Study reveals a reaction at the heart of many renewable energy technologies

New insights into how proton-coupled electron transfers occur at an electrode could help researchers design more efficient fuel cells and electrolyzers.

Peer-Reviewed Publication

MASSACHUSETTS INSTITUTE OF TECHNOLOGY

 

IMAGE: 

APPLYING AN ELECTRIC POTENTIAL CAUSES A PROTON TO TRANSFER FROM A HYDRONIUM ION (AT RIGHT) TO AN ELECTRODE'S SURFACE. USING ELECTRODES WITH MOLECULARLY DEFINED PROTON BINDING SITES, MIT RESEARCHERS DEVELOPED A GENERAL MODEL FOR THESE INTERFACIAL PROTON-COUPLED ELECTRON TRANSFER REACTIONS.

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CREDIT: MIT

CAMBRIDGE, MA — A key chemical reaction — in which the movement of protons between the surface of an electrode and an electrolyte drives an electric current — is a critical step in many energy technologies, including fuel cells and the electrolyzers used to produce hydrogen gas.

For the first time, MIT chemists have mapped out in detail how these proton-coupled electron transfers happen at an electrode surface. Their results could help researchers design more efficient fuel cells, batteries, or other energy technologies.

“Our advance in this paper was studying and understanding the nature of how these electrons and protons couple at a surface site, which is relevant for catalytic reactions that are important in the context of energy conversion devices or catalytic reactions,” says Yogesh Surendranath, a professor of chemistry and chemical engineering at MIT and the senior author of the study.

Among their findings, the researchers were able to trace exactly how changes in the pH of the electrolyte solution surrounding an electrode affect the rate of proton motion and electron flow within the electrode.

MIT graduate student Noah Lewis is the lead author of the paper, which appears today in Nature Chemistry. Ryan Bisbey, a former MIT postdoc; Karl Westendorff, an MIT graduate student; and Alexander Soudackov, a research scientist at Yale University, are also authors of the paper.

 

Passing protons

Proton-coupled electron transfer occurs when a molecule, often water or an acid, transfers a proton to another molecule or to an electrode surface, which stimulates the proton acceptor to also take up an electron. This kind of reaction has been harnessed for many energy applications.

“These proton-coupled electron transfer reactions are ubiquitous. They are often key steps in catalytic mechanisms, and are particularly important for energy conversion processes such as hydrogen generation or fuel cell catalysis,” Surendranath says.

In a hydrogen-generating electrolyzer, this approach is used to remove protons from water and add electrons to the protons to form hydrogen gas. In a fuel cell, electricity is generated when protons and electrons are removed from hydrogen gas and added to oxygen to form water.

Proton-coupled electron transfer is common in many other types of chemical reactions, for example, carbon dioxide reduction (the conversion of carbon dioxide into chemical fuels by adding electrons and protons). Scientists have learned a great deal about how these reactions occur when the proton acceptors are molecules, because they can precisely control the structure of each molecule and observe how electrons and protons pass between them. However, when proton-coupled electron transfer occurs at the surface of an electrode, the process is much more difficult to study because electrode surfaces are usually very heterogenous, with many different sites that a proton could potentially bind to.

To overcome that obstacle, the MIT team developed a way to design electrode surfaces that gives them much more precise control over the composition of the electrode surface. Their electrodes consist of sheets of graphene with organic, ring-containing compounds attached to the surface. At the end of each of these organic molecules is a negatively charged oxygen ion that can accept protons from the surrounding solution, which causes an electron to flow from the circuit into the graphitic surface.

“We can create an electrode that doesn’t consist of a wide diversity of sites but is a uniform array of a single type of very well-defined sites that can each bind a proton with the same affinity,” Surendranath says. “Since we have these very well-defined sites, what this allowed us to do was really unravel the kinetics of these processes.”

Using this system, the researchers were able to measure the flow of electrical current to the electrodes, which allowed them to calculate the rate of proton transfer to the oxygen ion at the surface at equilibrium — the state when the rates of proton donation to the surface and proton transfer back to solution from the surface are equal. They found that the pH of the surrounding solution has a significant effect on this rate: The highest rates occurred at the extreme ends of the pH scale — pH 0, the most acidic, and pH 14, the most basic.

To explain these results, researchers developed a model based on two possible reactions that can occur at the electrode. In the first, hydronium ions (H3O+), which are in high concentration in strongly acidic solutions, deliver protons to the surface oxygen ions, generating water. In the second, water delivers protons to the surface oxygen ions, generating hydroxide ions (OH-), which are in high concentration in strongly basic solutions.

However, the rate at pH 0 is about four times faster than the rate at pH 14, in part because hydronium gives up protons at a faster rate than water.

 

A reaction to reconsider

The researchers also discovered, to their surprise, that the two reactions have equal rates not at neutral pH 7, where hydronium and hydroxide concentrations are equal, but at pH 10, where the concentration of hydroxide ions is 1 million times that of hydronium. The model suggests this is because the forward reaction involving proton donation from hydronium or water contributes more to the overall rate than the backward reaction involving proton removal by water or hydroxide.

Existing models of how these reactions occur at electrode surfaces assume that the forward and backward reactions contribute equally to the overall rate, so the new findings suggest that those models may need to be reconsidered, the researchers say.

“That’s the default assumption, that the forward and reverse reactions contribute equally to the reaction rate,” Surendranath says. “Our finding is really eye-opening because it means that the assumption that people are using to analyze everything from fuel cell catalysis to hydrogen evolution may be something we need to revisit.”

The researchers are now using their experimental setup to study how adding different types of ions to the electrolyte solution surrounding the electrode may speed up or slow down the rate of proton-coupled electron flow.

“With our system, we know that our sites are constant and not affecting each other, so we can read out what the change in the solution is doing to the reaction at the surface,” Lewis says.

 

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The research was funded by the U.S. Department of Energy Office of Basic Energy Sciences.

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JOURNAL

Nature Chemistry

DOI

10.1038/s41557-023-01400-0 

Wrongly-enforced rules over “digital surrogates” by museums censors research and creative use, study warns

 NEWS RELEASE 16-JAN-2024

UNIVERSITY OF EXETER

Cultural institutions are censoring research, learning and creativity because of the way they police the reuse of digital copies of out-of-copyright artworks and artefacts, a new study warns.

Cultural institutions have created a “mess” by claiming and enforcing new rights over the reproduction images of works in their collections.

This allows museums and other organisations to refuse requests for the use of the images in education or research or charge high fees. This impedes free and creative expression and amounts to censorship, according to Dr Andrea Wallace from the University of Exeter Law School.

Researchers, educators and others regularly ask to use images of objects in museum and art gallery collections, but it is often complicated, too expensive or difficult to get permission. The way organisations charge or refuse rights to use “digital surrogates” are outdated and conflict with public missions, the study says.

It warns the UK cultural sector has not kept up with efforts to promote open access to digital collections ongoing elsewhere around the world and there is more concern with generating income through image licensing. This impedes the legitimate use of the public domain for those researching and studying, as well as for artists, the creative industries, and the public for learning and new creations.

The study proposes a new framework to help staff in cultural institutions make more accurate assessments of copyright rights in digital surrogates.

Dr Wallace said: “The current system is a mess, but this new framework can help to disentangle the use of surrogate rights from the ways that cultural institutions manage their collections. It allows lawyers, directors, and heritage practitioners to mend things themselves by distinguishing original from non-original reproduction media. This better captures the vast potential of our public domain cultural heritage in this digital age.

“Of course, cultural institutions cannot and should not uncritically digitize and publish all collections and data for free and unfettered reuse. But there is a clear need to provide access and improve legal certainty for the public who would like to use out-of-copyright collections.”

The framework aims to reduce barriers to people using collections while protecting legitimate intellectual property, curatorial and educational expertise. By encouraging cultural institutions to publish high-quality images online, visitors onsite and online will know they can get the best possible surrogate directly from the source.

Experience shows this can bring new relevance to cultural institutions and drive new income streams, as there may be business opportunities and partnerships made possible by open access.

Dr Wallace said: “The framework can also improve legal certainty around public reuse of surrogate images in the public domain while bolstering their compliance with legitimate reuse restrictions. Imagine how simple it would be if we could identify the artwork and assess its copyright status using the lifetime of the original artist, rather than the claim of the cultural institution asserting a surrogate copyright in the image.

“The data already tells us that most cultural institutions lose money by operating a copyright licensing service. They rarely bring in enough income to cover the costs of running them. Nor is a surrogate copyright necessary to generate revenue or enforce rights in the collection. Cultural institutions can still charge service fees for image creation and delivery. And rather than basing claims on surrogate copyright, institutions can focus infringement notices on legitimate claims, such as trademark, false advertising, or concerns with the specific use, thereby reducing operating costs and inefficiencies.

“The short-term benefits will be to help cultural institutions comply with copyright law, meet their public missions in a digital age and explore more sustainable business models around open access collections. The long-term benefits will be to support the publication of data that is better fit for purpose in the 21st century. Open datasets are invaluable for computational processing, machine learning, and artificial intelligence. If cultural institutions view collections data as within public domain and therefore are more wary of these risks, it may improve the pre-publication assessments of what materials should be digitized. Cultural institutions can then use technological safeguards to revise or restructure data, embed relevant context or information in the metadata, and provide guidelines to support more appropriate reuse and reduce harm.”

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ARTICLE TITLE

SURROGATE INTELLECTUAL PROPERTY RIGHTS IN THE CULTURAL SECTOR

 

Space solar power project ends first in-space mission with successes and lessons

Reports and Proceedings

CALIFORNIA INSTITUTE OF TECHNOLOGY

 

IMAGE: 

THE DOLCE STRUCTURE COMPLETELY DEPLOYED, OVER THE CANADIAN ARCTIC, ON SEPTEMBER 29, 2023. DOLCE STRUCTURE'S TRAC LONGERONS AND BATTENS ARE CLEARLY VISIBLE ABOVE THE ARCTIC ICE. THE FIBERGLASS BATTEN CONNECTORS ARE SHINING UNDER THE SUN (RIGHT PART).

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CREDIT: SPACE SOLAR POWER PROJECT/CALTECH

One year ago, Caltech’s Space Solar Power Demonstrator (SSPD-1) launched into space to demonstrate and test three technological innovations that are among those necessary to make space solar power a reality.

The spaceborne testbed demonstrated the ability to beam power wirelessly in space; it measured the efficiency, durability, and function of a variety of different types of solar cells in space; and gave a real-world trial of the design of a lightweight deployable structure to deliver and hold the aforementioned solar cells and power transmitters.

Now, with SSPD-1’s mission in space concluded, engineers on Earth are celebrating the testbed’s successes and learning important lessons that will help chart the future of space solar power.

"Solar power beamed from space at commercial rates, lighting the globe, is still a future prospect.  But this critical mission demonstrated that it should be an achievable future," says Caltech President Thomas F. Rosenbaum, the Sonja and William Davidow Presidential Chair and professor of physics. 

SSPD-1 represents a major milestone in a project that has been underway for more than a decade, garnering international attention as a tangible and high-profile step forward for a technology being pursued by multiple nations. It was launched on January 3, 2023, aboard a Momentus Vigoride spacecraft as part of the Caltech Space Solar Power Project (SSPP), led by professors Harry Atwater, Ali Hajimiri, and Sergio Pellegrino. It consists of three main experiments, each testing a different technology:

• DOLCE (Deployable on-Orbit ultraLight Composite Experiment): a structure measuring 1.8 meters by 1.8 meters that demonstrates the novel architecture, packaging scheme, and deployment mechanisms of the scalable modular spacecraft that will eventually make up a kilometer-scale constellation to serve as a power station.
• ALBA: a collection of 32 different types of photovoltaic (PV) cells to enable an assessment of the types of cells that can withstand punishing space environments.
• MAPLE (Microwave Array for Power-transfer Low-orbit Experiment): an array of flexible, lightweight microwave-power transmitters based on custom integrated circuits with precise timing control to focus power selectively on two different receivers to demonstrate wireless power transmission at distance in space.

"It’s not that we don’t have solar panels in space already. Solar panels are used to power the International Space Station, for example,” says Atwater, Otis Booth Leadership Chair of Division of Engineering and Applied Science; Howard Hughes Professor of Applied Physics and Materials Science; director of the Liquid Sunlight Alliance; and one of the principal investigators of SSPP. “But to launch and deploy large enough arrays to provide meaningful power to Earth, SSPP has to design and create solar power energy transfer systems that are ultra-lightweight, cheap, flexible, and deployable."

DOLCE: Deploying the Structure

Though all of the experiments aboard SSPD-1 were ultimately successful, not everything went according to plan. For the scientists and engineers leading this effort, however, that was exactly the point. The authentic test environment for SSPD-1 provided an opportunity to evaluate each of the components and the insights gleaned will have a profound impact on future space solar power array designs. 

For example, during the deployment of DOLCE—which was intended to be a three- to four-day process—one of the wires connecting the diagonal booms to the corners of the structure, which allowed it to unfurl, became snagged. This stalled the deployment and damaged the connection between one of the booms and the structure. 

With the clock ticking, the team used cameras on DOLCE as well as a full-scale working model of DOLCE in Pellegrino's lab to identify and try to solve the problem. They established that the damaged system would deploy better when warmed directly by the Sun and also by solar energy reflected off Earth. 

Once the diagonal booms had been deployed and the structure was fully uncoiled, a new complication arose: Part of the structure became jammed under the deployment mechanism, something that had never been seen in laboratory testing. Using images from the DOLCE cameras, the team was able to reproduce this kind of jamming in the lab and developed a strategy to fix it. Ultimately, Pellegrino and his team completed the deployment through a motion of DOLCE's actuators that vibrated the whole structure and worked the jam free. Lessons from the experience, Pellegrino says, will inform the next deployment mechanism.

"The space test has demonstrated the robustness of the basic concept, which has allowed us to achieve a successful deployment in spite of two anomalies," says Pellegrino, Joyce and Kent Kresa Professor of Aerospace and Civil Engineering and co-director of SSPP. "The troubleshooting process has given us many new insights and has sharply focused us on the connection between our modular structure and the diagonal booms. We have developed new ways to counter the effects of self-weight in ultralight deployable structures." 

ALBA: Harvesting Solar Energy

Meanwhile, the photovoltaic performance of three entirely new classes of ultralight research-grade solar cells, none of which had ever been tested in orbit before, were measured over the course of more than 240 days of operation by the ALBA team, led by Atwater. Some of the solar cells were custom-fabricated using facilities in the SSPP labs and the Kavli Nanoscience Institute (KNI) at Caltech, which gave the team a reliable and fast way to get small cutting-edge devices quickly ready for flight. In future work, the team plans to test large-area cells made using highly scalable inexpensive manufacturing methods that can dramatically reduce both the mass and the cost of these space solar cells.

Space solar cells presently available commercially are typically 100 times more expensive than the solar cells and modules widely deployed on Earth. This is because their manufacture employs an expensive step called epitaxial growth, in which crystalline films are grown in a specific orientation on a substrate. The SSPP solar cell team achieved low-cost nonepitaxial space cells by using cheap and scalable production processes like those used to make today's silicon solar cells. These processes employ high-performance compound semiconductor materials such as gallium arsenide that are typically used to make high-efficiency space cells today.

The team also tested perovskite cells, which have captured the attention of solar manufacturers because they are cheap and flexible, and luminescent solar concentrators with the potential to be deployed in large flexible polymer sheets.

Over ALBA's lifespan, the team collected enough data to be able to observe changes in the operation of individual cells in response to space weather events like solar flares and geomagnetic activity. They found, for example, tremendous variability in the performance of the perovskite cells, whereas the low-cost gallium arsenide cells consistently performed well overall.

"SSPP gave us a unique opportunity to take solar cells directly from the lab at Caltech into orbit, accelerating the in-space testing that would normally have taken years to be done. This kind of approach has dramatically shortened the innovation-cycle time for space solar technology," says Atwater.

MAPLE: Wireless Power Transfer in Space

Finally, as announced in June, MAPLE demonstrated its ability to transmit power wirelessly in space and to direct a beam to Earth—a first in the field. MAPLE experiments continued for eight months after the initial demonstrations, and in this subsequent work, the team pushed MAPLE to its limits to expose and understand its potential weaknesses so that lessons learned could be applied to future design. 

The team compared the performance of the array early in the mission with its performance at the end of the mission, when MAPLE was intentionally stressed. A drop in the total transmitted power was observed. Back in the lab on Earth, the group reproduced the power drop, attributing it to the degradation of a few individual transmitting elements in the array as well as some complex electrical–thermal interactions in the system. 

"These observations have already led to revisions in the design of various elements of MAPLE to maximize its performance over extended periods of time," says Hajimiri, Bren Professor of Electrical Engineering and Medical Engineering and co-director of SSPP. "Testing in space with SSPD-1 has given us more visibility into our blind spots and more confidence in our abilities." 

SSPP: Moving Forward

SSPP began after philanthropist Donald Bren, chairman of Irvine Company and a life member of the Caltech community, first learned about the potential for space-based solar energy manufacturing as a young man in an article in Popular Science magazine. Intrigued by the potential for space solar power, Bren approached Caltech's then-president Jean-Lou Chameau in 2011 to discuss the creation of a space-based solar power research project. In the years to follow, Bren and his wife, Brigitte Bren, a Caltech trustee, agreed to make a series of dona­tions (yielding a total commitment of over $100 million) through the Donald Bren Foundation to fund the project and to endow a number of Caltech professorships. 

"The hard work and dedication of the brilliant scien­tists at Caltech have advanced our dream of providing the world with abundant, reliable, and affordable power for the benefit of all humankind," Donald Bren says. 

In addition to the support received from the Brens, Northrop Grumman Corporation provided Caltech with $12.5 million between 2014 and 2017 through a spon­sored research agreement that aided technology development and advanced the project’s science.

With SSPD-1 winding down its mission, the testbed stopped communications with Earth on November 11. The Vigoride-5 vehicle that hosted SSPD-1 will remain in orbit to support continued testing and demonstration of the vehicle's Microwave Electrothermal Thruster engines that use distilled water as a propellant. It will ultimately deorbit and disintegrate in Earth's atmosphere.

Meanwhile, the SSPP team continues work in the lab, studying the feedback from SSPD-1 to identify the next set of fundamental research challenges for the project to tackle.  

Same-level workplace falls set to rise amid surge in older female workforce numbers

Falls from height associated with male sex, construction work, and severe injuries. Better prevention strategies needed to mitigate these risk factors, say researchers

Peer-Reviewed Publication

BMJ

Same-level falls in the workplace are set to rise amid rapid growth in the numbers of older female employees in the workforce, suggests Australian research published online first in the journal Occupational & Environmental Medicine.

Although workplace falls, overall, are more common among male employees, particularly falls from height, same-level falls are more common in older women, the findings indicate.

The prevalence and relative severity of workplace falls mean that better prevention strategies are needed to mitigate these sex-specific risk factors, conclude the researchers.

In 2016, an estimated 1.53 million deaths and 76.1 million years of lived disability were caused by workplace injuries, note the researchers. Falls accounted for more than a quarter of these figures.

The Australian workforce is ageing: 50–64 year olds made up 11% of employees in the mid-90s, rising to  21% in 2023. And ageing in general is associated with a heightened risk of falls, say the researchers.

In a bid to uncover the risk profiles of workplace falls, they analysed hospital admission records for the state of Victoria, Australia, between July 2017 and June 2022. Only patients older than 15 and admitted as a result of a work-related injury were included in the analysis. 

The researchers compared fall and other injuries; ‘falls from height’ and ‘same-level falls’ ; age and sex; presence of co-existing long term conditions; time and place of injury; work and injury types; body parts involved; injury severity; and length of hospital stay. 

Some 45,539 people were admitted to hospital for work-related injuries during the study period, of which 42,176 admissions were included in the final analysis 

The average annual rate of hospital admission for a work-related injury was 2.54 in every 1000 employees, but men outnumbered women: 3.91 vs 0.98/1000 employees. 

Around 1 in 5 of these admissions (8669; 21%) were associated with a fall, around half of which (52%) were falls from a height, while 37% were same-level/low falls.

Falls from ladder/scaffolds (21%), stairs/steps (9%), building/structure (8.5%) and different level falls (13.5%) made up those from height. Other specified and unspecified falls represented 1.5% and 10.5%, respectively. Over half of the fall injuries were fractures.

The average annual rate of hospital admission associated with a workplace fall was 0.52 in every 1000 employees: 0.68 for men and 0.34 for women. 

Most work-related falls occurred in 25–64 year olds, with men accounting for more than two thirds (69%) of all such falls. Women aged 45 and older, however, accounted for 1 in 5 (21%) of these falls and more than 5% of other workplace injuries. 

While the rates for height falls were higher in men than in women: 0.44 vs 0.08 per 1000 workers, especially among those aged 45 and older, same-level falls were higher in women: 0.21 vs 0.18, particularly after the age of 50. 

“It is possible that this higher rate of high falls among men is explained by the greater rates of men, particularly young men, relative to  women, working in sectors in which working at height is relatively common, for example, construction, telecommunications, and mechanical engineering,” suggest the researchers.

Same-level fall rates were relatively low in the youngest age groups, but rose sharply with increasing age, and were highest among the oldest female employees.

One in five (21%) of fallers had at least one co-existing health condition recorded during their hospital stay—30% of those with fall-related injuries and 19% of those with other work-related injuries. 

Co-existing health problems were more common among those who had experienced a same-level fall than among those who had fallen from height, particularly circulatory, respiratory, and musculoskeletal conditions.

Falls, especially those from height, were more common among those working in construction, while other work-related injuries were more common among those working in agriculture, forestry, fishing and manufacturing. 

Fall injuries were more likely to be serious, compared with other work-related injuries; this was particularly evident for falls from height. Prolonged length of stay was also more common for falls than for other types of injury. Nearly a third of hospital days due to work-related injuries were attributable to falls.

The findings relate to just one state in Australia so may not be more widely applicable, and the coding indicating where the fall occurred included a high proportion of ‘unspecified’ entries, acknowledge the researchers.

But they write: “Our findings add to a growing body of evidence suggesting that older working-aged women are at increased risk of same-level falls and fall-related injuries, particularly in the presence of comorbidity (whereas we observed a different risk profile for high falls, which were associated with males and which did not have a pronounced association with the number of comorbidities).”

They add: “For employers of middle-aged female workers, employers either need to consider a generalised approach to fall reduction among their entire workforce … or perhaps a targeted ‘screening’ approach in which workers are offered opportunities to share health information relevant to fall risk (including history of falls).”

And they conclude: “Fall injuries, particularly same-level falls, are likely to increase in workplaces with current demographic changes, and employers, regulators, and policy makers could usefully consider raising the profile of workplace falls and developing effective prevention strategies.”

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JOURNAL

Occupational and Environmental Medicine

DOI

10.1136/oemed-2023-109079 

METHOD OF RESEARCH

Observational study

SUBJECT OF RESEARCH

People

ARTICLE TITLE

Epidemiology of work-related fall injuries resulting in hospitalisation: individual and work risk factors and severity

ARTICLE PUBLICATION DATE

16-Jan-2024

 

Silkmoths: Different olfactory worlds of females and males

Female moths primarily use their sense of smell to find the best host plants on which to lay their eggs, with the deterrent effect of caterpillar feces playing an important role

Peer-Reviewed Publication

MAX PLANCK INSTITUTE FOR CHEMICAL ECOLOGY

 

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FEMALE SILKMOTH (BOMBYX MORI) ON THE LEAF OF A MULBERRY TREE, THE ONLY HOST PLANT FOR THE OFFSPRING OF THESE MOTHS. THE COMBED ANTENNAE, WHICH ACT AS THE INSECT'S "NOSE" TO DETECT ODORS, ARE CLEARLY VISIBLE. THE LATERAL BRANCHES OF THE ANTENNAE ARE COVERED WITH THOUSANDS OF HAIR-LIKE STRUCTURES CALLED SENSILLA, WHICH HOUSE THE SENSORY NEURONS FOR ODOR DETECTION.

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CREDIT: MARKUS KNADEN, MAX PLANCK INSTITUTE FOR CHEMICAL ECOLOGY

The world smells different for female silkmoths than for males

In humans, the sense of smell is similarly developed in men and women, although women have slightly more olfactory neurons and therefore a slightly more sensitive nose. On the whole, however, they perceive the same odors. Male moths, on the other hand, live in a completely different olfactory world to their female counterparts. For example, the antennae of male silkmoths - their "nose" - are highly specialized to detect female sex pheromones, while females cannot even smell their own pheromones. There are thousands of sensilla on the antennae, hair-like structures, which can be divided into morphologically and functionally distinct groups. The most common sensilla in males are long and contain two sensory neurons. One is specialized to detect bombykol, the sex pheromone of females, while the other responds to bombykal, a component of the pheromone of other moth species. While bombykol is highly attractive to male silkmoths, bombykal is a deterrent.

"Because female silkmoths cannot smell their own pheromone, it was long thought that their long sensilla also have a very specific function that is only found in females. After mating, the female's only task is to find a suitable plant on which to lay her eggs. It has therefore been suggested that the long sensilla of females are specialized to detect the attractive odor of mulberry trees. We wanted to test this assumption", says Sonja Bisch-Knaden, who leads a project group in the Department of Evolutionary Neuroethology at the Max Planck Institute for Chemical Ecology.

Long sensilla of female silkmoths recognize silkworm feces

Electrophysiological methods, such as measuring the activity of individual sensilla (single-sensillum recording), were crucial for the study’s results. The scientists not only tested many different individual odors, but also natural odor mixtures, such as those found in the leaves of the mulberry tree, caterpillar droppings, the body odor of moths or the meconium, a liquid that moths secrete when they hatch. All these odors, which play an ecological role in the silkmoth's environment, had been collected. The research team was also able to match the expression of olfactory receptors to the corresponding sensillum type. 

"We were surprised to find that neurons in the long sensilla of female silkmoths were not specialized to detect the odor of the host plant, as expected, but that one of the two neurons in the long sensilla is very sensitive to odors such as isovaleric acid and benzaldehyde. The detection of the odor of the mulberry leaf itself is carried out by neurons in medium-length sensilla", summarizes Sonja Bisch-Knaden.

Isovaleric acid and benzaldehyde are odor components of silkworm feces. Using a simple Y-maze test with an entrance arm that splits into two side arms through which either an odor or clean air (control) is introduced, the research team was able to elicit behavior in the otherwise immobile females that expressed attraction or aversion. Major differences became apparent when comparing virgin and mated females. The researchers showed that odors associated with caterpillar droppings did not trigger a specific reaction in virgin females, but had a deterrent effect on mated females. Presumably, the smell of feces helps females avoid mulberry trees, which are already full of silkworms when they lay their eggs.

In search of the male silkmoth pheromone

The pheromone of female silkmoths, bombykol, was chemically characterized as early as 1959 - the first insect pheromone ever. So far, scientists have not been able to identify a male counterpart. The current study provides clues, but no answers to the question of a male pheromone. "The second neuron in the females’ long sensilla is highly specific for (+)-linalool, an odor already identified as a component of the male pheromone in other butterfly species. However, no linalool could be found in the body odor of male silkmoths, and (+)-linalool alone had neither an attractive nor a repellent effect on female silkmoths in behavioral experiments", says Sonja Bisch-Knaden.

Special features of the odor perception of silkmoths

While investigating the molecular basis of odor detection in female silkmoths, the researchers noticed a peculiarity in the spatial organization of olfactory receptors. There are two families of olfactory receptors, the evolutionary older ionotropic receptors (IRs), which detect mainly acids, and the odorant receptors (ORs), which detect a wide range of chemically diverse compounds. Based on studies in the model fly Drosophila melanogaster, it was long thought that neurons expressing IRs or ORs usually occur in different types of sensilla, and that IRs never occur in long sensilla. In the silkmoth, however, an IR co-receptor for the detection of acids and the obligate OR co-receptor are both found in the same neurons located in long sensilla. This co-expression of IRs and ORs increases the chemical receptivity of the sensory neurons. Odors detected by both receptor types are processed and transmitted together, which could be advantageous for the unambiguous detection of ecologically important odor mixtures. "It is amazing that research on insect olfaction continues to produce surprising results. Our study shows that it is important to study more than just one model," says Bill Hansson, head of the Department of Evolutionary Neuroethology.

The researchers also found this co-expression of the two receptor types in the long sensilla of male silkmoths, which is why they assume that the detection of acids could also play an important ecological role in males. Further investigations will now clarify this.

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JOURNAL

Proceedings of the Royal Society B Biological Sciences

DOI

10.1098/rspb.2023.2578 

METHOD OF RESEARCH

Experimental study

SUBJECT OF RESEARCH

Animals

ARTICLE TITLE

Females smell differently: characteristics and significance of the most common olfactory sensilla of female silkmoths

ARTICLE PUBLICATION DATE

17-Jan-2024

ARACHNOLOGY

Spider venom heart drug a step closer

A spider venom molecule being investigated by a University of Queensland team has met critical benchmarks towards becoming a treatment for heart attack and stroke.

 NEWS RELEASE 16-JAN-2024

UNIVERSITY OF QUEENSLAND

 

IMAGE: 

RESEARCHERS SOURCED A MOLECULE FROM FUNNEL WEB SPIDER VENOM WHICH IS SHOWING PROMISE TO TREAT HEART ATTACKS.

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CREDIT: INSTITUTE FOR MOLECULAR BIOSCIENCE, UNIVERSITY OF QUEENSLAND

A spider venom molecule being investigated by a University of Queensland team has met critical benchmarks towards becoming a treatment for heart attack and stroke.

Associate Professor Nathan Palpant and Professor Glenn King from UQ’s Institute for Molecular Bioscience have previously shown that the drug candidate Hi1a protects cells from the damage caused by heart attack and stroke.

Dr Palpant said a subsequent study has put the drug through a series of preclinical tests designed to mimic real-life treatment scenarios.

“These tests are a major step towards helping us understand how Hi1a would work as a therapeutic – at what stage of a heart attack it could be used and what the doses should be,” Dr Palpant said.

“We established that Hi1a is as effective at protecting the heart as the only cardioprotective drug to reach Phase 3 clinical trials, a drug that was ultimately shelved due to side effects.

“Importantly, we found that Hi1a only interacts with cells in the injured zone of the heart during an attack and doesn’t bind to healthy regions of the heart – reducing the chance of side effects.”

Professor King, who recently won the Prime Minister’s Prize for Innovation for developing the world’s first insecticides from spider venom, discovered Hi1a in the venom of the K’gari funnel web spider.

“Hi1a could reduce damage to the heart and brain during heart attacks and strokes by preventing cell death caused by lack of oxygen,” Professor King said.

“Our testing and safety studies from independent contract research organisations has provided evidence that Hi1a could be an effective and safe therapeutic.”

Infensa Bioscience, a company co-founded by the researchers, raised $23 million in 2022 to develop Hi1a for commercial purposes.

Infensa CEO and UQ researcher, Associate Professor Mark Smythe, said cardiovascular disease is the leading cause of death globally.    

“Most deaths from cardiovascular disease are caused by heart attacks and strokes, yet there are no drugs on the market that prevent the damage they cause,” Dr Smythe said.  

“An effective drug to treat heart attacks would have worldwide impact, providing a breakthrough to improve the lives of millions of individuals living with heart disease.”

The research team included Dr Meredith Redd from IMB as well as Dr Melissa Reichelt and Dr Yusuke Yoshikawa from UQ’s School of Biomedical Sciences.

The study was published in the world’s leading cardiac journal The European Heart Journal.

 

Video: https://youtu.be/73zFDfeuTv8

 

 

 

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JOURNAL

European Heart Journal

DOI

10.1093/eurheartj/ehad793 

METHOD OF RESEARCH

Experimental study

SUBJECT OF RESEARCH

Animals

ARTICLE TITLE

Acid-sensing ion channel 1a blockade reduces myocardial injury in rodent models of myocardial infarction

 

A manned submersible found a fault scarp of the 2011 Tohoku-oki megaquake in the Japan Trench

Peer-Reviewed Publication

NIIGATA UNIVERSITY

 

IMAGE: 

THIS VERTICAL CLIFF CONSISTS OF SOFT MUD DEPOSITED ON THE JAPAN TRENCH BOTTOM AND WAS UPLIFTED ~60 M BY THE 2011 MEGAQUAKE. THIS WAS THE FIRST TIME THAT THE FAULT SCARP OF A TRENCH-TYPE EARTHQUAKE WAS OBSERVED AND VISUALLY RECORDED.

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CREDIT: NIIGATA UNIVERSITY

Niigata, Japan – On September 4, 2022, a geologist Hayato Ueda in Niigata University boarded a submarine vehicle with a pilot Chris May and had a dive into the Japan Trench within the epicenter area of the 2011 Tohoku-oki megaquake, which caused the devastating tsunami disaster. On the 7,500 m deep trench bottom, they found a 26 m high nearly vertical cliff on the eastern slope of a 60 m high ridge. Previous bathymetric surveys from the sea surface have revealed that the ridge did not exist before, and appeared just after the megaquake accompanied with a fault on its eastern flank. He and his colleague scientists on deck thus concluded that the cliff was a surface expression of a coseismic movement of the fault. The cliff consisted of unconsolidated soft mud. The lower slope than the cliff was occupied by abundant debris of the same soft mud blocks, which obviously supplied from the cliff. The observed sharp fracture surfaces and highly angular edges, both on the cliff and debris blocks, imply very quick increase of stress that fractured the soft muds before they plastically flowed, and thus support a coseismic origin of the cliff.

The vehicle traversed the ridge across the fault precisely measuring the topography using acoustic transponder and pressure gauge. The height and uplifted volume of the ridge both suggest a coseismic slip of the fault as large as 80–120 m (the value depends on the assumed dip angle of the underlying fault) in the Japan Trench. This estimation is greater than the previously estimated fault slip (~65 m) beneath the slope on the west of the trench axis. They attributed the excess fault slip in the trench to local enhancement owing to the uneven top surface of the subducting Pacific plate, which modified the fault geometry and stability.

The 2011 megaquake resulted from rupture and slip of the plate boundary fault between the northeast Honshu Island of Japan (Okhotsk plate) and the subducting Pacific plate. After the earthquake, many geodetic and geophysical studies have proposed that this coseismic fault movement probably propagated to the trench. Because topographic change by near-surface fault movement is one of the major causes of tsunamis, it is important to precisely know what occurred in the deep-sea trench when the trench-type earthquake such as the 2011 event occurred. However, because of great depths, no submersible vehicles (neither manned nor remotely operated) had been able to access to the Japan Trench bottom. This study was the first time to observe, visually record, and precisely measure the topographic change (including fault cliff) in the trench by a single trench-type megaquake event. It verified that the fault slip surely propagated to the surface at the 2011 event, and deduced that the amount of the slip was at least locally as great as 100 m. These results are expected to contribute to our understanding of genesis and to hazards of tsunamis triggered by trench-type earthquakes. This study was published by the journal communications earth & environment on Dec. 26, 2023 https://doi.org/10.1038/s43247-023-01118-4

The submersible “DSV Limiting Factor” used for the survey. 

This vehicle has an ability to dive into the depth of 11,000 m, the world’s deepest ocean bottom, and thus is called as a “full-depth submersible”. It enabled researchers to approach to the Japan Trench bottom in the epicenter area for the first time more than 10 years after the megaquake. Without in situ observation using this submersible, the fault scarp in the ultra-deep sea would not have discovered.

CREDIT

Niigata University

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JOURNAL

Communications Earth & Environment

DOI

10.1038/s43247-023-01118-4 

ARTICLE TITLE

The submarine fault scarp of the 2011 Tohoku-oki Earthquake in the Japan Trench