings, they identify five characteristics of the disease occurrence that are not obviously explained by any of the currently leading hypotheses. These include the east-west asymmetries of the RA and GCA outbreaks and the periodicities of the incidences in concert with the solar cycle. Among the possible causal pathways the authors consider are reduced production of the hormone melatonin, an anti-inflammatory mediator with immune-enhancing effects, and increased formation of free radicals in susceptible individuals. A study of 142 electrical power workers found that excretion of melatonin — a proxy used to estimate production of the hormone — was reduced by 21 percent on days with increased geomagnetic activity.

Confirming a causal link between outbreaks of RA and GCA and geomagnetic activity would be an important step towards developing strategies for mitigating the impact of the activity on susceptible individuals. These strategies could include relocating to lower latitudes and developing methods to counteract direct causal agents that may be controlled by geomagnetic activity. For now, say the authors, their findings warrant further investigations covering longer time periods, additional locations and other autoimmune diseases.

PPPL, on Princeton University’s Forrestal Campus in Plainsboro, N.J., is devoted to creating new knowledge about the physics of plasmas — ultra-hot, charged gases — and to developing practical solutions for the creation of fusion energy. Results of PPPL research have ranged from a portable nuclear materials detector for anti-terrorist use to universally employed computer codes for analyzing and predicting the outcome of fusion experiments. The Laboratory is managed by the University for the U.S. Department of Energy’s Office of Science, which is the largest single supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

This work was funded from NIH grants (NIAMS R01 AR046849, NIA R01 AG034676). This research was supported in part by the Intramural Research Program of the NIH, National Institute of Environmental Health Sciences. This work has also benefited from the works funded by NSF grants (ATM-0802715, AGS-1058456, ATM09002730, AGS1203299), NASA grants (NNX13AE12G, NNH09AM53I, NN09AK63I, NNH11AR07I), and DOE contract (DE-AC02-09CH11466).

Read the abstract

Wing, Simon; Rider, Lisa G.; Johnson, Jay R.; Miller, Frederick W.; Matteson, Eric L.; Crowson, Cynthia S.; Gabriel, Sherine E. “Do solar cycles influence giant cell arteritis and rheumatoid arthritis incidence?” BMJ Open, May 2015

Putting two and two together to make unexplored chemicals (J. American Chemical Society)

Schematic for cobalt-catalyzed [2pi+2pi] reaction.

Schematic for cobalt-catalyzed [2pi+2pi] reaction. Image credit: Chirik group, Princeton University

By Tien Nguyen, Department of Chemistry

Researchers at Princeton have developed a new catalyst that may give unprecedented access to cyclobutanes, four-membered ring-containing molecules that have been relatively unexplored. Held back by the limited scope of previous methods, called [2π+2π] reactions, many cyclobutanes compounds have been out of reach, along with any unique properties that may be of interest to the pharmaceutical or fine chemical industry.

Led by Paul Chirik, the Edwards S. Sanford Professor of Chemistry, the team published the new cobalt-catalyzed [2π+2π] reaction and a thorough investigation of its mechanism in the Journal of the American Chemical Society on June 1.

“Because examples of this reaction are so rare, we wanted to understand why these cobalt complexes were special and how they worked in the reaction,” said Valerie Schmidt, lead author on the article and a postdoctoral researcher in the Chirik lab.

The new cobalt-catalyzed reaction overcame limitations that have plagued other similar methods, such as poor selectivity or requiring very reactive alkenes, which are chemical structures composed of two carbons joined by a double bond, as starting materials. The research team suspected their success came from certain molecules, called bis(imino)pyridine ligands, that are attached to the cobalt center and which are capable of passing electrons to and from the metal.

The Chirik group has used these redox active ligands previously, attached instead to iron to catalyze a [2π+2π] reaction reported in 2006. But the iron catalyst is highly sensitive to air and moisture, an issue that could be mitigated by switching to a less reactive metal like cobalt.

Replacing iron with cobalt presented a unique challenge in analysis because it altered the complex’s overall magnetic state from diamagnetic to paramagnetic. Unlike diamagnetic compounds, paramagnetic compounds can be difficult to identify by nuclear magnetic resonance (NMR) spectroscopy, a technique that uses a strong magnet to pulse atomic nuclei to reveal their environments, and a primary tool for characterizing molecules.

“We really had to be creative in finding ways to confirm our hypotheses about the catalyst,” Schmidt said. One extremely useful tool, analogous to nuclear magnetic resonance but that pulses electrons instead of nuclei, was electron paramagnetic resonance (EPR). This technique allowed the researchers to track the unpaired electrons, called radicals, throughout the reaction.

Additional data gathered from theoretical calculations, kinetic studies and x-ray crystal structure elucidation allowed the research team to sketch out a detailed reaction mechanism. They proposed that the cycle begins with successive coordination of the two tethered alkenes to the metal center.

Coordination of the second alkene was crucial, Schmidt explained, because it changed cobalt’s geometry, from square planar to tetrahedral, and effectively moved the unpaired electron from the ligand to the metal. Only then can the metal based radical promote the carbon-carbon forming event and push the reaction forward.

This action leads to the formation of a metallacycle—a pentagon shaped ring of four carbons and one cobalt atom. Cobalt is then squeezed out of the ring to release the final four-membered cyclobutane product in a process called reductive elimination. After testing a series of catalysts with varying size and electronic properties, the researchers suggested that reductive elimination was the turnover-limiting step, essentially the bottleneck of the reaction.

Armed with a deeper understanding of the cobalt catalyst system, the researchers hope to continually enhance its performance. “We want to make it as easy as possible to access cyclobutane containing molecules, because without this ability, we really have no idea what we are missing out on,” Schmidt said.

Read the abstract.

Schmidt, V. A.; Hoyt, J. M.; Margulieux, G. W.; Chirik, P. J. “Cobalt-Catalyzed [2π+2π] Cycloadditions of Alkenes: Scope, Mechanism and Elucidation of Electronic Structure of Catalytic Intermediates.” Journal of the American Chemical Society 2015, Just Accepted Manuscript.

This work was supported by the National Institutes of Health Ruth L. Kirschstein National Research Service Award (F32 GM109594) and Princeton University Intellectual Property Accelerator Fund.

 

Giant structures called plasmoids could simplify the design of future tokamaks (Physical Review Letters)

Plasmoid formation in plasma simulation

Left: Plasmoid formation in simulation of NSTX plasma during CHI. Credit: Fatima Ebrahimi, PPPL / Right: Fast-camera image of NSTX plasma shows two discrete plasmoid-like bubble structures. Credit: Nishino-san, Hiroshima University

By Raphael Rosen, Princeton Plasma Physics Laboratory

Researchers at the U.S. Department of Energy’s Princeton Plasma Physics Laboratory (PPPL) have for the first time simulated the formation of structures called “plasmoids” during Coaxial Helicity Injection (CHI), a process that could simplify the design of fusion facilities known as tokamaks. The findings, reported in the journal Physical Review Letters, involve the formation of plasmoids in the hot, charged plasma gas that fuels fusion reactions. These round structures carry current that could eliminate the need for solenoids – large magnetic coils that wind down the center of today’s tokamaks – to initiate the plasma and complete the magnetic field that confines the hot gas.

“Understanding this behavior will help us produce plasmas that undergo fusion reactions indefinitely,” said Fatima Ebrahimi, a physicist at both Princeton University and PPPL, and the paper’s lead author.

Ebrahimi ran a computer simulation that modeled the behavior of plasma and the formation of plasmoids in three dimensions thoughout a tokamak’s vacuum vessel. This marked the first time researchers had modeled plasmoids in conditions that closely mimicked those within an actual tokamak. All previous simulations had modeled only a thin slice of the plasma – a simplified picture that could fail to capture the full range of plasma behavior.

Researchers validated their model by comparing it with fast-camera images of plasma behavior inside the National Spherical Torus Experiment (NSTX), PPPL’s major fusion facility. These images also showed plasmoid-like structures, confirming the simulation and giving the research breakthrough significance, since it revealed the existence of plasmoids in an environment in which they had never been seen before. “These findings are in a whole different league from previous ones,” said Roger Raman, leader for the Coaxial Helicity Injection Research program on NSTX and a coauthor of the paper.

The findings may provide theoretical support for the design of a new kind of tokamak with no need for a large solenoid to complete the magnetic field. Solenoids create magnetic fields when electric current courses through them in relatively short pulses. Today’s conventional tokamaks, which are shaped like a donut, and spherical tokamaks, which are shaped like a cored apple, both employ solenoids. But future tokamaks will need to operate in a constant or steady state for weeks or months at a time. Moreover, the space in which the solenoid fits – the hole in the middle of the doughnut-shaped tokamak – is relatively small and limits the size and strength of the solenoid.

A clear understanding of plasmoid formation could thus lead to a more efficient method of creating and maintaining a plasma through transient Coaxial Helicity Injection. This method, originally developed at the University of Washington, could dispense with a solenoid entirely and would work like this:

  • Researchers first inject open magnetic field lines into the vessel from the bottom of the vacuum chamber. As researchers drive electric current along those magnetic lines, the lines snap closed and form the plasmoids, much like soap bubbles being blown out of a sheet of soapy film.
  • The many plasmoids would then merge to form one giant plasmoid that could fill the vacuum chamber.
  • The magnetic field within this giant plasmoid would induce a current in the plasma to keep the gas tightly in place. “In principle, CHI could fundamentally change how tokamaks are built in the future,” says Raman.

Understanding how the magnetic lines in plasmoids snap closed could also help solar physicists decode the workings of the sun. Huge magnetic lines regularly loop off the surface of the star, bringing the sun’s hot plasma with them. These lines sometimes snap together to form a plasmoid-like mass that can interfere with communications satellites when it collides with the magnetic field that surrounds the Earth.

While Ebrahimi’s findings are promising, she stresses that much more is to come. PPPL’s National Spherical Torus Experiment-Upgrade (NSTX-U) will provide a more powerful platform for studying plasmoids when it begins operating this year, making Ebrahimi’s research “only the beginning of even more exciting work that will be done on PPPL equipment,” she said.

PPPL, on Princeton University’s Forrestal Campus in Plainsboro, N.J., is devoted to creating new knowledge about the physics of plasmas — ultra-hot, charged gases — and to developing practical solutions for the creation of fusion energy. Results of PPPL research have ranged from a portable nuclear materials detector for anti-terrorist use to universally employed computer codes for analyzing and predicting the outcome of fusion experiments. The Laboratory is managed by the University for the U.S. Department of Energy’s Office of Science, which is the largest single supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

Read the abstract

Ebrahimi and R. Raman. “Plasmoids Formation During Simulations of Coaxial Helicity Injection in the National Spherical Torus Experiment. Physical Review Letters. Published May 20, 2015. DOI: http://dx.doi.org/10.1103/PhysRevLett.114.205003

A little drop will do it: Tiny grains of lithium can dramatically improve the performance of fusion plasmas (Nuclear Fusion)

Fusion reaction image

Left: DIII-D tokamak. Right: Cross-section of plasma in which lithium has turned the emitted light green. (Credits: Left, General Atomics / Right, Steve Allen, Lawrence Livermore National Laboratory)

By Raphael Rosen, Princeton Plasma Physics Laboratory

Scientists from General Atomics and the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) have discovered a phenomenon that helps them to improve fusion plasmas, a finding that may quicken the development of fusion energy. Together with a team of researchers from across the United States, the scientists found that when they injected tiny grains of lithium into a plasma undergoing a particular kind of turbulence then, under the right conditions, the temperature and pressure rose dramatically. High heat and pressure are crucial to fusion, a process in which atomic nuclei – or ions – smash together and release energy — making even a brief rise in pressure of great importance for the development of fusion energy.

“These findings might be a step towards creating our ultimate goal of steady-state fusion, which would last not just for milliseconds, but indefinitely,” said Tom Osborne, a physicist at General Atomics and lead author of the paper. This work was supported by the DOE Office of Science.

The scientists used a device developed at PPPL to inject grains of lithium measuring some 45 millionths of a meter in diameter into a plasma in the DIII-D National Fusion Facility – or tokamak – that General Atomics operates for DOE in San Diego. When the lithium was injected while the plasma was relatively calm, the plasma remained basically unaltered. Yet as reported this month in a paper in Nuclear Fusion, when the plasma was undergoing a kind of turbulence known as a “bursty chirping mode,” the injection of lithium doubled the pressure at the outer edge of the plasma. In addition, the length of time that the plasma remained at high pressure rose by more than a factor of 10.

Experiments have sustained this enhanced state for up to one-third of a second. A key scientific objective will be to extend this enhanced performance for the full duration of a plasma discharge.

Physicists have long known that adding lithium to a fusion plasma increases its performance. The new findings surprised researchers, however, since the small amount of lithium raised the plasma’s temperature and pressure more than had been expected.

These results “could represent the birth of a new tool for influencing or perhaps controlling tokamak edge physics,” said Dennis Mansfield, a physicist at PPPL and a coauthor of the paper who helped develop the injection device called a “lithium dropper.” Also working on the experiments were researchers from Lawrence Livermore National Laboratory, Oak Ridge National Laboratory, the University of Wisconsin-Madison and the University of California-San Diego.

Conditions at the edge of the plasma have a profound effect on the superhot core of the plasma where fusion reactions take place. Increasing pressure at the edge region raises the pressure of the plasma as a whole. And the greater the plasma pressure, the more suitable conditions are for fusion reactions. “Making small changes at the plasma’s edge lets us increase the pressure further within the plasma,” said Rajesh Maingi, manager of edge physics and plasma-facing components at PPPL and a coauthor of the paper.

Further experiments will test whether the lithium’s interaction with the bursty chirping modes — so-called because the turbulence occurs in pulses and involves sudden changes in pitch — caused the unexpectedly strong overall effect.

PPPL, on Princeton University’s Forrestal Campus in Plainsboro, N.J., is devoted to creating new knowledge about the physics of plasmas — ultra-hot, charged gases — and to developing practical solutions for the creation of fusion energy. Results of PPPL research have ranged from a portable nuclear materials detector for anti-terrorist use to universally employed computer codes for analyzing and predicting the outcome of fusion experiments. The Laboratory is managed by the University for the U.S. Department of Energy’s Office of Science, which is the largest single supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

Read the abstract

T.H. Osborne, G.L. Jackson, Z. Yan, R. Maingi, D.K. Mansfield, B.A. Grierson, C.B. Chrobak, A.G. McLean, S.L. Allen, D.J. Battaglia, A.R. Briesemeister, M.E. Fenstermacher, G.R. McKee, P.B. Snyder and The DIII-D Team. “Enhanced H-mode pedestals with lithium injection in DIII-D.” Nuclear Fusion. Published May 8, 2015. DOI:10.1088/0029-5515/55/6/063018

 

Reshaping mountains in the human mind to save species facing climate change (Nature Climate Change)

2015_05_18_Himalaya_ElsenBy Morgan Kelly, Office of Communications

People commonly perceive mountain ranges as jumbles of pyramid-shaped masses that steadily narrow as they slope upward.

While that’s certainly how they appear from a ground-level human viewpoint, a new study shows that pyramid-shaped mountains are not only a minority in nature, but also that most ranges actually increase in area at higher elevations. Besides reshaping the mountains in our mind’s eye, the findings could lead scientists to reconsider conservation strategies — which are often based on misconceptions about mountain terrain — for mountain animal species threatened by climate change.

Researchers at Princeton University and the University of Connecticut conducted the first study to map the shape of the world’s major mountain ranges and found that the classic triangular form in which land-area uniformly decreases as elevation increases only applies to roughly one-third of the world’s mountain ranges, according to a report in the journal Nature Climate Change.

Instead, the 182 mountain ranges the researchers studied take on four principal shapes: diamond, pyramid, inverted pyramid and hourglass. The researchers analyzed high-resolution topography maps for every mountain range to determine land area by elevation. They found that for all the range shapes except pyramid, land availability can be greater at higher elevations than it is farther down the mountainside.

The researchers found that the 182 mountain ranges they studied have four principal shapes. Diamond-shaped ranges such as the Rocky Mountains (a) increase in land area from the bottom until mid-elevation before contracting quickly. Pyramid-shaped mountains such as the Alps (b) have sides that rise sharply and consistently decrease in area the higher they go. The Kunlun Mountains (c) of China take the form of inverse pyramids, which gradually expand in area as elevation increases before suddenly widening toward their peaks. For hourglass-shaped mountain ranges such as the Himalayas (d), land area rises slightly then decreases at mid-elevations before increasing sharply at higher elevations. The three-dimensional images (second row) represent each range shape as viewed from the side. Moving from bottom to top, the width of the shape changes to represent an increase or decrease in area at a specific elevation. Elevation spans from zero to more than 8,685 meters (28,494 feet), and is denoted by the color scale from blue (lowest elevation) to brown (highest elevation). (Image by Paul Elsen, Princeton University Department of Ecology and Evolutionary Biology; Morgan Tingley, University of Connecticut; and Mike Costelloe)

The researchers found that the 182 mountain ranges they studied have four principal shapes. Diamond-shaped ranges such as the Rocky Mountains (a) increase in land area from the bottom until mid-elevation before contracting quickly. Pyramid-shaped mountains such as the Alps (b) have sides that rise sharply and consistently decrease in area the higher they go. The Kunlun Mountains (c) of China take the form of inverse pyramids, which gradually expand in area as elevation increases before suddenly widening toward their peaks. For hourglass-shaped mountain ranges such as the Himalayas (d), land area rises slightly then decreases at mid-elevations before increasing sharply at higher elevations. The three-dimensional images (second row) represent each range shape as viewed from the side. Moving from bottom to top, the width of the shape changes to represent an increase or decrease in area at a specific elevation. Elevation spans from zero to more than 8,685 meters (28,494 feet), and is denoted by the color scale from blue (lowest elevation) to brown (highest elevation). (Image by Paul Elsen, Princeton University Department of Ecology and Evolutionary Biology; Morgan Tingley, University of Connecticut; and Mike Costelloe)

Yet, people’s idea that land area steadily shrinks as a mountain rises is so entrenched that it has come to guide conservation plans and research related to climate change, said first author Paul Elsen, a Princeton graduate student of ecology and evolutionary biology. Scientists project that as mountain species move to higher elevations to escape rising global temperatures they will face a consistent loss of territory — as well as an increase in resource competition — that all but ensures their eventual extinction.

While this risk exists in pyramid-shaped ranges, many species in other range types might in fact benefit from seeking higher altitudes if they move to an elevation with more land area than the one they left, Elsen said. The researchers’ results could be used to more precisely identify those elevation zones where species will encounter territory losses and potentially become more threatened as they move upward, he said. The limited resources that exist for conservation could then be targeted to those species.

“This work should completely change the way we see mountains,” Elsen said. “No one has looked at the shapes of mountain ranges across the entire globe, and I don’t think anyone would expect that only 30 percent of the ranges in the world have this pyramid shape that we have assumed is the dominant shape of mountains.

“That has been the prevailing image of mountains in the public perception and the scientific perception, and it’s really had a big influence on how scientists think mountain species will respond to climate change,” he said.

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The researchers are the first to measure available area by elevation — known as the hypsographic curve — at the scale at which animals actually live, said co-author Morgan Tingley, a University of Connecticut assistant professor of ecology and evolutionary biology and a past postdoctoral research associate in the Program in Science, Technology and Environmental Policy in Princeton’s Woodrow Wilson School of Public and International Affairs.

“People have explored the global pattern wherein you take all the surface area on the Earth and look at availability versus elevation. If you do that, then you do get a nice pyramidal pattern for all mountain ranges because there are so many low-elevation non-mountainous parts of the world,” Tingley said.

“But that’s not a relevant scale for species or conservation. There is no globally distributed mountain species,” he said. “At the spatial scales at which species live, the majority of mountain regions are not pyramids.”

Map

The researchers examined ranges on every continent except Antarctica and found that the pyramid form in which land-area uniformly decreases as elevation increases only applies to roughly one-third of the world’s mountain ranges. A majority, or 39 percent, of the ranges they studied are diamond-shaped (red), whereas pyramid-shaped mountains (green) constitute only 32 percent. The hourglass shape (blue) characterizes 23 percent of ranges, and only 6 percent of ranges take the form of an inverse pyramid (purple).(Image by Paul Elsen, Princeton University Department of Ecology and Evolutionary Biology, and Morgan Tingley, University of Connecticut)

Elsen and Tingley examined ranges on every continent except Antarctica spanning altitudes from zero to more than 8,500 meters (27,887 feet), which is the approximate maximum height of the Himalayas. A majority of the ranges they studied (39 percent) such as the Rocky Mountains are diamond-shaped, meaning that land-area increases from the bottom until the mid-elevation range before contracting quickly.

Hourglass-shaped mountain ranges such as the Himalayas make up 23 percent of ranges. Land area in these types rises slightly then decreases at mid-elevations before increasing sharply at higher elevations.

The nearby Kunlun Mountains of China are representative of the 6 percent of ranges worldwide that take the form of inverse pyramids, which gradually expand in area as elevation increases before, like the hourglass ranges, suddenly widening toward their peaks.

A mainstay of the human mind, pyramid-shaped mountains such as the Alps constitute only 32 percent of the mountain ranges that Elsen and Tingley studied. These mountains have sides that rise sharply and consistently decrease in area the higher they go.

On the other hand, the other range shapes are formed by a series of slopes that rise to open, wide plateaus situated at the base of yet more slopes, Elsen said. These mountains are akin to scaling a giant table where a leg represents a steep, limited-area climb that leads to a high-altitude expanse, he said.

“We expected some interesting exceptions to the pyramid shape – it turned out that pyramids are by far the exception. It’s something that twists your mind around,” Elsen said. “I really encourage people trying to grasp this for the first time to take less of a two-dimensional perspective of looking from the side and picture the range from above — a mountain range is a very three-dimensional system.”

The researchers point out that animals that could benefit from an increase in elevation may still face other threats — habitat loss, food availability and exposure to existing animals and diseases, for instance. Even the range shapes themselves provide unique areas of concern — hourglass-shaped ranges such as the Himalayas, for instance, present a “bottleneck” at mid-elevation that could become overwhelmed with species moving upslope from more expansive lower elevations.

“Not every elevation holds equal value for conservation,” Tingley said. Our research suggests that some gradients, and some portions of gradients, will be more important than others. Protecting land within an elevational bottleneck, for example, will be critical. That is where species will be greatly pressured, and often long before they reach the mountaintop.”

Read the abstract.

Paul R. Elsen and Morgan W. Tingley. 2015. Global mountain topography and the fate of montane species under climate change. Nature Climate Change. Article published online May 18, 2015. DOI: 10.1038/nclimate2656.

The work was supported by Princeton University, the National Science Foundation Graduate Research Fellowship Program (grant no. DGE-1148900), and the D.H. Smith Conservation Research Fellowship administered by the Society for Conservation Biology and financially supported by the Cedar Tree Foundation.

Solving streptide from structure to biosynthesis (Nature Chemistry)

Streptide (Image source: Seyedsayamdost Lab)

(Image source: Seyedsayamdost Lab)

By: Tien Nguyen

Bacteria speak to one another using peptide signals in a soundless language known as quorum sensing. In a step towards translating bacterial communications, researchers at Princeton University have revealed the structure and biosynthesis of streptide, a peptide involved in the quorum sensing system common to many streptococci.

Leah Bushin, Class of 2014

Leah Bushin, Class of 2014

“It’s extremely rare for one research group to do both natural products discovery and mechanistic enzymology,” said Leah Bushin, a member of the Seyedsayamdost lab and co-first author on the article published on April 20 in Nature Chemistry. Bushin worked on elucidating the structure of streptide as part of her undergraduate senior thesis project and will enter Princeton Chemistry’s graduate program in the fall.

To explore how bacteria communicate, first she had to grow them, a challenging process in which oxygen had to be rigorously excluded. Next she isolated the streptide and analyzed it using two-dimensional (2D) nuclear magnetic resonance (NMR) spectroscopy, a technique that allows scientists to deduce the connections between atoms in a molecule by pulsing their nuclei with powerful magnets to pulse atomic nuclei.

The experiments revealed that streptide contained an unprecedented crosslink between two unactivated carbons on lysine and tryptophan, constituting a new class of macrocyclic peptides. “We didn’t think it would be as cool as a carbon-carbon bond between two amino acid side chains, so it was definitely a surprise.” said Bushin.

To figure out how this novel bond was being formed, the researchers took a closer look at the gene cluster that produced streptide. Within the gene cluster, they suspected a radical S-adenosyl methionine (SAM) enzyme, which they dubbed StrB, could be responsible for this unusual modification.

Kelsey Schramma

Kelsey Schramma, a graduate student in the Seyedsayamdost lab

“Radical SAM enzymes catalyze absolutely amazing chemistries,” said Kelsey Schramma, a graduate student in the Seyedsayamdost lab and co-first author on the article. “There are over 48,000 radical SAM enzymes, but only about 50 have been characterized and just a dozen or so studied in detail,” she said.

To probe the enzyme’s role in making streptide, the researchers created a mutated version of the bacteria lacking the strB gene. The mutant failed to produce streptide, confirming that the StrB enzyme was significant and warranted further study.

Schramma determined that in order to function properly, the StrB enzyme required some key components: the pre-crosslinked substrate, which she prepared synthetically, cofactor SAM, reductant, and two iron-sulfur (Fe-S) clusters carefully assembled in the protein interior. The team then showed that one of the FeS clusters reductively activated one molecule of SAM, kicking off a chain of one-electron (radical) reactions that gave rise to the novel carbon-carbon bond.

“The synergy between Leah and Kelsey was great,” said Mohammad Seyedsayamdost, an assistant professor of chemistry at Princeton who led the research team. “They expressed interest in complementary aspects of the project and the whole ended up being greater than the sum of its parts,” he said.

Their efforts included not only chemical and biological approaches, but also theoretical computational studies. While the 2D NMR experiments revealed the flat structure of streptide, its three-dimensional conformation was still unknown.

“Since the crosslink had never been reported, we had to code the modification into the program, which took a bit of creativity,” Bushin said. After corresponding with the software creator, they were able to confidently assign a key residue in the macrocycle with the S-configuration.

Future work will target streptide’s biological function—its meaning in the bacterial language—as well as confirming its production by other streptococcal bacteria strains.

“What we have revealed is a new and unusual mechanism that nature uses to synthesize macrocyclic peptides. There is a lot of novel chemistry to be discovered by interrogating bacterial secondary metabolite biosynthetic pathways,” Seyedsayamdost said.

Read the article here:

Schramma, K. R.; Bushin, L. B.; Seyedsayamdost, M. R. “Structure and biosynthesis of a macrocyclic peptide containing an unprecedented lysine-to-tryptophan crosslink.Nature Chemistry, 2015, 7, 431.

This work was supported by the National Institutes of Health (grant no. GM098299), and by Princeton University start-up funds.

New research will help forecast bad ozone days over the western U.S. (Nature Communications)

The contribution of stratospheric ozone to US surface ozone peaks in the western Rockies during late spring. This map shows mean contribution in parts per billion by volume (ppbv) for May to June. Credit: NOAA

The contribution of stratospheric ozone to US surface ozone peaks in the western Rockies during late spring. This map shows mean contribution in parts per billion by volume (ppbv) for May to June. Credit: NOAA

New research published in Nature Communications led by Meiyun Lin of NOAA’s Geophysical Fluid Dynamics Laboratory and NOAA’s cooperative institute at Princeton University, reveals a strong connection between high ozone days in the western U.S. during late spring and La Niña, an ocean-atmosphere phenomena that affects global weather patterns.

Recognizing this link offers an opportunity to forecast ozone several months in advance, which could improve public education to reduce health effects. It would also help western U.S. air quality managers prepare to track these events, which can have implications for attaining the national ozone standard.

Exposure to ozone is harmful to human health, can cause breathing difficulty, coughing, scratchy and sore throats, and asthma attacks, and can damage sensitive plants.

NOAA scientists used a lidar aboard this Twin Otter aircraft to study the movement of ozone from the stratosphere to the lower atmosphere above California in 2010. Credit: NOAA

NOAA scientists used a lidar aboard this Twin Otter aircraft to study the movement of ozone from the stratosphere to the lower atmosphere above California in 2010. Credit: NOAA

“Ozone in the stratosphere, located 6 to 30 miles (10 to 48 kilometers) above the ground, typically stays in the stratosphere,” said Lin, an associate research scholar in the Program in Atmospheric and Oceanic Sciences at Princeton University. “But not on some days in late spring following a strong La Niña winter. That’s when the polar jet stream meanders southward over the western U.S. and facilitates intrusions of stratospheric ozone to ground level where people live.”

Over the last two decades, there have been three La Niña events – 1998-1999, 2007-2008 and 2010-2011. After these events, scientists saw spikes in ground level ozone for periods of two to three days at a time during late spring in high altitude locations of the U.S. West.

While high ozone typically occurs on muggy summer days when pollution from cars and power plants fuels the formation of regional ozone pollution, high-altitude regions of the U.S. West sometimes have a different source of high ozone levels in late spring. On these days, strong gusts of cold dry air associated with downward transport of ozone from the stratosphere pose a risk to these communities.

Lin and her colleagues found that these deep intrusions of stratospheric ozone could add 20 to 40 parts per billion of ozone to the ground-level ozone concentration, which can provide over half the ozone needed to exceed the standard set by the U.S. Environmental Protection Agency. The EPA has proposed tightening that standard currently set at 75 parts per billion for an eight-hour average to between 65 and 70 parts per billion.

In the spring after La Niña winters, when the polar jet stream meanders southward over the western US, it facilitates intrusions of stratospheric ozone to ground level where people live. Credit: NOAA

In the spring after La Niña winters, when the polar jet stream meanders southward over the western US, it facilitates intrusions of stratospheric ozone to ground level where people live. Credit: NOAA

Under the Clean Air Act, these deep stratospheric ozone intrusions can be classified as “exceptional events” that are not counted towards EPA attainment determinations. As our national ozone standard becomes more stringent, the relative importance of these stratospheric intrusions grows, leaving less room for human-caused emissions to contribute to ozone pollution prior to exceeding the level set by the U.S. EPA.

“Regardless of whether these events count towards non-attainment, people are living in these regions and the possibility of predicting a high-ozone season might allow for public education to minimize adverse health effects,” said Arlene Fiore, an atmospheric scientist at Columbia University and a co-author of the research.

Predicting where and when stratospheric ozone intrusions may occur would also provide time to deploy air sensors to obtain evidence as to how much of ground-level ozone can be attributed to these naturally occurring intrusions and how much is due to human-caused emissions.

The study involved collaboration across two NOAA laboratories, NOAA’s cooperative institutes at Princeton and the University of Colorado Boulder, and scientists at partner institutions in the U.S., Canada and Austria. It was also supported in part by the NASA Air Quality Applied Sciences Team whose mission is to apply earth science data to help address air quality management needs.

“This study brings together observations and chemistry-climate modeling to help understand the processes that contribute to springtime high-ozone events in the western U.S.,” said Andrew Langford, an atmospheric scientist at NOAA’s Earth System Research Laboratory in Boulder, Colorado, whose teams measure ozone concentrations using lidar and balloon-borne sensors.

“You’ve heard about good ozone, the kind found high in the stratosphere that protects the earth from harmful ultraviolet radiation,” said Langford. “And you’ve heard about bad ozone at ground level. This study looks at the factors that cause good ozone to go bad.”

Lin, Fiore and Langford conducted the research with Larry Horowitz of NOAA’s Geophysical Fluid Dynamics Laboratory; Samuel Oltmans of the Cooperative Institute for Research in Environmental Sciences at the University of Colorado Boulder, who works in NOAA’s Earth System Research Laboratory; David Tarasick of Environment Canada; and Harald Rieder of the University of Graz in Austria.

Read the article in Nature Communications.

Citation:

Meiyun Lin, Arlene M. Fiore, Larry W. Horowitz, Andrew O. Langford, Samuel J. Oltmans, David Tarasick & Harald E. Rieder. Climate variability modulates western US ozone air quality in spring via deep stratospheric intrusions. Nature Communications 6, No 7105 doi:10.1038/ncomms8105

Courtesy of National Oceanic and Atmospheric Administration (NOAA) Communications & External Affairs