Tag Archives: #salt

Researchers Discover How Cells Survive in High Salt Concentrations (Biology)

Researchers from IRB Barcelona and UPF have identified a chloride channel involved in cell volume recovery under osmotic stress.

The results have been published in the journal PNAS.

Cells have to constantly adapt to their surroundings in order to survive. A sudden increase in the environmental levels of an osmolyte, such as salt, causes cells to lose water and shrink. In a matter of seconds, they activate a mechanism that allows them to recover their initial water volume and avoid dying.

Finding out which genes are involved in surviving osmotic stress was the subject of a study led by the laboratories of Dr. Posas and Dr. de Nadal at the Institute for Research in Biomedicine (IRB Barcelona) and Dr. Valverde at Pompeu Fabra University (UPF), in collaboration with a group led by Dr. Moffat from the University of Toronto (Canada). wide-genome genetic screening, the scientists discovered the central role of a gene known as LRRC8A in cellular ability to survive osmotic shock.

This gene codes for a protein that forms channels in the membrane and that allow chloride ions to leave the cell. “Using a human epithelial cell model, as well as other human and mouse cell types, we have been able to demonstrate that this channel opens shortly after the cells are exposed to a high concentration of sodium chloride (NaCl),” explains Dr. De Nadal, who, together with Dr. Francesc Posas, heads the Cell Signalling laboratory at IRB Barcelona. The authors have also identified the molecular mechanism that causes this rapid opening. The chloride channel phosphorylates, which means a phosphate group is added to a specific amino acid in its sequence, thus activating the channel.

Fluorescence microscopic image showing the changes in chloride concentration in two cells over time, using a pseudo colour scale © IRB Barcelona

“This has been a very complex project, and it has taken us years to see the light,” explains Dr. Miguel Ángel Valverde, head of UPF’s Laboratory of Molecular Physiology. “We have also shown how vital it is for this channel to become activated and remove chloride in order to start the volume recovery process and for cells to survive over time,” he adds.

The use of a violet dye that stains only living cells has allowed the researchers to observe that cell death increases by approximately 50% when the activity of this chloride channel is blocked with a particular compound.

A journey through time to answer old questions

In the ’90s, various landmark scientific papers on cell volume regulation described the process by which cells regulate their volume to survive. It was known that the proteins responsible for volume recovery under salt stress require low intracellular concentrations in order to become activated, but it was not known how this occurred under such adverse conditions. With this discovery, the authors have answered a question posed by researchers years ago: how does chloride exit the cell to start the whole process? In the words of the paper’s main co-author, Dr. Selma Serra (UPF): “Now we have the answer to that question. It is the LRRC8A channel that brings down the chloride levels in a cell. Until now we had a good understanding of the role played by this channel in cell adpatation to environments with very low salt concentrations. The big challenge was to find out how the same chloride channel could be crucial in the opposite mechanism. At the beginning of the project, it seemed to go against any kind of scientific logic that a channel used to shrink cells could also swell them.”

Using electrophysiological and fluorescence microscopy techniques in living cells to ascertain intracellular chloride levels, the researchers have demonstrated the involvement of the LRRC8A chloride channel in responses to high-salt stimuli.

A major technical and conceptual challenge

Studying this process at the molecular level has posed a considerable challenge for the team involved in this project. Because it is very complicated to conduct in vivo studies of cells while they undergo osmotic shock and shrink.  “Imagine you’re looking at a juicy grape, and suddenly it looks like a raisin, that makes things very complicated for us,” say the authors.

Another high-impact factor is that, under these stress conditions, the mechanism for activating the chloride channel is very different to what has been described so far in the literature. The article’s lead co-author, Predrag Stojakovic, says, “It came as a big surprise to find out that the signalling pathways in response to stress, the MAP kinase, proteins we’ve been studying in the lab for months, are directly responsible for activating this channel”. MAP kinases are a group of signalling proteins that add phosphate groups to other proteins, thus activating or deactivating them. Using molecular techniques, the authors have looked throughout the channel’s protein to find the target sequence of these kinase proteins. “We have been able to identify the specific residue of the chloride channel that leads to activation under the control of the MAP kinase channel in response to stress,” says doctoral student Stojakovic.

Future implications

“This new piece of research opens up new possibilities for studying cell adaptation and survival  salt stress. Certain organs of the body, such as the kidneys, are often exposed to high salt concentration, which can threaten their survival. Knowing what molecules control survival under these conditions could be very useful for understanding certain pathologies that entail volume recovery in response to salts,” explains Dr. Posas.

In addition, discovering the role of this channel in these cell regulation processes is highly relevant in many pathologies involving proteins regulated by LRRC8A. This may be significant in situations such as certain kinds of arterial hypertension or cerebral ischemia.

Featured image: Image of a cell “ruptured” by a fire-polished micropipette © UPF – IRB Barcelona

Reference article: Selma A Serra, Predrag Stojakovic, Ramon Amat, Fanny Rubio-Moscardo, Pablo Latorre, Gerhard Seisenbacher, David Canadell, René Böttcher, Michael Aregger, Jason Moffat, Eulàlia de Nadal, Miguel A. Valverde & Francesc Posas, “LRRC8A-containing chloride channel is crucial for cell volume recovery and survival under hypertonic conditions”, PNAS (2021).

Provided by IRB Barcelona

How To Get Salt Out of Water: Make it Self-eject (Material Science)

Crystallizing salts can grow “legs,” then tip over and fall away, potentially helping to prevent fouling of metal surfaces, researchers find.

About a quarter of a percent of the entire gross domestic product of industrialized countries is estimated to be lost through a single technical issue: the fouling of heat exchanger surfaces by salts and other dissolved minerals. This fouling lowers the efficiency of multiple industrial processes and often requires expensive countermeasures such as water pretreatment. Now, findings from MIT could lead to a new way of reducing such fouling, and potentially even enable turning that deleterious process into a productive one that can yield saleable products.

The findings are the result of years of work by recent MIT graduates Samantha McBride PhD ’20 and Henri-Louis Girard PhD ’20 with professor of mechanical engineering Kripa Varanasi. The work, reported today in the journal Science Advances, shows that due to a combination of hydrophobic (water repelling) surfaces and heat, dissolved salts can crystallize in a way that makes it easy to remove them from the surface, in some cases by gravity alone.

When the researchers began studying the way salts crystallize on such surfaces, they found that the precipitating salt would initially form a partial spherical shell around a droplet. Unexpectedly, this shell would then suddenly rise on a set of spindly leg-like extensions grown during evaporation. The process repeatedly produced  multilegged shapes, resembling elephants and other animals, and even sci-fi droids. The researchers dubbed these formations “crystal critters” in the title of their paper.

After many experiments and detailed analysis, the team determined the mechanism that was producing these leg-like protrusions. They also showed how the protrusions varied depending on temperature and the nature of the hydrophobic surface, which was produced by creating a nanoscale pattern of low ridges. They found that the narrow legs holding up these critter-like forms continue to grow upward from the bottom, as the salty water flows downward through the straw-like legs and precipitates out at the bottom, somewhat like a growing icicle, only balanced on its tip. Eventually the legs become so long they are unable to support the critter’s weight, and the blob of salt crystal breaks off and falls or is swept away.

The work was motivated by the desire to limit or prevent the formation of scaling on surfaces, including inside pipes where such scaling can lead to blockages, Varanasi says. “Samantha’s experiment showed this interesting effect where the scale pretty much just pops off by itself,” he says.

“These legs are hollow tubes, and the liquid is funneled down through these tubes. Once it hits the bottom and evaporates, it forms new crystals that continuously increase the length of the tube,” McBride says. “In the end, you have very, very limited contact between the substrate and the crystal, to the point where these are going to just roll away on their own.”

McBride recalls that in doing the initial experiments as part of her doctoral thesis work, “we definitely suspected that this particular surface would work well for eliminating sodium chloride adhesion, but we didn’t know that a consequence of preventing that adhesion would be the ejection of the entire thing” from the surface.

One key, she found, was the exact scale of the patterns on the surface. While many different length scales of patterning can yield hydrophobic surfaces, only patterns at the nanometer scale achieve this self-ejecting effect. “When you evaporate a drop of salt water on a superhydrophobic surface, usually what happens is those crystals start getting inside of the texture and just form a globe, and they don’t end up lifting off,” McBride says. “So it’s something very specific about the texture and the length scale that we’re looking at here that allows this effect to occur.”

This self-ejecting process, based simply on evaporation from a surface whose texture can be easily produced by etching, abrasion, or coating, could be a boon for a wide variety of processes. All kinds of metal structures in a marine environment or exposed to seawater suffer from scaling and corrosion. The findings may also enable new methods for investigating the mechanisms of scaling and corrosion, the researchers say.

By varying the amount of heat along the surface, it’s even possible to get the crystal formations to roll along in a specific direction, the researchers found. The higher the temperature, the faster the growth and liftoff of these forms takes place, minimizing the amount of time the crystals block the surface.

Heat exchangers are used in a wide variety of different processes, and their efficiency is strongly affected by any surface fouling. Those losses alone, Varanasi says, equal a quarter of a percent of the GDP of the U.S. and other industrialized nations. But fouling is also a major factor in many other areas. It affects pipes in water distribution systems, geothermal wells, agricultural settings, desalination plants, and a variety of renewable energy systems and carbon dioxide conversion methods.

This method, Varanasi says, might even enable the use of untreated salty water in some processes where that would not be practical otherwise, such as in some industrial cooling systems. Further, in some situations the recovered salts and other minerals could be salable products.

While the initial experiments were done with ordinary sodium chloride, other kinds of salts or minerals are expected to produce similar effects, and the researchers are continuing to explore the extension of this process to other kinds of solutions.

Because the methods for making the textures to produce a hydrophobic surface are already well-developed, Varanasi says, implementing this process at large industrial scale should be relatively rapid, and could enable the use of salty or brackish water for cooling systems that would otherwise require the use of valuable and often limited fresh water. For example, in the U.S. alone, a trillion gallons of fresh water are used per year for cooling. A typical 600-megawatt power plant consumes about a billion gallons of water per year, which could be enough to serve 100,000 people. That means that using sea water for cooling where possible could help to alleviate a fresh-water scarcity problem.

“This work shows a remarkable and interesting phenomenon,” says Neelesh Patankar, a professor of mechanical engineering at Northwestern University, who was not associated with this research. The findings, he says, “may lead to an entirely new approach to mitigate mineral fouling in industrial processes. Not only is this work interesting from a fundamental science perspective, in my opinion it is also of practical importance.”

The work was supported by Equinor through MIT Energy Initiative, the MIT Martin Fellowship Program, and the National Science Foundation.

Featured image: When the researchers began studying the way salts crystallize on certain surfaces, they found that the process repeatedly produced predictable multi-legged shapes. The researchers dubbed them collectively as “crystal critters” in the title of their paper. Credits:Courtesy of the researchers

Reference: Samantha A. McBride, Henri-Louis Girard, Kripa K. Varanasi, “Crystal critters: Self-ejection of crystals from heated, superhydrophobic surfaces”, Science Advances  28 Apr 2021: Vol. 7, no. 18, eabe6960 DOI: 10.1126/sciadv.abe6960

Provided by MIT

Reducing Salt in Parmigiano Reggiano Cheese Might Not Negatively Affect its Flavor (Food)

Aged cheeses pack a punch of nutty, sharp flavor. Before they’re fully mature, aged cheeses are either waxed or placed in brine for weeks to create a natural rind. However, the high salt content in brined cheeses deters some consumers. Now, researchers reporting in ACS Food Science & Technology present a shortened brining time for Parmigiano Reggiano that results in a less salty product, while still potentially maintaining the cheese’s distinctive texture and flavor compounds. 

Parmigiano Reggiano is a lactose-free, crumbly and hard cheese. Manufactured in select provinces in Italy, its protected designation of origin status requires that certain production processes, such as a minimum 12-month ripening period, be performed. Ripening or maturing imparts the cheese’s recognizable taste as milk solids are converted to flavor compounds. But before that, cheese wheels are placed in a saturated brine solution for weeks. The added salt plays a key role in the ripening process by modulating microbial growth, enzyme activity and the separation of solids from liquids, hardening the final product. One enzyme-mediated reaction is lipolysis, in which triglyceride fats in milk break down into their key components — free fatty acids and diacylglycerides. Free fatty acids not only contribute to the taste of the cheese but are also precursors to other flavor molecules. So, Silvia Marzocchi and colleagues wanted to test the impact of brining time on the lipolysis reactions responsible for the free fatty acids involved in Parmigiano Reggiano’s flavor profile and distinctive characteristics.

The researchers had five Parmigiano Reggiano dairies brine several cheese wheels by immersing them in a saturated salt solution for either 18 days or a shorter 12-day period. Then the wheels were ripened for 15 months under conditions typical for this type of cheese. Salt content in fully ripened cheese was 9% lower in the samples brined for a shorter time than the group with the longer procedure. Unexpectedly, the researchers found no difference in the moisture level, cholesterol and total fat in the two sets of cheeses. The team also observed no major variations in compounds involved in the flavor profile, as most of the 32 free fatty acids had overlapping concentration ranges between the two groups. Yet in the cheeses with the shorter salting time, overall, the total free fatty acids and the total diacylglycerides concentration ranges were 260% and 100% higher, respectively, than the traditionally brined version, suggesting the lower salt to moisture ratio resulted in more water available to lipolysis reactions and more rapid enzymatic activity breaking down triglycerides. The researchers say a reduced brining time for Parmigiano Reggiano could result in a product appealing to salt-conscious consumers, but sensory tests are still needed to indicate if they can detect differences to the overall taste and texture. 

The authors acknowledge funding from the PARENT Project, the European Regional Development Fund to the Emilia-Romagna Region and the Consejo Nacional de Investigaciones Cientifí cas y Técnicas.

Featured image: Shortening the brining time for Parmigiano Reggiano cheese might not negatively affect its flavor. Credit: Natali Zakharova/Shutterstock.com

Reference: “Study of the Effect of NaCl on Lipolysis in Parmigiano Reggiano Cheese”, ACS Food Science & Technology, 2021.

Provided by American Chemical Society

Researchers Establish Molecular Link between Rice Clock Components and Salt Tolerance (Botany)

Excess sodium ion (Na+), the most widespread soluble cation in salinized soil, can damage plants by the sequential osmotic stress and oxidative stress, especially for glycophyte crops including rice. 

The model of core clock components regulating rice salt tolerance (Image by Dr. WANG Lei’s group)

The circadian clock, the endogenous time-keeping system in higher plants, has been demonstrated to function as an important integrator of multiple abiotic stresses signals, including salt stress in Arabidopsis. Nevertheless, whether rice core clock components participate in salt tolerance and the underlying mechanisms remain largely unclear.  

In a new study published in The EMBO Journal on December 21, a research group led by Prof. WANG Lei from the Institute of Botany of the Chinese Academy of Sciences has made great progress in indentifying a new molecular link between clock core components and salt stress tolerance in rice.  

By making use of CRISPR/Cas9 approach, the researchers systematically generated the loss-of-function mutants of OsPRRs, among which OsPRR73 is the unique member required for rice salt tolerance. Moreover, it was validated that OsPRR73 acts as a clock component in rice.  

Notably, the researchers found that the grain size and yield of osprr73 null mutants were significantly decreased in the presence of salt stress. And the osprr73 mutant plants are hypersensitive to Na+ treatment, suggesting that OsPRR73 is required for salt adaptation.  

Further, they identified OsHKT2;1, encoding a plasma membrane-localized Na+ influx transporter, as a direct transcriptional target of OsPRR73 in mediating salt tolerance.  

Thus, upon salt treatment, the increased OsPRR73 can efficiently repress the expression of OsHKT2;1 to reduce the accumulation of Na+.  

Immunoprecipitation-mass spectrometry assays further identified HDAC10 as nuclear interactor of OsPRR73 to repress OsHKT2;1 transcription. Furthermore, it was found that OsHKT2;1 is a major downstream component to mediate the salt hypersensitivity of osprr73 plants.  

“The OsPRR73-OsHKT2;1 transcriptional module confers the salt tolerance in rice via regulating Na+ homeostasis, which represents a novel molecular link between circadian clock and salt tolerance,” said Prof. WANG.  

These findings pave a way for further deciphering the regulatory networks of rice circadian clock-conferred abiotic stress responses in rice. The related genetic resources in this study may be useful for breeding the salt-tolerant rice varieties in the future. 

Reference: Hua Wei, Xiling Wang, Yuqing He, Hang Xu, Lei Wang, “Clock component OsPRR73 positively regulates rice salt tolerance by modulating OsHKT2;1‐mediated sodium homeostasis”, EMBO J (2020)e105086
https://doi.org/10.15252/embj.2020105086 https://www.embopress.org/doi/full/10.15252/embj.2020105086

Provided by Chinese Academy of Sciences

ALMA Detected Salt, Water, Silicon Compounds and Methyl Cyanide around Two Massive Protostars (Astronomy)

Astronomers reported results of 0.”05 -resolution observations toward the O-type proto-binary system IRAS 16547–4247, located 9,500 light-years away in the constellation of Scorpius, with the Atacama Large Millimeter/submillimeter Array. They detected sodium chloride, silicon compounds, and water vapor in the circumstellar disks — as well as methyl cyanide in the circumbinary disk.

An artist’s impression of the massive proto-binary system IRAS 16547-4247. Image credit: ALMA / ESO / NAOJ / NRAO.

Sodium chloride is familiar to us as table salt, but it is not a common molecule in the Universe. This was only the second detection of sodium chloride around massive young stars. The first example was around Orion KL Source I, but that is such a peculiar source that we were not sure whether salt is suitable to see gas disks around massive stars.

Their results confirmed that salt is actually a good marker. Since baby stars gain mass through disks, it is important to study the motion and characteristics of disks to understand how the baby stars grow.

The astronomers also found that the twin circumstellar disks around IRAS 16547-4247 stars are counter-rotating. The counter-rotation of the disks may indicate that these two stars are not actual twins, but a pair of strangers which were formed in separated clouds and paired up later. Yeah, if the stars are born as twins in a large common gaseous disk, then naturally the disks rotate in the same direction.

This ALMA composite image shows the massive proto-binary system IRAS 16547-4247. Different colors show the different distributions of dust particles (yellow), methyl cyanide (red), salt (green), and water vapor (blue). Bottom insets are the close-up views of each component. Dust and methyl cyanide are distributed widely around the binary system, whereas salt and water vapor are concentrated in the disk around each protostar. In the wide-field image, the jets from one of the protostars, seen as several dots in the above image, are shown in light blue. Image credit: ALMA / ESO / NAOJ / NRAO / Tanaka et al.

The team expects that further observations will provide more dependable information on the secrets of massive binary systems’ birth.

The presence of water vapor and sodium chloride, which were released by the destruction of dust particles, suggests the hot and dynamic nature of disks around massive protostars.

Interestingly, investigations of meteorites indicate that the disk of the proto-Solar System also experienced high temperatures in which dust particles were evaporated.

These new results suggested that these “hot-disk” lines may be common in innermost disks around massive protostars, and have great potential for future research of massive star formation. They also tentatively found that the twin disks are counter-rotating, which might give a hint of the origin of the massive proto-binary system IRAS 16547–4247.

References: Kei E.I. Tanaka et al. 2020. Salt, Hot Water, and Silicon Compounds Tracing Massive Twin Disks. ApJL 900 (1), L2; doi: 10.3847/2041-8213/abadfc link: https://iopscience.iop.org/article/10.3847/2041-8213/abadfc