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Understanding Life's Origins: NASA Research Delves into Molecular Mysteries

Published November 25, 2024
2 months ago

In the quest to understand the origins of life on Earth, scientists have consistently been baffled by one peculiar characteristic: life's preference for molecules of a specific orientation, known as homochirality. A recent study funded by NASA, and detailed in Nature Communications, has added another layer of complexity to this enigma, suggesting that the routes to life’s building blocks might be less predetermined than previously assumed.





At the heart of biological activity is DNA, which directs the synthesis of proteins, the molecular machines essential for life. Proteins are composed of 20 different amino acids arranged in numerous sequences to fulfill various functions. Interestingly, while amino acids can exist in two mirror-image forms (left-handed and right-handed), life as we know it predominantly uses the left-handed versions.


The study led by Irene Chen from the University of California, Los Angeles, and her team delved into the RNA world hypothesis, which posits that RNA, a molecule similar to DNA, could have originally catalyzed the formation of proteins before the evolution of DNA. The research investigated whether RNA had an inherent bias toward producing left-handed amino acids, which might explain life's current chiral preferences.


Through meticulous experiments that replicated what might have been the conditions of early Earth, Chen's group analyzed the behavior of ribozymes—RNA molecules that can catalyze chemical reactions. The team tested various ribozyme combinations to determine their preference in synthesizing the amino acid phenylalanine in either its left-handed or right-handed form.


Contrary to what might have been expected, the results revealed that ribozymes could equally favor the creation of both left- and right-handed amino acids. This suggests that RNA did not inherently lean towards producing the left-handed amino acids dominating in today’s proteins. "The experiment demonstrated that RNA worlds, in general, would not necessarily have a strong bias for the form of amino acids we observe in biology now," stated Chen in her report.


The implications of these findings are profound. They suggest that life’s homochirality, the uniform use of left-handed amino acids, might not be a result of chemical determinism but could have emerged through evolutionary pressures over billions of years.


Supporting this inquiry, Jason Dworkin from NASA’s Goddard Space Flight Center highlighted the broader implications for astrobiology. The study of life’s chemical properties extends beyond Earth, aiding the search for life across the solar system. Dworkin, involved in analyzing samples from the asteroid Bennu via NASA’s OSIRIS-REx mission, underscored the importance of understanding molecular chirality in recognizing potential extraterrestrial life signatures.


As researchers continue to decipher life’s earliest molecular orientations, these insights not only deepen our understanding of life on Earth but also refine our strategies in the ongoing search for life in the cosmos.


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