Category: 7. Science

Now, two of the researchers involved — Aster Taylor of the U-M Department of Astronomy and Darryl Seligman of Michigan State University — have authored a new study starting to characterize this far-flung object, dubbed 3I/ATLAS.

Interstellar objects are born outside our solar system and cruise through it without falling into a stable orbit around the sun. 3I/ATLAS and its two predecessors have opened rare, invaluable opportunities for researchers to learn new things about distant parts of our galaxy.

“This is what we’re here for — finding objects like this, making the public aware of them and generating excitement,” said Aster Taylor, a Fannie and John Hertz Fellow in the U-M Department of Astronomy.

That public excitement, in turn, keeps momentum going for funding and the new tools to enable future discoveries. For example, the Vera C. Rubin Observatory, which is supported by the U.S. National Science Foundation and the U.S. Department of Energy, came online this summer. Although it did not discover 3I/ATLAS, it’s projected to find one or two new interstellar objects per year, Taylor said.

“It’s an auspicious time to find cool objects,” Taylor said. “We’re excited about three, but if we can get to 10 or more of these things, then we’ll have a reasonable sample and we’ll be really excited about that.”

Both reports are available as preprints on arXiv. Taylor and Seligman also authored an op-ed about the discovery for Space.com.

Tale of the tape

The discovery of 3I/ATLAS was made possible by NASA’s Asteroid Terrestrial-impact Last Alert System. ATLAS consists of four telescopes — two in Hawaii, one in Chile and one in South Africa — that automatically scan the whole sky several times every night looking for moving objects.

ATLAS’s name hints at one of the most pressing factoids about this object: It’s not going to make terrestrial impact. That is, it won’t crash into Earth. In fact, it won’t get any closer to us than we are to the sun.

Also, it’s likely a comet, Taylor said. It’s enveloped by what’s known as a coma, a fuzzy cloud of gas and dust around its rocky nucleus. As 3I/ATLAS nears the sun, that coma will likely evolve and reveal interesting clues about its composition.

“3I/ATLAS likely contains ices, especially below the surface, and those ices may start to activate as it nears the sun,” said Seligman, a postdoctoral fellow at MSU. “But until we detect specific gas emissions, like H2O, CO or CO2, we can’t say for sure what kinds of ice or how much there is.”

Over the coming months, space telescopes like Hubble and JWST will be able to zoom in on 3I/ATLAS to probe these and other questions about its size, spin and how it reacts to being heated.

“We have these images of 3I/ATLAS where it’s not entirely clear and it looks fuzzier than the other stars in the same image,” said James Wray, a professor at the Georgia Institute of Technology who was involved in the discovery. “The object is pretty far away and, so, we just don’t know.”

Still, the researchers were able to work out some important characteristics from their initial observations. Specifically, 3I/ATLAS is faster, larger and older than its predecessors, 1I/’Oumuamua and 2I/Borisov.

3I/ATLAS has a hyperbolic velocity of just under 60 kilometers per second — roughly 130,000 miles per hour — compared to 26 for ‘Oumuamua and 32 for Borisov. The diameter of 3I/ATLAS is currently estimated to be as much as 10 kilometers, or 6 miles, which would be 100 times that of ‘Oumuamua and 10 times that of Borisov.

But Taylor is confident those numbers will shrink as astronomers get better observations of 3I/ATLAS. Such a large size would imply galaxies are way more efficient at making these kinds of objects than is physically possible.

Finally, ‘Oumuamua and Borisov have ages measured in millions of years, while 3I/ATLAS appears to be between 3 billion and 11 billion years old.

“It’s a wide range,” Taylor said. “But 11 billion years is pretty old. It’s about as old as the galaxy.”

This is another number that Taylor suspects will ultimately turn out to be toward the smaller end of the range. But it will be interesting regardless because it can provide more clues about how our galaxy was forming stars, planets and other objects earlier in its history.

The discovery

Taylor was recruited for the project while traveling to help confirm 3I/ATLAS was an interstellar object and make early characterizations. And there was a time crunch. If the ATLAS team had noticed 3I, odds were other astronomers had, too, and the team wanted to confirm its suspicions and get the news out first.

“I was fully on vacation in Fiji with my family when this was announced. When I heard, I just thought, ‘All right. Well, that’s my next two days,’” Taylor said. “It’s very exciting, but it’s also more stressful than you might think.”

Seligman had a little bit more notice, but not much. News started to spread within the group on July 1.

“I heard something about the object before I went to bed, but we didn’t have a lot of information yet,” Seligman said. “By the time I woke up around 1 a.m., my colleagues, Marco Micheli from the European Southern Observatory and Davide Farnocchia from NASA’s Jet Propulsion Laboratory, were emailing me that this was likely for real. I started sending messages telling everyone to turn their telescopes to look at this object.”

Larry Denneau, a member of the ATLAS team, reviewed and submitted the discovery observations from the European Southern Observatory’s Very Large Telescope in Chile shortly after it was observed.

“We have had false alarms in the past about interesting objects, so we know not to get too excited on the first day,” Denneau said. “But the incoming observations were all consistent, and late that night it looked like we had the real thing.”

John Tonry, another member of ATLAS and professor at the University of Hawaii, was instrumental in the design and construction of ATLAS, the survey that discovered 3I.

“It’s really gratifying every time our hard work surveying the sky discovers something new, and this comet that has been traveling for millions of years from another star system is particularly interesting,” he said.

Once 3I/ATLAS was confirmed, Seligman and Karen Meech, faculty chair for the Institute for Astronomy at the University of Hawaii, both managed the communications flow and worked on getting the data pulled together for submitting the paper.

“Once 3I/ATLAS was identified as likely interstellar, we mobilized rapidly,” Meech said. “We activated observing time on major facilities like the Southern Astrophysical Research Telescope and the Gemini Observatory to capture early, high-quality data and build a foundation for detailed follow-up studies.”

Other contributors to this research include the European Space Agency Near-Earth Objects Coordination Centre in Italy, California Institute of Technology, Auburn University, Universidad de Alicante in Spain, Universitat de Barcelona in Spain, European Southern Observatory in Germany, Villanova University, Lowell Observatory, University of Maryland, Las Cumbres Observatory, University of Belgrade in Serbia, Politecnico di Milano in Italy, University of Western Ontario in Canada, Universidad Diego Portales, Santiago in Chile and Boston University.

Like bees breathing life into gardens, providing pollen and making flowers blossom, little cellular machines called mitochondria breathe life into our bodies, buzzing with energy as they produce the fuel that powers each of our cells. Maintaining mitochondrial metabolism requires input from many molecules and proteins-some of which have yet to be discovered.

Salk Institute researchers are taking a closer look at whether mitochondria rely on microproteins-small proteins that have been difficult to find and, consequently, underestimated for their role in health and disease. In their new study, a microprotein discovered just last year at Salk, called SLC35A4-MP, was found to play a critical role in upholding mitochondrial structure and regulating metabolic stress in mouse fat cells. The findings plant the seed for future microprotein-based treatments for obesity, aging, and other mitochondrial disorders.

The study, published in Science Advances on August 29, 2025, is part of a series of recent discoveries at Salk that showcase the functional importance of microproteins in cellular biology, metabolism, and stress.

“Microproteins have long been dismissed as random genetic junk, but our work adds to a growing body of research demonstrating that many of them are actually crucial regulators of cell physiology,” says senior author Alan Saghatelian, professor and Dr. Frederik Paulsen Chair at Salk. “Here we reveal that a microprotein is responsible for preserving mitochondrial structure and function in brown fat tissue, which regulates body temperature and energy balance.”

In the late spring of 2024, Saghatelian’s lab discovered the genetic code for SLC35A4-MP hidden in an upstream open reading frame on a strand of messenger RNA (mRNA). The longstanding belief was that each mRNA strand codes for a single protein-a one-to-one ratio of mRNA-to-protein, always. So, when scientists found additional sections of genetic material- upstream open reading frames-on mRNA strands, they thought they must be either 1) random noncoding junk or 2) regulatory code that influences the translation of that mRNA.

But as genetic probing and sequencing technology became more sophisticated, researchers soon realized some of those upstream open reading frames coded for functional microproteins. This discovery brought an entirely new dimension to cellular life, as microproteins long hidden in disregarded upstream open reading frames are now in full bloom-ready to be plucked and studied.

Some of the first functional microproteins to be described were involved in metabolism and mitochondrial regulation. This includes Saghatelian’s 2024 study, in which the lab first discovered SLC35A4-MP in the walls of mitochondria. Further tests suggested the microprotein might be helping maintain healthy cellular metabolism.

But these findings were based on data collected from biochemical assays in test tubes and cells cultured in petri dishes. To fully confirm and describe SLC35A4-MP’s physiological role, they would have to test its function in a living system.

“SLC35A4-MP is among the first microproteins to be functionally characterized in mice,” says first author Andréa Rocha, a postdoctoral researcher in Saghatelian’s lab. “Indeed, we found that SLC35A4-MP regulates mitochondrial function and lipid metabolism in mice, which really goes to show that microproteins cannot be overlooked as we search for biological factors that regulate health.”

To classify SLC35A4-MP, the researchers looked at an exemplary metabolic tissue that works its mitochondria especially hard: brown fat. Brown fat cells are metabolically demanding, as they regulate energy balance and body temperature. The researchers removed SLC35A4-MP entirely from mouse brown fat cells, then induced metabolically stressful events like cold exposure or a high-fat diet.

Without SLC35A4-MP, mice were unable to dial up their metabolism during cold exposure. Their mitochondria were structurally compromised, enlarged, dysfunctional, and inflamed. Outside of the mitochondria, other parts of the brown fat cells were also affected. The researchers saw signs of cell interior remodeling and further inflammation-trademarks of metabolic decline in obesity-related conditions.

The findings demonstrate the fundamental role SLC35A4-MP plays in regulating brown fat cell function and response to metabolic stress. And because mitochondria, our buzzing cellular bees, are in every cell type in the body, the findings extend everywhere, too. SLC35A4-MP could be a powerful therapeutic target for any disease or disorder that impacts metabolic and mitochondrial function, from obesity to aging and beyond.

Microprotein research is finally springing to life, and the team sees bright blooms ahead in the search for more functional microproteins.

“As scientists have been able to add more microproteins to our protein databases, the question has remained, do these microproteins have any physiological relevance?” says Saghatelian. “And our study says yes, they are important physiological regulators. I hope that adds more fuel to the study of microproteins moving forward.”

Other authors include Antonio Pinto, Jolene Diedrich, Huanqi Shan, Eduardo Vieira de Souza, Joan Vaughan, and Mark Foster of Salk; Christian Schmedt of Novartis Research Foundation and Integrate Bioscience; Guy Perksin and Mark Ellisman of UC San Diego; Kaja Plucińska and Paul Cohen of Rockefeller University; and Srinath Sampath of Novartis Research Foundation and UC San Diego.

The work was supported by the National Institutes of Health (P30 CA014195, R01 GM102491, U24 NS120055, R01 NS108934, R01 GM138780, R01 AG065549, S10 OD021784, RC2 DK129961, NIA R01 AG081037, NIA R01 AG062479, NIMH RF1 MH129261, NIH-NCI CCSG P30 CA014195, NIH-NIA San Diego Nathan Shock Center P30 AG068635, NIH-NIA Alzheimer’s Disease Research Center P30 AG062429), National Science Foundation (2014862), American Heart Association Allen Initiative, California Institute for Regenerative Medicine, Henry L. Guenther Foundation, Helmsley Charitable Trust, and George E. Hewitt Foundation for Medical Research.

Symmetry in crystal structures plays a pivotal role in determining emergent phenomena in condensed matter systems, including unique electronic band structures with robust spin-momentum locking^1,2,3, time-reversal symmetry broken states^4,5, and topological swirling spin textures known as magnetic skyrmions⁶. Skyrmions have garnered significant attention for their potential applications in spintronic devices. Their helicity is highly dependent on the symmetry of their host material⁷. Known bulk skyrmion hosts include MnSi⁸, FeGe⁹, Fe_1−xCo_xSi¹⁰, and Cu₂OSeO₃^11,12, which crystallize in the cubic P2₁3 space group, as well as GaV₄(S/Se)₈ in R3m^13,14 and VOSe₂O₅ in P4cc ¹⁵. In these systems, the stabilization of the multiple-q skyrmion lattice (SkL) phase originates from the Dzyaloshinskii-Moriya interaction (DMI) within the helimagnetic ground state, a consequence of the relativistic spin–orbit coupling^16,17. Notably, skyrmions in P2₁3 systems are of the Bloch type, whereas in hosts with R3m symmetry, Néel-type skyrmions are observed.

Among these hosts, Cu₂OSeO₃ stands out as the first insulating material in which skyrmions were experimentally discovered. Its insulating nature enables electric-field manipulation of the SkL phase^{18,19,20,21,22}, a property complemented by other phenomena such as the stabilization of an independent SkL phase at low temperature^23,24 and novel magnetic and functional behaviors^25,26,27,28. Under high pressure, Cu₂OSeO₃ undergoes a series of structural phase transitions: first to an orthorhombic P2₁2₁2₁ phase, then to a monoclinic P2₁ structure, and finally to a triclinic P₁ polymorph^29,30. Remarkably, pressure has been shown to extend the stability range of the SkL phase up to room temperature³⁰. These attributes make Cu₂OSeO₃ a model system for advancing skyrmion physics. Recent studies have also demonstrated that when skyrmion hosts are confined in nanoparticles, approaching the size of a single skyrmion, the magnetic phase diagram is significantly altered, leading to modifications of the topological spin textures existing in bulk crystals and even lead to the emergence of novel ones^31,32,33,34. However, due to the finite spin–lattice coupling in the aforementioned SkL hosts, it is imperative to discuss the underlying crystal structure, especially while the particle size approaches the diameter of a single isolated skyrmion.

In this work, we present the discovery of a new polymorph of Cu₂OSeO₃. Through detailed crystallographic studies and density functional theory calculations, we show that this novel polymorph crystallizes in the trigonal space group R3m, belonging to the same C_3v point group symmetry than the Néel-type skyrmions hosts GaV₄(S/Se)₈. This structural change suggests that size effects could potentially drive a transformation from Bloch-type to Néel-type skyrmions in Cu₂OSeO₃. Our findings offer a possible alternate explanation for the unexpected observations of Néel-type skyrmions at the surfaces of bulk Cu₂OSeO₃ crystals³⁵.

For this study, bulk and few hundred micron sized single crystals were grown by chemical vapor transport. They were characterized using X-ray diffraction (XRD). Fifty single crystals exhibited a chiral enantiopure structure, with equal distribution between “right-handed” (denoted as I) and “left-handed” (denoted as I’) enantiomorphs. Both conform to the chiral space group P2₁3, with structure I matching prior reports on Cu₂OSeO₃ structure^7,36. No new polymorph was found in single crystals with size down to few tens of microns. Cu₂OSeO₃ nanoparticles were synthesized via a wet chemical process. Their crystal structure was determined using electron diffraction (ED) (Fig. 1a).

Of the ten analyzed nanoparticles, eight consisted of twins combining both enantiomorphs, typically comprising ~ 80% of I and ~ 20% of I’ (Fig. 1b). Two nanoparticles displayed F-centered cubic unit cell (Fig. 1c), with lattice parameters a = 8.893(5)Å (Table 1). The corresponding structure (denoted as II) was refined in the trigonal space group R3m (nonstandard F3m) with twinning along the twofold axes (100), (010), and (001) of the cubic basis (Fig. 1e). Refinement yielded R_1obs = 0.0862 and wR_all = 0.0656. To assess the stability of the trigonal structure II, density functional theory (DFT) calculations were performed within the generalized gradient approximation (GGA). The results yielded relatively small Hellmann–Feynman forces, suggesting that the structure is close to a local energy minimum. This was further validated by a direct structural optimization, using the experimental unit cell parameters and internal atomic coordinates as input. The total GGA energy of the optimized R3m phase was found to be approximately 0.8 eV/f.u. higher than that of the cubic P2₁3 phase. However, surface effects, prominent in nanoparticles, cannot be accounted in the DFT calculations but could significantly alter the energy balance and stabilize the R3m phase. Detailed refinement parameters and characteristics of structure II are provided in Tables S1, S2 and S3. Atomic positions and interatomic parameters of the trigonal phase II obtained by refinement of the ED data and by DFT are compared in Table 2 and Table S4, respectively.

All three structures I, I’ and II contain a similar substructure unit with Cu₂OSe composition and which has a cubic symmetry with the F-43m space group. Cu₂OSeO₃ is obtained by adding two O sites with half occupancy (half-filled pink circles in Fig. 1f). Based on this structural similarity, a prototype model of the ambient-pressure Cu₂OSeO₃ structure is proposed. The prototype is constructed from the substructure unit and the two additional O-sites (Fig. 1f and Table S5). However, this leads to unacceptably long Se-O distances of 2.23 Å (Table S3). These structure anomalies may be resolved by reducing the structure symmetry in two ways: (i) from F-43m to P2₁3 characteristic of I and I’ (Fig. 1d) or (ii) from F-43m to R3m_trigonal = F3m_cubic characteristic of II (Fig. 1e). During the refinement, the Se–O distances decrease to an acceptable 1.70 ± 0.01 Å in both cases (Table S3). We attribute the difference in the crystal structure to the size of the nanoparticles. Indeed, the crystals showing the I–I’ twinned structure are well-formed nanoparticles as indicated by the rather bright experimental reflections with a low background (Fig. 1b). The crystals exhibiting the structure II are characterized by weaker and split experimental reflections with a much lower intensity (Fig. 1c), indicating smaller attached nanoparticles. Unlike the pure enantiomorph bulk crystals grown from a single nucleus, multiple nucleation centers form during the synthesis process after selenious acid leaching from CuSeO₃·2H₂O precursor. This leads to nanoparticles with multiple twinning. The smaller particle size observed in the R3m polymorph suggests the existence of a critical size threshold below which the cubic form of Cu₂OSeO₃ cannot be stabilized. This hypothesis warrants further investigation.

Figure 2 illustrates both the similarities and differences among the three structural forms of Cu₂OSeO₃. The fundamental building unit consists of two corner-sharing oxygen-centered tetrahedrons, forming structural [O₂Cu₇] dimers ⁷. Across all structures, the interatomic distances and Cu–O–Cu bond angles remain comparable (see Table S3 in the Supplementary Information). In the cubic structure, these [O₂Cu₇] dimers exhibit ferrimagnetic ordering, with Cu1 and Cu2 carrying opposing magnetic moments. In all structures, including the prototype (Fig. 2b), the structural dimers are arranged in hexagonal rings oriented perpendicular to the threefold axis along the four diagonals of the cubic lattice (Figs. 2c-d). Similar hexagonal arrangements appear in the trigonal lattice along the (001) plane, as well as the (021), (-221), and (2–21) planes (Fig. 2e). However, the arrangement of the [O₂Cu₇] dimers within these hexagonal rings differs between the cubic and trigonal structures. In the cubic structure, hexagons consist of alternating O1-Cu1-O3 and O3-Cu2-O1 bonds (Figs. 2c-d), whereas in the trigonal structure, they are built with six O1-Cu2-O4 bonds, with O4-Cu1-O1 acting as bridges along the threefold symmetry axis (Fig. 2e). The distinct arrangement of dimers in the trigonal structure, as compared to the cubic phase, suggests a different magnetic ordering and hierarchy of energy scales, which may give rise to fundamentally different magnetic structures in the trigonal polymorph.

In the cation-centered polyhedral representation (Fig. 3), Cu1 and Cu2 are positioned within a trigonal bipyramid and a tetragonal pyramid, respectively. The Cu2-centered tetragonal pyramids differ between the two structures in terms of Cu–O interatomic distances: in the cubic structure, the apical Cu–O bond is longer than the equatorial ones, whereas in the trigonal structure, all five Cu–O distances are similar. Although the Cu1- and Cu2-containing polyhedra share edges and follow a similar arrangement (Fig. 3a), the connectivity of Cu2-centered polyhedra varies due to differences in the positioning of SeO₃ groups. In the cubic lattice, these tetragonal pyramids contribute to a three-dimensional framework, while in the trigonal structure, they form a flat triangular arrangement (Fig. 3b). Consequently, the trigonal polymorph of Cu₂OSeO₃ exhibits a layered-like structural organization (Fig. 3b).

This structural distinction may help explain a previously unpredicted observation reported by Zhang et al³⁵. who used resonant elastic X-ray scattering (REXS) at the Cu–L₂ absorption edge. At this energy, the X-ray penetration depth is limited to only a few tens of nanometers which is the size range of the Cu₂OSeO₃ nanoparticles studied here. The unexpected Néel-type swirls observed at the surface of bulk Cu₂OSeO₃ could be attributed to a local symmetry lowering, potentially reflecting the trigonal structure similar to the one discussed in this work. While our single-crystal XRD results rule out the presence of the R3m polymorph in the bulk, they do not preclude the possibility of this lower-symmetry phase existing at the surface.

In conclusion, this study reveals the discovery of a new polymorph of Cu₂OSeO₃, observed exclusively in nanoparticles. Electron diffraction based crystallographic analysis and DFT calculations confirm its R3m space group. While both trigonal and cubic polymorphs share a [O₂Cu₇] dimer-based framework, differences in SeO₃ positioning result in distinct connectivity between Cu-centered polyhedra, leading to a layered-like structure in the trigonal phase. The trigonal polymorph exhibits C_3v symmetry, like Néel-type skyrmion hosts, suggesting that size effects may drive a transformation from Bloch-type to Néel-type skyrmions in Cu₂OSeO₃. This discovery opens several promising directions for future research. First and foremost is the development of synthesis methods or deposition protocols capable of producing phase-pure trigonal nanoparticles or thin films. Such samples would allow precise determination of the stoichiometry of the trigonal phase, either confirming the composition deduced from structural analysis or revealing an off-stoichiometry required to stabilize this polymorph. They would also enable the investigation of skyrmion behavior under C_3v symmetry in Cu₂OSeO₃. If successful, this would open the door to a range of studies, including the identification of a cycloidal magnetic ground state, the emergence of a field-induced Néel-type skyrmion lattice, potential magnetoelectric coupling, electric-field-driven skyrmion dynamics, and the collective behavior of magnon modes in the microwave regime.

Scientists have discovered a clever new way to control the light emitted by quantum dots — tiny crystals that can release individual photons.

The advance could lead to faster, cheaper, and more practical quantum technologies, from ultra-secure communication systems to experiments that explore the strange foundations of quantum physics.

The Challenge of Single-Photon Sources

Quantum dots are tiny semiconductor structures capable of releasing single photons on demand, making them strong candidates for future photonic quantum computers. The difficulty is that no two quantum dots are exactly the same, and each can emit light at slightly different colors. This variation prevents researchers from combining multiple dots to create multi-photon states.

To work around this, scientists typically rely on a single quantum dot and then split its light into different spatial and temporal modes with the help of a fast electro-optic modulator. The drawback is that these modulators are costly, often require highly customized designs, and can be inefficient, leading to energy losses within the system.

An Elegant Optical Solution Emerges

A research collaboration led by Vikas Remesh of the Photonics Group at the Department of Experimental Physics, University of Innsbruck, together with partners from the University of Cambridge, Johannes Kepler University Linz, and other institutions, has now demonstrated a way to bypass these challenges. Their method relies on a fully optical process known as stimulated two-photon excitation. This technique allows quantum dots to emit streams of photons in distinct polarization states without the need for electronic switching hardware.

In tests, the researchers successfully produced high-quality two-photon states while maintaining excellent single-photon characteristics.

How the Technique Works in Practice

“The method works by first exciting the quantum dot with precisely timed laser pulses to create a biexciton state, followed by polarization-controlled stimulation pulses that deterministically trigger photon emission in the desired polarization,” explain Yusuf Karli and Iker Avila Arenas, the study’s first authors.

“It was a fantastic experience for me to work in the photonics group for my master’s thesis, remembers Iker Avila Arenas, who was part of 2022-2024 cohort of the Erasmus Mundus Joint Master’s program in Photonics for Security Reliability and Safety and spent 6 months in Innsbruck.

Moving Complexity to the Optical Stage

“What makes this approach particularly elegant is that we have moved the complexity from expensive, loss-inducing electronic components after the single photon emission to the optical excitation stage, and it is a significant step forward in making quantum dot sources more practical for real-world applications,” notes Vikas Remesh, the study’s lead researcher.

Looking ahead, the researchers envision extending the technique to generate photons with arbitrary linear polarization states using specially engineered quantum dots.

Real-World Quantum Applications

“The study has immediate applications in secure quantum key distribution protocols, where multiple independent photon streams can enable simultaneous secure communication with different parties, and in multi-photon interference experiments which are very important to test even the fundamental principles of quantum mechanics,” explains Gregor Weihs, head of the photonics research group in Innsbruck.

The research, published in npj Quantum Information, represents a collaborative effort involving expertise in quantum optics, semiconductor physics, and photonic engineering.

Reference: “Passive demultiplexed two-photon state generation from a quantum dot” by Yusuf Karli, Iker Avila Arenas, Christian Schimpf, Ailton Jose Garcia Junior, Santanu Manna, Florian Kappe, René Schwarz, Gabriel Undeutsch, Maximilian Aigner, Melina Peter, Saimon F. Covre da Silva, Armando Rastelli, Gregor Weihs and Vikas Remesh, 11 August 2025, npj Quantum Information.
DOI: 10.1038/s41534-025-01083-0

The work was supported by the Austrian Science Fund (FWF), the Austrian Research Promotion Agency (FFG), and the European Union’s research programs.

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New technique to image single lipids: Lipids are notoriously difficult to detect with light microscopy. Using a new chemical labeling strategy, the Dresden team has overcome this limitation, enabling novel insights into where specific lipids are located and how they are transported in cells.

Map of lipid flow: The researchers used the new lipid imaging method to answer the long-standing question how cells transport specific lipids to their target organelle membranes. The study revealed that non-vesicular lipid transport by proteins is the primary mechanism that maintains the membrane composition of specific organelles.

Understanding the role of lipids in diseases: Lipid imbalances play a role in several metabolic or neurodegenerative diseases. The new lipid-imaging technique will help understand the role of lipid transport in health and disease. The identification of the proteins involved in selective lipid transport can accelerate further discoveries of new drug targets for lipid-associated diseases.

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Lipid molecules, or fats, are crucial to all forms of life. Cells need lipids to build membranes, separate and organize biochemical reactions, store energy, and transmit information. Every cell can create thousands of different lipids, and when they are out of balance, metabolic and neurodegenerative diseases can arise. It is still not well understood how cells sort different types of lipids between cell organelles to maintain the composition of each membrane. A major reason is that lipids are difficult to study, since microscopy techniques to precisely trace their location inside cells have so far been missing.

In a long-standing collaboration André Nadler, a chemical biologist at the Max Planck Institute of Molecular Cell Biology and Genetics (MPI-CBG) in Dresden, Germany teamed up with Alf Honigmann, a bioimaging specialist at Biotechnology Center (BIOTEC) at the TUD Dresden University of Technology, to develop a method that enables visualizing lipids in cells using standard fluorescence microscopy. After the first successful proof of concept, the duo brought mass-spectrometry expert Andrej Shevchenko (MPI-CBG), Björn Drobot at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), and the group of Martin Hof from the J. Heyrovsky Institute of Physical Chemistry in Prague on board to study how lipids are transported between cellular organelles.

Artificial lipids under the sunbed

“We started our project with synthesizing a set of minimally modified lipids that represent the main lipids present in organelle membranes. These modified lipids are essentially the same as their native counterparts, with just a few different atoms that allowed us to track them under the microscope,” explains Kristin Böhlig, a PhD student in the Nadler group and chemist who was in charge of creating the modified lipids.

The modified lipids mimic natural lipids and are “bifunctional,” which means they can be activated by UV light, causing the lipid to bind or crosslink with nearby proteins. The modified lipids were loaded in the membrane of living cells and, over time, transported into the membranes of organelles. The researchers worked with human cells in cell culture, such as bone or intestinal cells, as they are ideal for imaging.

After the treatment with UV light, we were able to monitor the lipids with fluorescence microscopy and capture their location over time. This gave us a comprehensive picture of lipid exchange between cell membrane and organelle membranes.”

Kristin Böhlig, PhD student

In order to understand the microscopy data, the team needed a custom image analysis pipeline. “To address our specific needs, I developed an image analysis pipeline with automated image segmentation assisted by artificial intelligence to quantify the lipid flow through the cellular organelle system,” says Juan Iglesias-Artola, who did the image analysis.

Speedy lipid transport by proteins

By combining the image analysis with mathematical modeling, done by Björn Drobot at the HZDR, the research team discovered that between 85% and 95% of the lipid transport between the membranes of cell organelles is organized by carrier proteins that move the lipids, rather than by vesicles. This non-vesicular transport is much more specific with regard to individual lipid species and their sorting to the different organelles in the cell. The researchers also found that the lipid transport by proteins is ten times faster than by vesicles. These results imply that the lipid compositions of organelle membranes are primarily maintained through fast, species-specific, non-vesicular lipid transport.

In a parallel set of experiments, the group of Andrej Shevchenko at the MPI-CBG used ultra-high-resolution mass spectrometry to see how the different lipids change their structure during the transport from the cell membrane to the organelle membrane.

A boost for lipids in cell biology and disease

This new approach provides the first-ever quantitative map of how lipids move through the cell to different organelles. The results suggest that non-vesicular lipid transport has a key role in the maintenance of each organelle membrane composition.

Alf Honigmann, research group leader at the BIOTEC says, “Our lipid-imaging technique enables the mechanistic analysis of lipid transport and function directly in cells, which has been impossible before. We think that our work opens the door to a new era of studying the role of lipids within the cell.”

Imaging of lipids will allow further discoveries and help to reveal the underlying mechanisms in diseases caused by lipid imbalances. The new technique could potentially help to develop new druggable targets and therapeutic approaches for lipid-associated diseases, such as nonalcoholic fatty liver disease.

“We knew that we were onto something big”

André Nadler, research group leader at MPI-CBG, looks back at the start of the study, “Imaging lipids in cells has always been one of the most challenging aspects of microscopy. Our project was no different. Alf Honigmann and I started discussing about solving the lipid imaging problem as soon as we got hired in close succession at MPI-CBG in 2014/15 and we quickly decided to go for it. It still took us almost five years from the start of the project to the point in autumn 2019 when the two of us finally produced a sample with a beautiful plasma membrane stain. That’s when we knew that we were onto something big. As a reward, certain well known global events meant we were required to shut down our laboratories a few months later. In the end, the delay was for the best. Before the revolution in the use of artificial intelligence in image segmentation, we would not have been able to properly quantify the imaging data, so our conclusions would have been much more limited.”

Researchers still need to determine which lipid-transfer proteins drive the selective transport of different lipid species. They also need to identify the energy sources that power lipid transport and ensure that each organelle keeps its own unique membrane composition.

In an analysis of the genomes of all known amblyopsid species, the researchers found that the different species colonized caves systems independently of each other and separately evolved similar traits — such as the loss of eyes and pigment — as they adapted to their dark cave environments.

Their findings are published in the journal Molecular Biology and Evolution.

By studying the genetic mutations that caused the fishes’ eyes to degenerate, the researchers developed a sort of mutational clock that allowed them to estimate when each species began losing their eyes. They found that vision-related genes of the oldest cavefish species, the Ozark cavefish (Troglichthys rosae), began degenerating up to 11 million years ago.

The technique provides a minimum age for the caves that the fishes colonized since the cavefish must have been inhabiting subterranean waters when their eyesight began devolving, the researchers said.

“The ancient subterranean ecosystems of eastern North America are very challenging to date using traditional geochronological cave-dating techniques, which are unreliable beyond an upper limit of about 3 to 5 million years,” said Chase Brownstein, a student in Yale’s Graduate School of Arts and Sciences, in the Department of Ecology & Evolutionary Biology, and the study’s co-lead author. “Determining the ages of cave-adapted fish lineages allows us to infer the minimum age of the caves they inhabit because the fishes wouldn’t have started losing their eyes while living in broad daylight. In this case we estimate a minimum age of some caves of over 11 million years.”

Maxime Policarpo of the Max Planck Institute for Biological Intelligence and the University of Basel is the co-lead author.

For the study, the researchers reconstructed a time-calibrated evolutionary tree for amblyopsids, which belong to an ancient, species-poor order of freshwater fishes called Percopsiformes, using the fossil record as well as genomic data and high-resolution scans of all living relevantspecies.

All the cavefish species have similar anatomies, including elongated bodies and flattened skulls, and their pelvic fins have either been lost or severely reduced. Swampfish (Chologaster cornuta), a sister to cavefish lineage that inhabits murky surface waters, also has a flattened skull, elongated body, and no pelvic fin. While it maintains sight and pigment, there is softening of the bones around its eyes, which disappear in cavefishes. This suggests that cavefishes evolved from a common ancestor that was already equipped to inhabit low-light environments, Brownstein said.

To understand when the cavefish began populating caves — something impossible to discern from the branches of an evolutionary tree — the researchers studied the fishes’ genomes, examining 88 vision-related genes for mutations. The analysis revealed that the various cavefish lineages had completely different sets of genetic mutations involved in the loss of vision. This, they said, suggests that separate species colonized caves and adapted to those subterranean ecosystems independently of each other.

From there, the researchers developed a method for calculating the number of generations that have passed since cavefish species began adapting to life in caves by losing the functional copies of vision-related genes.

Their analysis suggests that cave adaptations occurred between 2.25 and 11.3 million years ago in Ozark cavefish and between 342,000 to 1.70 million years ago (at minimum) and 1.7 to 8.7 million years ago (at maximum) for other cavefish lineages. The findings support the conclusion that at least four amblyopsid lineages independently colonized caves after evolving from surface-dwelling ancestors, the researchers said.

The maximum ages exceed the ranges of traditional cave-dating methods, which includes isotope analysis of cosmogenic nuclides that are produced within rocks and soils by cosmic rays, the researchers noted.

The findings also suggest potential implications for human health, said Thomas Near, professor of ecology and evolutionary biology in Yale’s Faculty of Arts and Sciences (FAS), and senior author of the study.

“A number of the mutations we see in the cavefish genomes that lead to degeneration of the eyes are similar to mutations that cause ocular diseases in humans,” said Near, who is also the Bingham Oceanographic Curator of Ichthyology at the Yale Peabody Museum. “There is the possibility for translational medicine through which by studying this natural system in cavefishes, we can glean insights into the genomic mechanisms of eye diseases in humans.”

The other co-authors are Richard C. Harrington of the South Carolina Department of Natural Resources, Eva A. Hoffman of the American Museum of Natural History, Maya F. Stokes of Florida State University, and Didier Casane of Paris-Cité University.

Physical interactions between proteins influence anything from cell signaling and growth to immune responses, so the ability to control these interactions is of great interest to biologists. Researchers have used neural networks to help develop new proteins called binders that are designed to attach to therapeutically relevant targets, in the same way our immune systems use antibodies to bind to pathogens. But these systems, which use deep learning to predict protein shapes from sequences of amino acid building blocks, require computer science expertise.

“Traditional binder discovery methods involve screening tens of thousands of protein candidates, which requires experimental capabilities and computational expertise that not every lab can afford or has,” says Lennart Nickel, a PhD student in the Laboratory of Protein Design and Immunoengineering (LPDI), led by Bruno Correia, in EPFL’s School of Engineering. “BindCraft grew out of a desire to develop a more accessible, user-friendly tool that would only need to test a handful of proteins to get a binder.”

Instead of feeding amino acid sequences into a neural network and painstakingly screening the resulting binders for a good fit, the EPFL team, in collaboration with scientists at MIT, used structures fed into Google DeepMind’s AlphaFold2 system to generate sequences for new binders based on a set of desired functional properties – like binding to a specific target.

Reverse-engineering

With BindCraft, we essentially reverse-engineer the current pipeline by using the protein structure prediction network right from the start to generate novel binders that have the properties we’re looking for.”

Christian Schellhaas, PhD student 

By focusing on a small number of binder designs, rather than high-throughput screening of vast libraries of candidates, BindCraft makes protein design more efficient as well as more democratized. The team has recently published their results in Nature, in collaboration with researchers across Switzerland, in the US, and in the Netherlands.

Targeting quality over quantity

For their study, the team validated binders designed to interact with a dozen biotechnological and therapeutic molecules, including AAVs (adeno-associated viruses), which are used to deliver therapeutic genes into target cells; the CRISPR-Cas9 nuclease, which is used in gene editing applications; and certain common allergens. Overall, experiments showed that the team’s binders attached to their intended targets with an average success rate of 46%, offering the possibility of greater therapeutic control.

“For AAVs, the idea is to use these new binders to enable gene delivery only to specific cells and tissues while minimizing the risk of potential side effects. In the case of CRISPR-Cas9, our binders can stop its gene editing activity and keep it from acting when and where it shouldn’t,” explains first author and LPDI scientist Martin Pacesa.

Since the initial publication of BindCraft as a preprint last fall, the platform has already seen swift and enthusiastic uptake by the biology community, sparking requests from users for modifications and additional functionalities.

“We were surprised by how quickly our tool has been adopted – it is even already being used in industry. The requests from users are a great inspiration to continue developing our method. We are already working on adapting BindCraft for smaller therapeutically relevant molecules like peptides,” Pacesa says.

Recent advancements in glycobiology have challenged the traditional understanding of molecular interactions, and a new study published in Engineering titled “Can DNA be glycosylated?” by Wei Wang further explores this emerging field. The study delves into the potential for DNA glycosylation, a process that, if confirmed, could significantly expand our understanding of cellular biology and molecular regulation.

The central dogma of molecular biology, which describes the flow of genetic information from DNA to RNA to proteins, has long been the cornerstone of biological understanding. However, recent discoveries in glycobiology have introduced the concept of the paracentral dogma, positioning glycans as a third alphabet of life, complementing nucleic acids and proteins. This new perspective has been particularly highlighted by the discovery that RNA molecules can undergo glycosylation, a process where glycans are attached to RNA bases, fundamentally altering their chemical properties and biological functions.

The study by Wei Wang examines the potential for DNA glycosylation, drawing parallels with the well-documented phenomenon of RNA glycosylation. RNA glycosylation has been observed in various small noncoding RNAs, including small nuclear RNAs (snRNAs), ribosomal RNAs (rRNAs), small nucleolar RNAs (snoRNAs), transfer RNAs (tRNAs), Y-RNAs, and microRNAs. These glycosylated RNAs, known as glycoRNAs, exhibit distinct molecular functions compared to their non-glycosylated counterparts. The attachment of glycans to RNA bases is mediated by enzymes such as glycosyltransferases, which are traditionally involved in protein glycosylation. This process is tightly regulated and involves specific sites for glycan attachment, such as 3-(3-amino-3-carboxypropyl) uridine (acp3U) in tRNAs.

The biological significance of glycoRNAs is profound. They are predominantly localized on the surface of living cells, where they interact with immune receptors such as sialic acid-binding immunoglobulin-like lectins (Siglecs), modulating inflammation, pathogen recognition, and immune tolerance. GlycoRNAs also serve as biomarkers for cellular health and disease, with aberrant glycosylation patterns potentially signaling pathological states like cancer or autoimmune disorders. Their dual composition of RNA sequences and complex glycan structures allows them to integrate genetic information with cellular signaling networks, making them versatile molecules with diverse biological functions.

While DNA glycosylation has not yet been experimentally confirmed, the study by Wang suggests that it is a promising area for future research. DNA glycosylation, if it exists, would involve the direct enzymatic addition of glycans to DNA, potentially impacting DNA structure, gene regulation, and cellular functions. Although no direct evidence currently supports enzymatic DNA glycosylation, non-enzymatic DNA glycation demonstrates that sugar modifications on DNA are chemically feasible. This process, which occurs when reducing sugars react with DNA, leads to the formation of advanced glycation end products (AGEs) and has been linked to increased mutation rates, compromised DNA stability, and accelerated aging-related processes in pathological conditions like diabetes.

The hypothetical mechanisms of DNA glycosylation would likely involve specialized enzymatic machinery adapted to DNA’s unique structure. Such enzymes might function in specific cellular compartments, such as the nucleus or mitochondria, and could be regulated by factors like cell cycle phase, DNA damage, or metabolic state. If proven, DNA glycosylation could introduce new functional and structural roles within the cell, including epigenetic regulation, DNA repair and stability, immune recognition, and cell-cell communication.

The exploration of DNA glycosylation represents a frontier ripe for discovery, with the potential to uncover novel pathways and molecular interactions that expand our understanding of DNA’s role in cellular biology and disease. As glycomedicine continues to expand, the possibility of DNA glycosylation could bridge the gap between the central and paracentral dogmas of molecular biology, offering transformative insights into the molecular mechanisms governing life.

 

TOKYO – A research team at a Japanese university has found that the world’s oceans during the Cretaceous period, roughly 70 million to 100 million years ago, were dominated by squid.

In a report published recently in the journal Science by the researchers from the Department of Earth and Planetary Sciences at Hokkaido University, evidence suggested that squid far outnumbered ammonites and fish — the opposite of previous assumptions.

Being soft-bodied creatures, squid rarely fossilized, with typically only their beaks remaining after decomposition.

The team developed a technique to digitally produce three-dimensional recreations of even the tiniest fossils by repeatedly photographing rock slices just one-hundredth of a millimeter thick.

Analyzing Cretaceous period rocks found on Japan’s northern main island of Hokkaido, the team identified 263 fossils of squid beaks, averaging about 4 mm in length.

Based on the shapes of the beaks, the team was able to classify the squid into 40 species, some of which were similar to modern squid.

Observations of rocks from different periods suggest that squid appeared around 100 million years ago and diversified rapidly over the course of around 6 million years.

It is believed that their population grew so much that it surpassed that of the prosperous ammonites.

In contrast to the shelled ammonites, their fellow cephalopods, squid are thought to have evolved fast swimming abilities and intelligence that were advantageous for catching food, according to the team.

Squid established their position in the marine ecosystem earlier than fish and whales, diversified after the mass extinction event at the end of the Cretaceous period, and have remained a central presence to this day, it said.

What can the Galactic Habitable Zone (GHZ), which is a galaxy’s region where complex life is hypothesized to be able to evolve, teach scientists about finding the correct stars that could have habitable planets? This is what a recent study accepted for publication in Astronomy & Astrophysics hopes to address as an international team of researchers investigated a connection between the migration of stars, commonly called stellar migration, and what this could mean for finding habitable planets within our galaxy. This study has the potential to help scientists better understand the astrophysical parameters for finding habitable worlds beyond Earth and even life as we know it.

For the study, the researchers used a series of computer models to simulate how stellar migration could influence the location and parameters of the GHZ. The models included scenarios both with and without stellar migration to ascertain the statistical probabilities for terrestrial (rocky) planets forming around stars throughout the galaxy. The researchers also used a chemical evolution model to ascertain the formation and evolution of our galaxy, specifically regarding its thickness.

In the end, the researchers found that stellar migration influences the formation of habitable planets within the outer regions of the galaxy. This is because stellar migration results in a redistribution of stars throughout the galaxy, with the team estimating a 5 times greater likelihood of stellar migration resulting in stars hosting habitable planets compared to a lack of stellar migration. Additionally, the team found that gas giant planets could influence the formation of terrestrial planets within the inner regions of the galaxy.

The paper notes in its conclusions, “In this study, we have significantly expanded the exploration of the parameter space defining the Galactic Habitable Zone, compared to previous analyses present in literature. Our findings are particularly relevant in the context of upcoming space missions, such as the ESA [European Space Agency] PLAnetary Transits and Oscillations of Stars (PLATO), the ESA Ariel space mission and Large Interferometer For Exoplanets (LIFE). These missions will deliver unprecedented data on planetary properties, orbital architectures, and atmospheric compositions.”

The notion of the GHZ builds off the longstanding idea of the stellar habitable zone (HZ), which is the specific distance a planet must orbit its star for liquid water to exist on its surface, which was first introduced in the 1950s. Like all scientific notions, the idea of a GHZ has evolved over time since it was first introduced in the 1980s, but the overarching idea is this region is comprised of heavier elements (i.e., iron, silicon, and oxygen) that are used to form terrestrial planets like Earth. As this study notes, the exact size of the GHZ is still being debated, but the consensus in the scientific community is that the GHZ does not exist in the center of the galaxy, as this region hosts countless supernovae and other celestial events that would limit habitable planets from forming.

As the study notes, there are several ESA missions in the pipeline whose goals will be to expand our knowledge of both how and where to find life beyond Earth. For example, the PLATO mission, which is slated to launch in December 2026, will have the goal of scanning one million stars to observe and identify exoplanets that cross in front of them, known as a transit, and is one of the most common methods for discovering exoplanets to date.

The Ariel mission, which is slated to launch in 2029, will have the goal of observing at least 1,000 confirmed exoplanets to learn more about their chemical and heat compositions. Finally, the LIFE mission has was started in 2017 with the goal of studying the atmospheres of terrestrial exoplanets to identify potential signs of life known as biomarkers.

What new discoveries about the GHZ and stellar migration will researchers make in the coming years and decades? Only time will tell, and this is why we science!

As always, keep doing science & keep looking up!