Category: Chemistry

Many owners of electric cars have wished for a battery pack that could power their vehicle for more than a thousand miles on a single charge. Researchers at the Illinois Institute of Technology (IIT) and U.S. Department of Energy’s (DOE) Argonne National Laboratory have developed a lithium-air battery that could make that dream a reality. The team’s new battery design could also one day power domestic airplanes and long-haul trucks.

The main new component in this lithium-air battery is a solid electrolyte instead of the usual liquid variety. Batteries with solid electrolytes are not subject to the safety issue with the liquid electrolytes used in lithium-ion and other battery types, which can overheat and catch fire.

More importantly, the team’s battery chemistry with the solid electrolyte can potentially boost the energy density by as much as four times above batteries”>lithium-ion batteries, which translates into longer driving range.

“For over a decade, scientists at Argonne and elsewhere have been working overtime to develop a lithium battery that makes use of the oxygen in air,” said Larry Curtiss, an Argonne Distinguished Fellow. “The lithium-air battery has the highest projected energy density of any battery technology being considered for the next generation of batteries beyond lithium-ion.”

In past lithium-air designs, the lithium in a lithium metal anode moves through a liquid electrolyte to combine with oxygen during the discharge, yielding lithium peroxide (Li₂O₂) or superoxide (LiO₂) at the cathode. The lithium peroxide or superoxide is then broken back down into its lithium and oxygen components during the charge. This chemical sequence stores and releases energy on demand.

The team’s new solid electrolyte is composed of a ceramic polymer material made from relatively inexpensive elements in nanoparticle form. This new solid enables chemical reactions that produce lithium oxide (Li₂O) on discharge.

“The chemical reaction for lithium superoxide or peroxide only involves one or two electrons stored per oxygen molecule, whereas that for lithium oxide involves four electrons,” said Argonne chemist Rachid Amine. More electrons stored means higher energy density.

The team’s lithium-air design is the first lithium-air battery that has achieved a four-electron reaction at room temperature. It also operates with oxygen supplied by air from the surrounding environment. The capability to run with air avoids the need for oxygen tanks to operate, a problem with earlier designs.

The team employed many different techniques to establish that a four-electron reaction was actually taking place. One key technique was transmission electron microscopy (TEM) of the discharge products on the cathode surface, which was carried out at Argonne’s Center for Nanoscale Materials, a DOE Office of Science user facility. The TEM images provided valuable insight into the four-electron discharge mechanism.

Past lithium-air test cells suffered from very short cycle lives. The team established that this shortcoming is not the case for their new battery design by building and operating a test cell for 1000 cycles, demonstrating its stability over repeated charge and discharge.

“With further development, we expect our new design for the lithium-air battery to also reach a record energy density of 1200 watt-hours per kilogram,” said Curtiss. “That is nearly four times better than lithium-ion batteries.”

This research was published in a recent issue of Science. Argonne authors include Larry Curtiss, Rachid Amine, Lei Yu, Jianguo Wen, Tongchao Liu, Hsien-Hau Wang, Paul C. Redfern, Christopher Johnson and Khalil Amine. Authors from IIT include Mohammad Asadi, Mohammadreza Esmaeilirad and Ahmad Mosen Harzandi. And Authors from the University of Illinois Chicago include Reza Shahbazian-Yassar, Mahmoud Tamadoni Saray, Nannan Shan and Anh Ngo.

More information: Alireza Kondori et al, A room temperature rechargeable Li 2 O-based lithium-air battery enabled by a solid electrolyte, Science (2023). DOI: 10.1126/science.abq1347

Journal information: Science 

Provided by Argonne National Laboratory

A research group from VTT Technical Research Center of Finland has unlocked the secret behind the extraordinary mechanical properties and ultra-light weight of certain fungi. The complex architectural design of mushrooms could be mimicked and used to create new materials to replace plastics. The research results were published on February 22, 2023, in Science Advances.

VTT’s research shows for the first time the complex structural, chemical, and mechanical features adapted throughout the course of evolution by Hoof mushroom (Fomes fomentarius). These features interplay synergistically to create a completely new class of high-performance materials.

Research findings can be used as a source of inspiration to grow from the bottom up the next generation of mechanically robust and lightweight sustainable materials for a variety of applications under laboratory conditions. These include impact-resistant implants, sports equipment, body armor, exoskeletons for aircraft, electronics, or surface coatings for windshields.

Unraveling the unique microstructure of Fomes fungus

Nature provides insights into design strategies evolved by living organisms to construct robust materials. The tinder fungus Fomes is a particularly interesting species for advanced material applications. It is a common inhabitant of the birch tree, with the important function of releasing carbon and other nutrients from the dead trees. The Fomes fruiting bodies are ingeniously lightweight biological designs, simple in composition but efficient in performance. They fulfill a variety of mechanical and functional needs, for example, protection against insects or fallen branches, propagation, survival (unpreferred texture and taste for animals), and a thriving multi-year fruiting body through changing seasons.

VTT’s new research reveals that the Fomes fruiting body is a functionally graded material with three distinct layers that undergo multiscale hierarchical self-assembly.

“The mycelium network is the primary component in all layers. However, in each layer, mycelium exhibits a very distinct microstructure with unique preferential orientation, aspect ratio, density, and branch length. An extracellular matrix acts as a reinforcing adhesive that differs in each layer in terms of quantity, polymeric content, and interconnectivity,” said Pezhman Mohammadi, Senior scientist at VTT.

Alterable structure enables different features

The structure of Fomes is extraordinary because it can be modified to create diverse materials with distinct performances. Minimal changes in the cell morphology and extracellular polymeric composition result in diverse materials with different physico-chemical features that surpass most natural and man-made materials. While traditional materials are usually confronted by property tradeoffs (e.g., increasing weight or density to increase strength or stiffness), Fomes achieves high performance without this tradeoff.

“Architectural design and biochemical principles of the Fomes fungus open new possibilities for material engineering, such as manufacturing ultra-lightweight technical structures, fabricating nanocomposites with enhanced mechanical properties, or exploring new fabrication routes for the next generation of programmable materials with high-performance functionalities.

“Furthermore, growing the material using simple ingredients could help to overcome the cost, time, mass production, and sustainability of how we make and consume materials in the future,” explains Pezhman.

More information: Robert Pylkkänen et al, The complex structure of Fomes fomentarius represents an architectural design for high-performance ultralightweight materials, Science Advances (2023). DOI: 10.1126/sciadv.ade5417

Journal information: Science Advances 

Provided by VTT Technical Research Centre of Finland 

A recent study published in the journal Science China Life Sciences was led by Dr. Nan Qiao (Laboratory of Health Intelligence, Huawei Cloud Computing Technologies), Dr. Hualiang Jiang (Shanghai Institute of Materia Medica, Chinese Academy of Sciences) and Dr. Mingyue Zheng (Shanghai Institute of Materia Medica, Chinese Academy of Sciences).

“Over the past year, the parameter size of the language model has continued to grow, exceeding 175 billion GPT3s. Recently, ChatGPT, a new-generation language model, interacts with users in a more real-life way, such as answering questions, admitting mistakes, questioning incorrect questions or rejecting inappropriate requests, and is even thought to subvert search engines,” Dr. Qiao says.

In addition to language models, areas such as image, video and multimodality were refreshed by transformer architectures these years at the same time. These large models usually use self-supervised learning, which can greatly reduce the workload and achieve better performance in long tail tasks. However, in the AI for drug discovery field, there has been no really big model to accelerate drug research and development and improve the efficiency.

Xinyuan Lin and Zhaoping Xiong, together with lab director Nan Qiao, sought to build a big model for drug discovery that can be used for drug discovery tasks such as molecular property prediction, molecular generation and optimization. The team proposes a novel graph-to-sequence (graph2seq) asymmetric structure, which is different from the classical sequence-to-sequence (seq2seq) and graph-to-graph (graph2graph) variational auto-encoding processes.

The model is pre-trained for 1.7 billion druglike molecules (currently the largest), the input is a two-dimensional undirected cyclic graph of drug-like molecules, and the output is the corresponding chemical formula or SMILES string. Humans read images of chemical structures and write down the text of the corresponding formulas, so after billions of repetitions, Pangu can learn the relationship between chemical structures and formula strings, similar to human cognitive transformations.

After pre-training with 1.7 billion druglike small molecules, the model achieved state-of-the-art results in 20 drug discovery tasks, including molecular property prediction. (predicting ADMET properties, compound-protein interactions, drug-drug interactions, and chemical reaction yields) , molecular generation and molecular optimization.

The Pangu Molecular Generator has also generated a new drug screening library of 100 million drug-like small molecules with a novelty of 99.68%, which can also effectively generate new compounds with similar physicochemical properties to a given distribution. This library can be used to supplement the existing compound database. In addition, the Pangu Molecular Optimizer can optimize the chemical structure of the starting molecule and improve the characteristics of the molecule of interest.

More information: Xinyuan Lin et al, PanGu Drug Model: learn a molecule like a human, Science China Life Sciences (2022). DOI: 10.1007/s11427-022-2239-y

Provided by Science China Press 

A team from Florida State University and Lawrence Berkeley National Laboratory has developed a new strategy to build solid-state batteries that are less dependent on specific chemical elements, particularly pricey metals with supply chain issues.

Their work was published in the journal Science.

Bin Ouyang, an associate professor in the Department of Chemistry and Biochemistry, first developed the idea for this work while finishing his postdoctoral research at the University of California, Berkeley, along with his co-first author Yan Zeng, and their postdoctoral adviser Gerbrand Ceder. In their study, they demonstrated that a mix of various solid-state molecules could result in a more conductive battery that was less dependent on a large quantity of an individual element.

“There’s no hero element here,” Ouyang said. “It’s a collective of diverse elements that make things work. What we found is that we can get this highly conductive material as long as different elements can assemble in a way that atoms can move around quickly. And there are many situations that can lead to these so-called atom diffusion highways, regardless of which elements it may contain.”

Solid-state batteries operate almost the same way as other batteries—they store energy and then release it to power devices. But rather than liquid or polymer gel electrolytes found in lithium-ion batteries, they use solid electrodes and a solid electrolyte. This means that a higher energy density can occur in the battery because lithium metal can be used as the anode. Additionally, they have lower fire risk and potentially increase the mileage of electric vehicles.

However, many of the batteries constructed thus far are based on critical metals that are not available in large quantities. Some aren’t found at all in the United States. Given that the U.S. and many other countries plan to replace all vehicles with electric vehicles by 2050, there is an enormous strain being put on the supply chain for critical metals.

The research team considered the straightforward path of using one element to replace commonly used ones, but that approach raised its own supply chain issues. Instead, the team approached the problem by designing materials that weren’t beholden to one specific element. For example, instead of creating a battery made with germanium, which rarely appears naturally in high concentrations, the team created a mixture of titanium, zirconium, tin, and hafnium.

“With such a feature, we need to assemble those elements in a way so that we have many ‘good’ local configurations which can form a network for the fast transport of atoms or energy,” Ouyang said. “Think of it as a highway. As long as there is a connected highway for atom diffusion, the atoms can move quickly.”

This study opened a new area of research for Ouyang and his colleagues as they work to build more efficient solid-state batteries.

Government, research and academia have heavily invested in the development of solid-state batteries because batteries that contain liquids are more prone to overheating, fire and loss of charge. Smaller solid-state batteries already power devices like smartwatches and pacemakers. Still, many manufacturers believe that breakthroughs in this area could mean solid-state batteries could one day be helping electric vehicles or aircraft.

More information: Yan Zeng et al, High-entropy mechanism to boost ionic conductivity, Science (2022). DOI: 10.1126/science.abq1346

Journal information: Science 

Provided by Florida State University 

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Researchers at Kanazawa University report in Angewandte Chemie International Edition how the formation and deformation speed of interlocked molecular structures called rotaxanes can be tuned—a discovery that may lead to an enhanced functionality of rotaxanes as building blocks for molecular machines.

Rotaxanes are molecules with a two-component structure: a dumbbell-shaped part (the “axle”) threaded through a ring-like part (the “wheel”). The two components are normally not chemically bound but mechanically interlocked. Rotaxanes are of particular interest because of their potential as building blocks for molecular machines, exploiting the rotation of the wheel or its motion along the axle.

An extra level of rotaxane functionality is achieved if the wheel can be removed from the axle (dissociation) and put back (formation) in a controlled way. Shigehisa Akine, Yoko Sakata, and colleagues from Kanazawa University have now developed a new approach for controlled rotaxane dissociation and formation.

Earlier methods for the formation and dissociation of rotaxanes involved chemical modifications. One approach is to chemically replace one end (also called stopper) of the axle by a less bulky one so that the wheel can slide over it more easily. Another is to enlarge the wheel size. These two modifications result in “pseudorotaxanes,” however: rotaxanes for which the wheel can easily slide off the structure since at least one stopper doesn’t block the wheel anymore.

Akine, Sakata, and colleagues performed experiments with a proper rotaxane. At the center of the dumbbell is a palladium atom. At opposite sides to it, two identical organic groups (called 2,3-diaminotriptycene) are bound. For the wheel, they used a so-called crown ether, consisting of 9 oxygen atoms and 18 carbon atoms arranged in a symmetric, cyclic way.

The palladium rotaxanes did not form immediately when mixing axle and wheel parts. Nuclear magnetic resonance measurements showed that only after 10 hours, conversion to the rotaxane structure—confirmed by X-ray analysis—was complete. The researchers found that the rotaxane formation involves a temporary cleavage of the axle part: one 2,3-diaminotriptycene group disconnects from the palladium atom, the crown ether wheel then slides onto the part with the palladium atom, after which the “loose” 2,3-diaminotriptycene group connects back. A similar cleavage process, with the wheel leaving the structure, results in dissociation.

Akine, Sakata, and colleagues then looked for a way to speed up the processes. They discovered that halide ions, and in particular bromine ions, had an accelerating effect on both formation and dissociation. The former was accelerated 27 times with the right amount of bromine ions added, and the latter 52 times. To achieve dissociation, though, the scientists had to add cesium ions to the mixture. A cesium ion easily forms a complex with a crown ether wheel; the cesium ion sits in the center of the wheel and prevents it from sliding back onto an axle molecule.

The use of accelerators as shown for this particular palladium-containing rotaxane is expected to be applicable to other molecules too. The scientists conclude that this strategy can be applied to the speed tuning of the formation/dissociation of various types of interlocked molecules based on metal coordination bonds.

Rotaxanes background

A rotaxane is a mechanically interlocked molecular structure consisting of a dumbbell-shaped molecule (axle) threaded through a circular molecule (wheel). The two components are locked because the ends of the dumbbell (called stoppers) are bigger than the internal diameter of the wheel, which prevents unthreading (dissociation) of the components. (A significant amount of distortion would be required to achieve unthreading.)

Most of the interest in rotaxanes and other mechanically interlocked molecular architectures lies in their potential as building blocks for molecular machines—nanoscale components that produce mechanical motion in response to particular external stimuli. Rotaxanes can act as molecular shuttles, for example: the wheel can be made to slide between the stoppers, from one side to the other, by stimuli such as light, solvents or ions.

Shigehisa Akine, Yoko Sakata, and colleagues from Kanazawa University have now studied the formation and dissociation process of a palladium-containing rotaxane. They discovered an intermediate cleavage phase in the formation/dissociation process and found that both the formation and the dissociation process can be significantly sped up by introducing accelerators, such as bromine ions.

More information: Yoko Sakata et al, Speed Tuning of the Formation/Dissociation of a Metallorotaxane, Angewandte Chemie International Edition (2023). DOI: 10.1002/anie.202217048

Journal information: Angewandte Chemie International Edition 

Provided by Kanazawa University 

After more than two years since its discovery, six million deaths, and half a billion reported cases, there is still no effective cure for COVID-19. Even though vaccines have lowered the impact of outbreaks, patients that contract the disease can only receive supportive care while they wait for their own body to clear the infection.

A promising COVID-19 treatment strategy that has been gaining traction lately is targeting angiotensin-converting enzyme 2 (ACE2). This is a receptor found on the cell membrane that allows entry of the virus into the cell due to its high affinity for SARS-CoV-2’s spike protein. The idea is that reducing the levels of ACE2 on the membrane of cells could be a way to prevent the virus from entering them and replicating, thereby lowering its infectious capabilities.

In a recent study published in PLOS ONE, a team of scientists including Associate Professor Shun-Ichiro Ogura from Tokyo Institute of Technology, Japan, analyzed the potential of a natural amino acid called 5-Aminolevulinic acid (ALA) to reduce the expression of ACE2. This research was performed in collaboration with SBI Pharmaceuticals Co. Ltd.

As the researchers explain in their paper, ALA had been identified in 2021 as a compound that seemed to reduce the infectivity of SARS-CoV-2. However, the underlying mechanisms that led to this phenomenon remained unknown, until now.

The team hypothesized that the results of the 2021 study could be explained by an effect of ALA on the expression of ACE2. To test their hypothesis, they prepared human cell cultures, administered ACE2 on some of them, and compared the levels of ACE2 in treated cells versus control cells. As expected, the amount of available ACE2 in treated cells was significantly lower than in control cells.

But the story doesn’t end there. Upon uptake, cells transform ALA into a molecule called protoporphyrin IX (PpIX) and subsequently into heme—a precursor of hemoglobin and other useful proteins. This hinted that the expression of ACE2 could be linked to the production of either of these compounds.

Thus, the team checked the levels of PpIX and heme in cells treated with ALA. “We observed significant increases in the concentration of intracellular PpIX, suggesting that ALA was uptaken into the cell and converted into PpIX,” remarks Ogura, “However, only a slight increase in heme concentration was observed, which might be due to the lack of an iron source to convert PpIX into heme.”

After introducing an iron source in the form of sodium ferrous citrate, the intracellular levels of heme increased significantly and the expression of ACE2 became even lower. These results suggest ACE2 expression is kept in check by heme production, the latter of which can be boosted by the co-administration of ALA and an iron source.

Overall, this study sheds light on how ALA and the heme production pathway could form the basis of a cure for COVID-19. “We believe ALA could be developed into a potential anti-viral agent for SARS-CoV-2, which may play an important role in the eradication of the disease in a global scale in the near future,” concludes Dr. Ogura.

More information: Eriko Nara et al, Suppression of angiotensin converting enzyme 2, a host receptor for SARS-CoV-2 infection, using 5-aminolevulinic acid in vitro, PLOS ONE (2023). DOI: 10.1371/journal.pone.0281399

Journal information: PLoS ONE 

Provided by Tokyo Institute of Technology 

Led by scientists at the University of Manchester, a series of new stable, porous materials that capture and separate benzene have been developed. Benzene is a volatile organic compound (VOC) and is an important feedstock for the production of many fine chemicals, including cyclohexane. But it also poses a serious health threat to humans when it escapes into the air and is thus regarded as an important air pollutant.

The research published today (Feb 24) in the journal Chem, demonstrates the high adsorption of benzene at low pressures and concentrations, as well as the efficient separation of benzene and cyclohexane. This was achieved by the design and successful preparation of two families of stable metal-organic framework (MOF) materials, named UiO-66 and MFM-300.

These highly porous materials are made from metal nodes bridged by functionalized organic molecules that act as struts to form 3-dimensional lattices incorporating empty channels into which volatile compounds can enter.

VOCs such as benzene are common indoor air pollutants, showing increasing emissions from anthropogenic activities and causing many environmental problems. They are also linked with millions of premature deaths each year. Benzene is one of the most toxic VOCs, and is classified by the World Health Organization as a Group 1 carcinogen to humans.

“The really exciting thing about these materials is that they allow us not only to capture and remove benzene from the air, but also to separate benzene from cyclohexane, which is an important industrial product often prepared from benzene,” says Professor Martin Schröder, lead author of the paper published in Chem.

“Because of the small difference in their boiling points (just 0.6 ℃) the separation of benzene and cyclohexane is currently extremely difficult and expensive to achieve via distillation or other methods.”

Conventional adsorbents, such as activated carbons and zeolites, often suffer from structural disorder which can restrict their effectiveness in capturing benzene. This new research also reports a comprehensive study of the adsorption of benzene and cyclohexane in these ultra-stable materials to afford a deep understanding of why and how they work.

“The crystalline nature of MOF materials enables the direct visualization of the host-guest chemistry at the atomic scale using advanced diffraction and spectroscopic techniques,” says Professor Sihai Yang, another lead author on the paper.

“Such fundamental understanding of the structure-property relationship is crucial to the design of new sorbent materials showing improved performance in benzene capture.”

More information: Martin Schröder, Control of the Pore Chemistry in Metal-Organic Frameworks for Efficient Adsorption of Benzene and Separation of Benzene/Cyclohexane, Chem (2023). DOI: 10.1016/j.chempr.2023.02.002. www.cell.com/chem/fulltext/S2451-9294(23)00066-9

Journal information: Chem 

Provided by University of Manchester 

Hafnium (Hf) has no independent ore in nature; it is always closely symbiotic with zirconium (Zr) in a homogeneous form, and accounts for only approximately 2% of Zr.

Zr and Hf have similar physical and chemical properties. Their nuclear properties such as neutron absorption cross section are completely opposite. Additionally, Zr and Hf have similar outer electronic structures, and due to the shrinkage of the lanthanide series, the atomic radius and ionic radius differ only slightly. Therefore, the separation of Zr and Hf, especially the enrichment of Hf, is very difficult.

In a study published in Journal of Membrane Science, the research group led by Prof. Yang Fan from Fujian Institute of Research on the Structure of Matter of the Chinese Academy of Sciences developed an advanced ion-imprinted membrane (IIMs) separation system to achieve highly efficient separation and enrichment of Hf.

The researchers prepared ion-imprinted membranes (IIMs) using Hf ions as the imprinted ion, N, N-di-2-ethylhexyl diglycolamic acid (D2EHDGAA) as the carrier molecule, and cellulose triacetate (CTA) as the base polymer, and IIMs were applied to the separation and enrichment of Hf from zirconium oxychloride solution.

They found that IIMs can increase CHf/CZr from 2.33:100 to 33.33:100 within 1 h compared with polymer inclusion membranes (PIMs) and ionic liquid supported liquid membranes (SLMs), which increased by 3.33 and 3.67 times, respectively. The separation factor (SF) was increased by 1.13 and 1.40 times, respectively. The recovery rate of Hf was 29.2%, and separation-regeneration cycle experiments showed that the stability of IIMs was relatively good.

Additionally, the researchers revealed that IIMs, PIMs and SLMs can selectively separate and extract Hf ions in zirconium oxychloride solution, and the selectivity to Hf decreases in the order of IIMs > PIMs > SLMs. This selectivity is mainly attributed to the mutual structural matching between the imprinted holes of IIMs and Hf template ions and the complementary functional groups.

This study suggests that IIMs, as a new idea for the efficient separation and enrichment of Hf from zirconium oxychloride solution, may have good potential for industrial application.

More information: Tingting Tang et al, Highly efficient separation and enrichment of hafnium from zirconium oxychloride solutions by advanced ion-imprinted membrane separation technology, Journal of Membrane Science (2022). DOI: 10.1016/j.memsci.2022.121237

Provided by Chinese Academy of Sciences 

Cultures from across the globe have used plant and animal extracts as food and traditional medicine. For instance, Asians, especially in Korea, China, and Japan, have used sea cucumber extracts to treat arthritis, frequent urination, impotence, and even cancer. While it is easy to be dismissive of these traditional medicines, sea cucumbers and, in fact, several other marine invertebrates may hold the key to new medicine.

A class of compounds called “sulfated fucans” (SFs), essentially fucose-rich sulfated polysaccharides found in sea cucumbers and sea urchins, are renowned for their anticoagulant, antiviral, and anticancer properties. Recently, they have been investigated for their potency against the SARS-CoV-2 virus.

To study these SFs, one needs to reduce their molecular weight by breaking them down into oligosaccharides. This is often done using a process called “mild acid hydrolysis.” Therefore, it is important to know the structural modifications caused by this mild acid hydrolysis on SFs.

This is where a team of researchers led by Professor Seon Beom Kim from Pusan National University in Korea and Assistant Professor Vitor H. Pomin from the University of Mississippi, U.S. came in. In a recent study published in Carbohydrate Polymers, they studied the mild acid hydrolysis of SFs extracted from two sea cucumber species, Isostichopus badionotus and Holothuria floridana, and one sea urchin species, Lytechinus variegatus, to see the effects of this process during oligosaccharide production.

The study involved contributions from Dr. Marwa Farrag, Dr. Sushil K. Mishra, Dr. Sandeep K. Mishra, Dr. Joshua S. Sharp, and Dr. Robert J. Doerksen, all of them collaborating with Dr. Pomin’s group.

Speaking about the motivation behind their study, Prof. Kim explains, “One of the keys to being an antiviral agent without showing other biological activities is controlling the molecular weight of the polysaccharide. However, specific enzymes that can depolymerize marine polysaccharides are not widely known. As a result, the mild acid hydrolysis route is often the way to go. Therefore, there is an urgent need for physiochemical studies of SFs during the chemical hydrolysis process.”

Following the extraction of the SFs, the team characterized the structure of each of these SFs, revealing that they take the form of long chains of repeating blocks of four sugars containing sulfate (SO₄^2-) ions. Thus, they were classified as 3-linked tetrasaccharide-repeating SFs. Next, these SFs were subjected to mild sulfuric acid and the oligosaccharide produced was investigated to see the changes caused by the hydrolysis.

The researchers found that all three SFs showed a selective 2-desulfation in which the second sugar in the repeating tetrasaccharide lost the sulfate ion attached to it. This caused the long chains to break up and produce an 8-sugar-long oligosaccharide.

“The phenomenon of acid hydrolysis is constantly emphasized for the depolymerization of sulfated fucans. Our study shows that selective 2-desulfation is a common and expected phenomenon in oligosaccharide production by mild acid hydrolysis of SFs,” says Prof. Kim. “These results will help further the research on the medicinal properties of SFs, and could potentially result in new medicines for a wide variety of illnesses.”

More information: Seon Beom Kim et al, Selective 2-desulfation of tetrasaccharide-repeating sulfated fucans during oligosaccharide production by mild acid hydrolysis, Carbohydrate Polymers (2022). DOI: 10.1016/j.carbpol.2022.120316

Provided by Pusan National University