Friday, January 19, 2024

 

The American Journal of Clinical Nutrition launches new article series to educate physicians and other health care professionals on nutrition


Peer-Reviewed Publication

AMERICAN SOCIETY FOR NUTRITION






Rockville, MD (January 16, 2024) – To educate physicians and other health care professionals on the fundamentals of nutrition, The American Journal of Clinical Nutrition has launched a new article series titled Nutrition for the Clinician. The effort supports the White House National Strategy on Hunger, Nutrition, and Health and its directives to expand nutrition knowledge of health care providers, an effort long supported by the American Society for Nutrition. Nancy Krebs, MD, MS, Professor of Pediatrics, University of Colorado School of Medicine, is the Associate Editor for the series. 

Through case-based learning, Nutrition for the Clinician provides continuing education that enhances clinical reasoning and use of the best nutrition evidence in practice. Each clinical case will feature a clearly identified nutrition problem and defined learning objectives. Cases will be published in the journal’s regular issues periodically throughout the year. 

“Nutrition plays a pivotal role in health and disease,” stated Christopher Duggan, MD, MPH, Editor-in-Chief, The American Journal of Clinical Nutrition. “By presenting nutritional challenges seen in hospital and outpatient care and describing evidence-based treatment approaches, we hope physicians will gain a deeper understanding of how nutrition significantly impacts patient outcomes, as well as see firsthand the clinical reasoning process of top clinicians.” 

Titled “A Perfect Storm in a Pandemic – A Child with Complex Medical History and Special Diet Encounters COVID,” the inaugural case highlights a six-year-old child with undernutrition and acute COVID-19 infection. 

Authors Nancy Krebs, MD and Stephanie Waldrop, MD (University of Colorado) provide medical history, laboratory results, and clinical findings and offer commentary and questions to guide readers through the case. The authors analyze the differential diagnosis and treatment considerations at the outset and reassess them as new data emerges over the course of care. 

The case is freely accessible at the following link: https://ajcn.nutrition.org/article/S0002-9165(23)66234-3/fulltext. The American Society for Nutrition is accredited by the Accreditation Council for Continuing Medical Education (ACCME) to provide continuing medical education for physicians. The ASN designates this activity for a maximum of 1.00 AMA PRA Category 1 Credit™. For details on claiming CME credit for reading Nutrition for the Clinicianclick here

“Having knowledge of nutrition is important for all medical specialists, yet studies have shown that nutrition education and training in medical schools and residency programs is lacking,” expressed Kevin Schalinske, PhD, President, American Society for Nutrition. “We hope this new resource will pique the interest of physicians and advanced practice providers and inspire them to learn more about nutrition care in clinical practice.” Dietitians also may find interest in the range of medical scenarios and accompanying nutritional diagnostics and therapies presented. 

The AJCN welcomes contributions to this new series from both individual providers and interprofessional teams. Prospective authors can direct pre-submission inquiries to ajcn.editorialoffice@jjeditorial.com

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About The American Journal of Clinical Nutrition
The American Journal of Clinical Nutrition, one of the most influential journals in biology and medicine, publishes research in human nutrition and fosters the application of science into clinical practice. Topics include high-impact clinical, observational, public health, and epidemiologic studies in all areas of nutrition including obesity and metabolism; micronutrients; body composition; and nutrition in clinical settings. Genetic and novel precision nutrition approaches are featured. Visit us online at ajcn.nutrition.org or follow us on X (formerly Twitter) @AJCNutrition #AJCN.

About the American Society for Nutrition (ASN)
The American Society for Nutrition (ASN) is the preeminent professional organization for scientists and clinicians around the world. Founded in 1928, the society brings together the top nutrition researchers, medical practitioners, policy makers and industry leaders to advance the science, education, and practice of nutrition, reaching more than 55 million people annually. ASN publishes four peer-reviewed journals and provides education and professional development opportunities year-round. Since 2018, the American Society of Nutrition has presented NUTRITION, the leading global annual meeting for nutrition professionals. Visit us at www.nutrition.org.

 

Cryo-microscopy reveals nano-sized copy machine implicated in origin of life


RNA is thought to have sparked the origin of life by self-copying. Researchers reveal the atomic structure of an "RNA copy machine". This breakthrough sheds light on a primordial RNA world and fuels advancements in RNA nanotechnology and medicine


Peer-Reviewed Publication

AARHUS UNIVERSITY

Atomic structure of RNA polymerase ribozyme thought to be implicated in the origin of life 

IMAGE: 

THE PICTURE SHOWS AN RNA POLYMERASE RIBOZYME THOUGHT TO BE IMPLICATED IN THE ORIGIN OF LIFE. THE RIBOZYME IS SHOWN FROZEN IN ICE TO SYMBOLIZE HOW IT WAS FROZEN IN TIME FOR IMAGING AND HOW IT WORKS BEST UNDER ICE-COLD CONDITIONS. THE ACTIVE SITE IS HIGHLIGHTED BY A YELLOW/RED LIGHT AND THE PROPOSED POSITION OF THE TEMPLATE-PRODUCT HELIX IS SHOWN IN TRANSPARENT.

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CREDIT: RUNE KIDMOSE





How the intricate molecular machinery of life arose from simple beginnings has been a long-standing question. Several lines of evidence point towards a primordial "RNA world", where an "RNA copy machine" (a so-called replicase) started making copies of itself and other RNA molecules to kick-start evolution and life itself. However, the ancient replicase appears to have been lost in time and its role in modern biology has been taken over by more efficient protein machines. To support the RNA world hypothesis, researchers have been seeking to re-create an equivalent of the RNA replicase in the laboratory. While such molecular “Doppelgangers” of the ancient replicase have been discovered, both their detailed molecular structure and mode of action has remained elusive due to the difficulty of determining the structure of dynamic RNA molecules.

Structure of an ice-loving RNA replicase

In a research paper published in PNAS, a team of researchers now report the first atomic structure of an RNA replicase using cryogenic electron microscopy (cryo-EM). The RNA replicase being studied was developed by the Holliger lab (MRC LMB Cambridge, UK) to be efficient at copying long templates using nucleotide triplets in the eutectic ice phase (similar to slush-ice). Returning from postdoctoral studies in the Holliger lab, Emil L. Kristoffersen, currently assistant professor at Aarhus University, facilitated a collaboration with the Andersen lab (Aarhus University, Denmark) to determine the structure of the RNA replicase by cryo-EM. Interestingly, the structure shows striking similarities to protein-based polymerases with domains for template binding, polymerization, and substrate discrimination arranged in a molecular shape resembling an open hand.

"It was surprising to find that a ribozyme that we evolved artificially in the test tube would display features of naturally occurring protein polymerases. This indicates that evolution can discover convergent molecular solutions no matter if the material is RNA or protein", explains Philipp Holliger, program leader at MRC LMB Cambridge, UK.

Model for RNA synthesis in an RNA world

To better understand how the RNA replicase works, the researchers did a comprehensive mutational study to highlight the crucial elements of the RNA structure. This analysis confirmed features of the catalytic site but also revealed the importance of two so-called kissing-loop interactions, which bind the scaffolding and the catalytic subunits together, as well as the importance of a specific RNA domain for fidelity, that is the accuracy with which the replicase copies RNA strands. While the researchers could not determine the structure of the replicase “in-action” while actively copying RNA, it was possible to build a model for RNA-based RNA copying that is consistent with all experimental data.

"Cryo-EM is a powerful method for studying the structure and dynamical features of RNA molecules. By combing cryo-EM data with experiments, we were able to build a model of the inner workings of this complex RNA machine", tells Ewan McRae, who did the cryo-EM work as a postdoc in the Andersen lab at Aarhus University but has now started his own research group at Houston Methodist Research Institute, Texas, USA.

Inspiration for RNA nanotechnology and medicine

The study provides an exciting first glimpse of an RNA replicase thought to reside at the very root of the tree of life. The currently developed RNA-based replicases are however very inefficient (as compared to protein-based polymerases) and cannot yet sustain their own replication and evolution. The structural insight provided by the reported study may help in designing more efficient replication mechanisms and thus get us closer to developing RNA world scenarios in the test tube.

"The properties of RNA replicases may be further improved by using chemical modifications that could exist in an RNA world. In addition, research into the origin of life leads to the discovery of several novel RNA building blocks that may be used in the emerging field of RNA nanotechnology and medicine", explains Ebbe Sloth Andersen, associate professor at Aarhus University, Denmark.

About the research

External funding:

The research was funded by Independent Research Fund Denmark (9040-00425B), Novo Nordisk Foundation (NNF21OC0070452), Canadian Natural Sciences and Engineering Research Council (532417), Carlsberg Foundation (CF20-0635, CF17-0809), Lundbeck Foundation (R250-2017-1502), Medical Research Council, as part of United Kingdom Research and Innovation (also known as UK Research and Innovation (UKRI)) (MC_U105178804), Volkswagen Foundation (96 755), Herchel Smith studentship (2017), and Marie Curie fellowship (H2020-MSCA-IF-2018-845303).

Conflicts of interest:
The researchers declare that there are no conflicts of interest in connection with this research.

Link to the scientific article:

Cryo-EM structure and functional landscape of an RNA polymerase ribozyme
Ewan K. S. McRae, Christopher J. K. Wan, Emil L. Kristoffersen, Kalinka Hansen, Edoardo Gianni, Isaac Gallego, Joseph F. Curran, James Attwater, Philipp Holliger, and Ebbe S. Andersen
Proceedings of the National Academy of Sciences (PNAS) Vol. 121, No. 2 (January 9, 2024)
https://doi.org/10.1073/pnas.2313332121

 

Online versus reality: social media influences perceptions


Peer-Reviewed Publication

CORNELL UNIVERSITY





ITHACA, N.Y. – People may form inaccurate impressions about us from our social media posts, finds new Cornell University research that is the first to examine perceptions of our personalities based on online posts.

An analysis of Facebook status updates found substantial discrepancies between how viewers saw the authors across a range of personality traits, and the authors’ self-perceptions. Viewers rated the Facebook users on average as having lower self-esteem and being more self-revealing, for example, than the users rated themselves.

Status updates containing photos, video or links in addition to text facilitated more accurate assessments than those with just text, the researchers found. Overall, they said, the study sheds light on the dynamic process by which a cyber audience tries to make sense of who we are from isolated fragments of shared information, jointly constructing our digital identity.

“The impression people form about us on social media based on what we post can differ from the way we view ourselves,” said Qi Wang, professor of psychology and director of the Culture & Cognition Lab. “A mismatch between who we are and how people perceive us could influence our ability to feel connected online and the benefits of engaging in social media interaction.”

Wang is the lead author of “The Self Online: When Meaning-Making is Outsourced to the Cyber Audience,” published in PLOS One.

Prior research has focused on perceptions of personality traits gleaned from personal websites, such as blogs or online profiles, finding that readers can assess them accurately. The Cornell researchers believe their study is the first to investigate audience perceptions of social media users through their posts, on platforms where users often don’t share cohesive personal narratives while interacting with “friends” they may know only a little or sometimes not at all.

Interestingly, the study found that Facebook status updates generated perceptions of users that were consistent with cultural norms in offline contexts concerning gender and ethnicity – even though viewers were blind to their identities. For example, female Facebook users were rated as more extraverted than male users, in line with general findings that women score higher on extraversion. White Facebook users were seen as being more extraverted and having greater self-esteem than Asian users, whose cultures place more emphasis on modesty, Wang said.

“We present ourselves in line with our cultural frameworks,” she said, “and others can discern our ‘cultured persona’ through meaning making of our posts.”

The scholars said future research should explore this “outsourced meaning-making process” with larger samples of posts, and on other popular platforms such as Instagram and X, formerly known as Twitter.

Wang said the findings could help developers design interfaces that allow people to express themselves most authentically. For users, misunderstandings about who they are on social media might not cause direct harm, she said, but could hinder their efforts to foster good communication and relationships.

“If people’s view of us is very different from who we actually are, or how we would like to be perceived,” Wang said, “it could undermine our social life and well-being.”

For additional information, see this Cornell Chronicle story.

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Real-time photonic processor for dynamic RF interference with picosecond latency



Peer-Reviewed Publication

LIGHT PUBLISHING CENTER, CHANGCHUN INSTITUTE OF OPTICS, FINE MECHANICS AND PHYSICS, CAS

Photonic blind interference canceller 

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A, SCHEMATIC OF THE PHOTONIC PROCESSOR. PIC, PHOTONIC INTEGRATED CIRCUIT. MRR, MICRORING RESONATOR. MOD, MODULATOR. BPD, BALANCED PHOTODETECTOR. TIA, TRANSIMPEDANCE AMPLIFIER. FPGA, FIELD-PROGRAMMABLE GATE ARRAY. SIGNAL PATHWAY STARTS AT MRR MOD AND ENDS AT BPD, COMPOSING AN ON-CHIP WAVEGUIDE WITH A LENGTH OF 1.6 MM, WHICH HAS AN INDEX OF REFRACTION NEAR 2.44. THE LATENCY IS, ACCORDINGLY, THE LIGHT PROPAGATION TIME, WHICH IS ABOUT 15 PS. B, PACKAGED PALM-SIZED PHOTONIC PROCESSOR. THE SETUP COMPRISES TWO PRINTED CIRCUITED BOARDS PILED TOGETHER AND CONNECTED BY A RIBBON CABLE. THE TOP BOARD MOUNTS THE PIC IS IMPEDANCE ENGINEERED FOR HANDLING HIGH-FREQUENCY SIGNALS. THE BOTTOM BOARD IS POPULATED WITH MULTICHANNEL DIGITAL-TO-ANALOGUE CONVERTERS (DACS), PROVIDING TUNING CURRENTS AND BIASING VOLTAGES FOR COMPONENTS ON THE PIC. C, ZOOMED-IN VIEW OF THE PACKAGED PIC, TIAS, AND FIBRE ARRAY

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CREDIT: BY WEIPENG ZHANG, JOSHUA LEDERMAN, THOMAS FERREIRA DE LIMA, JIAWEI ZHANG, SIMON BILODEAU, LEILA HUDSON, ALEXANDER TAIT, BHAVIN SHASTRI, AND PAUL PRUCNAL





Radar altimeters are the sole indicators of altitude above a terrain. Spectrally adjacent 5G cellular bands pose significant risks of jamming altimeters  and impacting flight landing and take-off. As wireless technology expands in frequency coverage  and utilises spatial multiplexing, similar detrimental radio-frequency (RF) interference becomes a pressing issue. To address this interference, RF front-ends with exceptionally low latency are crucial for industries like transportation, healthcare, and the military, where the timeliness of transmitted messages is critical. Future generations of wireless technologies will impose even more stringent latency requirements on RF front-ends due to increased data rate, carrier frequency, and user count. Additionally, challenges arise from the physical movement of transceivers, resulting in time-variant mixing ratios between interference and signal-of-interest (SOI). This necessitates real-time adaptability in mobile wireless receivers to handle fluctuating interference, particularly when it carries safety-to-life critical information for navigation and autonomous driving, such as aircraft and ground vehicles.

 

In a new paper published in Light: Science & Applications, a team of scientists, led by Professor Paul Prucnal from Lightwave Lab, Department of Electrical and Computer Engineering, Princeton University, USA, and co-workers have introduced a system-on-chip (SoC) that employs silicon photonics to tackle dynamic radio-frequency (RF) interference, a growing issue in fields like transportation, healthcare, and military operations. This innovation is particularly crucial in light of the increased risk of radar altimeter jamming by adjacent 5G cellular bands, posing threats to aircraft safety.

 

The heart of this technological leap lies in photonic integrated circuits (PICs), which can process broadband information by converting radio frequencies into optical frequencies. Unlike traditional analogue RF components or digital electronics, PICs dramatically reduce latency through direct analogue processing, a critical feature as wireless technologies progress towards higher frequencies.

 

However, integrating a complete system on a chip for microwave processing has faced challenges in design, control, and packaging. Current PICs typically require bulky external devices for signal analysis and control, leading to impractical size, weight, and power metrics for real-world deployment.

 

Addressing these challenges, the research introduces a compact, palm-sized standalone photonic device. This device integrates modulators, microring resonator (MRR) weight banks, and photodetectors on a single chip, significantly reducing processing latency to less than 15 picoseconds. In addition, a field-programmable gate array (FPGA) with integrated peripherals handles high-throughput statistical analysis and high-level blind source separation (BSS) algorithms. This setup enables real-time execution at a refresh rate of 305 Hz, a marked improvement over previous systems.

 

The research team successfully tested this device in two dynamic interference scenarios - mobile communications and radar altimeters. The results were convincible, demonstrating error-free operation and maintaining signal-to-noise ratios over 15 dB. This breakthrough showcases the device's potential to address real-world interference challenges effectively.

 

This research marks a significant step forward in the development of photonic processors. It pioneered the development of a PIC capable of real-time online learning and rapid adjustment of photonic weights. As the research progresses, enhancements in form factor, performance, and online adaptiveness are anticipated. These advancements will broaden the applicability of photonic processors to a range of demanding tasks, including model predictive control and neuromorphic computing. The study marks a substantial step forward in the field of photonic signal processing, highlighting its potential in addressing complex, real-world challenges.

CHEMISTRY

Researchers step closer to mimicking nature’s mastery of chemistry


New approach to synthesis of chiral organic molecules


Peer-Reviewed Publication

UNIVERSITY OF CALIFORNIA - DAVIS

Researchers Step Closer to Mimicking Nature’s Mastery of Chemistry 

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CHEMISTS AT UC DAVIS ARE USING CATALYSTS (SHOWN IN GRAY SPHERES) TO MAKE ORGANIC COMPOUNDS (BLUE STICKS) WITH A SPECIFIC CHIRALITY, OR “HANDEDNESS.” MOST BIOLOGICAL MOLECULES ARE CHIRAL, INCLUDING MANY PRESCRIPTION DRUGS. THE DISCOVERY COULD MAKE IT EASIER TO SYNTHESIZE PHARMACEUTICALS WITH THE CORRECT SYMMETRY. 

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CREDIT: WILLIAM DESNOO/UC DAVIS




In nature, organic molecules are either left- or right-handed, but synthesizing molecules with a specific “handedness” in a lab is hard to do. Make a drug or enzyme with the wrong “handedness,” and it just won’t work. Now chemists at the University of California, Davis, are getting closer to mimicking nature’s chemical efficiency through computational modeling and physical experimentation.  

In a study appearing Jan. 10 in Nature, Professor Dean Tantillo, graduate students William DeSnoo and Croix Laconsay, and colleagues at the Max Planck Institute in Germany report the successful synthesis of specific chiral, or “handed,” molecules using rearrangements of simple hydrocarbons in the presence of complex organic catalysts. Most biological compounds, including many prescription drugs, are chiral.

Tantillo and colleagues hope the findings will enable scientists to better harness hydrocarbons for a variety of purposes, such as precursors to medicines and materials.

“The novelty of this paper is that this is really the first time, to my knowledge, that someone has been able to get a carbocation shift that makes one of the mirror image products rather than the other with high selectivity,” Tantillo said.  

Little balls of grease

In chemistry, chirality is a property that refers to a pair of molecules that share atomic makeup but are mirror images of each other. Like your left and right hands, they can’t be superimposed on each other.

“Synthetic chemists often want to make molecules that come in mirror image forms, but they only want one of them,” Tantillo said. “For example, if you want to make a drug molecule, often you need one of the two chiral forms to bind selectively to a protein or enzyme target.”

Achieving this can be difficult in a lab setting because such molecules, according to Tantillo, are often like “little balls of grease with some positive charge smeared around them.”

The greasy-like nature of these molecules typically makes binding by a chemical catalyst in one orientation over another difficult due to the lack of charged groups for the catalyst to grab on to.

But the researchers found a solution. Using a chiral organic acid, imidodiphosphorimidate, as a catalyst, the team successfully performed rearrangements of achiral alkenyl cycloalkanes, producing chiral molecules of interest called cycloalkenes. Using computational methods, Tantillo and colleagues deduced how the catalyst selectively produces one chiral form over the other.       

Similarities to nature

Tantillo said that the resulting reaction is similar to how enzymes that make hydrocarbon products called terpenes behave in nature. Part of Tantillo’s research concerns mapping terpene reaction pathways using quantum mechanical methods.

“If there are multiple possible pathways to a product, then every time you stop at an intermediate on that pathway, you have the possibility to get byproducts that come from that intermediate,” he said. “So it is important to know when and why a carbocation wants to stop en route to a given terpene if one wants to understand and ultimately re-engineer terpene-forming enzymes.”

The new method published in Nature could in principle be harnessed to produce both natural molecules and nonnatural molecules.  

“Whether these things will ever be done is hard to say, but petroleum is a source of a lot of hydrocarbons, and if you could catalytically turn those into molecules with defined chirality, you’ve increased the value of those molecules,” Tantillo said.  

Additional co-authors are: Vijay Wakchaure, Markus Leutzsch and Benjamin List, Max Planck Institut für Kohlenforschung, Mülheim an der Ruhr, Germany; and Nobuya Tsuji, Hokkaido University, Sapporo, Japan.

The work was supported in part by the Max Planck Society, the Deutsche Forschungsgemeinschaft and the European Research Council, and the U.S. National Science Foundation.