Theoretical origin of life; lab work cannot reproduce (Introduction)

by David Turell , Thursday, October 27, 2016, 05:01 (2732 days ago) @ David Turell

Using pure starting points with careful lab controls humans cannot produce RNA or anything like it:

http://inference-review.com/article/two-experiments-in-abiogenesis

"This advance by Carell and his team relied on the use of pre-formylated purines and pyrimidines; this made possible their coupling with commercially purchased homochiral ribose. The authors did mention the problems raised by the oxidative instability of aminopyrimidines. There is no reason to suppose that nature could have commanded these exquisite laboratory skills. Often seven major products, and many more minor products, were formed in these reactions, where the combined yield of the anomeric nucleosides could be as high as 60%. When starting with racemic glyceraldehydes and glycoaldehyde, rather than purified homochiral ribose, the yields of the racemic nucleosides dropped to less than 1%, and that 1% contained as many as 16 different isomers. No attempt was made to extract the trace, which was likely less than 0.1%, of targeted nucleosides from the other >99.9% of the gross reaction mixtures.

"This work underscores the difficulties in obtaining even trace amounts of a single desired nucleoside. To make matters worse, it was obtained along with an unusable mixture of products. Impurities are not innocuous. They retard subsequent reactions, first by consuming precious starting materials, and then by consuming the reaction’s final product. The synthesis was complicated, no matter the advanced chemical methods, no matter the purified starting materials, no matter the oxygen-free containment systems, and no matter the most sophisticated laboratories.

***

"This reaction provides only ribose traces in unusable mixtures. Carell and his coworkers assumed ribose as a given. They also used purified aminopyrimidines, relying on research that generated them from small molecules, such as guanidine and hydrogen cyanide. The published protocols on which they reply report equally troubling mixtures of products. No overall bookkeeping standards are maintained from one published work to another. The shortcomings of past generations are subsumed in current work without ever being acknowledged.

Comment: In a highly sophisticated article written in advanced biochemicalese LeTour is saying you can't get there from here, even if you cheat by starting with exactly purified reagents at the start, not likely to b on early ?Eath when life started.

“'It is assumed,” Carell and his colleagues remark, “that life originated from a simple set of small molecules.” His work dispels any such illusions. Reckless general claims are a characteristic of the field. In describing the RNA-world hypothesis, Carrell and his colleagues argue that it would be easy to go from molecules to nucleosides, then to informational polymers, and finally to self-replicating systems. This is to assume, without evidence, that in prebiotic chemistry great oaks follow naturally from small acorns. Views such as this are acceptable in today’s scientific journals.

***

"Hud and his group used a rich characterization suite and their chemical data analyses are superbly done. Had they confined themselves to supramolecular assembly of chiral conjoiners, their article would be a worthwhile contribution to the literature. But, it is a stretch to suggest that these proto-RNA structures—the MMP and BMP hexads—could have been the ancestral forms of canonical structures. Their article leaves the reader wondering. Are they suggesting that the recurring strings of hydrogen-bonded BMP-MMP in some way served as a template for RNA? Can there be anything meaningfully encoded in an alphabet-restricted regularly patterned hexad? Simple regular patterns cannot encode complex function.

"Or are Hud and his colleagues suggesting that something transformed self-assembled BA and melamine into the canonical four bases? There is no conceivable prebiotic synthetic transformation that makes this plausible.

"This cannot be what the authors are suggesting."

Comment: In a highly sophisticated article written in advanced biochemicalese, Tour is saying you can't get there from here, even if you cheat by starting with exactly purified reagents at the start, not likely to be on early Earth when life started, as shown in very sophisticated biochemical labs.