A September 17, 2025 news item from ScienceDaily announced research from Harvard University focused on more sustainable ways to recycle protein by breaking down keratin,
Key Takeaways
SEAS [School of Engineering and Applied Sciences] researchers have discovered the chemical mechanism by which certain salt compounds break down protein waste, like wool and feathers.
The discovery enables a gentler and more sustainable protein recycling process.
The textile and meat-processing industries produce billions of tons of waste annually in the form of feathers, wool and hair, all of which are rich in keratin – the strong, fibrous protein found in hair, skin and nails.
Turning all that animal waste into useful products – from wound dressings to eco-friendly textiles to health extracts – would be a boon for the environment and for new, sustainable industries. But upcycling proteins is challenging: Breaking down, or de-naturing, proteins into their component parts typically requires corrosive chemicals in large, polluting facilities, keeping any cost-effective protocol out of reach.
Researchers in the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have uncovered key fundamental chemistry of how proteins like keratin de-nature in the presence of certain salt compounds – an insight that could take protein recycling to the next level.
…
Caption: An artist’s depiction of hair, made out of keratin, denaturing when ions are present. Credit: Michael Rosnach
A team led by Kit Parker, the Tarr Family Professor of Bioengineering and Applied Physics at SEAS, combined experiments and molecular simulations to better illuminate the chemical mechanisms by which salts cause proteins to unfold. They’ve shown that a solution of concentrated, a salt compound known to break apart keratin, interacts with the protein molecules in a completely unexpected way – not by binding to the proteins directly, as was conventional wisdom, but by changing the structure of the surrounding water molecules to create a setting more favorable for spontaneous protein unfolding.
This insight allowed the researchers to design a gentler, more sustainable keratin extraction process, separating the protein out of solution easily and without the need for harsh chemicals. The process can also be reversed with the same salt mixture, enabling recovery and reuse of lithium bromide denaturants.
The research is published in Nature Communicationsand is also featured in a Behind the Paper blog post.
Inspired by keratin biomaterials
First author Yichong Wang, a graduate student in chemistry who works in Parker’s group, said the research builds on the lab’s longstanding interest in developing keratin biomaterials with shape memory for biomedical applications. They had previously observed that keratin extracted from lithium bromide solvents can form thick, shapeable gels that readily separate from the surrounding solution and solidify almost immediately when placed back in water. While useful, they found the behavior odd, and they wanted to understand it better.
“We thought there might be a gap between current mechanistic understanding of how de-naturation works, and what we were seeing,” Wang said. “That’s when we got very interested in the mechanism itself to see if we could optimize our extraction procedures by explaining this phenomenon better.”
Molecular dynamics reveals shifts in surrounding water
To dig deeper, the team turned to the lab of Professor Eugene Shakhnovich in the Department of Chemistry and Chemical Biology, whose expertise is in protein biophysics. Molecular dynamics simulations led by co-author Junlang Liu allowed them to see that the lithium bromides were not working on the proteins at all, but rather, on the water around them.
It turns out lithium bromide ions cause water molecules to shift into two different populations – normal water, and water molecules that become trapped by the salt ions. As the normal water volume decreases, the proteins start to unfold due to the thermodynamic shift in the environment, rather than being directly ripped apart like in other de-naturation methods. “Making the water less like water, allows the protein to unfold itself,” Wang said. They had similar results by testing simpler proteins like fibronectin, pointing to a universal mechanism.
Better understanding and designing protein extraction methods that are less energy-intensive and less polluting than conventional ones opens potential avenues for protein-upcycling industries. In the Parker lab, using keratin as a substrate for tissue engineering is a major research thrust; having a reliable, sustainable method to extract and re-use such products would bolster their efforts.
What’s more, the process could lay a path for a whole new biomaterials industry, turning a massive waste stream like hair or chicken feathers into low-cost recycled materials, possibly as an alternative for traditional plastics, for example.
The research had many sources of federal support, including the National Institutes of Health (R35GM139571 and R01EY030444) and the National Science Foundation through the Harvard University Materials Research Science and Engineering Center (DMR-2011764). Other funding came from the Health@InnoHK program of the Innovation and Technology Commission, part of the Hong Kong SAR Government; and the Medical and Health Informatics Laboratories at NTT Research, Inc.
Here’s a link to and a citation for the paper,
Entropy-driven denaturation enables sustainable protein regeneration through rapid gel-solid transition by Yichong Wang, Junlang Liu, Michael M. Peters, Ryoma Ishii, Dianzhuo Wang, Sourav Chowdhury, Kevin Kit Parker & Eugene I. Shakhnovich. Nature Communications volume 16, Article number: 6907 (2025) DOI: https://doi.org/10.1038/s41467-025-61959-9 Published online: 26 July 2025 Version of record: 26 July 2025
This paper is open access.
There’s also an August 1, 2025 posting by Yichong Wang and Kit Parker (two of the paper’s authors) on SpringerNature’s Behind the Paper blog,
From Hofmeister’s Curiosity to an Interesting Mechanism
In 1888, Franz Hofmeister published a curious observation: salts affect protein solubility in water in systematic ways. This led to the famous “Hofmeister Series,” a ranking of ions based on their ability to precipitate or solubilize proteins. Over the next century, many studies expanded on these observations of salt-induced effects on protein folding, but a unifying theory explaining how ions influence protein structure remained elusive.
Our recent study originated from a practical challenge rather than a theoretical hypothesis. In our lab’s ongoing work to study the shape memory effect of regenerated keratin — a structural protein abundant in wool, hair, and feathers — we observed some puzzling behaviors. When keratin is extracted using concentrated lithium bromide (LiBr), it does not form a fully solubilized protein solution. Instead, we observed that the proteins spontaneously aggregate into a thick, cohesive gel that can be readily separated from the surrounding solution. More unexpectedly, this protein gel solidifies almost immediately upon rehydration, without the need for dialysis or removal of the denaturants. These phenomenon contrasted sharply with the behavior observed when using organic denaturants such as urea or guanidine hydrochloride.
Illustration by Michael Rosnach (Disease Biophysics Group, Harvard University)
None of these phenomenon matched existing explanations for how LiBr supposedly works. If LiBr denatures proteins by directly binding to them, why would the keratin spontaneously separate out of solution? Why would it renature so quickly just by being placed back in water? …
A Jan. 18, 2017 news item on Nanowerk announces research into hair strength from the University of California at San Diego (UCSD or UC San Diego),
In a new study, researchers at the University of California San Diego investigate why hair is incredibly strong and resistant to breaking. The findings could lead to the development of new materials for body armor and help cosmetic manufacturers create better hair care products.
Hair has a strength to weight ratio comparable to steel. It can be stretched up to one and a half times its original length before breaking. “We wanted to understand the mechanism behind this extraordinary property,” said Yang (Daniel) Yu, a nanoengineering Ph.D. student at UC San Diego and the first author of the study.
“Nature creates a variety of interesting materials and architectures in very ingenious ways. We’re interested in understanding the correlation between the structure and the properties of biological materials to develop synthetic materials and designs — based on nature — that have better performance than existing ones,” said Marc Meyers, a professor of mechanical engineering at the UC San Diego Jacobs School of Engineering and the lead author of the study.
In a study published online in Dec. in the journal Materials Science and Engineering C, researchers examined at the nanoscale level how a strand of human hair behaves when it is deformed, or stretched. The team found that hair behaves differently depending on how fast or slow it is stretched. The faster hair is stretched, the stronger it is. “Think of a highly viscous substance like honey,” Meyers explained. “If you deform it fast it becomes stiff, but if you deform it slowly it readily pours.”
Hair consists of two main parts — the cortex, which is made up of parallel fibrils, and the matrix, which has an amorphous (random) structure. The matrix is sensitive to the speed at which hair is deformed, while the cortex is not. The combination of these two components, Yu explained, is what gives hair the ability to withstand high stress and strain.
And as hair is stretched, its structure changes in a particular way. At the nanoscale, the cortex fibrils in hair are each made up of thousands of coiled spiral-shaped chains of molecules called alpha helix chains. As hair is deformed, the alpha helix chains uncoil and become pleated sheet structures known as beta sheets. This structural change allows hair to handle a large amount deformation without breaking.
This structural transformation is partially reversible. When hair is stretched under a small amount of strain, it can recover its original shape. Stretch it further, the structural transformation becomes irreversible. “This is the first time evidence for this transformation has been discovered,” Yu said.
“Hair is such a common material with many fascinating properties,” said Bin Wang, a UC San Diego PhD alumna from the Department of Mechanical and Aerospace Engineering and co-author on the paper. Wang is now at the Shenzhen Institutes of Advanced Technology in China continuing research on hair.
The team also conducted stretching tests on hair at different humidity levels and temperatures. At higher humidity levels, hair can withstand up to 70 to 80 percent deformation before breaking (dry hair can undergo up to 50 percent deformation). Water essentially “softens” hair — it enters the matrix and breaks the sulfur bonds connecting the filaments inside a strand of hair. Researchers also found that hair starts to undergo permanent damage at 60 degrees Celsius (140 degrees Fahrenheit). Beyond this temperature, hair breaks faster at lower stress and strain.
“Since I was a child I always wondered why hair is so strong. Now I know why,” said Wen Yang, a former postdoctoral researcher in Meyers’ research group and co-author on the paper.
The team is currently conducting further studies on the effects of water on the properties of human hair. Moving forward, the team is investigating the detailed mechanism of how washing hair causes it to return to its original shape.
Here’s a link to and a citation for the paper,
Structure and mechanical behavior of human hair by Yang Yua, Wen Yang, Bin Wang, Marc André Meyers. Materials Science and Engineering: C Volume 73, 1 April 2017, Pages 152–163 http://dx.doi.org/10.1016/j.msec.2016.12.008
Brazilian researchers are working with melanin to make biosensors and other bioelectronic devices according to a Dec. 20, 2016 news item on phys.org,
Bioelectronics, sometimes called the next medical frontier, is a research field that combines electronics and biology to develop miniaturized implantable devices capable of altering and controlling electrical signals in the human body. Large corporations are increasingly interested: a joint venture in the field has recently been announced by Alphabet, Google’s parent company, and pharmaceutical giant GlaxoSmithKline (GSK).
One of the challenges that scientists face in developing bioelectronic devices is identifying and finding ways to use materials that conduct not only electrons but also ions, as most communication and other processes in the human organism use ionic biosignals (e.g., neurotransmitters). In addition, the materials must be biocompatible.
Resolving this challenge is one of the motivations for researchers at São Paulo State University’s School of Sciences (FC-UNESP) at Bauru in Brazil. They have succeeded in developing a novel route to more rapidly synthesize and to enable the use of melanin, a polymeric compound that pigments the skin, eyes and hair of mammals and is considered one of the most promising materials for use in miniaturized implantable devices such as biosensors.
Some of the group’s research findings were presented at FAPESP Week Montevideo during a round-table session on materials science and engineering.
The symposium was organized by the Montevideo Group Association of Universities (AUGM), Uruguay’s University of the Republic (UdelaR) and FAPESP and took place on November 17-18 at UdelaR’s campus in Montevideo. Its purpose was to strengthen existing collaborations and establish new partnerships among South American scientists in a range of knowledge areas. Researchers and leaders of institutions in Uruguay, Brazil, Argentina, Chile and Paraguay attended the meeting.
“All the materials that have been tested to date for applications in bioelectronics are entirely synthetic,” said Carlos Frederico de Oliveira Graeff, a professor at UNESP Bauru and principal investigator for the project, in an interview given to Agência FAPESP.
“One of the great advantages of melanin is that it’s a totally natural compound and biocompatible with the human body: hence its potential use in electronic devices that interface with brain neurons, for example.”
Application challenges
According to Graeff, the challenges of using melanin as a material for the development of bioelectronic devices include the fact that like other carbon-based materials, such as graphene, melanin is not easily dispersible in an aqueous medium, a characteristic that hinders its application in thin-film production.
Furthermore, the conventional process for synthesizing melanin is complex: several steps are hard to control, it can last up to 56 days, and it can result in disorderly structures.
In a series of studies performed in recent years at the Center for Research and Development of Functional Materials (CDFM), where Graeff is a leading researcher and which is one of the Research, Innovation and Dissemination Centers (RIDCs) funded by FAPESP, he and his collaborators managed to obtain biosynthetic melanin with good dispersion in water and a strong resemblance to natural melanin using a novel synthesis route.
The process developed by the group at CDMF takes only a few hours and is based on changes in parameters such as temperature and the application of oxygen pressure to promote oxidation of the material.
By applying oxygen pressure, the researchers were able to increase the density of carboxyl groups, which are organic functional groups consisting of a carbon atom double bonded to an oxygen atom and single bonded to a hydroxyl group (oxygen + hydrogen). This enhances solubility and facilitates the suspension of biosynthetic melanin in water.
“The production of thin films of melanin with high homogeneity and quality is made far easier by these characteristics,” Graeff said.
By increasing the density of carboxyl groups, the researchers were also able to make biosynthetic melanin more similar to the biological compound.
In living organisms, an enzyme that participates in the synthesis of melanin facilitates the production of carboxylic acids. The new melanin synthesis route enabled the researchers to mimic the role of this enzyme chemically while increasing carboxyl group density.
“We’ve succeeded in obtaining a material that’s very close to biological melanin by chemical synthesis and in producing high-quality film for use in bioelectronic devices,” Graeff said.
Through collaboration with colleagues at research institutions in Canada [emphasis mine], the Brazilian researchers have begun using the material in a series of applications, including electrical contacts, pH sensors and photovoltaic cells.
More recently, they have embarked on an attempt to develop a transistor, a semiconductor device used to amplify or switch electronic signals and electrical power.
“Above all, we aim to produce transistors precisely in order to enhance this coupling of electronics with biological systems,” Graeff said.
I’m glad to have gotten some information about the work in South America. It’s one of FrogHeart’s shortcomings that I have so little about the research in that area of the world. I believe this is largely due to my lack of Spanish language skills. Perhaps one day there’ll be a universal translator that works well. In the meantime, it was a surprise to see Canada mentioned in this piece. I wonder which Canadian research institutions are involved with this research in South America.
Melanin does not have a reputation as a strengthening agent so why these scientists tested it for that purpose is a mystery. From a Nov. 9, 2016 news item on phys.org,
Melanin is the natural molecule in animals’ skin, hair and the iris of eyes that gives them color and helps protect them from ultraviolet light. Someday soon, the pigment could be found in unexpected places such as sofa cushions or clothing—but not for its hue. Scientists have found that adding a small amount of melanin to polyurethane makes it far stronger than the material by itself. …
From durable foam seating and insulation to glossy coatings and stretchy textiles, polyurethane is used in a huge range of products. Although already fairly versatile, polyurethane still has room for improvement. To make it more durable, scientists have tried adding fillers, including silica, carbon nanotubes and graphene oxide. But these efforts have often led to the enhancement of only one physical property at a time, such as tensile strength — how hard a material can be pulled before it snaps — but not toughness — how much energy it can absorb without breaking. Mingqing Chen, Weifu Dong and colleagues wanted to try a new approach: adding melanin, a biomolecule increasingly used in various other materials.
The researchers found that polyurethane containing just 2 percent melanin, extracted from the ink sacs of cuttlefish, had improved tensile strength and toughness. These properties were enhanced about 10 fold, increasing from 5.6 megapascals and 33 megajoules per cubic meter in plain polyurethane to 51.5 MPa and 413 MJ/m3, respectively. Polyurethane by itself could stretch 770 percent before breaking, whereas the melanin-infused version stretched 1,880 percent before rupturing.
