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New approach uncovers the complete chemical complexity of quantum decoherence

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Rochester researchers have reported a strategy for understanding how molecules in completely chemically complex solvents lose their quantum coherence. This discovery opens the door to rational tuning of quantum coherence through chemical design and functionalization.

Credit: Annie Ostau de Lafon

This discovery can be used to design molecules with custom quantum coherence properties, laying the chemical basis for new quantum technologies.

In quantum mechanics, particles can exist in multiple states at the same time, which defies the logic of everyday experience. This property, known as quantum superposition, is the basis for new quantum technologies that promise to transform computing, communications, and sensing. However, quantum superposition faces a serious challenge: quantum decoherence. During this process, interaction with the surrounding environment disrupts the delicate superposition of quantum states.

Quantum decoherence challenges

To unlock the power of chemistry and build complex molecular architectures for practical quantum applications, scientists need to understand and control quantum decoherence so they can engineer molecules with specific quantum coherence properties. must be. To do so, we need to know how to rationally modify the chemical structure of molecules to modulate or alleviate quantum decoherence. To do this, scientists need to know the “spectral density,” a quantity that summarizes the speed at which the environment moves and the strength of its interactions with the quantum system.

A breakthrough in spectral density measurement

Until now, quantifying this spectral density in a way that accurately reflects molecular complexity has remained difficult in theory and experiment. However, a team of scientists has developed a way to extract the spectral density of molecules in a solvent using a simple resonance Raman experiment, a method that fully captures the complexity of the chemical environment.

A team led by Ignacio Franco, an associate professor of chemistry and physics at the University of Rochester, published their findings in Proceedings of the National Academy of Sciences.

Relationship between molecular structure and quantum decoherence

Using the extracted spectral density, we can not only understand how quickly decoherence occurs, but also determine which parts of the chemical environment are primarily responsible for decoherence. As a result, scientists can now map decoherence pathways and link molecular structure to quantum decoherence.

“Chemistry is built on the idea that molecular structure determines the chemical and physical properties of matter. This principle guides the modern design of molecules for medical, agricultural, and energy applications.” Using our strategy, we can finally begin to develop chemical design principles for emerging quantum technologies,” said Ignacio Gustin, a chemistry graduate student at the University of Rochester and lead author of the study.

Resonant Raman experiments: an important tool

The breakthrough came when the team realized that resonance Raman experiments provided all the information needed to study decoherence in its full chemical complexity. Although such experiments are routinely used to study photophysics and photochemistry, their usefulness for quantum decoherence had not been evaluated. The key insight was shared by David McCamant, an associate professor in the Department of Chemistry at the University of Rochester and an expert in Raman spectroscopy, and Jang Woo Kim, currently on the faculty at Chonnam National University in South Korea and an expert in quantum decoherence. This became clear from the discussion. He was a postdoctoral fellow at the University of Rochester.

Case study: Thymine decoherence

The researchers used their method to show for the first time how the superposition of electrons in thymine, one of the building blocks of humans, occurs. DNA, it takes only 30 femtoseconds (one femtosecond is one billionth of a billionth of a second) after absorbing ultraviolet light. They found that some vibrations within the molecule were dominant in the early stages of the decoherence process, while the solvent was dominant in the later stages. Furthermore, they found that chemical modifications to thymine significantly altered the decoherence rate, with hydrogen bonding interactions near the thymine ring resulting in more rapid decoherence.

Future implications and applications

Ultimately, the team’s research paves the way to understanding the chemical principles governing quantum decoherence. “We are excited to use this strategy to finally understand quantum decoherence in molecules of full chemical complexity and use it to develop molecules with robust coherence properties.” Franco said.

Reference: “Mapping the intramolecular electron decoherence pathway” by Ignacio Gustin, Chan Woo Kim, David W. McCamant, and Ignacio Franco, November 28, 2023. Proceedings of the National Academy of Sciences. DOI: 10.1073/pnas.2309987120

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New Research Uncovers the Secrets of Sarcomeres

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Diagram of interacting thick and thin filaments within cardiac sarcomeres based on structural cryo-electron tomography data. Credit: MPI of Molecular Physiology

Scientists have captured the first true-to-life 3D images of the thick filaments of a mammal’s heart muscle.

Atrial fibrillation, heart failure, and stroke are among the serious health conditions that can result from hypertrophic cardiomyopathy and are important factors in sudden cardiac death in people under 35 years of age.

“The heart muscle is the central engine of the human body. Of course, if you know how engines are made and how they work, it’s easy to repair a broken engine,” says Stefan Lunser. say. “At the beginning of our study of muscle, we were able to use cryo-electron microscopy to visualize the structure of key muscle components and how they interact.”

“But these were still images of proteins taken from living cells. We just don’t teach them much,” Rounser said.

through thick and thin

Skeletal and cardiac muscles contract through the interaction of two types of parallel protein filaments (thin and thick) within the sarcomere. Sarcomeres are subdivided into several regions called zones and bands, and these filaments are arranged in different ways.

Thin filaments are composed of F-actin, troponin, tropomyosin, and nebulin. Thick filaments are formed by myosin, titin, and myosin-binding protein C (MyBP-C). The latter can form bonds between filaments, while the so-called motor protein myosin interacts with thin filaments to generate force and muscle contraction.

Thick filament structures within relaxed cardiac sarcomeres. The image above shows a tomographic slice of a cardiac sarcomere. Thin filaments are marked with green marks, thick filaments with purple arrows. The middle image shows reconstructed thick filaments (purple) and thin filaments (green). The image below shows the structure of thin filaments spanning several sarcomere regions. Scale bar indicates 50 nm. credit:
Molecular Physiology MPI

Muscle research milestones

“If we want to fully understand how muscles work at the molecular level, we need to delineate their components in their natural environment. This is one of the biggest challenges in biological research today. and cannot be addressed using traditional experimental approaches,” says Rounser.

To overcome this obstacle, his team developed an electron cryo-tomography workflow specifically for examining muscle samples. The scientists flash-frozen mammalian heart muscle samples produced by his Gautel group in London at very low temperatures (-175°C). ).

3D structure of a sarcomere showing thick filaments (purple) and thin filaments (green). Credit: MPI of Molecular Physiology

This maintains moisture and microstructure, keeping it pristine. Next, a focused ion beam (FIB milling) is applied to thin the sample to a thickness of approximately 100 nanometers, ideal for transmission electron microscopy, and multiple images are acquired while tilting the sample along its axis. Masu. Finally, computational methods reconstruct his three-dimensional image in high resolution.

In recent years, Raunser’s group has successfully applied customized workflows and recently published two groundbreaking publications. They created the first high-resolution images of sarcomeres and, so far, a misty muscle protein called nebulin. Both studies investigated the 3D organization of muscle proteins in sarcomeres, such as how myosin binds to actin to control muscle contraction, and how nebulin binds to actin to stabilize it and its We provide unprecedented insight into the 3D organization of muscle proteins in sarcomeres, including what determines their length.

complete the picture

In the current study, scientists have created, for the first time, high-resolution images of the heart’s thick filaments spanning several regions of the sarcomere. “With a length of 500 nm, this makes it the longest and largest structure ever resolved by cryo-ET,” said Davide Tamborini of MPI Dortmund, lead author of the study. Masu.

Even more impressive is the new insight gained into the molecular organization of the thick filaments and, by extension, their function. The arrangement of myosin molecules depends on their position within the filament.

Scientists believe that this allows the thick filaments to sense and process a large number of muscle-regulating signals and adjust the strength of muscle contractions depending on the sarcomere area. They also revealed how titin chains run along the filament. Titin chains intertwine with myosin and serve as a scaffold for its assembly, likely regulating length-dependent sarcomere activation.

“Our goal is to one day paint a complete picture of sarcomeres. The images of thick filaments in this study are ‘only’ snapshots of the muscle in its relaxed state. “We want to analyze sarcomeres in different states, such as during contraction, to fully understand how they function and how they are regulated,” says Rounser.

Comparisons with samples from patients with muscle diseases will ultimately contribute to a better understanding of diseases such as hypertrophic cardiomyopathy and the development of innovative treatments.

Reference: “Structure of native myosin filaments in relaxed cardiac sarcomeres” Davide Tamborrini, Zhexin Wang, Thorsten Wagner, Sebastian Tacke, Markus Stabrin, Michael Grange, Ay Lin Kho, Martin Rees, Pauline Bennett, Mathias Gautel, Stefan Raunser, 2023 October 32nd Nature.
DOI: 10.1038/s41586-023-06690-5

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Study uncovers long-term health hazards

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New research reveals significant metabolic and health risks associated with long-term coconut oil supplementation, including hormonal changes, weight gain, and inflammation. Lead researcher Marcio Alberto Torsoni advises against consuming coconut oil blindly and recommends a moderate amount according to dietary guidelines.

Scientists at the State University of Campinas observed changes in eating patterns, weight gain, signs of anxiety, and increased inflammation in the brain, adipose tissue, and liver in mice.

Article published in Functional food journal We report on a research study in which oral administration of extra virgin coconut oil supplements to mice showed significant changes in eating habits, weight gain, anxiety levels, and inflammation in the central nervous system, adipose tissue, and liver.

Researchers also discovered that leptin, an important metabolic hormone, insulin The ability to activate cellular mechanisms involved in satiety and blood sugar control may be impaired, and biochemical mechanisms involved in fat synthesis may be stimulated.

Researcher insights

Marcio Alberto Torsoni, a researcher at the Institute of Metabolic Disorders, said: “The results of this study suggest that although the process occurs slowly and quietly, long-term coconut oil supplementation contributes to the development of obesity and related comorbidities. “This suggests that it may cause significant metabolic changes.” LabDiMe) is conducted at the Faculty of Applied Sciences of the State University of Campinas (FCA-UNICAMP), São Paulo State, Brazil. He holds a PhD in Functional and Molecular Biology and completed postdoctoral studies at the UNICAMP Faculty of Medicine and the University of Michigan, USA.

LabDiMe is part of the Obesity and Comorbidity Research Center (OCRC), one of FAPESP’s Research, Innovation, and Dissemination Centers (RIDCs), and the Center for Metabolic Programming and Perinatal Management (MPPM), which receives funding from the U.S. We are collaborating with National Institutes of Health (NIH (National Institutes of Health).

Animal fat and coconut oil risks

Excessive intake of animal fats is associated with an increased risk of: cardiovascular disease, as well as obesity and diabetes. One of the components of this diet is cholesterol, but this type of fat also contains saturated fatty acids, which can activate inflammatory processes through Toll-like receptor 4 (TLR-4) and cause disease. there is.

Saturated fatty acids are also available from other sources, such as plants. For example, it makes up 90% of the fat in coconut oil. Although short-chain fatty acids make up the majority and are beneficial as they reduce inflammation, the saturated fatty acids found in coconut oil are sufficient to activate inflammatory pathways and damage many different types of cells.

“Consumption of coconut oil, either as part of the regular diet or as a dietary supplement, has increased significantly in the population,” Torsoni says. The problem is that most of the time it is consumed without the guidance of a nutritionist who can adjust the daily intake according to the individual’s needs.

experimental model

To find out whether daily consumption of coconut oil over long periods of time could cause health problems, the research group used an animal model involving healthy mice that were given coconut oil daily for eight weeks. did. This amount of coconut oil is equivalent to about 1 soup spoon (13g) of calories per day, or 5% of the calories from saturated fat in the diet of an adult of appropriate weight for his or her age and height.

Torsoni said coconut oil should be used in small amounts as part of seasonings and sauces, preferably with fresh or minimally processed vegetables. This is also the advice of the Ministry of Health’s Dietary Guidelines for Brazilian Citizens, which also recommends “an appropriate and healthy diet that combines quantity and quality and meets the needs of variety, balance, moderation and enjoyment.” I am.

“Coconut oil is not recommended as a supplement to treat disease or restore health,” Torsoni says.

Reference: “CO 2 supplementation induces lipogenesis in adipose tissue, leptin and insulin resistance in healthy Swiss mice” Alana Carolina Costa Veras, Larissa da Silva Bruzasco, Ana Beatriz Profiro Lopes, Beatriz da Silva Franco, Written by Alessandro Spencer de Souza Holanda, Andrea Maculano Estevez, Marcian Milanski, Adriana Souza Torsoni, Leticia Martins Ignacio-Sousa, Marcio Alberto Torsoni, June 4, 2023. Functional food journal.
DOI: 10.1016/j.jff.2023.105600

This study was funded by the São Paulo Research Foundation.

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