It’s possible that I shall make an ass of myself. But in that case one can always get out of it with a little dialectic. I have, of course, so worded my proposition as to be right either way (K.Marx, Letter to F.Engels on the Indian Mutiny)
Saturday, April 10, 2021
First images of cells exposed to COVID-19 vaccine reveal native-like Coronavirus spikes
New research has for the first time compared images of the protein spikes that develop on the surface of cells exposed to the Oxford-AstraZeneca vaccine to the protein spike of the SARS-CoV-19 coronavirus. The images show that the spikes are highly similar to those of the virus and support the modified adenovirus used in the vaccine as a leading platform to combat COVID-19.
The SARS-CoV-2 virus, which causes COVID-19, has a large number of spikes sticking out of its surface that it uses to attach to, and enter, cells in the human body. These spikes are coated in sugars, known as glycans, which disguise parts of the viral proteins to the human immune system.
The vaccine developed by the University of Oxford and AstraZeneca is an adenovirus-vectored vaccine, which involves taking a safe version of a virus and adding in the information from part of a pathogen, in this case the SAR-CoV-2 spike, in order to generate neutralising antibodies against that target.
In this new study, published in the journal ACS Central Science, scientists from the University of Oxford and the University of Southampton, worked together to characterise the SARS-CoV-2 spikes manufactured by the cells presented with the Oxford-AstraZeneca vaccine. The Oxford work was led by Professors Teresa Lambe, Peijun Zhang and Sarah Gilbert and Professor Max Crispin led the work in Southampton.
CAPTION
Graphic depicting how the protein spikes form on the surface of cells presented with the vaccine.
CREDIT
University of Southampton
The Scientists exposed a range of cells in vitro to the Oxford-AstraZeneca vaccine. Using an imaging technique known as cryo-electron microscopy (cryoEM) they took thousands of images which they then combined to build up a clear picture of the resulting protein spikes on the cells. Professor Peijun Zhang, of the University of Oxford and the Electron Bio-Imaging Centre (eBIC) at Diamond Light Source, who led the imaging work said, "CryoEM is an immensely powerful technique which enabled us to visualise the dense array of spikes that had been manufactured and presented on the surface of the cells".
Further chemical analysis of the glycans that coat the newly developed protein spikes revealed that they bear a high resemblance to those surrounding the SARS-CoV-2 spikes. This is an essential feature of the vaccine as it means that it can deliver close mimics of the coronavirus that are important in triggering the immune response needed to protect against COVID-19.
Professor Crispin said, "In this study we set out to see how closely the vaccine induced spikes resembled those of the infectious virus. We were really pleased to see a large amount of native-like spikes."
"This study will hopefully provide further understanding for the public, helping them see how the Oxford-AstraZeneca vaccine works. Many people may not realise how their cells become little factories manufacturing viral spikes that then trigger the immune response needed to fight off the disease. This may also provide reassurance that the vaccine is doing its job and generating the material that we need to present to our immune systems."
CAPTION
Artist imaging of protein spike on the surface of cells exposed to the vaccine.
CREDIT
University of Southampton
Lessons in equity from the frontlines of COVID-19 vaccination
Cambridge, Mass. - When the first COVID-19 vaccines were approved for emergency use in December 2020, healthcare systems across the Unites States needed to rapidly design and implement their own approaches to distribute COVID-19 vaccines equitably and efficiently. This new role has required Beth Israel Lahey Health (BILH) to develop new strategies and build large operational teams to organize and successfully vaccinate more than 14,000 patients a week across Eastern Massachusetts. In an Insight article published in JAMA Health Forum, Leonor Fernandez, MD, Assistant Professor of Medicine in the Department of Medicine at Beth Israel Deaconess Medical Center (BIDMC) and Peter Shorett, MPP, Chief Integration Officer at BILH, identify five key lessons about health equity that have emerged from BILH's vaccination campaign for the health system's approximately 1.6 million patients.
"This is an unprecedented public health campaign for a health system," said Fernandez, a primary care physician and Director of Patient Engagement at Health Care Associates, BIDMC's primary care practice. "Organizing our approach to COVID 19 vaccination is teaching us a lot about what we do well and how we can further advance the delivery of equitable health care. To ensure that all patients, including Black, Latinx, and other marginalized communities can access these life-saving vaccines, we have to be able to reach out, create trust, and speak their language."
Fernandez and Shorett describe five actions that help promote vaccine equity: obtain reliable patient demographic data; address structural inequalities intentionally in order to achieve equitable results; communicate with patients in understandable terms and in their preferred languages; involve diverse stakeholders in decisions; and embrace equity, diversity and inclusion as fundamental organizational values.
Obtain reliable patient demographic data The authors note that accurate and complete demographic data are essential to identifying and deploying strategies to reach and engage patients, but data are not consistently elicited or accurate. Information about patients' race, ethnicity, preferred language and geography is helping drive greater understanding and accountability in the health system's efforts to address historic racial and ethnic health disparities.
Intentionally addressing structural inequalities and speaking patients' languages "BILH's strategy has been to invite patients in three waves for each eligible phase, focusing first on our patients associated with our healthcare centers in Dorchester and Chelsea," said Shorett, who led the patient vaccination efforts for the health system. "We then move to patients in towns and neighborhoods in our region that have been disproportionately impacted by COVID-19, and shortly after that to randomized cohorts of eligible patients."
BILH teams developed a broader communications approach, deploying a mix of SMS texting, outgoing phone messages in many languages, and live phone outreach to patients in highly affected communities. Community health centers and primary care practices in highly affected communities have been and will continue to be critically important in the vaccination invitation, outreach and communication process as trusted messengers for their patients.
"Relying exclusively on digital invitations can mean that patients and those who lack familiarity and access to digital technology or speak a language other than English will have less access to vaccination," said Fernandez, who is also a member of the health system's vaccination leadership team.
Involving diverse stakeholders for better decision making and embracing equity as a fundamental value to create greater change
Following the widespread civil unrest in response to several high-profile incidents of police brutality, BILH's Diversity, Equity and Inclusion Taskforce developed recommendations for action incorporated in part from listening sessions including thousands of employees. This backdrop, along with extreme health disparities observed during the pandemic, made the issue of health equity both more familiar and more urgent within the health system. "The integration of diverse institutional and community stakeholders into decisions enables better recognition of structural inequities, provides needed knowledge and skill sets, and supports more effective strategies to help the health system address health disparities," noted Shorett.
Vaccinating the U.S. population against COVID-19 will require an unprecedented ongoing public health campaign. "Sustaining this positive momentum will rely on the shared understanding that when it comes to health, we are all in this together," said Fernandez.
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The authors reported no funding or disclosures.
About Beth Israel Lahey Health
Beth Israel Lahey Health is a new health care system that brings together academic medical centers and teaching hospitals, community and specialty hospitals, more than 4,800 physicians and 36,000 employees in a shared mission to expand access to great care and advance the science and practice of medicine through groundbreaking research and education. For more information, visit http://www.bilh.org.
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SOMEONE TELL KENNEY
More nuanced approach to deciding who gets COVID-19 vaccine needed in face of third wave
Job site and neighborhood risks should be taken into account when setting priorities, authors argue
UNIVERSITY OF ALBERTA FACULTY OF MEDICINE & DENTISTRY
IMAGE: FINLAY MCALISTER LED AN ANALYSIS THAT INDICATES PEOPLE IN NEIGHBOURHOODS AND WORKPLACES WITH A HIGHER RISK OF COVID-19 INFECTIONS SHOULD BE PRIORITIZED FOR VACCINATION AS CANADA FACES A THIRD WAVE... view more
CREDIT: FACULTY OF MEDICINE & DENTISTRY, UNIVERSITY OF ALBERTA
It's time for a more nuanced approach to vaccine prioritization, as more contagious COVID-19 variants become prevalent and a third wave of infections threatens to overwhelm hospitals in some provinces, according to an analysis published today in the Canadian Medical Association Journal.
"It's time to move the debate away from age and medical risk factors," said lead author Finlay McAlister, professor in the University of Alberta's Faculty of Medicine & Dentistry.
"The third wave is showing us that the most vulnerable are people in economically marginalized neighbourhoods, Amazon factories and Superstores, where there are a lot of people in close proximity, a group that wasn't prioritized for vaccination before."
McAlister and three other authors, including U of A infectious disease professor Lynora Saxinger, who co-chairs the scientific advisory group for Alberta Health Service's COVID-19 Emergency Coordination Centre, analyzed data for 61,000 Canadian patients using data from the Canadian Community Health Survey. They identified how many have conditions which are recognized as risk factors for severe COVID-19 disease, including high blood pressure, diabetes and smoking.
"At least 75 per cent have at least one risk factor and one third have two or more," McAlister said. "When 75 per cent of people are eligible, that's not really prioritization."
It was appropriate to give seniors living in communal settings and the very elderly shots first, as they were clearly the most likely to face severe disease and death at the time, McAlister said, but now the focus should be more targeted to neighbourhoods and workplaces facing a higher risk of infection. He applauded the Alberta government's recent announcement that it will open vaccine clinics at the Cargill meat packing plant in High River, as an example of the new direction that should be taken.
McAlister also supports the recommendation from the National Advisory Committee on Immunization to give first doses to as many Canadians as possible, even if it means waiting up to three months to administer second doses while supplies are limited.
"The science is evolving rapidly and there is accumulating evidence now, showing that after the first shot we are getting about 80 per cent efficacy, so it looks like delaying that second dose is a good approach," McAlister said. "Of course, how long that first-dose protection will last, we will only know in retrospect."
He noted that some groups should be given special consideration to get their second dose more quickly, for example evidence shows cancer and transplant patients do not develop the same level of immunity from the first dose as others.
"They seem to get only partial immunity, which means they are at a greater risk for infection, giving the virus another chance to develop a variant and get passed on," McAlister explained. "We want as many people as possible to develop immunity as quickly as possible so there's less chance for new variants to develop."
He also reiterated that until we know whether vaccines protect against all of the variants of concern and until the Canadian population has reached herd immunity, thought to be around 70 per cent, we will have to continue public health measures such as wearing masks, socially distancing and washing hands frequently.
One in ten have long-term effects 8 months following mild COVID-19
IMAGE: RESEARCHERS CHARLOTTE THÅLIN AND SEBASTIAN HAVERVALL AT DANDERYD HOSPITAL AND KAROLINSKA INSTITUTET. view more
CREDIT: LUDVIG KOSTYAL
Eight months after mild COVID-19, one in ten people still has at least one moderate to severe symptom that is perceived as having a negative impact on their work, social or home life. The most common long-term symptoms are a loss of smell and taste and fatigue. This is according to a study published in the journal JAMA, conducted by researchers at Danderyd Hospital and Karolinska Institutet in Sweden.
Since spring 2020, researchers at Danderyd Hospital and Karolinska Institutet have conducted the so-called COMMUNITY study, with the main purpose of examining immunity after COVID-19. In the first phase of the study in spring 2020, blood samples were collected from 2,149 employees at Danderyd Hospital, of whom about 19 percent had antibodies against SARS-CoV-2. Blood samples have since then been collected every four months, and study participants have responded to questionnaires regarding long-term symptoms and their impact on the quality of life.
In the third follow-up in January 2021, the research team examined self-reported presence of long-term symptoms and their impact on work, social and home life for participants who had had mild COVID-19 at least eight months earlier. This group consisted of 323 healthcare workers (83 percent women, median age 43 years) and was compared with 1,072 healthcare workers (86 percent women, median age 47 years) who did not have COVID-19 throughout the study period.
The results show that 26 percent of those who had COVID-19 previously, compared to 9 percent in the control group, had at least one moderate to severe symptom that lasted more than two months and that 11 percent, compared to 2 percent in the control group, had a minimum of one symptom with negative impact on work, social or home life that lasted at least eight months. The most common long-term symptoms were loss of smell and taste, fatigue, and respiratory problems.
"We investigated the presence of long-term symptoms after mild COVID-19 in a relatively young and healthy group of working individuals, and we found that the predominant long-term symptoms are loss of smell and taste. Fatigue and respiratory problems are also more common among participants who have had COVID-19 but do not occur to the same extent," says Charlotte Thålin, specialist physician, Ph.D. and lead researcher for the COMMUNITY study at Danderyd Hospital and Karolinska Institutet. "However, we do not see an increased prevalence of cognitive symptoms such as brain fatigue, memory and concentration problems or physical disorders such as muscle and joint pain, heart palpitations or long-term fever."
"Despite the fact that the study participants had a mild COVID-19 infection, a relatively large proportion report long-term symptoms with an impact on quality of life. In light of this, we believe that young and healthy individuals, as well as other groups in society, should have great respect for the virus that seems to be able to significantly impair quality of life, even for a long time after the infection," says Sebastian Havervall, deputy chief physician at Danderyd Hospital and PhD student in the project at Karolinska Institutet.
The COMMUNITY study will now continue, with the next follow-up taking place in May when a large proportion of study participants are expected to be vaccinated. In addition to monitoring immunity and the occurrence of re-infection, several projects regarding post- COVID are planned.
"We will, among other things, be studying COVID-19-associated loss of smell and taste more closely, and investigate whether the immune system, including autoimmunity, plays a role in post-COVID," says Charlotte Thålin.
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The article has been peer-reviewed and published as a Research Letter in the journal JAMA.
Facts about the COMMUNITY study:
The study is conducted in close collaboration between Danderyd Hospital (principal of the study), Karolinska Institutet, KTH, SciLifeLab, Uppsala University, and the Public Health Agency of Sweden.
The research group includes the following investigators: from Danderyd Hospital and Karolinska Institutet, specialist physician, medical doctor, and principal researcher Charlotte Thålin and deputy chief physician Sebastian Havervall (PhD student in the project); from Karolinska Institutet and the Public Health Agency of Sweden, associate professor Jonas Klingström; from KTH, professors Sophia Hober and Peter Nilsson; and from Uppsala University, associate professor and associate senior lecturer Sara Mangsbo and Professor Mia Phillipson.
The study is funded by the Jonas & Christina af Jochnick Foundation, Leif Lundblad with family, Region Stockholm, the Knut and Alice Wallenberg Foundation, SciLifeLab, the Erling-Persson Family Foundation, and Atlas Copco.
Publication: "Symptoms and Functional Impairment Assessed 8 Months After Mild COVID-19 Among Health Care Workers", Sebastian Havervall, Axel Rosell, Mia Phillipson, Sara M. Mangsbo, Peter Nilsson, Sophia Hober, Charlotte Thålin. JAMA: Journal of the American Medical Association, online 7 April 2021, doi: 10.1001/jama.2021.5612.
Carbon dioxide levels reflect COVID-19 risk
University of Colorado Boulder duo confirms value of measuring carbon dioxide to estimate infection risk
IMAGE: BECAUSE INFECTIOUS PEOPLE EXHALE CO2 AND VIRUSES TOGETHER, TRACKING CARBON DIOXIDE LEVELS INDOORS IS AN INEXPENSIVE AND POWERFUL WAY TO MONITOR THE RISK OF PEOPLE GETTING COVID-19, ACCORDING TO A... view more
CREDIT: IMAGE COURTESY OF SPANISH NEWSPAPER EL PAIS: HTTPS://TINYURL.COM/C2JSB8R9
Tracking carbon dioxide levels indoors is an inexpensive and powerful way to monitor the risk of people getting COVID-19, according to new research from the Cooperative Institute for Research in Environmental Sciences (CIRES) and the University of Colorado Boulder. In any given indoor environment, when excess CO2 levels double, the risk of transmission also roughly doubles, two scientists reported this week in Environmental Science & Technology Letters.
The chemists relied on a simple fact already put to use by other researchers more than a decade ago: Infectious people exhale airborne viruses at the same time as they exhale carbon dioxide. That means CO2 can serve as a "proxy" for the number of viruses in the air.
"You're never safe indoors sharing air with others, but you can reduce the risk," said Jose-Luis Jimenez, co-author of the new assessment, a CIRES Fellow and professor of chemistry at the University of Colorado Boulder.
"And CO2 monitoring is really the only low-cost and practical option we have for monitoring," said Zhe Peng, a CIRES and chemistry researcher, and lead author of the new paper. "There is nothing else."
For many months, researchers around the world have been searching for a way to continually monitor COVID-19 infection risk indoors, whether in churches or bars, buses or hospitals. Some are developing instruments that can detect viruses in the air continually, to warn of a spike or to indicate relative safety. Others tested existing laboratory-grade equipment that costs tens of thousands of dollars.
Jimenez and colleagues turned to commercially available carbon dioxide monitors, which can cost just a few hundred dollars. First, they confirmed in the laboratory that the detectors were accurate. Then, they created a mathematical "box model" of how an infected person exhales viruses and CO2, how others in the room inhaled and exhaled, and how the viruses and gas accumulate in the air of a room or are removed by ventilation. The model takes into consideration infection numbers in the local community, but it does not detail air flow through rooms--that kind of modeling requires expensive, custom analysis for each room.
It's important to understand that there is no single CO2 level at which a person can assume a shared indoor space is "safe," Peng emphasized. That's partly because activity matters: Are people in the room singing and talking loudly or exercising, or are they sitting quietly and reading or resting? A CO2 level of 1,000 ppm, which is well above outside levels of about 400 ppm, could be relatively safe in a quiet library with masks but not in an active gym without masks.
But in each indoor space, the model can illuminate "relative" risk: If CO2 levels in a gym drop from 2,800 to 1,000 ppm (~2,400 above background levels to 600), the risk of COVID-19 transmission drops, too, to one-quarter of the original risk. In the library, if an influx of people makes CO2 jump from 800 to 1,600 (400 to 1,200 above background), COVID transmission risk triples.
In the new paper, Peng and Jimenez also shared a set of mathematical formulae and tools that experts in building systems and public health can use to pin down actual, not just relative, risk. But the most important conclusion is that to minimize risk, keep the CO2 levels in all the spaces where we share air as low as practically possible.
"Wherever you are sharing air, the lower the CO2, the lower risk of infection," Jimenez said.
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Surgical sutures inspired by human tendons
Next-generation sutures can deliver drugs, prevent infections, and monitor wounds
IMAGE: SCANNING ELECTRON MICROSCOPE IMAGE OF THE CROSS-SECTION OF TGS SUTURE. view more
CREDIT: ZHENWEI MA, MCGILL UNIVERSITY
Sutures are used to close wounds and speed up the natural healing process, but they can also complicate matters by causing damage to soft tissues with their stiff fibers. To remedy the problem, researchers from Montreal have developed innovative tough gel sheathed (TGS) sutures inspired by the human tendon.
These next-generation sutures contain a slippery, yet tough gel envelop, imitating the structure of soft connective tissues. In putting the TGS sutures to the test, the researchers found that the nearly frictionless gel surface mitigated the damage typically caused by traditional sutures.
Conventional sutures have been around for centuries and are used to hold wounds together until the healing process is complete. But they are far from ideal for tissue repair. The rough fibers can slice and damage already fragile tissues, leading to discomfort and post-surgery complications.
Part of the problem lies in the mismatch between our soft tissues and the rigid sutures that rub against contacting tissue, say the researchers from McGill University and the INRS Énergie Matériaux Télécommunications Research Centre.
Inspired by the tendon
To tackle the problem, the team developed a new technology that mimics the mechanics of tendons. "Our design is inspired by the human body, the endotenon sheath, which is both tough and strong due to its double-network structure. It binds collagen fibers together while its elastin network strengthens it," says lead author Zhenwei Ma, a PhD student under the supervision of Assistant Professor Jianyu Li at McGill University.
The endotenon sheath not only forms a slippery surface to reduce friction with surrounding tissues in joints, but it also delivers necessary materials for tissue repair in a tendon injury. In the same way, TGS sutures can be engineered to provide personalized medicine based on a patient's needs, say the researchers.
Personalized wound treatment
"This technology provides a versatile tool for advanced wound management. We believe it could be used to deliver drugs, prevent infections, or even monitor wounds with near-infrared imaging," says Li of the Department of Mechanical Engineering.
"The ability to monitor wounds locally and adjust the treatment strategy for better healing is an exciting direction to explore," says Li, who is also a Canada Research Chair in Biomaterials and Musculoskeletal Health.
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About this study
"Bioinspired tough gel sheath for robust and versatile surface functionalization" by Zhenwei Ma, Zhen Yang, Qiman Gao, Guangyu Bao, Amin Valiei, Fan Yang, Ran Huo, Chen Wang, Guolong Song, Dongling Ma, Zu-Hua Gao, and Jianyu Li was published in Science Advances.
New biosensor makes control hormone auxin visible in cells
Scientists at the University of Bayreuth and the Max Planck Institute for Developmental Biology in Tübingen have developed a novel sensor that provides real-time insights into the inner life of plants
IMAGE: SEEDLING OF THALE CRESS (ARABIDOPSIS THALIANA). THE MAGNIFYING GLASS SHOWS THE ROOT TIP. THE CELL NUCLEI ARE COLOURED FROM BLUE TO GREEN AND YELLOW TO RED AS THE AMOUNT OF... view more
CREDIT: GRAPHIC: S. SHANMUGARATNAM, A.C. STIEL, M. KOLB.
The hormone auxin is of central importance for the development of plants. Scientists at the University of Bayreuth and the Max Planck Institute for Developmental Biology in Tübingen have now developed a novel sensor that makes the spatial distribution of auxin in the cells of living plants visible in real time. The sensor opens up completely new insights into the inner workings of plants for researchers. Moreover, the influences of changing environmental conditions on growth can now also be quickly detected. The team presents its research results in the journal Nature.
The effects of the plant hormone auxin were first described scientifically almost 100 years ago. Today we know that auxin controls countless processes in plant cells - be it in the development of the embryo in the seed, the formation of the root system, or the orientation of growth to incident sunlight. In all cases, the hormone has the function of coordinating the plant's responses to external stimuli. To do this, it must always be present in the cell tissue where the response to an external stimulus needs to be triggered. Indeed, it is often the case that auxin is needed at very different places in the cell tissue within a very short space of time. This leads to rapid spatial redistribution. With the new biosensor, called AuxSen for short, the dynamics of these processes can be observed in real time for the first time. Light signals indicate where the auxin is located in the cell tissue. What is special about this sensor is that it is not a technical device that has to be introduced into the plants, but an artificial protein that the plants are engineered to produce themselves.
The application of the biosensor has already led to some surprising findings. One example is the rapid redistribution of auxin when a plant is turned upside down. When the root tip no longer points downwards but diagonally upwards, the auxin molecules responsible for root growth collect on the new underside of the root tip within just one minute. And upon being placed right-side up, the old distribution of auxin is restored after just one minute.
Protein biochemistry and plant biology in combination
The development of the biosensor is the result of many years of interdisciplinary collaboration. A team led by Prof. Dr. Birte Höcker, Professor of Protein Design at the University of Bayreuth, and a team led by Prof. Dr. Gerd Jürgens at the Max Planck Institute for Developmental Biology, have combined their knowledge and many years of experience. "It is to be expected that the new biosensor will uncover many more unforeseen insights into the inner workings of plants and their reaction to external stimuli over the coming years. The development of the sensor has been a long process in which we have gained fundamental insights into how proteins can be selectively altered to bind specific small molecules," says Prof. Dr. Birte Höcker.
"There is already a great deal of interest in the new sensor, and it is to be expected that optimised variants of AuxSen will be developed over the next few years to enable even better analysis of the diverse auxin-regulated processes in plants. With our new publication in Nature, we wish to encourage the scientific community to increase research in this direction. Our results so far are an example of how fruitful interdisciplinary cooperation can be in this field," explains Prof. Dr. Gerd Jürgens from the Max Planck Institute for Developmental Biology in Tübingen.
Advantages of the biosensor: High signal quality and optimal binding strength to auxin
At the beginning of the biosensor's development was a protein in the bacterium E. coli, which binds to the amino acid tryptophan, but much more poorly to the chemically-related auxin. This protein was coupled with two proteins that fluoresce when excited with light of a certain wavelength. If these partner proteins come very close to each other, their fluorescence increases considerably. A fluorescence resonance energy transfer (FRET) then occurs. The next step was crucial: the initial protein was to be genetically modified so that it binds better to auxin and less well to tryptophan. At the same time, the FRET effect of the partner molecules should always occur when the protein binds to auxin, and only then. With this goal in mind, about 2,000 variants of the protein were created and tested until finally a molecule was found that fulfilled all requirements. Thus, the biosensor AuxSen was born: strong fluorescent signals indicating where in the cell tissue the vital hormone is located.
Another challenge was to enable plants to produce AuxSen themselves. On the one hand, it had to be ensured that AuxSen would bind to the existing auxin molecules in as many cells as possible. This was the only way to map the spatial distribution of auxin in the cell completely and to produce high signal quality. On the other hand, however, the auxin molecules were not to be permanently prevented from fulfilling their original tasks in the plant organism because of binding to AuxSen. Nevertheless, the two research teams succeeded in finding a compromise solution. Plants were genetically modified in such a way as to produce a large amount of AuxSen throughout their cell tissue. But this would only happen when stimulated to do so by a special substance - and then only for a short time. In this way, the biosensor provides precise snapshots of auxin distribution in cells without permanently affecting the processes controlled by auxin.
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Better solutions for making hydrogen may lie just at the surface
IMAGE: THE UNIQUE INTERACTIONS BETWEEN PEROVSKITE OXIDE, ITS CHANGING SURFACE LAYER, AND IRON SPECIES THAT ARE ACTIVE TOWARD THE OER PAVES A NEW PATH FOR THE DESIGN OF ACTIVE AND STABLE... view more
CREDIT: ARGONNE NATIONAL LABORATORY
A clean energy future propelled by hydrogen fuel depends on figuring out how to reliably and efficiently split water. That's because, even though hydrogen is abundant, it must be derived from another substance that contains it -- and today, that substance is often methane gas. Scientists are seeking ways to isolate this energy-carrying element without using fossil fuels. That would pave the way for hydrogen-fueled cars, for example, that emit only water and warm air at the tailpipe.
Water, or H2O, unites hydrogen and oxygen. Hydrogen atoms in the form of molecular hydrogen must be separated out from this compound. That process depends on a key -- but often slow -- step: the oxygen evolution reaction (OER). The OER is what frees up molecular oxygen from water, and controlling this reaction is important not only to hydrogen production but a variety of chemical processes, including ones found in batteries.
"The oxygen evolution reaction is a part of so many processes, so the applicability here is quite broad." -- Pietro Papa Lopes, Argonne assistant scientist
A study led by scientists at the U.S. Department of Energy's (DOE) Argonne National Laboratory illuminates a shape-shifting quality in perovskite oxides, a promising type of material for speeding up the OER. Perovskite oxides encompass a range of compounds that all have a similar crystalline structure. They typically contain an alkaline earth metal or lanthanides such as La and Sr in the A-site, and a transition metal such as Co in the B-site, combined with oxygen in the formula ABO3. The research lends insight that could be used to design new materials not only for making renewable fuels but also storing energy.
Perovskite oxides can bring about the OER, and they are less expensive than precious metals such as iridium or ruthenium that also do the job. But perovskite oxides are not as active (in other words, efficient at accelerating the OER) as these metals, and they tend to slowly degrade.
"Understanding how these materials can be active and stable was a big driving force for us," said Pietro Papa Lopes, an assistant scientist in Argonne's Materials Science division who led the study. "We wanted to explore the relationship between these two properties and how that connects to the properties of the perovskite itself."
Previous research has focused on the bulk properties of perovskite materials and how those relate to the OER activity. The researchers wondered, however, whether there was more to the story. After all, the surface of a material, where it reacts with its surroundings, can be completely different from the rest. Examples like this are everywhere in nature: think of a halved avocado that quickly browns where it meets the air but remains green inside. For perovskite materials, a surface that becomes different from the bulk could have important implications for how we understand their properties.
In water electrolyzer systems, which split water into hydrogen and oxygen, perovskite oxides interact with an electrolyte made of water and special salt species, creating an interface that allows the device to operate. As electrical current is applied, that interface is critical in kicking off the water-splitting process. "The material's surface is the most important aspect of how the oxygen evolution reaction will proceed: How much voltage you need, and how much oxygen and hydrogen you're going to be producing," Lopes said.
Not only is the perovskite oxide's surface different from the rest of the material, it also changes over time. "Once it's in an electrochemical system, the perovskite surface evolves and turns into a thin, amorphous film," Lopes said. "It's never really the same as the material you start with."
The researchers combined theoretical calculations and experiments to determine how the surface of a perovskite material evolves during the OER. To do so with precision, they studied lanthanum cobalt oxide perovskite and tuned it by "doping" the lanthanum with strontium, a more reactive metal. The more strontium was added to the initial material, the faster its surface evolved and became active for the OER -- a process the researchers were able to observe at atomic resolution with transmission electron microscopy. The researchers found that strontium dissolution and oxygen loss from the perovskite were driving the formation of this amorphous surface layer, which was further explained by computational modelling performed using the Center for Nanoscale Materials, a DOE Office of Science User Facility.
"The last missing piece to understand why the perovskites were active towards the OER was to explore the role of small amounts of iron present in the electrolyte," Lopes said. The same group of researchers recently discovered that traces of iron can improve the OER on other amorphous oxide surfaces. Once they determined that a perovskite surface evolves into an amorphous oxide, then it became clear why iron was so important.
"Computational studies help scientists understand reaction mechanisms that involve both the perovskite surface and the electrolyte," said Peter Zapol, a physicist at Argonne and study co-author. "We focused on reaction mechanisms that drive both activity and stability trends in perovskite materials. This is not typically done in computational studies, which tend to focus solely on the reaction mechanisms responsible for the activity."
The study found that the perovskite oxide's surface evolved into a cobalt-rich amorphous film just a few nanometers thick. When iron was present in the electrolyte, the iron helped accelerate the OER, while the cobalt-rich film had a stabilizing effect on the iron, keeping it active at the surface.
The results suggest new potential strategies for designing perovskite materials -- one can imagine creating a two-layer system, Lopes said, that is even more stable and capable of promoting the OER.
"The OER is a part of so many processes, so the applicability here is quite broad," Lopes said. "Understanding the dynamics of materials and their effect on the surface processes is how we can make energy conversion and storage systems better, more efficient and affordable."
CAPTION
Surface evolution of a lanthanum cobalt oxide perovskite during electrochemical cycling occurs via A-site dissolution and oxygen lattice evolution, forming an amorphous film that is active for oxygen evolution.
CREDIT
Argonne National Laboratory
The study is described in a paper published and highlighted on the Feb. 24 cover of the Journal of the American Chemical Society, "Dynamically Stable Active Sites from Surface Evolution of Perovskite Materials during the Oxygen Evolution." In addition to Lopes and Zapol, coauthors include Dong Young Chung, Hong Zheng, Pedro Farinazzo Bergamo Dias Martins, Dusan Strmcnik, Vojislav Stamenkovic, Nenad Markovic and John Mitchell at Argonne; Xue Rui and Robert Klie at the University of Illinois at Chicago; and Haiying He at Valparaiso University. This research was funded by DOE's Office of Basic Energy Sciences.
About Argonne's Center for Nanoscale Materials
The Center for Nanoscale Materials is one of the five DOE Nanoscale Science Research Centers, premier national user facilities for interdisciplinary research at the nanoscale supported by the DOE Office of Science. Together the NSRCs comprise a suite of complementary facilities that provide researchers with state-of-the-art capabilities to fabricate, process, characterize and model nanoscale materials, and constitute the largest infrastructure investment of the National Nanotechnology Initiative. The NSRCs are located at DOE's Argonne, Brookhaven, Lawrence Berkeley, Oak Ridge, Sandia and Los Alamos National Laboratories. For more information about the DOE NSRCs, please visit https://science.osti.gov/User-Facilities/User-Facilities-at-a-Glance.
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