Tuesday, August 02, 2022

 What’s new under the sun? Offering an alternate view on how “novel” structures evolve

Peer-Reviewed Publication

MARINE BIOLOGICAL LABORATORY

The freshwater crustacean Daphnia 

IMAGE: THE FRESHWATER CRUSTACEAN DAPHNIA (WATER FLEA) IS A COMMON RESEARCH ORGANISM IN ECOLOGY, TOXICOLOGY, EVOLUTIONARY DEVELOPMENTAL BIOLOGY, AND OTHER FIELDS. view more 

CREDIT: PROYECTO AGUA

WOODS HOLE, Mass. – Many crustaceans, including lobster, crabs, and barnacles, have a cape-like shell protruding from the head that can serve various roles, such as a little cave for storing eggs, or a protective shield to keep gills moist.

This shell (carapace), it’s been proposed, didn’t evolve from any similar structure in the crustacean ancestor, but appeared de novo (or out of the blue) through somewhat random co-option of the genes that also specify insect wings.

However, in a new study from the Marine Biological Laboratory (MBL), Research Associate Heather Bruce and Director Nipam Patel provide evidence for an alternate view: The carapace, along with other plate-like structures in arthropods (crustaceans, insects, arachnids, and myriapods) all evolved from a lateral leg lobe in a common ancestor.

This evidence buttresses their proposal for a new concept of how novel structures evolve – one which suggests that they aren’t so novel, after all. The study, on the carapace of the crustacean Daphnia, appears online in Current Biology.

“How novel structures arise is a central question in evolution,” Bruce says. “The prevailing idea, called gene co-option, is that genes that are functioning in one context, say to make insect wings, end up in an unrelated context, where they make, say, a carapace,” says Bruce. “But here we show that the Daphnia carapace didn’t just pop out of nowhere.”

Rather, they propose the ancestral, plate-like leg lobe that evolved into both the wing and the carapace was likely present in the ancestor of all living arthropods. But because the wing and carapace look so different from this ancestral plate, and from other plates in neighboring arthropod lineages, no one realized that they were all the same thing.

“We are starting to realize that structures that don’t look anything alike – wings, carapaces, tergal plates – are actually homologous,” Bruce says. “That suggests they have a single origin that is way more ancient than anyone would have thought, way back in the Cambrian period, [500 million] years ago.”

It was there all along (cryptic persistence)

Bruce calls her model for how novel structures emerge “cryptic persistence of serial homologs.”

“Serial homologs are things like hands and feet, or the vertebrae of our spine, or the many legs repeating down a centipede’s body,” she says. “The [repeats] can look really different, but you can see similarities, and they are all built using the same initial genetic pathways. In some cases, the full structure doesn’t grow out – you may get a truncated centipede leg, or it’s really subtle and tiny. While the cells have been programmed to form the leg, they aren’t actually growing out the leg.”

In Bruce’s view, these dormant rudiments - legs, plates, etc - can persist over millions of years, as long as another repeat of the structure is still present somewhere else in the animal. And when the time is right, the structure may grow out again and take different forms in different species – a wing in an insect, say, or a carapace in a crustacean.

“If an ancestral structure is no longer needed, nature probably just truncates or reduces that tissue rather than deleting it completely. But the tissue is still there and can be elaborated again in later lineages, and appear to us to be novel,” Bruce says.

“This kind of truncation is probably common in evolution because genetic networks are so interdependent, “Bruce explains. “if a genetic pathway or tissue were to be deleted, some other pathway or tissue would be affected.” 

“I think cryptic persistence can be an explanation for a lot of ‘novel’ structures,” Bruce says.

The authors drew their conclusions by analyzing gene expression patterns in several arthropod species, and by eliminating other hypotheses of how the carapace may have evolved.

“The ancient, common origin of all these plate-like structures [in arthropods] suggests the gene networks that pattern these structures are very evolvable and plastic. They are capable of generating an awesome amount of diversity,” Bruce says.

CAPTION

The ancestral arthropod had multiple plates on each leg on every body segment, similar to the living crustacean Parhyale. Later arthropods repress most of these, but any plate can be derepressed on any body segment to form what appears to be novel structures. The Daphnia carapace evolved by de-repressing and elaborating the blue head plate and the insect wing evolved by de-repressing and elaborating the pink thoracic plate.

CREDIT

Bruce and Patel, Current Biology, 2022.

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The Marine Biological Laboratory (MBL) is dedicated to scientific discovery – exploring fundamental biology, understanding marine biodiversity and the environment, and informing the human condition through research and education. Founded in Woods Hole, Massachusetts in 1888, the MBL is a private, nonprofit institution and an affiliate of the University of Chicago.

VegSense makes sense for forest studies

Rice bioscientists use mixed-reality headset, custom software to measure vegetation in the field

Peer-Reviewed Publication

RICE UNIVERSITY

0727_HOLO-reach980-lg.jpg 

IMAGE: RICE UNIVERSITY GRADUATE STUDENT DANIEL GORCZYNSKI CREATED AN OPEN-SOURCE APP CALLED VEGSENSE TO GATHER FIELD DATA ABOUT UNDERSTORY VEGETATION USING MICROSOFT’S HOLOLENS HEADSET. THE APP ALLOWS FIELD RESEARCHERS TO GATHER DATA AS THEY WALK AND LOOK AT VEGETATION. SPATIAL DATA IS DISPLAYED ON THE HOLOLENS SCREEN IN REAL TIME AND CAN BE STORED FOR LATER ANALYSIS. view more 

CREDIT: JEFF FITLOW/RICE UNIVERSITY

HOUSTON – (Aug. 1, 2022) – Ecologists won’t always need expensive and bulky equipment to measure vegetation in the wild. Rice University scientists have discovered a modern heads-up display works pretty well.

Rice researchers set up a Microsoft HoloLens as a mixed-reality sensor to feed VegSense, their application to measure understory vegetation, plant life that grows between the forest canopy and floor.

A proof-of-concept study by graduate student Daniel Gorczynski and bioscientist Lydia Beaudrot shows VegSense could be a suitable alternative to traditional classical field measurements at a low cost.

Their study in Methods in Ecology and Evolution shows the hardware-software combination excels at quantifying relatively mature trees in the wild, which is one measure of a forest’s overall health.

Gorczynski came up with the idea to try HoloLens, commonly marketed as a productivity tool for manufacturing, health care and education. He developed the open-source software for the device and noted that while the combination is less effective at picking up saplings and small branches, there’s ample room for improvement.

Gorczynski said he was introduced to mixed-reality sensing while an undergraduate at Vanderbilt University and recognized its potential for biological studies. “It seemed sort of like a natural fit,” he said. Gorczynski brought the idea to Beaudrot in 2019 shortly after his arrival at Rice.

The combination of stock hardware and custom software cost far less than systems based on lidar (for “light detection and ranging”) most often used in three-dimensional field studies, said Gorczynski, who developed VegSense on a platform geared more toward 3D games and interactive experiences than hard science.

Field tests at Houston’s Memorial Park showed that at least for mature trees, the smaller solution is just as good. In their case study, VegSense easily detected 48 of 50 such trees in the target area, a circle about 30 feet in diameter that Gorczynski walked, looking up, down and around to build the 3D database. (“Imagine an asterisk with a circle around it,” he said, describing the data-capture pattern.)

“For this study, we wanted to be really deliberate in trying to replicate more traditional understory vegetation structure measurements,” Gorczynski said. “We tried to get that level of detail.”

What he sees as he scans the environment is a holograph-like grid pattern that tracks the surfaces of vegetation. “What’s really cool about that is you can see what the scanner is picking up, but also the spots you missed,” Gorczynski said. “The idea is to get the mesh to cover as much of the vegetation as possible because that’s what gets you the best scan.”

“The results were so nice that Dan quickly wrote it up for publication,” Beaudrot said, noting that Gorczynski expanded his validation of the gear during a subsequent field trip to Tanzania, the focus of one of 15 tropical forests in a recent rainforest study by the Rice group.

“This device can facilitate a lot of great ecological research, particularly because it’s so cost-effective,” she said. “Collecting vegetation information on the forest floor right now is really hard to do without a lot of manual labor, or a really expensive lidar system.”

“So this is a groundbreaking, cost-effective device,” Beaudrot said. “It’s not going to give you the same resolution data that lidar will, but this is just the first application. We hope making VegSense open-source to the ecological research community will spur all the potential ways it can be developed.”

Northrop Grumman, Conservation International and Rice supported the research.

-30-

Peer-reviewed paper:

“Measuring understorey vegetation structure using a novel mixed-reality device” | Methods in Ecology and Evolution | DOI: 10.1111/2041-210X.13927

Daniel Gorczynski and Lydia Beaudrot

https://besjournals.onlinelibrary.wiley.com/doi/10.1111/2041-210X.13927


Links:

VegSense software repository: https://zenodo.org/record/6624972#.YufyZi-B2L0

Beaudrot Lab: lydiabeaudrot.weebly.com

Department of BioSciences: biosciences.rice.edu

Wiess School of Natural Sciences: naturalsciences.rice.edu


Video:

https://youtu.be/dBHfxvhMChU
A Rice University lab that specializes in applying data science to the study of conservation biology has created an open-source app to harvest field data from Microsoft’s HoloLens mixed-reality headset. Daniel Gorczynski, a graduate student in the lab of Rice data scientist and conservation biologist Lydia Beaudrot, created the software package called VegSense. It works with the Microsoft headset to gather field data about understory vegetation in specific locations. The app allows researchers to gather data as they walk and look at vegetation. Spatial data is displayed on the HoloLens screen in real time and can be stored for later analysis. (Video by Brandon Martin/Rice University)

CAPTION

Rice University’s open-source VegSense app for the Microsoft HoloLens headset allows researchers to record data about vegetation they see as they walk through a field site and create downloadable files for later analysis.

CREDIT

Brandon Martin/Rice University

Image downloads:

https://news-network.rice.edu/news/files/2022/07/0727_HOLO-reach980-lg.jpg
CAPTION: Rice University graduate student Daniel Gorczynski created an open-source app called VegSense to gather field data about understory vegetation using Microsoft’s HoloLens headset. The app allows field researchers to gather data as they walk and look at vegetation. Spatial data is displayed on the HoloLens screen in real time and can be stored for later analysis. (Photo by Jeff Fitlow/Rice University)

https://news-network.rice.edu/news/files/2022/07/0727_HOLO-HLsplt-lg.jpg
CAPTION: Rice University’s open-source VegSense app allows researchers to gather field data about understory vegetation as they walk and look at vegetation using Microsoft’s HoloLens headset. This split-screen image shows what VegSense creator Daniel Gorczynski sees through the headset (top) while he walks and looks at vegetation beneath trees on Rice’s campus (bottom). (Photo by Brandon Martin/Rice University)

https://news-network.rice.edu/news/files/2022/07/0727_HOLO-HLhnd-lg.jpg
CAPTION: Rice University’s open-source VegSense app for the Microsoft HoloLens headset allows researchers to record data about vegetation they see as they walk through a field site and create downloadable files for later analysis. (Photo by Brandon Martin/Rice University)

https://news-network.rice.edu/news/files/2022/07/0727_HOLO-hdsup832s-lg.jpg
CAPTION: Rice Ph.D. student Daniel Gorczynski wearing a Microsoft HoloLens headset. Gorczynski, a data scientist and conservation biologist, wrote an open-source app for the headset to streamline the collection of field data about understory vegetation. (Photo by Jeff Fitlow/Rice University)

https://news-network.rice.edu/news/files/2022/07/0727_HOLO-lb160-lg.jpg
CAPTION: Data scientist and conservation biologist Lydia Beaudrot is an assistant professor of biosciences at Rice University. (Photo by Jeff Fitlow/Rice University)

CAPTION

Rice Ph.D. student Daniel Gorczynski wearing a Microsoft HoloLens headset. Gorczynski, a data scientist and conservation biologist, wrote an open-source app for the headset to streamline the collection of field data about understory vegetation.

CREDIT

Jeff Fitlow/Rice University


Related stories:

Camera traps reveal newly discovered biodiversity relationship - March 3, 2021
news.rice.edu/news/2021/camera-traps-reveal-newly-discovered-biodiversity-relationship

National parks preserve more than species – Sept. 9, 2020
news.rice.edu/news/2020/national-parks-preserve-more-species

Where lions operate, grazers congregate … provided food is great – Aug. 17, 2020
news.rice.edu/news/2020/where-lions-operate-grazers-congregate-provided-food-grea


This release can be found online at news.rice.edu.

Follow Rice News and Media Relations via Twitter @RiceUNews.

Located on a 300-acre forested campus in Houston, Rice University is consistently ranked among the nation’s top 20 universities by U.S. News & World Report. Rice has highly respected schools of Architecture, Business, Continuing Studies, Engineering, Humanities, Music, Natural Sciences and Social Sciences and is home to the Baker Institute for Public Policy. With 4,240 undergraduates and 3,972 graduate students, Rice’s undergraduate student-to-faculty ratio is just under 6-to-1. Its residential college system builds close-knit communities and lifelong friendships, just one reason why Rice is ranked No. 1 for lots of race/class interaction and No. 1 for quality of life by the Princeton Review. Rice is also rated as a best value among private universities by Kiplinger’s Personal Finance.

Scientists found a new way to protect crops

They discovered how to modify crop genes


URAL FEDERAL UNIVERSITY

Alexander Ermoshin is a member of the research group that deals with plant genetics. 
view more
Credit: UrFU / Gleb Eremenko.


A gene that enhances plant protection against fungi, bacteria, and adverse environmental factors was identified by scientists from the Ural Federal University (UrFU) and the Pushchino Scientific Center of the Russian Academy of Sciences. Modifying plants with this gene will help protect crops from common diseases. Experiment results are published in the journal Plants.

Stilbene Synthase is the gene responsible for the synthesis of resveratrol in plants. This compound is highly biologically active, helping plants protect themselves from drought, frost, salinity and other negative environmental factors. Scientists extracted the Stilbene Synthase Gene from grape leaves and used it to create modified plants that are resistant to a number of common bacterial and fungal pathogens.

“We have demonstrated that adding Stilbene Synthase to the genome of plants increases their resistance not only to physical and chemical factors, but also to infections. In the future, our results can be used to protect plants from diseases,” said Alexander Ermoshin, Associate Professor at the Department of Experimental Biology and Biotechnologies, UrFU.

Stilbene Synthase-modified plants showed high resistance to pathogens dangerous to agroindustry, including Erwinia, Fusarium, Botrytis gray and other fungi and bacteria. These pathogens cause disease in a large number of crops, and infection with them can lead to the loss of a large part of the crop.

One of the tobacco species served as a model plant for the scientists of UrFU and the Branch of the Institute of Bioorganic Chemistry of the Russian Academy of Sciences. Special agrobacterium "loaded" with this gene was used to add Stilbene Synthase to the genome. According to the scientists, this is a completely natural process, repeating one of the mechanisms of natural plant mutation.

“An important part of the study was to analyze the effect of Stilbene Synthase on other characteristics of the modified plants. The tests showed that our transgenic tobacco does not differ from the usual tobacco, except for increased resistance to pathogens,” said Alexander Ermoshin.

It should be noted that specialists from Voronezh State University of Forestry and Technologies and the Federal Budget Institution of Science "State Research Center for Applied Microbiology and Biotechnology" also participated in the study. In the future, the research team intends to investigate the beneficial effects of plant modification with other genes.

Research Brief: The role of behavioral medicine in addressing climate-change related health inequities

Peer-Reviewed Publication

UNIVERSITY OF MINNESOTA MEDICAL SCHOOL

An article published in Translational Behavioral Medicine explores the role of behavioral medicine in addressing climate change-related health inequities.

“Structural racism has led to longstanding health inequities for communities that have been subjected to marginalization. Climate change is exacerbating these longstanding health inequities for frontline communities – which are those communities that are hit first and worst by climate change,” said Kristi White, PHD, LP, ABPP, an assistant professor and clinical health psychologist at the University of Minnesota Medical School. “We as behavioral medicine professionals have an important role to play in addressing climate-related health inequities in our research, clinical and other professional practices.”

The article highlights six strategies with the greatest potential for addressing climate-related health inequities: 

  • Adopt standards for the measurement and reporting of race as a sociopolitical construct in all behavioral medicine research and practices, including those directed at addressing climate change.

  • Operationalize the concept of structural racism in all behavioral medicine research and practices, including those directed at addressing climate change.

  • Incorporate environmental justice efforts into behavioral medicine research and practices.

  • Center the voices of communities targeted for marginalization in all behavioral medicine research and practices, including those that address climate and environmental justice.

  • Prioritize policy action on climate change and health equity.

  • Identify effective communication strategies to foster action on climate change and health equity issues.

Researchers say future studies should be aimed at dismantling structural racism, incorporating environmental justice efforts, and identifying effective communication strategies that promote action on climate change and health equity.

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About the University of Minnesota Medical School
The University of Minnesota Medical School is at the forefront of learning and discovery, transforming medical care and educating the next generation of physicians. Our graduates and faculty produce high-impact biomedical research and advance the practice of medicine. We acknowledge that the U of M Medical School, both the Twin Cities campus and Duluth campus, is located on traditional, ancestral and contemporary lands of the Dakota and the Ojibwe, and scores of other Indigenous people, and we affirm our commitment to tribal communities and their sovereignty as we seek to improve and strengthen our relations with tribal nations. For more information about the U of M Medical School, please visit med.umn.edu.

Study finds cable news networks have grown more polarized


An analysis of 10 years of cable TV news reveals a growing partisan gap as networks like Fox and MSNBC have shifted to the right or the left of the political spectrum, especially in their primetime programming.

Peer-Reviewed Publication

UNIVERSITY OF PENNSYLVANIA

Even though it seems that Americans are constantly on their phones, studies have shown that the majority of Americans still get their news from television. At the beginning of 2020, the average American adult consumed around nine-and-a-half hours of television news per week, according to Nielsen.

Cable news channels like CNN, Fox, and MSNBC are widely understood to have political leanings, but a new study published today in the Proceedings of the National Academy of Sciences surveyed a decade of cable news to measure that bias on a granular scale—by the day, the week, and even the hour. It found that all three networks became more polarized over the period studied, particularly following the 2016 election, becoming more out of sync, with Fox moving to the right in response to events that caused MSNBC and CNN to move to the left. 

“There has always been this assumption that media bias is fairly fixed,” says Yphtach Lelkes, co-author on the study and an associate professor at the University of Pennsylvania’s Annenberg School for Communication, “just ‘Fox News is the right. And MSNBC is the left.’ But what we see is that it moves, and pretty quickly.”

Lelkes and his colleagues focused on one form of media bias for their study: visibility bias. For example, if the majority of guests on a news channel are considered liberal, then the channel itself would be seen as liberal. They analyzed thousands of hours of CNN, Fox, and MSNBC to figure out who appeared on screen during news shows on these channels for at least 10 hours total between January 2010 and August 2020.

Each one of these guests was assigned a media bias score based on their financial contributions to political candidates and organizations, as found in Stanford University’s Database on Ideology, Money in Politics, and Elections (DIME).

“If a person donates to Ted Cruz and Donald Trump, they're assigned a media bias score based on their financial contributions to political candidates and organizations considered more conservative,” Lelkes says. “And if they donate to Barack Obama and Hillary Clinton, they’re more liberal. So when we identify people on screen, we can also identify their ideology.” 

Using these scores as evidence, the team confirmed that during the past decade Fox has moved further to the right while both CNN and MSNBC have moved further to the left. More specifically, they pinpointed when the ideological gap between the channels became extreme: after the 2016 Presidential election. 

“For many years, Fox News was to the right of MSNBC and CNN,” Lelkes says, “but they used to track each other. When Fox moved to the right, so did MSNBC and CNN. They all flowed together. After Trump came into office, they responded to events in the news by leaning away from each other and more strongly toward their respective ideologies.” 

Interestingly, this gap between channels is more pronounced when it comes to primetime programming. Compared to other shows on their respective networks, primetime shows like “Anderson Cooper 360” on CNN and “The Rachel Maddow Show” on MSNBC skew more sharply to the left, while “Tucker Carlson Tonight” on Fox skews far more to the right. 

“We don't really see that dramatic polarization for the morning and afternoon shows,” Lelkes says, “which are more hard news, more fact-based shows.” 

Another recent study in the journal Science Advances, authored by University of Pennsylvania Stevens University Professor Duncan Watts and colleagues, also studied the partisanship of TV news by focusing on the audience partisanship. It found that Americans who get their news from TV, as opposed to reading it online, are far more likely to watch channels that reflect their ideology, and are less likely to stray outside their partisan bubble. 

Taken together, the two studies paint a concerning picture that partisan audiences on cable news are growing while the outlets themselves become more extreme.

Lelkes’s findings have raised a number of additional questions for the researchers: Do good ratings on a particular show encourage an entire network to move to the right or the left? Do viewer boycotts affect the ideology of a news channel? Will the ideological gap between channels ever get smaller or will it just keep growing?

For now, the team is working on opening up its data to the public.  

“Soon we will have a platform where people can play with the data—where they can go down to the show level and see what the bias scores are for any one show,” Lelkes says.

In addition to Lelkes, “Measuring Dynamic Media Bias” is co-authored by Columbia University Assistant Professor of Political Science and Annenberg Alum Eunji Kim and University of Utah Assistant Professor of Political Science Josh McCrain.

 

A flexible device that harvests thermal energy to power wearable electronics

Peer-Reviewed Publication

UNIVERSITY OF WASHINGTON

Flexible device 

IMAGE: UNIVERSITY OF WASHINGTON RESEARCHERS HAVE CREATED THE FIRST-OF-ITS KIND FLEXIBLE, WEARABLE THERMOELECTRIC DEVICE THAT CONVERTS BODY HEAT TO ELECTRICITY. THIS DEVICE IS SOFT AND STRETCHABLE, YET STURDY AND EFFICIENT — PROPERTIES THAT CAN BE CHALLENGING TO COMBINE. view more 

CREDIT: HAN ET AL./ADVANCED ENERGY MATERIALS

Wearable electronics, from health and fitness trackers to virtual reality headsets, are part of our everyday lives. But finding ways to continuously power these devices is a challenge.

University of Washington researchers have developed an innovative solution: the first-of-its kind flexible, wearable thermoelectric device that converts body heat to electricity. This device is soft and stretchable, yet sturdy and efficient — properties that can be challenging to combine.

The team published these findings July 24 in Advanced Energy Materials

"It’s a 100% gain if we harvest thermal energy that would otherwise be wasted to the surroundings. Because we want to use that energy for self-powered electronics, a higher power density is needed," said Mohammad Malakooti, a UW assistant professor of mechanical engineering. "We leverage additive manufacturing to fabricate stretchable electronics, increase their efficiency and enable their seamless integration into wearables while answering fundamental research questions."

Even after more than 15,000 stretching cycles at 30% strain, the researchers' prototype device remains fully functional, a highly desirable feature for wearable electronics and soft robotics. The device also shows a 6.5 times increase in power density compared to previous stretchable thermoelectric generators.

To create these flexible devices, the researchers 3D printed composites with engineered functional and structural properties at each layer. The filler material contained liquid metal alloys, which provide high electrical and thermal conductivity. These alloys address limitations in previous devices, including an inability to stretch, inefficient heat transfer and a complex fabrication process.

The team also embedded hollow microspheres to direct the heat to the semiconductors at the core layer and reduce the weight of the device.

The researchers showed that they could print these devices on stretchable textile fabrics and curved surfaces, which suggests that future devices could be applied to clothing and other objects. The team is excited about the future possibilities and real-life applications of wearable electronics.

"One unique aspect of our research is that it covers the whole spectrum, all the way from material synthesis to device fabrication and characterization," said Malakooti, who is also a researcher in the UW's Institute for Nano-Engineered Systems. "This gives us the freedom to design new materials, engineer every step in the process and be creative."

Youngshang Han, UW master's student in mechanical engineering, was lead author on the paper. Leif-Erik Simonsen is an additional co-author. This research was funded by the National Science Foundation.

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How benign water transforms into harsh hydrogen peroxide

Peer-Reviewed Publication

STANFORD UNIVERSITY

A new study has put a remarkable and unexpected chemical genesis on more solid footing.

Back in 2019, Stanford University researchers and colleagues revealed the surprising discovery that hydrogen peroxide – a caustic substance used for disinfecting surfaces and bleaching hair – spontaneously forms in microscopic droplets of ordinary, benign water. Researchers have since aimed to flesh out how the newfound reaction occurs, as well as exploring potential applications, such as eco-friendlier cleaning methods.

The latest study has revealed that when sprayed microdroplets of water strike a solid surface, a phenomenon known as contact electrification happens. Electric charge jumps between the two materials, liquid and solid, producing unstable molecular fragments called reactive oxygen species. Pairs of these species known as hydroxyl radicals, and which have the chemical formula OH, can then combine to form hydrogen peroxide, H2O2, in minuscule but detectable quantities.

The new study further demonstrated that this process occurs in humid environments when water touches particles of soil as well as fine particles in the atmosphere. Those additional findings suggest that water can transform into small amounts of reactive oxygen species, such as hydrogen peroxide, wherever microdroplets naturally form, including in fogs, mists, and raindrops, bolstering results from a related 2020 study.

“We have a real understanding now that we didn’t have before about what is causing this hydrogen peroxide formation to happen,” said study senior author Richard Zare, the Marguerite Blake Wilbur Professor in Natural Science and a professor of chemistry in the Stanford School of Humanities and Sciences. “Furthermore, it appears that contact electrification yielding hydrogen peroxide is a universal phenomenon at water-solid interfaces.”

Zare led this work, collaborating with researchers from two universities in China, Jianghan University and Wuhan University, as well as the Chinese Academy of Sciences. The study was published Aug. 1 in the Proceedings of the National Academy of Sciences (PNAS).

On the origins of the hydrogen peroxide

For the study, the researchers built a glass apparatus with microscopic channels in it where water could be forcibly injected. The channels formed an airtight water-solid boundary. The researchers perfused the water with a fluorescent dye that glows in the presence of hydrogen peroxide. An experiment showed the presence of the harsh chemical in the glass microfluidic channel, but not in a bulk sample of water also containing the dye. Additional experiments elaborated that the hydrogen peroxide formed quickly, within a matter of seconds, at the boundary between the water and the solid.

To gauge if the extra oxygen atom in the hydrogen peroxide (H2O2) came from a reaction with the glass or within the water (H2O) itself, the researchers treated the glass lining of some microfluidic channels. These treated channels contained a heavier isotope or version of oxygen, dubbed oxygen-18 or 18O. Comparing the post-reaction mix of water and hydrogen peroxide fluid from the treated and untreated channels showed the signal of 18O in the former, implicating the solid as the source of the oxygen in the hydroxyl radicals and ultimately in hydrogen peroxide.

The new findings could help settle some of the debate that has ensued in the scientific community since the Stanford researchers initially announced their novel detection of hydrogen peroxide in water microdroplets three years ago. Other studies have emphasized the major contributions of hydrogen peroxide production via chemical interactions with the gas ozone, O3, and a process called cavitation, when vapor bubbles arise in low-pressure areas within accelerated liquids. Zare pointed out that both of those processes also clearly yield hydrogen peroxide, and in comparatively greater amounts.

“All of these processes contribute to hydrogen peroxide production, but the present work confirms that this production is also intrinsic to the way microdroplets are made and interact with solid surfaces through contact electrification,” said Zare.

Turning the tables on seasonal respiratory viruses

Nailing down how and in what situations water can transform into reactive oxygen species, such as hydrogen peroxide, has a host of real-world insights and applications, Zare explained. Among the most compelling is understanding the formation of hydroxyl radicals and hydrogen peroxide as an overlooked contributor to the well-known seasonality of many viral respiratory diseases, including colds, flus, and likely COVID-19 once the disease eventually becomes fully endemic.

Viral respiratory infections are transmitted in the air as aqueous droplets when people who are sick cough, sneeze, sing, or even just talk. These infections tend to spike in winter and ebb in summer, a trend chalked up in part to people spending more time indoors and in close, transmissible proximity during the cold weather season. However, between work, school, and sleeping at night, people actually end up spending about the same amount of time indoors during the hot weather months as well. Zare said the new study’s findings offer a possible explanation for why winter is correlated with more flu cases: The key variable at work is humidity, the amount of water in the air. In the summer, the higher relative levels of indoor humidity – tied to higher humidity in the warm air outside – likely facilitate reactive oxygen species in droplets having enough time to kill viruses. Contrastingly, in winter – when the air inside buildings is heated and its humidity lowered – the droplets evaporate before the reactive oxygen species can act as a disinfectant.

“Contact electrification provides a chemical basis for partly explaining why there is seasonality to viral respiratory diseases,” said Zare. Accordingly, Zare added, future research should investigate any links between indoor humidity levels in buildings and the presence and spread of contagions. If links are further borne out, simply adding humidifiers to heating, ventilation, and cooling systems could lessen disease transmission.

“Taking a fresh approach to disinfecting surfaces is just one of the great practical consequences of this work involving the fundamental chemistry of water in the environment,” said Zare. “It just goes to show that we think we know so much about water, one of the most commonly encountered substances, but then we’re humbled.”

Zare is also a member of Stanford Bio-X, the Cardiovascular Institute, the Stanford Cancer InstituteStanford ChEM-H, the Stanford Woods Institute for the Environment, and the Wu Tsai Neurosciences Institute.

The research was funded in part by grants from the Strategic Priority Research Program of the Chinese Academy of Sciences, the National Natural Science Foundation of China, the National Key Research and Development Program of China, the Youth Talent Support Program of Jianghan University, and the U.S. Air Force Office of Scientific Research.