The light-collecting antennae of plants and bacteria are a model for this. They capture a broad spectrum of light for photosynthesis, but are very complex in structure and require many different dyes to transmit the energy of the absorbed light and focus it on a central point.

The light-harvesting systems developed by humans to date also have disadvantages:

Although inorganic semiconductors such as silicon are panchromatic, they only absorb light weakly. In order to absorb enough light energy, very thick layers of silicon in the micrometre range are therefore required — making solar cells relatively bulky and heavy.

Organic dyes that are suitable for solar cells are much thinner: their layer thickness is only around 100 nanometres. However, they are barely able to absorb a broad spectral range and are therefore not particularly efficient.

Thin Layer Absorbs a Lot of Light Energy

Researchers at Julius-Maximilians-Universität (JMU) Würzburg in Bavaria, Germany, in the journal Chem have now presented an innovative light-harvesting system that differs significantly from previous systems.

“Our system has a band structure similar to that of inorganic semiconductors. This means that it absorbs light panchromatically across the entire visible range. And it uses the high absorption coefficients of organic dyes. As a result, it can absorb a great deal of light energy in a relatively thin layer, similar to natural light-harvesting systems,” says JMU chemistry professor Frank Würthner. His team from the Institute of Organic Chemistry / Center for Nanosystems Chemistry designed the light-harvesting system at JMU and investigated it together with Professor Tobias Brixner’s group from the Institute of Physical and Theoretical Chemistry.

Four Dyes in an Ingenious Arrangement

Put simply, the innovative light-harvesting antenna from Würzburg consists of four different merocyanine dyes that are folded and thereby stacked closely together. The elaborate arrangement of the molecules enables ultra-fast and efficient energy transport within the antenna.

The researchers have given the prototype of the new light-harvesting system the name URPB. The letters stand for the light wavelengths that are absorbed by the four dye components of the antenna: U for ultraviolet, R for red, P for purple, B for blue.

Proven Performance Via Fluorescence

The researchers have demonstrated that their novel light-collecting system works so well by measuring the so-called fluorescence quantum yield. This involves measuring how much energy the system emits in the form of fluorescence. This allows conclusions to be drawn about the amount of light energy that it has previously collected.

The result: the system converts 38 per cent of the irradiated light energy over a broad spectral range into fluorescence — the four dyes on their own, on the other hand, manage less than one per cent to a maximum of three per cent. The right combination and skilful spatial arrangement of dye molecules in the stack therefore make a big difference.

For the Cornell researchers trying to date the famous Hellenistic-era Kyrenia shipwreck, which was discovered and recovered off the north coast of Cyprus in the 1960s, the real treasure was not gold coins, but thousands of almonds found in jars among the cargo.

The almonds, combined with newly cleaned wood samples and the team’s modeling and radiocarbon-dating expertise, led the Cornell Tree-Ring Laboratory to identify the likeliest timeline of the Kyrenia’s sinking as between 296-271 BCE, with a strong probability it occurred between 286-272 BCE.

The team’s paper, “A Revised Radiocarbon Calibration Curve 350-250 BCE Impacts High-Precision Dating of the Kyrenia Ship,” will publish June 26 at 2 pm ET in PLoS ONE. The lead author is Sturt Manning, Distinguished Professor of Arts and Sciences in Classical Archaeology in the College of Arts and Sciences.

The Kyrenia has a storied legacy as the first major Greek Hellenistic-period ship to be found, in 1965, with a largely intact hull. From 1967-69, it was excavated along with its cargo, which included hundreds of ceramic vessels, then reassembled offsite and scientifically studied.

“Kyrenia was one of the first times it was realized this type of rich evidence from the classical world could be found largely intact more than 2,000 years later on the seabed, if you could find it,” said Sturt Manning. “It was a bit of a landmark moment, the idea that you actually could dive, excavate and bring up a classical-era ship and so discover this long-past world directly. Shipwrecks are unique time capsules, and you can get amazing preservation.”

For the last six decades, the Kyrenia has provided archeologists and historians with key insights into the development of ancient ship technology, construction practices and maritime trade. To date, no fewer than three Kyrenia replicas have been produced and launched, and these reconstructions have yielded considerable information on ancient ships and their sailing performance. However, the timeline of the Kyrenia’s provenance and the exact date of its sinking has always been vague at best. The initial efforts to date the ship were based on its recovered artifacts, such as the pottery on board and a small batch of coins, which initially led researchers to estimate the ship was built and sank in the later 300s BCE.

“Classical texts and finds at port sites already told us this era was significant for widespread maritime trade and connections all around the Mediterranean — an early period of globalization,” Manning said. “But the discovery of the Kyrenia ship, just under 15 meters long, likely with a crew of four, dramatically made this all very immediate and real. It yielded key insights into the practicalities of the earlier part of a millennium of intense maritime activity in the Mediterranean, from Greek through Late Antique times.”

The first volume of the final publication of the Kyrenia ship project, released last year, argued the wrecking date was a little later, closer to 294-290 BCE, but the primary piece of evidence — a poorly preserved, nearly illegible coin — was not watertight.

Manning’s team, which included co-authors Madeleine Wenger ’24 and Brita Lorentzen, ’06, Ph.D. ’15, sought to secure a date.

The perils of polyethylene glycol

The biggest hurdle for accurately dating the Kyrenia has been another artifact, one from the 20th century: polyethylene glycol (PEG). Excavators and preservationists often applied the petroleum-based compound to waterlogged wood to prevent it from decomposing after it was lifted out of the ocean’s oxygen-free environment.

“PEG was a standard treatment for decades. The trouble is it’s a petroleum product,” Manning said, “which means that if you’ve got PEG in the wood, you have this contamination from ancient fossil carbon that makes radiocarbon dating impossible.”

Manning’s team worked with researchers at the University of Groningen in the Netherlands to develop a new method to clean PEG out of wood, and they demonstrated it on PEG-treated Roman-era samples from Colchester, England, that already had established dendrochronological (tree-ring sequence) dates.

“We removed the PEG from the wood, we radiocarbon dated it and we showed that in each case, we got a radiocarbon age consistent with the real (known) age,” Manning said. “We basically got 99.9% of the PEG removed.”

They used that technique to remove PEG from a Kyrenia sample that Manning and collaborators had tried, and failed, to accurately date 10 years ago. The team also now dated a tiny, twisted piece of wood that was salvaged from the Kyrenia in the late 1960s but was too small to be included in the reconstruction, thus avoiding PEG-treatment. It subsequently sat in a jar of water in a museum for 50-odd years.

The dates showed that the most recent preserved tree-rings from these timbers grew in the mid-later 4th century BCE. Because the samples did not include bark, the researchers couldn’t determine the exact date the original trees were felled, but could say the date was likely after approximately 355-291 BCE.

Organic evidence

Working with the Kyrenia’s original excavation team, the researchers examined its various artifacts, including the pottery and coins, with a focus on organic materials, including an astragalus (a sheep or goat ankle bone once used for games and divining rituals in several ancient cultures) and thousands of fresh green almonds found in some of the large amphorae, i.e., ceramic jars. These “short-lived” sample materials helped define the date of the ship’s last voyage.

The team applied combined statistical modeling with the dendrochronology of the wood samples to get a level of dating that was much more precise than previous efforts. The modeling identified the most likely range of dates for the final voyage to be between 305-271 BCE (95.4% probability) and 286-272 BCE (68.3% probability) — several years more recent than current estimations.

But there was one big hiccup along the way. The new dates didn’t align with the international radiocarbon calibration curve, which is based on known-age tree-rings and is used to convert radiocarbon measurements into calendar dates for the northern hemisphere.

Manning took a closer look at data behind the calibration curve, which has been assembled over many decades by dozens of labs and hundreds of scientists. He discovered that the period between 350 and 250 BCE had no modern accelerator mass spectrometry (AMS) radiocarbon data behind it. Instead, the calibration curve in this period relied on only a few measurements conducted in the 1980s and 1990s using an older type of radiocarbon-dating technology. With collaborators in the U.S. and the Netherlands, the team measured known-age single-year sequoia and oak samples to re-calibrate the curve for the period 433-250 BCE. That not only helped clarify a big spike in radiocarbon production caused by a minimum of solar activity centered around 360 BCE, but also led to important revisions to the curve in the period around 300 BCE — improvements that were critical to dating the Kyrenia.

Manning anticipates the new findings will not only clarify the timeline of the Kyrenia and its cargo but will also help researchers using the calibration curve for very different projects.

“This revised curve 400-250 BCE now has relevance to other problems that researchers are working on whether in Europe or China or somewhere else in the northern hemisphere,” he said. “Half of the people who cite the paper in the future will be citing the fact that we’ve revised the radiocarbon calibration curve in this period, and only half will be saying the Kyrenia shipwreck is really important and has a much better date.”

Co-authors include researchers from the Oxford Dendrochronology Laboratory, the University of Groningen and the University of California, Irvine.

A new study in the journal Science Advances, conducted by a team of international researchers, has uncovered a biological explanation for long-term memories. It centers on the discovery of the role of a molecule, KIBRA, that serves as a “glue” to other molecules, thereby solidifying memory formation.

“Previous efforts to understand how molecules store long-term memory focused on the individual actions of single molecules,” explains André Fenton, a professor of neural science at New York University and one of the study’s principal investigators. “Our study shows how they work together to ensure perpetual memory storage.”

“A firmer understanding of how we keep our memories will help guide efforts to illuminate and address memory-related afflictions in the future,” adds Todd Sacktor, a professor at SUNY Downstate Health Sciences University and one of the study’s principal investigators.

It’s been long-established that neurons store information in memory as the pattern of strong synapses and weak synapses, which determines the connectivity and function of neural networks. However, the molecules in synapses are unstable, continually moving around in the neurons, and wearing out and being replaced in hours to days, thereby raising the question: How, then, can memories be stable for years to decades?

In a study using laboratory mice, the scientists focused on the role of KIBRA, or kidney and brain expressed protein, the human genetic variants of which are associated with both good and poor memory. They focused on KIBRA’s interactions with other molecules crucial to memory formation — in this case, protein kinase Mzeta (PKMzeta). This enzyme is the most crucial molecule for strengthening normal mammalian synapses that is known, but it degrades after a few days.

Their experiments reveal that KIBRA is the “missing link” in long-term memories, serving as a “persistent synaptic tag,” or glue, that sticks to strong synapses and to PKMzeta while also avoiding weak synapses.

“During memory formation the synapses involved in the formation are activated — and KIBRA is selectively positioned in these synapses,” explains Sacktor, a professor of physiology, pharmacology, anesthesiology, and neurology at SUNY Downstate. “PKMzeta then attaches to the KIBRA-synaptic-tag and keeps those synapses strong. This allows the synapses to stick to newly made KIBRA, attracting more newly made PKMzeta.”

More specifically, their experiments in the Science Advances paper show that breaking the KIBRA-PKMzeta bond erases old memory. Previous work had shown that randomly increasing PKMzeta in the brain enhances weak or faded memories, which was mysterious because it should have done the opposite by acting at random locations, but the persistent synaptic tagging by KIBRA explains why the additional PKMzeta was memory enhancing, by only acting at the KIBRA tagged sites.

“The persistent synaptic tagging mechanism for the first time explains these results that are clinically relevant to neurological and psychiatric disorders of memory,” observes Fenton, who is also on the faculty at NYU Langone Medical Center’s Neuroscience Institute.

The paper’s authors note that the research affirms a concept introduced in 1984 by Francis Crick. Sacktor and Fenton point out that his proposed hypothesis to explain the brain’s role in memory storage despite constant cellular and molecular changes is a Theseus’s Ship mechanism — borrowed from a philosophical argument stemming from Greek mythology in which new planks replace old ones to maintain Theseus’s Ship for years.

“The persistent synaptic tagging mechanism we found is analogous to how new planks replace old planks to maintain Theseus’s Ship for generations, and allows memories to last for years even as the proteins maintaining the memory are replaced,” says Sacktor. “FrancisCrick intuited this Theseus’s Ship mechanism, even predicting the role for a protein kinase. But it took 40 years to discover that the components are KIBRA and PKMzeta and to work out the mechanism of their interaction.”

The study also included researchers from Canada’s McGill University, Germany’s University Hospital of Münster, and University of Texas Medical School at Houston.

This work was supported by grants from the National Institutes of Health (R37 MH057068, R01 MH115304, R01 NS105472, R01 MH132204, R01 NS108190), the Natural Sciences and Engineering Research Council of Canada Discovery (203523), and the Garry and Sarah S. Sklar Fund.

A Combination of Novel Techniques Solves the Enigma

Using innovative multidisciplinary tools, the research team co-led by Gerard Talavera from the Institut Botànic de Barcelona (IBB, CSIC-CMCNB), Tomasz Suchan from the W. Szafer Institute of Botany, and Clément Bataille, associate professor inthe Department of Earth and Environmental Sciences at the University of Ottawa — with Megan Reich, a postdoctoral researcher from the Department of Biology at uOttawa, Roger Vila and Eric Toro Delgado, scientists from the Institute of Evolutionary Biology (IBE, CSIC-UPF) and Naomi Pierce, a professor of Biology in the Department of Organismic and Evolutionary Biology at Harvard University — embarked on a scientific mission to track the journey and origin of those mysterious Painted Ladies.

First, the research team reconstructed wind trajectories for the period preceding the arrival of these butterflies in October 2013. They found exceptionally favorable wind conditions that could support a transatlantic crossing from western Africa, opening the possibility that those individuals might have flown across the entire ocean.

After sequencing the genomes of these individuals and analyzing them in comparison to populations globally, researchers discovered that the butterflies had a closer genetic relatedness to African and European populations. This result eliminated the likelihood of these individuals coming from North America, thereby reinforcing the hypothesis of an oceanic journey.

Researchers leveraged a unique combination of next-generation molecular techniques. They sequenced the DNA of pollen grains carried by these butterflies. They identified two species of plants that only grow in tropical Africa indicating that the butterflies nectared on African flowers before engaging into their transatlantic journey. They analyzed hydrogen and strontium isotopes in the butterflies’ wings, a chemical signal that acts as a “fingerprint” of the region of natal origin. Combining isotopes with a model of habitat suitability for larval growth revealed potential natal origin in western Europe, possibly France, Ireland, the United Kingdom, or Portugal.

Dr. Bataille underlines the methodological novelty of this study: “It is the first time that this combination of molecular techniques including isotope geolocation and pollen metabarcoding is tested on migratory insects. The results are very promising and transferable to many other migratory insect species. The technique should fundamentally transform our understanding of insect migration.”

“We usually see butterflies as symbols of the fragility of beauty, but science shows us that they can perform incredible feats. There is still much to discover about their capabilities,” emphasizes Roger Vila, a researcher at the Institute of Evolutionary Biology (CSIC-Pompeu Fabra University) and co-author of the study.

Buoyed by the Winds

The researchers assessed the viability of a transatlantic flight by analyzing the energy expenditure for the journey. They predicted that the flight over the ocean, lasting 5 to 8 days without stops, was feasible due to advantageous wind conditions. “The butterflies could only have completed this flight using a strategy alternating between active flight, which is costly energetically, and gliding the wind. We estimate that without wind, the butterflies could have flown a maximum of 780 km before consuming all their fat and, therefore, their energy,” comments Eric Toro-Delgado, one of the article’s co-authors.

The Saharan air layer is emphasized by researchers as a significant aerial route for dispersion. These wind currents are known to transport large amounts of Saharan dust from Africa to America, fertilizing the Amazon. This study now shows that these air currents are capable of transporting living organisms.

The Potential Impact of Migrations in the Context of Global Change

This finding indicates that natural aerial corridors connecting continents may exist, potentially facilitating the dispersal of species on a much larger scale than previously imagined.

“I think this study does a good job of demonstrating how much we tend to underestimate the dispersal abilities of insects. Furthermore, it’s entirely possible that we are also underestimating the frequency of these types of dispersal events and their impact on ecosystems,” comments Megan Reich, a Postdoctoral Fellow at the University of Ottawa who also coauthored the study.

Gerard Talavera, the study’s lead researcher, adds, “Throughout history, migratory phenomena have been important in defining species distributions as we observe them today.”

Researchers emphasize that due to global warming and changing climate patterns, we may witness more notable changes and a potential increase in long-distance dispersal events. This could significantly impact biodiversity and ecosystems worldwide. “It is essential to promote systematic monitoring routines for dispersing insects, which could help predict and mitigate potential risks to biodiversity resulting from global change,” concludes Gerard Talavera.