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Boston Globe
2 days ago
- Science
- Boston Globe
Franklin W. Stahl, 95, dies; helped create a ‘beautiful' DNA experiment
Dr. Stahl's name and that of his collaborator, Matthew Meselson, were immortalized by the Meselson-Stahl Experiment, which is referenced in biology textbooks and taught in molecular genetics courses worldwide. In 2015, 'Helix Spirals,' a musical tribute to the experiment, was composed by Augusta Read Thomas and performed by a string quartet in Boston. Get Starting Point A guide through the most important stories of the morning, delivered Monday through Friday. Enter Email Sign Up The two biologists proved a theory advanced by Nobel Prize winners James Watson and Francis Crick, who discovered DNA's helical structure in 1953. Watson and Crick posited in the journal Nature that DNA replicates in a so-called semi-conservative fashion. Advertisement In 1958, Meselson and Dr. Stahl, postdoctoral fellows in Linus Pauling's laboratory at the California Institute of Technology in Pasadena, proved that Watson and Crick were correct, by using an experiment that was celebrated for its design, execution, and results. 'It has been termed the most beautiful experiment in biology, and rightfully so,' Diana Libuda, an associate professor of biology at the University of Oregon and a member of the Institute of Molecular Biology there, said in an interview. Advertisement The experiment demonstrated that after DNA unwinds and is replicated, each new DNA molecule contains one original, or parental, strand and one newly copied strand. Dr. Stahl and Meselson proved this by using E. coli bacteria, which reproduce rapidly. Because nitrogen is a crucial component of DNA, the two scientists propagated the bacteria over multiple generations in a medium containing heavy nitrogen, which was absorbed by the bacteria and integrated into their DNA. The bacteria were subsequently transferred to a medium containing the normal isotope of nitrogen. With the two types of nitrogen now in the medium, Dr. Stahl and Meselson could trace the production of new DNA strands. The experiment provided powerful evidence that DNA is replicated semi-conservatively, which means that each new DNA molecule is a hybrid, composed of one old strand and one newly made strand. That finding was considered a landmark discovery. Their results were published in Proceedings of the National Academy of Sciences in 1958. The Meselson-Stahl experiment has since been praised as a model of simplicity and innovation. 'Watson and Crick had produced a pretty model, but had no hard data,' Andy Stahl said. 'But that's what the Meselson-Stahl Experiment did: It proved how DNA replicates.' In 2020, Meselson, an emeritus professor of molecular biology and genetics at Harvard University, discussed each of the experiment's steps in a video produced by iBiology, part of the nonprofit Science Communication Lab in Berkeley, Calif. Reminiscing in the video about the intellectual freedom at Caltech in the late 1950s, Meselson recalled an era of big ideas: 'We could do whatever we wanted. It was very unusual for such young guys to do such an important experiment. We had a wonderful house, a big house across the street from the lab. We talked about these experiments at almost every dinner. So we had this wonderful intellectual atmosphere.' Advertisement In the same video, Franklin Stahl marveled that he and Meselson had been able to achieve such definitive results. He noted that X-ray images of the centrifuged test medium unequivocally revealed the bands of DNA with light and heavy nitrogen, proving the helical molecule's semi-conservative replication. 'Most of the time, when you get an experimental result it doesn't speak to you with such clarity,' he said. 'These pictures of the DNA bands interpreted themselves.' Franklin William Stahl was born Oct. 28, 1929, in Needham. He was the only son of Oscar Stahl, who worked for the telephone company and fixed radios on the side to earn extra cash during the Great Depression, and Elinor (Condon) Stahl, who managed the home while Franklin and his sisters attended local schools. 'He wanted to go to Brown, but went to Harvard instead,' Andy Stahl said. 'He was a commuter student and could save money by living at home.' Franklin Stahl graduated from Harvard in 1951 with a bachelor's degree in biology. Later that year, he entered the University of Rochester, where he began work on a doctoral degree. He decided to specialize in genetics in 1952 after completing a short course at Cold Spring Harbor Laboratory, where he was introduced to bacteriophages, the viruses that infect bacteria. Also known simply as phages, the viruses are reliable tools in genetics and have been used to understand the genetic code and provide insight into how genes are regulated. Advertisement In Rochester, Dr. Stahl met Mary Morgan, a native of the city. They soon married, and she eventually became a research partner. Mary Morgan Stahl died in 1996. Dr. Stahl's research collaborator and former graduate student Henriette Foss then became his domestic partner; she died of Parkinson's disease in 2022. In addition to his son Andy, Dr. Stahl leaves a daughter, Emily Morgan, and eight grandchildren. Another son, Joshua Stahl, died in 1998. Dr. Stahl also had a prolific career as an author. He wrote 'The Mechanics of Inheritance,' published in 1964, and 'Genetic Recombination: Thinking About It in Phage and Fungi' in 1979. He was the recipient of two Guggenheim fellowships, one in 1975 and the other in 1985, the same year he was awarded a MacArthur fellowship. In 1996, Dr. Stahl received the Thomas Hunt Morgan Medal, an award given to scientists who have made major contributions to the field of genetics. This article originally appeared in
Yahoo
17-06-2025
- Science
- Yahoo
Half of ordinary matter in universe has long been 'missing.' Astronomers just found it.
Astronomers have long estimated that ordinary matter – basically, anything other than dark matter – makes up only a fraction of the known universe. The conclusion stemmed from a complex calculation involving observed light left over from the Big Bang roughly 13.8 billion years ago. But there was one major problem: they had no clue where about half of it was. Now, it seems as if a team of astronomers has finally tracked down that missing "ordinary" matter, which they discovered hiding as gas spread out in the vast expanses between galaxies. Revelations made possible by studying radio waves hurtling through space suggest that violent cosmic forces have played a role in the remote locations of almost all of the "missing" matter. "The question we've been grappling with was: Where is it hiding? The answer appears to be: in a diffuse wispy cosmic web, well away from galaxies," Harvard University astronomy Liam Connor, lead author of the study, told Reuters. Ordinary matter makes up everything from the cosmic (planets and stars) to the earthly (people and trees.) But it only accounts for about 15% of matter in all of the known universe. The vast majority of matter is dark – invisible until it is detected only through its gravitational effects. Unlike dark matter, ordinary matter emits light in various wavelengths, which allow it to easily be seen. Still, scientists have long struggled to account for where all of it is located since a large chunk of ordinary matter is spread so thin among galaxies and the vast spaces between them. For that reason, about half of ordinary matter has long been considered missing. Until now. Powerful bursts of radio waves emanating from 69 locations in the cosmos have helped researchers at long last find the missing matter. The discovery came from a team of astronomers at the California Institute of Technology and the Center for Astrophysics, a research institute jointly operated by the Harvard College Observatory and Smithsonian Astrophysical Observatory. The team studied brief, bright radio flashes in the distant cosmos, called fast radio bursts (FRBs), to illuminate the matter lying between the radio waves and Earth. Astronomers have been studying fast radio bursts from across the universe since 2007 when the first millisecond-long burst was discovered. The bright burst of electromagnetic radiation may be brief, but fast radio bursts are so powerful that they produce more energy than what our sun emits in an entire year, astronomers say. The 69 radio frequencies the team studied were located at distances ranging up to about 9.1 billion light-years from Earth – making the furthest one the most distant fast radio burst ever recorded. The previous record was a fast radio burst documented about 8 billion light-years away in 2023. By measuring how the light from the radio bursts spread and dispersed – not unlike how a prism turns sunlight into a rainbow – while traveling toward Earth, the astronomers were able to determine how much matter was in their path. "If you see a person in front of you, you can find out a lot about them," Vikram Ravi, a Caltech astronomer who coauthored the study, said in a statement. "But if you just see their shadow, you still know that they're there and roughly how big they are." The results revealed that about 75% of the universe's ordinary matter resides in the space between galaxies, also known as the intergalactic medium. How did it all end up in the middle of nowhere? Astronomers theorize it happens as gas is ejected from galaxies when massive stars explode in supernovas, or when supermassive black holes inside galaxies expel material after consuming stars or gas. The remaining 15% of the "missing" matter exists within either galaxies in the form of stars and cold galactic gas, or in the halos of diffuse material around them, according to the researchers. While this distribution is in line with predictions from advanced cosmological simulations, this is the first time it has been observed and confirmed, the researchers claim. The findings will help researchers better understand how galaxies grow. Caltech is also planning for its future deep-space radio telescope in the Nevada desert, the DSA-2000, to build upon the findings when it becomes operational. The radio array is being planned to detect up to 10,000 fast radio bursts per year. The findings were published June 16 in the journal Nature. Contributing: Reuters Eric Lagatta is the Space Connect reporter for the USA TODAY Network. Reach him at elagatta@ This article originally appeared on USA TODAY: Astronomers just found the universe's 'missing' matter: Here's how
USA Today
17-06-2025
- Science
- USA Today
Half of ordinary matter in universe has long been 'missing.' Astronomers just found it.
Half of ordinary matter in universe has long been 'missing.' Astronomers just found it. Revelations made possible by studying radio waves hurtling through space suggest that violent cosmic forces have played a role in the remote locations of almost all of the "missing" matter. Astronomers have long estimated that ordinary matter – basically, anything other than dark matter – makes up only a fraction of the known universe. The conclusion stemmed from a complex calculation involving observed light left over from the Big Bang roughly 13.8 billion years ago. But there was one major problem: they had no clue where about half of it was. Now, it seems as if a team of astronomers has finally tracked down that missing "ordinary" matter, which they discovered hiding as gas spread out in the vast expanses between galaxies. Revelations made possible by studying radio waves hurtling through space suggest that violent cosmic forces have played a role in the remote locations of almost all of the "missing" matter. "The question we've been grappling with was: Where is it hiding? The answer appears to be: in a diffuse wispy cosmic web, well away from galaxies," Harvard University astronomy Liam Connor, lead author of the study, told Reuters. What is 'missing' matter? Ordinary matter makes up everything from the cosmic (planets and stars) to the earthly (people and trees.) But it only accounts for about 15% of matter in all of the known universe. The vast majority of matter is dark – invisible until it is detected only through its gravitational effects. Unlike dark matter, ordinary matter emits light in various wavelengths, which allow it to easily be seen. Still, scientists have long struggled to account for where all of it is located since a large chunk of ordinary matter is spread so thin among galaxies and the vast spaces between them. For that reason, about half of ordinary matter has long been considered missing. What are fast radio bursts? Cosmic waves help measure matter Until now. Powerful bursts of radio waves emanating from 69 locations in the cosmos have helped researchers at long last find the missing matter. The discovery came from a team of astronomers at the California Institute of Technology and the Center for Astrophysics, a research institute jointly operated by the Harvard College Observatory and Smithsonian Astrophysical Observatory. The team studied brief, bright radio flashes in the distant cosmos, called fast radio bursts (FRBs), to illuminate the matter lying between the radio waves and Earth. Astronomers have been studying fast radio bursts from across the universe since 2007 when the first millisecond-long burst was discovered. The bright burst of electromagnetic radiation may be brief, but fast radio bursts are so powerful that they produce more energy than what our sun emits in an entire year, astronomers say. The 69 radio frequencies the team studied were located at distances ranging up to about 9.1 billion light-years from Earth – making the furthest one the most distant fast radio burst ever recorded. The previous record was a fast radio burst documented about 8 billion light-years away in 2023. By measuring how the light from the radio bursts spread and dispersed – not unlike how a prism turns sunlight into a rainbow – while traveling toward Earth, the astronomers were able to determine how much matter was in their path. "If you see a person in front of you, you can find out a lot about them," Vikram Ravi, a Caltech astronomer who coauthored the study, said in a statement. "But if you just see their shadow, you still know that they're there and roughly how big they are." Findings will help understand galaxy growth The results revealed that about 75% of the universe's ordinary matter resides in the space between galaxies, also known as the intergalactic medium. How did it all end up in the middle of nowhere? Astronomers theorize it happens as gas is ejected from galaxies when massive stars explode in supernovas, or when supermassive black holes inside galaxies expel material after consuming stars or gas. The remaining 15% of the "missing" matter exists within either galaxies in the form of stars and cold galactic gas, or in the halos of diffuse material around them, according to the researchers. While this distribution is in line with predictions from advanced cosmological simulations, this is the first time it has been observed and confirmed, the researchers claim. The findings will help researchers better understand how galaxies grow. Caltech is also planning for its future deep-space radio telescope in the Nevada desert, the DSA-2000, to build upon the findings when it becomes operational. The radio array is being planned to detect up to 10,000 fast radio bursts per year. The findings were published June 16 in the journal Nature. Contributing: Reuters Eric Lagatta is the Space Connect reporter for the USA TODAY Network. Reach him at elagatta@
Yahoo
13-06-2025
- Science
- Yahoo
Missing link star? Why this 'teenage vampire' white dwarf has scientists so excited
When you buy through links on our articles, Future and its syndication partners may earn a commission. Astronomers have discovered the "missing link" connecting the death of sunlike stars to the birth of white dwarf stellar remnants, in the form of a "teenage vampire" white dwarf. This vampire isn't interested in the blood that runs through your veins, though. The white dwarf in question, designated Gaia22ayj and located around 8,150 light-years from Earth, is ravenously feeding on stellar plasma from a companion star. The team that made this discovery observed the white dwarf using the Zwicky Transient Facility (ZTF) at the Palomar Observatory in California. The researchers scanned the night sky over the Northern Hemisphere, hunting "transients" — astronomical bodies undergoing rapid change. Gaia22ayj originally attracted the attention of astronomers with its rapidly pulsing signal, which led to it being classified as a detached double white dwarf binary — two white dwarf stars orbiting each other. However, this theory didn't quite match further observations of Gaia22ayj, which revealed it to be one of the most extreme pulsating objects ever seen, increasing in brightness by 700% over just a 2-minute span. That's because Gaia22ayj is actually a white dwarf feeding on a companion star, with this binary in a rare and short-lived phase of its life (or should that be death). Stars die after they use up the fuel needed for nuclear fusion. What kind of death, and afterlife, they experience depends on their mass. Stars with masses above eight times that of the sun die in violent supernova explosions and then become either highly dense neutron stars or black holes. Stars with masses closer to that of the sun don't "go nova," instead undergoing more muted transformations into white dwarfs. Our own sun will experience this latter transformation in around six billion years after shedding most of its mass during a swollen red giant phase, eventually sputtering out as a smoldering stellar ember. However, around half of all stars with masses similar to that of the sun have a binary companion star. And, if their companion stars get too close, white dwarfs can get a second burst of life by stripping them of stellar material. That vampiric mass transfer process is exactly what seems to be happening between the white dwarf of Gaia22ayj and its companion star. Gaia22ayj initially confused astronomers. The way that its light intensity varied over time — its light curve— made no sense for a detached double white dwarf binary. This led Tony Rodriguez, a graduate student in the California Institute of Technology's ZTF Stellar Group, to question why the light curve would take the shape it did. Gathering more data, Rodriguez and colleagues realized that Gaia22ayj is likely a white dwarf orbited by a "normal" low-mass star, not a second white dwarf. And they further determined that Gaia22ayj is highly magnetic, with its white dwarf component spinning at a rapid rate. This reminded them of a white dwarf pulsar, a highly magnetic dead star that sweeps electromagnetic radiation across the universe as it spins, like a cosmic lighthouse. However, the vampiric feeding process found in Gaia22ayj isn't something usually associated with white dwarf pulsars. The team eventually concluded that Gaia22ayj is a missing link in the life cycle of white dwarf pulsars, a rare and short-lived early phase of these objects. "We have already seen two infant systems, white dwarf stars in a binary system whose rapid spin builds up a strong magnetic field. And we had seen lots of adult star systems where the white dwarf star was spinning very slowly," Rodriguez said in a statement. "But this was the first star we've seen that is right in the middle of its 'teenage' phase, when it has already established a strong magnetic field and is just beginning to funnel matter from the companion star onto itself," he added. "We have never before caught a system in the act of spinning so rapidly but also slowing down dramatically, all while gaining mass from its companion." This discovery is even more exciting because this phase lasts for just around 40 million years. That might sound like an incredibly long period of time, but it's relatively short when considering that stars like the sun live for around 10 billion years before they even transform into white dwarfs. Thus, this "teenage phase" accounts for just 0.4% of a star's lifetime. For context, if the star were an average human, this teenage phase would last just around 107 days. Hardly enough time to paint your bedroom black. Related Stories: — Puffy white dwarfs could shed light on mysterious dark matter. Here's how. — White dwarfs are 'heavy metal' zombie stars endlessly cannibalizing their dead planetary systems — 'Daredevil' white dwarf star could be closest-known object to a weird black hole "The data taken at the W. M. Keck Observatory provided firm evidence that this system had a strong magnetic field and was funneling matter onto the white dwarf," Rodriguez said. "Additional data from the unique instruments available at Palomar Observatory showed that this system is, remarkably, slowing down." The team's research was published in February in the journal Publications of the Astronomical Society of the Pacific.
CNBC
10-06-2025
- Business
- CNBC
26. Iambic Therapeutics
Founders: Tom Miller (CEO), Fred ManbyLaunched: 2020Headquarters: San Diego, CaliforniaFunding: $220 millionValuation: N/AKey Technologies: Artificial intelligence, cloud computing, deep neural networks/deep learning, generative AI, machine learning, robotics, quantum computingIndustry: BiotechPrevious appearances on Disruptor 50 list: 0 It can take 10-15 years for today's biopharmaceutical companies to bring new drugs all the way through discovery and clinical trial. San Diego-based Iambic Therapeutics' AI-driven platform can accelerate the pace of drug discovery and development, enabling drug development in just a few years. The company has novel medications in its pipeline to treat breast cancer and other HER2 cancers, and recently formed a research collaboration with pharmaceutical giant Lundbeck for a small molecule therapeutic to treat migraines. By predicting how its new molecules will interact with human systems, Iambic's technology can also reduce the need for clinical trials. The company was originally called Entos, and was founded when CEO Thomas Miller, a theoretical chemist and professor at California Institute of Technology, teamed up with longtime collaborator Fred Manby. In its first iteration, the company worked on making better chemical predictions across many industries and worked with companies including Toyota and Procter & Gamble. But the founders saw applications for their work in what's called small molecule drug discovery. Small molecule drugs, often synthesized chemically, target specific proteins or cellular pathways. Iambic's platform for drug discovery is called Enchant. The company says it provides high-confidence predictions in data-poor situations, such as early-stage and clinical-stage drug programs. "(Cancer) is an area of huge need," Miller told an interviewer for the California Institute of Technology in 2022. "It's an incredibly fast, quickly advancing disease. Many people are afflicted by it. There's many varieties of it. It is the combination of those things that means that if you have the ability to design a new drug, there's a way to … have a relatively fast timescale to advance that to the point where it's in human trials." Rather than selling its drug-discovery services and software to pharmaceutical companies, Iambic has focused on producing its own drugs. "Instead of running around, trying to convince people that this software is so great, and they should buy it, you can actually just use it and execute with it, and actually make better molecules. Then those molecules can stand on their own two feet," Miller said. In 2024, Iambic completed a B round of funding, with investors including OrbiMed, Nvidia and Sequoia Capital, and announced a collaboration with Nvidia, which has been teaming up as a venture investor with many startups across sectors using AI, including, for example, agtech Disruptor Carbon Robotics. Iambic also moved into a new headquarters in San Diego last year and took its headcount to about 100, enabling the company to run experiments on thousands of newly discovered molecules each week. It also announced an update to NeuralPLexer, which predicts protein-ligand structures, and published data in Nature Machine Intelligence showing that NeuralPLexer outperformed AlphaFold, the Nobel Prize in Chemistry winner developed by Google's DeepMind. Iambic also hired its first CFO, Michael Secora, who previously worked at publicly held Recursion.
