From: me22over7@gmail.com   
      
   A perspective on OoL from Dr. Edward T. Peltzer. Quotes following are   
   interview excerpts.   
   _______   
      
   I did have many discussions with Miller and Bada on many subjects, but   
   the issues of pre-biotic chemistry and the origin of life were the most   
   common. Both were excellent chemists. You could ask them about almost   
   anything and they would have an answer or know where one could look to   
   find out. In some cases, I suspected they already knew, but wanted to   
   give me the experience of scouring the library to find out. One could   
   say that they taught me everything I new about prebiotic chemistry at   
   the time.   
      
   During his doctoral studies at the Scripps Institution of Oceanography   
   (SIO), he was mentored by two luminaries in prebiotic chemistry: Stanley   
   Miller, renowned for the Miller-Urey experiment simulating early Earth   
   conditions, and Jeffrey Bada, an expert in the field of amino acid   
   racemization and a prominent figure in the study of organic compounds in   
   meteorites.   
      
   As for the various individual [OoL] theories, here are a few of the   
   fatal errors. Hydrothermal vents do not make organic compounds, they   
   destroy them.   
      
   Surface based synthesis might yield a few useful compounds, but many   
   compounds with a diverse range of functionality are needed for the first   
   organism. RNA is too unstable outside a living cell to offer much hope   
   of it doing anything in the pre-biotic soup if somehow it was formed   
   (which is exceptionally unlikely).   
      
   My least favorite theory among all the options is the lipid world.   
   Assuming that one could get a collection of similar chain length fatty   
   acids bonded to glycerol to make triglycerides (which itself is highly   
   unlikely in the pre-biotic soup of randomly generated compounds), then   
   one could form an artificial vesicle (alternatively called a coacervate   
   or liposome) with a lipid bilayer film. What you then have is not much   
   more than a “soap bubble.” There is no interior metabolism, no   
   ion-transport pathways in the “membrane”; it is nothing more than a   
   film-coated droplet. How it would acquire an internal metabolism, etc.,   
   is anyone’s guess. But guesses, as entertaining as they might be, are   
   not a scientific explanation of how life arose abiotically.   
      
   Random undirected chemistry does not yield biopolymers. Organisms need   
   proteins, DNA &/or RNA, polysaccharides, etc. These polymers are uniform   
   in that they are composed of a monomeric class of compounds bound   
   together in very specific ways: proteins are chains of amino acids   
   linked by peptide bonds; DNA & RNA are chains of nucleotides linked by   
   phosphate bridges; polysaccharides (e.g., starch & cellulose) are chains   
   of glucose molecules linked by α-(1,4) glycosidic bonds in starch   
   (amylose) and β-(1,4) glycosidic bonds in cellulose. Random, undirected   
   chemical reactions do not yield these pure polymers. Instead, they yield   
   polymers formed by random condensations of whatever compounds are at   
   hand, producing high molecular weight compounds without a well-defined   
   structure. Examples of this are fulvic and humic acids, melanoids, etc.   
   Their structures are complex, involve monomers from a variety of   
   compound classes and without a common bonding pattern. As such, they   
   exhibit little to no biological activity and store no information.   
      
   The biggest challenge of all will be to convince the folks who dream up   
   the various theories for the origin of life to include the impact of   
   competing reactions on their pathways as opposed to writing “just so   
   stories.”   
      
   The origin of homochirality (D-sugars, L-amino acids, etc.) has proved   
   to be a difficult problem to solve. The goal needs to be chiral purity   
   otherwise just a single wrong isomer can completely foul the   
   functionality of the biopolymer (protein, DNA/RNA, etc.). Homochirality   
   is always up against racemization, the process by which chiral molecules   
   get mixed with their mirror images (enantiomers). Any such lack of   
   purity among chiral molecules is deadly to life. All three of the   
   proposed processes to achieve homochirality fail for such reasons.   
   First, they are slow and only achieve a partial enrichment of the   
   desired form. Second, racemization reactions work faster to undo this   
   enrichment. What little progress is made is quickly lost. Third, the   
   racemization rate increases with temperature. So, the condition needed   
   to speed-up other synthesis processes works against homochirality. The   
   source of homochirality remains an unsolved mystery.   
      
   Another problem for abiotic synthesis is that some amino acids have two   
   amino groups, and some have two carboxylic acid groups. This leads to   
   the possibility that the carboxlic acid group can bind with the wrong   
   amino group (or vice-versa) and thus branches can form in undirected   
   syntheses. None of the proteins in living systems have “branches” as   
   these would impair the proper folding of the proteins into the enzymatic   
   active forms.   
      
   Meanwhile, there are competing reactions that destroy the sugars. We   
   have already seen that the Maillard reaction of amino acids with sugars   
   yields a variety of melanoid products. And unless the environmental   
   conditions are just right and the pH gets too high, the Cannizzaro   
      
   [continued in next message]   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)