Our prehistoric Earth, bombarded with asteroids and lightening, rife with bubbling geothermal pools, may not seem hospitable today. Men et…
Our prehistoric Earth, bombarded with asteroids and lightening, rife with bubbling geothermal pools, may not seem hospitable today. Men et sted i den kemiske kaos fra vores tidlige planet, life did form. How? For decades, scientists have attempted to create miniature replicas of infant Earth in the lab. There, they hunt for the primordial ingredients that created the essential building blocks for life.
It’s attractive to chase our origin story. Men dette pursuit kan bringe mere end bare thrill. Knowledge of how Earth built its first cells could inform our search for extraterrestrial life. Ef við þekkjum innihaldsefnin og umhverfið sem þarf til að sparka spontan lífi, gætum við leitað að svipuðum aðstæðum á plánetum um allan heim.
Today, much of the origin-of-life research focuses on one specific building block: RNA. Mens nogle forskere tror at livet dannet fra enklere molekyler og først senere evolved. RNA, others look for evidence to prove (or disprove) that RNA formed first. A complex but versatile molecule, RNA stores and transmits genetic information and helps synthesize proteins, making it a capable candidate for the backbone of the first cells.
To verify this “RNA World Hypothesis,” researchers face two challenges. Først skal de identificere hvilke ingredienser der er dannet for at skabe RNA’s four nucleotides ̵
1; adenine, guanine, cytosine, and uracil (A, G, C, and U). And, second, they need to determine how RNA stored and copied genetic information in order to replicate itself.
So far, scientists have made significant progress finding precursors to C and U. But A and G remain elusive. Now, in a paper published in PNAS Jack W. Szostak, Professor of Chemistry and Chemical Biology at Harvard University, along with first-author and graduate student Seohyun (Chris) Kim suggests that RNA could have started with a different set of nucleotide bases. Instead of guanine, RNA could have relied on a surrogate – inosine.
“Our study suggests that the earliest forms of life (with A, U, C, and I) may have arisen from a different set of nucleobases than those found in modern life (A, U, C, and G), “said Kim. How did his team come to this conclusion? Lab was attempted to craft A and G, purine-based nucleotides, produced too many undesired side products. Recently, however, researchers discovered a way to make versions of adenosine and inosine – 8-oxo-adenosine and 8-oxo-inosine – from materials available on primeval Earth. So, Kim and his colleagues set out to investigate whether RNA constructed with these analogs could replicate efficiently.
But, the substitutes failed to perform. Like a cake baked with honey instead of sugar, the final product may look and taste similar, but it does not work as well. The honey-cake burns and drowns in liquid. The 8-oxo-purine RNA still performs, but it loses both the speed and accuracy needed to copy itself. If it replicates too slowly, it falls apart before completing the process. Ef það gerir of mörg villur, það getur ekki þjónað sem trúverðugur tól til að framleiða og þróa.
Despite their inadequate performance, the 8-oxo-purines brought an unexpected surprise. As part of the test, the team compared 8-oxo-inosine abilities against a control, inosine. In contrast to its 8-oxo counterpart, inosine enabled RNA to replicate with high speed and few errors. It “turns out to exhibit reasonable rates and fidelities in RNA copying reactions,” the team concluded. “We suggest that inosine could have served as a surrogate for guanosine in the early emergence of life.”
Szostak and Kim’s discovery could help substantiate the RNA world hypothesis. In de tijd kan hun werk RNA’s primaire rol in onze origineverhaal bevestigen. Or, wetenschappers zouden kunnen vinden dat vroegere aarde meerdere paths voor het leven om te groeien aangeboden. Uiteindelig, armed with this knowledge, scientists could identify other planets that have the essential ingredients and determine whether we share this universe or are, indeed, alone.