"Mystery Solved?" --Transition from Chemistry to Biology 4-Billion Years Ago. In the beginning, there were simple chemicals that produced amino acids that eventually became the proteins necessary to create single cells, which became plants and animals. Recent research is revealing how the primordial soup created the amino acid building blocks, and there is widespread scientific consensus on the evolution from the first cell into plants and animals. But it's still a mystery how the building blocks were first assembled into the proteins that formed the machinery of all cells.
Now, two long-time University of North Carolina scientists - Richard Wolfenden, PhD, and Charles Carter, PhD - have shed new light on the transition from building blocks into life some 4 billion years ago. Wolfenden and Carter argue that RNA did not work alone; in fact, it was no more likely that RNA catalyzed peptide formation than it was for peptides to catalyze RNA formation. The finding adds a new layer to the story of how life evolved billions of years ago. "Dr. Origins of Life On Earth & Beyond --"From Matter to Living Biology" (Weekend Feature)
What is the recipe for life? If you were to build a cell from scratch, what ingredients would you need? And what kind of environment would you need to cook inanimate matter into a living cell? These are the questions that occupy Harvard biochemist Jack Szostak, as he imagines the dynamic world where life was born. What Szostak is interested in finding out is how many different recipes there are for making life. How did life arise here on Earth, and might some other planet build life in a different way?
"We're looking at a very narrow slice of the whole problem," Szostak says. In his laboratory, Szostak re-creates the chemistry of the early Earth, the planet before life began, in order to see how life's basic building blocks-- lipids, nucleotides and amino acids -- first assembled into larger structures such as membranes, RNA molecules and peptides. But in the beginning, there were no proteins: So how did cells evolve to create them? The Daily Galaxy via origins.harvard.edu. DNA's Ability to Survive Extreme Conditions of Space --"Has Implications in Search for Extraterrestrial Life"
“This study provides experimental evidence that the DNA’s genetic information is essentially capable of surviving the extreme conditions of space and the re-entry into Earth’s dense atmosphere,” says study head Oliver Ullrich from the University of Zurich’s Institute of Anatomy. This extraordinary stability of DNA under space conditions also needs to be factored into the interpretion of results in the search for extraterrestrial life: “The results show that it is by no means unlikely that, despite all the safety precautions, space ships could also carry terrestrial DNA to their landing site. We need to have this under control in the search for extraterrestrial life,” points out Ullrich. Applied to the outer shell of the payload section of a rocket using pipettes, small, double-stranded DNA molecules flew into space from Earth and back again.
The experiment called DARE (DNA atmospheric re-entry experiment) resulted from a spontaneous idea: UZH scientists Dr. Cosmic Puzzle Solved? --"Why Every Organism on Earth is a Right-handed Double Helix" New research by University of Nebraska-Lincoln physicists and published in the Sept. 12 online edition of Physical Review Letters now gives support to a long-posited but never-proven hypothesis that electrons in cosmic rays -- which are mostly left-handed -- preferentially destroyed left-handed precursors of DNA on the primordial Earth.
Joan M. Dreiling and Timothy J. Gay of UNL focused circularly polarized laser light on a specially prepared crystal of gallium-arsenide to produce electrons whose spins were either parallel or anti-parallel to their direction of motion upon emission from the crystal -- essentially artificial beta rays. They then directed these electrons to strike target molecules of a substance called bromocamphor, which comes in both right- and left-handed varieties. They found that at the lowest electron energies they studied, left-handed electrons preferentially destroyed left-handed molecules and vice versa. "This has been an incredibly hard experiment," he said. "Sunlight in Titan's Lower Atmosphere can Kick-Start Complex Organic Chemistry" --NASA JPL. "Scientists previously thought that as we got closer to the surface of Titan, the moon's atmospheric chemistry was basically inert and dull," said Murthy Gudipati, the paper's lead author at JPL.
"Our experiment shows that's not true. The same kind of light that drives biological chemistry on Earth's surface could also drive chemistry on Titan, even though Titan receives far less light from the sun and is much colder. Titan is not a sleeping giant in the lower atmosphere, but at least half awake in its chemical activity. " Scientists have known since NASA's Voyager mission flew by the Saturn system in the early 1980s that Titan, Saturn's largest moon, has a thick, hazy atmosphere with hydrocarbons, including methane and ethane. These simple organic molecules can develop into smog-like, airborne molecules with carbon-nitrogen-hydrogen bonds, which astronomer Carl Sagan called "tholins. " The image below shows Titan's atmosphere, captured by the Cassini spacecraft. Image credit: NASA APOD. The Emergence of Life on Wet, Rocky Sunlit Planets --NASA JPL Science. RNA --Does It Harbor a Clue to the Origin of Life on Earth?
How did life on Earth begin? An giant step toward solving this puzzle was taken in the 1980's with the Nobel Prize–winning discovery by Tom Cech and Sidney Altman that RNA, the sister molecule of DNA, can catalyze certain chemical reactions inside cells, a job previously thought to be the exclusive domain of proteins. Until their discovery, RNA was thought to have just one function: storing the genetic information cells need to build proteins. This new revelation about RNA's dual role suggested to some scientists, including Harvard's Jack Szostak, that RNA likely existed long before DNA or proteins because it might be able to catalyze its own reproduction. Their discovery made it easier to think about how life began, Szostak says. "They inspired me to try to think of ways to make RNAs in the lab that could catalyze their own replication.
" Szostak and his team is working to recreate a hypothetical model of this process in the laboratory. The Daily Galaxy via hhmi.org. "Entire Solar Systems are Needed to Kick-Start Life" (A 2013 Most Popular) There is evidence that life on Earth could not have started without the other planets. The conditions on the prehistoric Earth would only have served to inhibit the formation of RNA. Mars, on the other hand, would have been just right. While there was some water on ancient Mars, there wouldn't have been enough to hamper the formation of RNA. Also, while the early Earth was starved of oxygen, Mars would have had enough to create oxidized molybdenum and boron, which are pivotal in the construction of RNA.
Autogenic forms are probably more widespread than life in the Universe as they can be constructed from many different materials. It's a generic type of chemistry which may be similar throughout the Universe, indicating that the process is more important that than the molecules themselves. The iamge below shows a microtubule in a cell --an example where something in life is created spontaneously with self assembly. The origin of life on Earth is still a hotly-debated topic. MIT Zooms in on 3-D Enigmas of RNA --"Not Obeying Rules of Thermodynamics in Living Cells" DNA stores the information of life, proteins provide the action, and in between sits elusive RNA, which serves both as a database of information and as a molecular machine. In the 1980's Walter Gilbert of Harvard coined the term RNA World, a primitive version of life on Early Earth that used RNA as both a catalyst and carrier of genetic information, which later evolved into a more efficent version in which DNA stored genetic information and proteins became the primary catalysts.
RNA is more flexible than DNA, and its three-dimensional structures are more complex than proteins. When studied in the laboratory, RNA bends into so many convolutions that it is nearly impossible to tease out which folds are worthy of scientific inquiry and which can safely be ignored. “There’s much that’s uncertain about RNA,” says co-author Manolis Kellis, an associate professor of computer science at MIT. Similar to proteins, RNA folds into 3-D structures that carry out complex molecular functions. "How Did Life Begin on Earth?" --A New Theory Embraces the Cosmic through Geological, Chemical, and Biological Stages. “When the Earth formed some 4.5 billion years ago, it was a sterile planet inhospitable to living organisms,” said Sankar Chatterjee, Horn Professor of Geosciences and curator of paleontology at the Museum of Texas Tech University.
“It was a seething cauldron of erupting volcanoes, raining meteors and hot, noxious gasses. One billion years later, it was a placid, watery planet teeming with microbial life – the ancestors to all living things.” “For may years, the debate on the origins of life centered on the chemical evolution of living cells from organic molecules by natural processes. Chatterjee said life began in four steps of increasing complexity – cosmic, geological, chemical and biological. By studying three sites containing the world’s oldest fossils, he believes he knows how the first single-celled organisms formed in hydrothermal crater basins. Larger meteorites that created impact basins of about 350 miles in diameter inadvertently became the perfect crucibles, he said.
Meteorite Contains Extraterrestrial Organic Molecules Never Found Before. Meteorite hunters found fragments of the rock, identified by the "fusion crust" that forms when it burns in the atmosphere. NASA and the SETI Institute in Mountain View, California, also mobilised a search team of about 30 scientists to search for the small black rocks. The meteorite turned out to be a very rare type of rock called CM chondrite, which makes up less than 1 per cent of the meteorites that fall to Earth.
According to Bill Cooke of NASA's Meteoroid Environment Office at the Marshall Space Flight Center in Huntsville, Alabama, it is not clear whether it is rare because it easily burns up in the atmosphere or there are just fewer of these rocks in space. The meteorite has now led to an important discovery concerning the possible inventory of molecules available to the early Earth. Coincidentally, Sutter’s Mill is also the gold discovery site that led to the 1849 California Gold Rush. “The test will be to measure calcium 48,” Dauphas said. The Daily Galaxy via ASU. Minerals Essential for Life on Earth Came from Mars --New Evidence.
“The evidence seems to be building that we are actually all Martians; that life started on Mars and came to Earth on a rock,” says Steven Benner of the Westheimer Institute for Science and Technology. “It’s lucky that we ended up here nevertheless, as certainly Earth has been the better of the two planets for sustaining life. If our hypothetical Martian ancestors had remained on Mars, there might not have been a story to tell. In addition, recent studies show that these conditions, suitable for the origin of life, may still exist on Mars. " Speaking at the at the annual Goldschmidt conference, Benner told geochemists that an oxidized mineral form of the element molybdenum, which may have been crucial to the origin of life, could only have been available on the surface of Mars and not on Earth. “It’s only when molybdenum becomes highly oxidized that it is able to influence how early life formed,” said Benner. The Water Paradox: water is commonly believed to be essential for life.
Searching for DNA on Mars & Beyond --New MIT Chip for Future Life-Detecting Missions. If there is life on Mars, it’s not too farfetched to believe that such Martian species may share genetic roots with life on Earth, based on RNA or DNA because more than 3.5 billion years ago, a blitz of meteors ricocheted around the solar system, passing material between the two fledgling planets. This may have left bits of Earth on Mars, and vice versa, creating a shared genetic ancestry between the two planets. Chris McKay, a planetary scientist with the Space Science Division of NASA’s Ames Research Center, says a radiation-resilient DNA-sequencing chip is a promising candidate for future life-detecting missions to Mars and other planets. This search is the focus for Christopher Carr, a research scientist in MIT’s Department of Earth, Atmospheric and Planetary Sciences, who's building a DNA sequencer that he hopes will one day be sent to Mars, where it can analyze soil and ice samples for traces of DNA and other genetic material.
Source: Christopher E. Comet Impacts on Early Earth Catalyst for Building Blocks for Life. "Why Don’t We See New Life Forms Today?" --New Research Provides Clue. Disappearance of the Earliest Manifestation of Life on Earth --Solved! "Titan's Atmosphere Points to Building Blocks of Life" --NASA Astrobiology. "Scientists previously thought that as we got closer to the surface of Titan, the moon's atmospheric chemistry was basically inert and dull," said Murthy Gudipati, the paper's lead author at JPL. "Our experiment shows that's not true. The same kind of light that drives biological chemistry on Earth's surface could also drive chemistry on Titan, even though Titan receives far less light from the sun and is much colder.
Titan is not a sleeping giant in the lower atmosphere, but at least half awake in its chemical activity. " Scientists have known since NASA's Voyager mission flew by the Saturn system in the early 1980s that Titan, Saturn's largest moon, has a thick, hazy atmosphere with hydrocarbons, including methane and ethane. These simple organic molecules can develop into smog-like, airborne molecules with carbon-nitrogen-hydrogen bonds, which astronomer Carl Sagan called "tholins. " RNA --"DNA's Messenger or the Origin of Life on Earth?" (Weekend Feature) Many biologists still view RNA as a messenger to shutlle inforamtion from DNA to the cell's protein manufacturing centers, ribosomes.
Like DNA, RNA is a string of four different kinds of nucleotide building blocks, except that RNA has a single chain rather than DNA's iconic double helix that uses a different sugar in its molecular architecture, and substitutes uracil instead of thymine. However, unlike DNA, RNA is capable of carrying both genetic information and getting metabolic work done making it the "" molecule capabable of both reproducing itself and carrying the code to guide the needed copying. Some bacterial cells can swim, morph into new forms and even become dangerously virulent - all without initial involvement of DNA. In 2009, Yale University researchers discovered how bacteria accomplish this amazing feat - and in doing so provided a glimpse of what the earliest forms of life on Earth may have looked like. The answer is what Breaker and other researchers call the RNA World.
Did Comets Deliver Amino Acids Needed for the Origin of Life on Earth? (Weekend Feature) The team created experiments with powerful laboratory "guns" and computer models that replicated the conditions that existed inside comets that hit Earth's atmosphere at almost 25,000 miles per hour and crashed down upon the surface. The research is part of a broader scientific effort to understand how amino acids and other ingredients for the first living things appeared on a planet that billions of years ago was barren and desolate. Amino acids make up proteins, which are the workhorses of all forms of life, ranging from microbes to people. "Our research shows that the building blocks of life could, indeed, have remained intact despite the tremendous shock wave and other violent conditions in a comet impact," Blank said.
"Comets really would have been the ideal packages for delivering ingredients for the chemical evolution thought to have resulted in life. We like the comet delivery scenario because it includes all of the ingredients for life — amino acids, water and energy. " Clues to the Origin of Carbohydrates --The Building Blocks of DNA and RNA. New Insights into Messenger RNA --"Biology's Most Important Molecule" New Clue to the Chemical Origins of Carbohydrates --The building blocks of DNA and RNA.
Messenger RNA Discovery: "Biology's Most Important Molecule" --Built-in 'Clock' Causes Its Ultimate Death. Did Life on Earth Emerge from Non-organic Matter? "DNA's Messenger": Harvard/MIT Researchers Discover RNA Lifecycle Key to Disease. "Was It the Origin of Life"? Biologists Create Self-replicating RNA Molecule.