Theoretical origin of life; Using UV light (Introduction)

by David Turell , Thursday, March 26, 2015, 00:45 (3530 days ago) @ David Turell

The latest plausible scenario. A series of lucky reactions requiring in the early Earth lucky components are all in the right places:-http://www.nature.com/articles/nchem.2202.epdf?referrer_access_token=uLrMKkacdApp_f6-xj_wINRgN0jAjWel9jnR3ZoTv0NIo3js7EMAlL7iCggjrUCBrW4ZYTThpc_6DIsDphT9-A1BfL9NwZH8DLA1qmS-mFJSmY_r7_REqDO0W-NgqQ41BcezUDi2H0ILyguqM67PmKg3u4Zyl0LsPNDFw0rZrhVz744QBMtFCv048nn_WhWK2S1q-v2r7llTu2ClJOfnVKo_Fyd-kMj1793zs4i4lKc%3D&tracking_referrer=news.sciencemag.org-This is carefully controlled intelligently designed chemistry in a laboratory:-"A minimal cell can be thought of as comprising informational, compartment-forming and metabolic subsystems. To imagine the abiotic assembly of such an overall system, however, places great demands on hypothetical prebiotic chemistry. The perceived differences and incompatibilities between these subsystems have led to the widely held assumption that one or other subsystem must have preceded the others. Here we experimentally investigate the validity of this assumption by examining the assembly of various biomolecular building blocks from prebiotically plausible intermediates and one-carbon feedstock molecules. We show that precursors of ribonucleotides, amino acids and lipids can all be derived by the reductive homologation of hydrogen cyanide and some of its derivatives, and thus that all the cellular subsystems could have arisen simultaneously through common chemistry. The key reaction steps are driven by ultraviolet light, use hydrogen sulfide as the reductant and can be accelerated by Cu(I)-Cu(II) photoredox cycling."-Note the word plausible, a weaker word than possible. (my bold)-Also:-http://news.sciencemag.org/biology/2015/03/researchers-may-have-solved-origin-life-conundrum-"The origin of life on Earth is a set of paradoxes. In order for life to have gotten started, there must have been a genetic molecule—something like DNA or RNA—capable of passing along blueprints for making proteins, the workhorse molecules of life. But modern cells can't copy DNA and RNA without the help of proteins themselves. To make matters more vexing, none of these molecules can do their jobs without fatty lipids, which provide the membranes that cells need to hold their contents inside. And in yet another chicken-and-egg complication, protein-based enzymes (encoded by genetic molecules) are needed to synthesize lipids.-"Now, researchers say they may have solved these paradoxes. Chemists report today that a pair of simple compounds, which would have been abundant on early Earth, can give rise to a network of simple reactions that produce the three major classes of biomolecules—nucleic acids, amino acids, and lipids—needed for the earliest form of life to get its start. Although the new work does not prove that this is how life started, it may eventually help explain one of the deepest mysteries in modern science.-"'This is a very important paper,” says Jack Szostak, a molecular biologist and origin-of-life researcher at Massachusetts General Hospital in Boston, who was not affiliated with the current research. “It proposes for the first time a scenario by which almost all of the essential building blocks for life could be assembled in one geological setting.'"- Valid criticism:-"The experiments by Patel et al. fill in this gap but at the cost of a serious amount of investigator intervention. To claim that the whole suite of "precursors of ribonucleotides, amino acids and lipids can all be derived by the reductive homologation of hydrogen cyanide and some of its derivatives" rests on how one defines what are plausible early Earth conditions. By admitting that the products vary depending upon reaction conditions and metallic co-ions, the idea of a one-pot synthesis is not viable in this scenario. They also stretch the concept of "plausibility" to new extreme. While it is easy to imagine a series of pools of the appropriate conditions and with the appropriate precursor compounds all feeding into a single pool, it would be wrong to conclude that what we can imagine is science. That begs the question of where is the point when randomness ends and intervention by someone or something is the more likely or probable explanation. The fact that any discussion of this issue was omitted from both the paper and its rave reviews in Science Magazine reveals that the paper was written for true believers and not to convince any skeptics."-http://www.evolutionnews.org/2015/03/solution_to_an_094611.html