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Comment by Dr. Krishna Kumari Challa on January 14, 2023 at 9:48am

Raman spectroscopy method for rapid identification of beer spoilage bacteria

In a study published in Analytical Methods, a research group proposed the rapid detection of beer spoilage bacteria based on label-free surface-enhanced Raman spectroscopy (SERS) technology.

Lactic acid bacteria are common spoilage bacteria in beer and need to be monitored and controlled at all stages of beer production. Traditional spoilage bacteria detection methods are time-consuming and cannot meet the demand for real-time, in-situ, rapid detection during the production process.

Raman spectroscopy has been widely used for microbial detection due to its fast, non-destructive and accurate properties, but conventional Raman spectroscopy has the disadvantage of poor signal-to-noise ratio, which affects the accuracy of microbial identification.

Compared with conventional Raman spectroscopy, the SERS technique has a stronger and more sensitive signal and is well suited to the detection of beer spoilage bacteria. Furthermore, the label-free SERS technique is ideal for commercialization due to its low cost and good results.

In this study, the researchers improved the existing process for the preparation of label-free SERS silver nanoparticles (AgNPs). The effect of the AgNPs@KCl agglomeration effect on SERS enhancement was investigated. Eight species of beer spoilage bacteria produced during the beer brewing process were identified by SERS.

The researchers further investigated the effect of the method on the final identification rate by combining the t-distributed stochastic neighbor embedding (t-SNE) dimensionality reduction analysis algorithm, Support Vector Machine (SVM), k-NearestNeighbor (KNN) and Linear Discriminant Analysis (LDA) machine learning algorithms. All three machine learning algorithms achieved an accuracy of around 90% and performed well in identifying beer spoilage bacteria.

In the stability analysis and mixing tests, two known spoilage bacteria were mixed with pure beer and incubated at constant temperature for a period of time to identify the bacteria in the beer. The two spoilage bacteria were successfully detected in the samples and had good spectral stability.

According to the final validation study, the technique can indeed identify the target spoilage bacteria from the simulated samples, which is of great significance to the rapid identification of spoilage bacteria in the beer brewing process.

Lindong Shang et al, Rapid detection of beer spoilage bacteria based on label-free SERS technology, Analytical Methods (2022). DOI: 10.1039/D2AY01221A

Comment by Dr. Krishna Kumari Challa on January 14, 2023 at 9:38am

How a biological pathway leads stem cells to die or regenerate

A new study has determined that altering a cellular process can lead stem cells—cells from which other cells in the body develop—to die or regenerate.

The findings, published in the journal Cell Stem Cell, may assist in the development of new drugs that can manipulate this process to slow or stop cancer from growing and spreading, and enable regeneration in the context of other diseases.

If you have too much cell division, you end up with tumors. If you have too little, you have poor replacement of old cells.

The body's cells are regulated by various biological pathways. Each pathway involves a series of molecular actions inside a cell that produce a change in the cell, like creating a new molecule, such as a protein.

For this study, investigators  observed the effects of a gene called Discs large 1 (Dlg1) on the Wnt signaling pathway. This pathway involves a series of molecular interactions that regulate the growth or death of stem cells.

The Wnt pathway, which begins on the surface of a cell and ends inside of it, is critical for stem cell renewal and tissue regeneration. Although the pathway has been studied extensively, much is still unknown about how small increases and decreases in the frequency of communication signals through the pathway may affect the creation of new cells.

The signals or instructions can vary over time and under different conditions of health and disease.

Investigators studied intestinal tissue samples from laboratory mice to learn how mutations in Dlg1 affect the interaction between Wnt signaling and stem cells in the highly regenerative gastrointestinal tract. By performing gene expression analysis on the samples, the team looked for changes in genes that typically send signals along the Wnt pathway.

Through this process, investigators were able to see how changes in signaling frequency affected the creation of stem cells. The investigators found that when they inhibited the expression of Dlg1 and then increased signaling along the Wnt pathway by the addition of a specific molecule, such as a virus or drug, the stem cells died rather than generate new daughter cells.

 Ophir D. Klein, A DLG1-ARHGAP31-CDC42 axis is essential for the intestinal stem cell response to fluctuating niche Wnt signaling, Cell Stem Cell (2023). DOI: 10.1016/j.stem.2022.12.008. www.cell.com/cell-stem-cell/fu … 1934-5909(22)00492-1

Comment by Dr. Krishna Kumari Challa on January 14, 2023 at 9:33am

Why chocolate feels so good

Lubrication science gives mechanistic insights into how food actually feels in the mouth. You can use that knowledge to design food with better taste, texture or health benefits.

Scientists have decoded the physical process that takes place in the mouth when a piece of chocolate is eaten, as it changes from a solid into a smooth emulsion that many people find totally irresistible.

During the moments it is in the mouth, the chocolate sensation arises from the way the chocolate is lubricated, either from ingredients in the chocolate itself or from saliva or a combination of the two.

Fat plays a key function almost immediately when a piece of chocolate is in contact with the tongue. After that, solid cocoa particles are released and they become important in terms of the tactile sensation, so fat deeper inside the chocolate plays a rather limited role and could be reduced without having an impact on the feel or sensation of chocolate.

The researchers used analytical techniques from a field of engineering called tribology to conduct the study, which included in situ imaging.

Tribology is about how surfaces and fluids interact, the levels of friction between them and the role of lubrication: in this case, saliva or liquids from the chocolate. Those mechanisms are all happening in the mouth when chocolate is eaten.

When chocolate is in contact with the tongue, it releases a fatty film that coats the tongue and other surfaces in the mouth. It is this fatty film that makes the chocolate feel smooth throughout the entire time it is in the mouth.

Siavash Soltanahmadi et al, Insights into the multiscale lubrication mechanism of edible phase change materials, ACS Applied Materials & Interfaces (2023). pubs.acs.org/doi/10.1021/acsami.2c13017

Comment by Dr. Krishna Kumari Challa on January 14, 2023 at 8:53am

Protein that counteracts key rattlesnake venom toxins identified

Venomous snakes cause an estimated 120,000 deaths and 400,000 disabling injuries worldwide each year. 

To reduce and mitigate the severity of venomous snake bites, a team of  biologists launched an investigation into the genome of the western diamondback rattlesnake (Crotalus atrox), a species with more venom toxins encoded in its genome than any other known rattlesnake. The team pinpointed a single protein—called FETUA-3—that inhibits a broad spectrum of rattlesnake venom toxins.

FETUA-3 inhibited a huge number of toxins—over 20—that we detected and even bound to and inhibited the toxins of venoms from several other rattlesnakes the researchers tested. There is a need to learn more about how broadly FETUA-3 can be applied or if it'll need some additional tinkering but knowing that this one protein can neutralize an entire class of toxins brings researchers even closer to creating a better anti-venom.

Published in the Proceedings of the National Academy of Sciences, the team's findings have notable implications for the development of improved snake bite treatments.

Fiona P. Ukken et al, A novel broad spectrum venom metalloproteinase autoinhibitor in the rattlesnake Crotalus atrox evolved via a shift in paralog function, Proceedings of the National Academy of Sciences (2022). DOI: 10.1073/pnas.2214880119

Comment by Dr. Krishna Kumari Challa on January 13, 2023 at 11:40am

Washing fabrics by hand reduces microplastic release compared with machine washing

From tiny plankton to massive whales, microplastics have been found throughout the ocean food chain. One major source of this pollution are fibers shed while laundering synthetic fabrics. Although many studies show microfibers are released during machine washing, it's been less clear how hand washing contributes. Now, researchers reporting in ACS Environmental Science & Technology Water report that hand washing can drastically cut the amount of fibers shed compared with using a machine.

When clothing made from plastic fibres, such as polyester and nylon, are laundered, the fabric sheds microscopic fibers that eventually end up in wastewater and the environment. Though researchers have investigated the amount and types of microplastic  fibers shed while laundering clothing, most studies have focused on washing machines. In many countries, however, it is still common to manually launder clothing. So researchers systematically tried to compare both types of washing and their effect  on the environment.

The team cleaned two types of fabric swatches made from 100% polyester and a 95% polyester-5% spandex blend with hand washing methods and a washing machine. The researchers found that:

• Manual methods released far fewer fibers. For example, the 100% polyester fabric shed an average of 1,853 microplastic pieces during hand washing compared with an average of 23,723 pieces from the same fabric that was machine laundered.
• By weight, machine laundering released over five times more microplastics than the traditional method.
• The fibers released from hand washing tended to be longer.
• Adding detergent, pre-soaking the fabrics and using a washboard increased the number of released fibers with manual methods, but still not to the same extent as using a machine.
• In contrast, they found that temperature, detergent type, wash time and the amount of water used had no meaningful effects on the amount of microplastics shed while hand washing.

The researchers say that these results will help clarify the sources of microplastic pollution in the environment and can provide guidance for "greener" laundering methods.

Chunhui Wang et al, Microplastic Fiber Release by Laundry: A Comparative Study of Hand-Washing and Machine-Washing, ACS ES&T Water (2023). DOI: 10.1021/acsestwater.2c00462

Comment by Dr. Krishna Kumari Challa on January 13, 2023 at 11:30am

Study clarifies mystery of crocodilian hemoglobin

We know a crocodile's ability to stay under water for a long time.  When the unseen apex predator lashes from the water to seize its prey the impala, its infamous teeth latch onto a hindquarter, jaws clenching with 5,000 pounds of force. Yet it's the water itself that does the killing, with the deep-breathed reptile dragging its prey to the deep end to drown.

The success of the croc's ambush lies in the nanoscopic scuba tanks—hemoglobins—that course through its bloodstream, unloading oxygen from lungs to tissues at a slow but steady clip that allows it to go hours without air. The hyper-efficiency of that specialized hemoglobin has led some biologists to wonder why, of all the jawed vertebrates in all the world, crocodilians were the lone group to hit on such an optimal solution to making the most of a breath.

By statistically reconstructing and experimentally resurrecting the hemoglobin of an archosaur, the 240-million-year-old ancestor of all crocodilians and birds, researchers have gleaned new insights into that why. Rather than requiring just a few key mutations, as earlier research suggested, the unique properties of crocodilian hemoglobin stemmed from 21 interconnected mutations that litter the intricate component of red blood cells.

That complexity, and the multiple knock-on effects that any one mutation can induce in hemoglobin, may have forged an evolutionary path so labyrinthine that nature failed to retrace it even over tens of millions of years, the researchers say.

All hemoglobin binds with oxygen in the lungs before swimming the bloodstream and eventually releasing that oxygen to the tissues that depend on it. In most vertebrates, hemoglobin's affinity for capturing and holding oxygen is dictated largely by molecules known as organic phosphates, which, by attaching themselves to the hemoglobin, can coax it into releasing its precious cargo.

But in crocodilians—crocodiles, alligators and their kin—the role of organic phosphates was supplanted by a molecule, bicarbonate, that is produced from the breakdown of carbon dioxide. Because hardworking tissues produce lots of carbon dioxide, they also indirectly generate lots of bicarbonate, which in turn encourages hemoglobin to dispense its oxygen to the tissues most in need of it.

It's a super-efficient system that provides a kind of slow-release mechanism that allows crocodilians to efficiently exploit their onboard oxygen stores. It's part of the reason they're able to stay underwater for so long.

Chandrasekhar Natarajan et al, Evolution and molecular basis of a novel allosteric property of crocodilian hemoglobin, Current Biology (2022). DOI: 10.1016/j.cub.2022.11.049

Comment by Dr. Krishna Kumari Challa on January 11, 2023 at 7:05am

Introduction to Marine Energy

Want to learn about different types of marine energy resources and technologies, their associated challenges and considerations, and how researchers are addressing these challenges? Watch this video ....

Comment by Dr. Krishna Kumari Challa on January 11, 2023 at 7:01am

Are we breathing airborne microplastics? Study finds higher concentrations indoors

People are likely exposed to thousands of airborne microplastics a year indoors, a new study has found.

Published in Environmental Science & Technology, the study investigated the abundance, distribution, form, and possible sources of microplastics (MPs) in indoor and outdoor sites in Sri Lanka, finding concentrations between 1 and 28 times higher indoors.

With people spending approximately 90% of their time indoors and based on the indoor and outdoor MPs levels identified in this study, the researchers calculated the average human exposure as 2,675 airborne microplastic particles per person every year.

Researchers collected air samples in different urban, rural, coastal, inland, industrial, and natural habitats with varying population densities.

The indoor MPs levels, made up of fibers and the occasional fragments mostly from textiles and clothing, were significantly higher than outdoor levels by a factor of 1–28 times, regardless of the type of outdoor environment. Transparent, blue, and black fibers in the size range of 0.10 to 0.50 millimeters were the dominant AMPs across all sites.

These initial results  show that the amount of indoor airborne microplastics is more related to indoor sources and the occupants' lifestyle than the outdoor environment.

In the outdoor samples, the amount of AMPs was always greater in high-density sites compared to the low-density areas, suggesting the abundance and distribution of AMPs was related to population density, level of industrialization, and human activity."

The dominant type of microplastics in both indoor and outdoor sites was PET fibers (polyethylene terephthalate), primarily originating from clothing and textiles.

This study is an important first step that shows the abundance of AMPs in a lower-middle income country in South Asia.

Kushani Perera et al, Airborne Microplastics in Indoor and Outdoor Environments of a Developing Country in South Asia: Abundance, Distribution, Morphology, and Possible Sources, Environmental Science & Technology (2022). DOI: 10.1021/acs.est.2c05885

Comment by Dr. Krishna Kumari Challa on January 11, 2023 at 6:56am

Peering inside a metal, one sees atoms arranged in neat repeating grids, called a crystal lattice. In a crystal, the atomic orbitals of the outermost electrons morph into one another. This allows the electrons to travel far from their original nucleus and carry current through the metal. In this solid setting, a version of orbital balloons still exists, but it's more common to visualize them not in space—where there are many huge and unwieldy orbitals—but as a function of the speed and direction of the traveling electrons. The fastest moving electrons in the crystal form their own balloon, a collective analog of atomic orbitals known as a Fermi surface.

The shape of the Fermi surface reflects the structure of the underlying crystal, which usually bears no resemblance to the orbital structure of single atoms. But for materials like YPtBi with very few mobile electrons, the Fermi surface is not very big. Because of this, it retains some of the properties of electrons that hardly move at all, which sit at the center of the Fermi surface.

The fact that nature figures out counterintuitive atomic arrangements that allow the Fermi surface to retain signatures of the atomic orbitals is rather cool and intricate.

To uncover this cool, counterintuitive Fermi surface, the researchers stuck a YPtBi crystal inside a magnetic field and measured the current flowing through the crystal as they tuned the field. By rotating the direction of the magnetic field, they were able to map out the speed of the fastest electrons in every direction. They found that akin to a higher angular momentum atomic orbital, the Fermi surface has a complex shape to it, with peaks and troughs along certain directions. The high symmetry of the crystal itself would normally lead to a more uniform, ball-like Fermi surface, so it was a surprise to find a more complicated structure. This pointed to the possibility that the collective electrons were exhibiting some of the higher angular momentum nature of atomic orbitals.

Indeed, theoretical calculations by the  team showed that the experimental results matched up with a high angular momentum model, leading the team to claim the first experimental observation of a high-angular momentum metal. The team cautions that even this experimental evidence could still be incomplete. What they measured depends not only on the Fermi surface but also on other properties of the electrons, such as their effective mass and the distribution of their velocities. In their work, the team systematically studied the angular dependence of these other quantities and demonstrated that it would be extremely unlikely for them to cause the observed peaks and troughs.

In addition to being fundamentally novel, this higher angular momentum metal has potential applications for quantum computing.

Hyunsoo Kim et al, Quantum oscillations of the j=3/2 Fermi surface in the topological semimetal YPtBi, Physical Review Research (2022). DOI: 10.1103/PhysRevResearch.4.033169

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Part2

Comment by Dr. Krishna Kumari Challa on January 11, 2023 at 6:54am

Electrons take new shape inside unconventional metal

One of the biggest achievements of quantum physics was recasting our vision of the atom. Out was the early 1900s model of a solar system in miniature, in which electrons looped around a solid nucleus. Instead, quantum physics showed that electrons live a far more interesting life, meandering around the nucleus in clouds that look like tiny balloons. These balloons are known as atomic orbitals, and they come in all sorts of different shapes—perfectly round, two-lobed, clover-leaf-shaped. The number of lobes in the balloon signifies how much the electron spins about the nucleus.

That's all well and good for individual atoms, but when atoms come together to form something solid—like a chunk of metal, say—the outermost electrons in the atoms can link arms and lose sight of the nucleus from where they came, forming many oversized balloons that span the whole chunk of metal. They stop spinning about their nuclei and flow through the metal to carry electrical currents, shedding the diversity of multi-lobed balloons.

Now researchers have produced the first experimental evidence that one metal—and likely others in its class—have electrons that manage to preserve a more interesting, multi-lobed structure as they move around in a solid. The team experimentally studied the shape of these balloons and found not a uniform surface, but a complex structure. This unusual metal is not only fundamentally interesting, but it could also prove useful for building quantum computers that are resistant to noise.

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