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Life From Chiral Crystals . . . Really?

The other day I made an offhand comment that the chirality problem was nowhere being solved. Yellow Shark was nice enough to provide a link to new research published in November, 2008. Now I was referring to scenarios which could occur in nature, not in lab conditions, and so I contacted some friends to see what they thought and to see if the research was indeed relevant to OOL scenarios.

Noorduin WL, Izumi T, Millemaggi A, Leeman M, Meekes H, Van Enckevort WJP, Kellogg RM, Kaptein B, Vlieg E, Blackmond DG. 2008. Emergence of a Single Solid Chiral State from a Nearly Racemic Amino Acid Derivative. Journal of the American Chemical Society 130 (4):1158-1159 • DOI: 10.1021/ja7106349

Many carbon-based molecules, including most amino acids, exist in mirror image forms designated either R or S enantiomers. Individual amino acids incorporated into proteins are enantiomerically pure, although some bacteria modify them to the other enantiomer after translation. When amino acids are made outside of living things, they typically come in a racemate; a 50:50 ratio of the R and S forms. How did proteins composed of enantiomerically pure amino acids come to be? One Darwinian speculation posits that they were produced from an enantiomerically pure solution of amino acids.

Noorduin et al. http://pubs.acs.org/doi/pdfplus/10.1021/ja7106349 experimentally demonstrated a technique for producing enantiomerically pure crystals and proposed a mechanism. Does this mean that the problem chirality presents for chemical evolution has been solved? Read on and judge for yourself.

When enantiomers form crystals, the crystals have different geometries resulting in enantiomerically pure differently shaped crystals reflecting the different geometries of their R and S enantiomer subunits. This phenomenon allowed Louis Pasteur to discover different enantiomers of tartaric acid, contributing greatly to modern understanding of stereochemistry. The technique of Noorduin et al. takes advantage of the same phenomenon.

A mixture of R and S crystals of the imine of 2-methyl-benzaldehyde and phenylglycinamide (a large complex molecule with a chiral center) was partially dissolved in methanol or acetonitrile, and stirred vigorously until equilibrium between the dissolved and solid phases of the solution was reached. Then glass beads were added along with a slight excess of one enantiomer and DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) – which catalyzes rapid conversation between the R and S enantiomers. Under these conditions, the original mixture of crystals converted over a matter of days to weeks to become purely which ever enantiomer was initially in slight excess. A similar result was achieved by seeding the solution with enantiomerically pure phenylglycine (Phg), possibly because it provided a chiral template for the larger and more complex molecules already in the solution.

What was so special about the glass beads? It seems they constantly abrading crystals resulting in faster dissolution of smaller abraded crystals while larger crystals tended to grow because they dissolved more slowly. The equilibrium was shifted in the direction of one enantiomer or the other by a dynamic process in which whatever crystal was present in the greatest abundance accrued new molecules in the configuration necessary to fit into the geometry of the crystal lattice while the other enantiomer in solution was constantly changed via DBU catalysis into the one that fit.

The authors propose that, while multiple artificial factors contributed to the rapid formation of enantiomerically pure crystals in this experiment, given eons of time a similar process could produce the enantiomerically pure solutions of amino acids that formed the first abiotically produced proteins.

That seems optimistic and untestable. Tellingly, simply stirring the solution without glass beads produced no enatiomeric excess and the other conditions used in this experiment do not reflect what could be realistically expected prior to life. On earth, the solvent would presumably be water, not methanol or acetonitrile, amino acids would need to be in such abundance that they precipitated, conversion between R and S enantiomers would presumably lack a catalyst and even if it didn’t, the production of proteins would have to occur in (or very close to) the solution of amino acids, not in the enantiomerically pure crystals. In other words, the solution of amino acids in this mechanism remains a racemate, which calls into question its utility as a starting point for enantiomerically pure proteins.
It is hard to conceive of where more favorable conditions could have existed in outer space if that is where biological molecules came from. Furthermore, the large molecules used by Noorduin et al. were not amino acids or other biologically abundant molecules.

Much as the Miller-Urey experiment demonstrated that it is possible to produce insignificant yields of a very few biologically important monomers in a laboratory device, Noorduin et al. demonstrated that chemists are capable of producing enantiomerically pure crystals under laboratory conditions. This laboratory technique fails to show a mechanism by which enatiomerically pure solutions of all 20 amino acids used in protein construction may have existed before the advent of life, not to mention the other chiral molecules found in living things. As a consequence, the chirality problem for chemical evolution remains unresolved by this technique.

Timothy G. Standish, PhD
Geoscience Research Institute
Loma Linda, California

Now Tim and another ID proponent had a conversation on this topic and they were nice enough to send me a copy.

The solvent issue was what struck me. I haven’t seen the crystallography data, but sometimes the solvent is part of the crystal structure or is at least a very important contributing factor – you want a crystallization solvent where the compound is soluble, but not too soluble so that it will promote crystal growth. Acetonitrile and methanol are not what I would expect on an early earth.

Tim: Yes, the solvent does seem relevant here. I’m assuming the solvent on a prebiotic earth would be water, but given the different solubility of different amino acids (not to mention other chiral molecules essential to life) how you would get anything like the conditions they used stretches the imagination. The idea that any amino acid would be present in such high concentrations that it was precipitating in water is incredible.

I question the validity of this experiment as an explanation of the early earth when a catalyst is used. Please correct me here if I’m wrong, but a catalyst only affects the kinetics of a reaction, and theoretically if this catalyst were not present then given enough time we would eventually get the same product. However, just because on paper the thermodynamic equations say this reaction is spontaneous, that doesn’t mean that the amount of time required to get this product is feasible, even on a large scale. And this might have been covered in the paper and I missed it, but how do we know that the product is the thermodynamic product and not the kinetic product? Since you’re using a catalyst, then how do we know that the reaction, left to itself over millions of years would produce this product at 100% of one enantiomer?

Tim: If a catalyst is present, it defeats the purpose of the experiment as it keeps the amino acids in solution a racemate. The proteins were not made from crystals, they were presumably made in a solution of amino acids. Here is how I can conceive of something working. Let’s say the D crystal is very insoluble for some reason and that it snaps up every D-amino acid that comes by, kind of like Maxwell’s demon. If the rate of conversion from L to D was very slow and the concentration of amino acids was high and there were lots of D crystals with lots of surface area, then you could get a fairly pure solution of an L-amino acid. Could anyone realistically believe conditions like that ever existed?

If conversion between D and L was slow (which I believe it is for most amino acids) and a mixture of crystals existed, it would take very special conditions to escape the crystals being destroyed before a significant enantiomeric excess had been achieved.

I haven’t looked up their experimental section, but I would be interested in seeing exactly how they grew their crystals. Crystallization can be a touchy process – did they heat and cool the vial?

Tim: No heating or anything special, just room temperature.

Did they just leave the reaction to react and crystals formed? How do the glass beads correspond to the early earth, or are they just another way to promote the kinetics of the reaction? They seem to play a more important role in the solubility of the product which is key to crystal growth; they seem to keep the smaller crystals (formed from one isomer) in solution while leaving the larger crystals (the other isomer). To get enantiomerically pure crystals, organic chemists will often exploit the slight solubility differences (if there are any) between the enantiomers so one recrystallizes while the other stays in solution. It sounds like they’re doing the same thing, but they are forcing one back into solution mechanically instead of chemically. That sounds like an essential function to the reaction, so how does it translate into an early earth scenario?

Tim: They don’t say.

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16 Responses to Life From Chiral Crystals . . . Really?

  1. Instead of trying to just get the right amino acids to form I’d like OOL researchers to get all the ingredients of the simplest cell we know of, throw the ingredients into the desired solution, and see if they form back into a cell. If they can’t form then we can disprove OOL by natural processess without even worrying about trying to get all of the ingredients in the first place. Then OOL researchers can stop wasting their time looking for purely naturalistic explanations. lol

    Cool post BTW! I had trouble following it, as I’m not completely aware of all the technical jargon, but its still interesting stuff!

  2. Oh, and even if these OOL researchers could get all of the correct sided amino acids, they’d still have the problem of getting the amino acids to join together in the exact order to create just one protein.

  3. Domoman,

    Excellent suggestion for a proper experiment to test this stuff. I’d like to see them try something even simpler: take a complete, dead, cell, with all the necessary proteins in place in the proper proportions and configurations, and re-initiate the cell’s living processes. If they manage to do that, then it would be worth going further back to see how the proteins came to be there. If they can’t find a plausible mechanism even to do that, then trying to go back still further looks like a waste of time.

  4. Com’ on dude, use your imagination. Obviously what happened was there were TWENTY pools, each with a very high concentration of amino acids all created just like in the Miller-Urey experiment, and then another empty one. When the enantiomeric crystals formed in each pool, the water dried up leaving the crystals sitting there, and there was an earthquake which shook them into the SPECIAL pool. So all the enantiomerically pure amino acid crystals fell into the SPECIAL pool and dissolved. When you have all twenty amino acids in solution together, the formation of life is pretty easy. Duh.

  5. Yes. As I recall, I wasn’t saying that the “chirality problem” had been solved in nature, I was replying to a comment that you’d made saying that chemists had been unable to produce anything more than a minor excess. You said:

    “Just this past week I read some research on this problem and everything found so far is still limited to producing a small excess, not the 100% required.”

  6. I have recently commented on this subject on another thread (“Scientific” vs “Supernatural”), in response to a specofoc question by squeehunter. I paste here from my post:

    “The proposed answer remains IMO extremely artificial and incomplete. First of all, it remains absolutely unreasonable that aminoacids could form in he abundance of concentrations necessary to make that kind of processes happen, in absence of life, enzymes, and so on. The Urey-Miller model is extremely ineffective in generating aminoacids. Do you really believe that primordial oceans were filled with aminoacids generated by lightning? And then? An enantiomeric eccess of L asparagine was created somehow in some point of the ocean, and by magical processes of gradual recristallization all the existing aminoacids were converted to L form? And that would be when? After the RNA world? Before?

    In your place, I would not be too worried by OOL theories: they are nothing but propaganda fantasies. Shapiro recently recognized that existing theories have no credible foundation, and that completely new approaches have to be developed.

    And remember, creating in the lab extremely artificial conditions which bear an extremely small occurrence of something which is vaguely in the direction of what the researchers really would like to demonstrate is not a good answer, from many points of view.”

    I would like to add here some brief but very important points about OOL “theories”, for discussion:

    1)Why concentrate on aminoacids, when the “chicken and egg” problem shows clearly (even to darwinists) that neither DNA nor proteins could ever be the first “component” of life? (in other words, aminoacids obviously had to come into existence at some point, chiral or not, but the real problem is: what was there “before”?)

    2) Can we realy even accept for discussion the “RNA world” hypothesis (probably the only currently viable OOL hypothesis in the darwinian field)?

    3) Let’s pretend we can (otherwise, we would have nothing to discuss, once the “red herring” of chiral aminoacids loses its flavor).

    4) Well, are we aware that the “RNA world” hypothesis is characteristically a “scientific” hypothesis without “any” empirical support? (there is simply no empirical evidence, I would definitely say not even a vague clue, that RNA based living beings ever existed in the whole universe). But let’s discuss it just the same. Let’s neglect the multiple impossibilities which are inherent in any non design theory of OOL, including RNA world, and let’s focus our attention on a couple of very specific problems which are often overlooked.

    5) What was the “primordial soup” (or whatever) full of? Nucleotides or aminoacids? Or both? In other words, were the primordial oceans (or volcanoes, or what) shattered by lightning (or pressure, or heat, or what) to generate extremely high concentrations of nucleotides, so that some “spontaneous” occurrence of a first RNA ribonuclease could try to magically appear? Or where they manipulated by some other mysterious force so that extremely high concentrations of racemic aminoacids could appear and then through complex procedures of crystallization and decrystallization become non racemic? Or did both things happen at the same time? Or sequentially? Or what? (Let’s remember that very high concentrations of a component are necessary so that we can at least begin to think of an OOL theory…) So, let’s for a moment enjoy this beautiful vision of huge primordial oceans, all of them repleted with random nucleotides and non racemic aminoacids, such a wonderful and hugely impossible scenario for the future impossibilities of life generation!

    6) And now, let’s take a leap of imagination, and here we are with our RNA world. The oceans are populated, at last, by our precious RNA beings. Please, imagine them as you like (be sure nobody will ever be able to falsify tou). A rich RNA life, “evolved” out of utter impossibility by a masterful “coup de theatre” of our graceful host, The Evolution Magician. And now?
    Well, just to overcome himself, our skillful showman will now perform the most difficult of his tricks: all of these beautiful and complex beings will now be transformed in something completely different, but equally wonderful and entertaining: DNA and protein beings.

    So that you can really admire the proficiency of our magician, I have to remind you of some very basic facts: RNA enzymes (ribozymes), the few which are known, would have been the only catalytic tool in those primordial RNA beings. But RNA is not protein. Those ribozymes had to incorporate a lot of CSI just to exist. Let’s say a primordial RNA bacterium possessed 500 RNA genes. That’s a lot of information, and what an impressing work must have been done to reach that level.

    But hey, we are not satisfied with that achievement: now we want a protein based primordial bacterium. After all, that cannot be so difficult. We have a lot of information already available, haven’t we?

    Available? But… we have a lot of information about functional ribozymes. But now, we need functional proteins!

    Is that information “transformable”? Obviously not. Let’s say we have a RNA ribonuclease and now we want a protein ribonuclease. The information in the ribozyme is about the nucleotide sequence necessary to obtain a functional RNA macromolecule. Is that connected to the information necessary to realize a protein molecule with the same function?

    No, it isn’t. RNA and protein are completely different molecules, with completely different building blocks and biochemical properties. You cannot use the information in one to build the other.

    And so, what are we left with? A wonderful RNA world, built up by strenuous imagination efforts, and now all the work must be done anew!

    But let’s not get discouraged. After all, we have those friendly oceans, pullulating with non racemic aminoacids…

  7. …take a complete, dead, cell, with all the necessary proteins in place in the proper proportions and configurations, and re-initiate the cell’s living processes…

    LOL Cell reanimation…19th century Darwinism brought us Frankenstein and 21st century Darwinism will bring us Frankencell. OOL researchers are the alchemists of our time.

  8. #5

    And as I already pointed out I was referring to reading about scenarios which occur in nature, which all so far produce limited excesses like I said. This scenario you pointed out is in lab conditions.

  9. bb,

    lol Nice comment! xD

    Has anybody every tried cell reanimation? I’d like to see their results.

  10. Chirality is something I always forget to include in any attempt at calculating abiogenesis. That “scrabble letters spelling 2 lines of hamlet” analogy should include the problem of both upper and lower case letters if you ask me.

  11. Regarding F2XL’s comment #10 above: I wrote a simple C++ program yesterday that was designed to blind search for target words based on the random generation of every letter at each iteration.

    The word “weasel” has a simple probability of 1 in 26^6 of being generated on each pass, if every letter in a six character string is randomly selected each time. I estimated my program to perform the task at a rate of 2.5*10^6 iterations per second. Given these numbers, it should generate the word “weasel” on average every ~123.5 seconds.

    If my search were to include upper case as well as lower case letters, the odds would increase to 1 in 52^6 requiring an average of around 7,908 seconds (2 hours ~11 minutes). This is a 64x difference for a 6 letter word.

    For the entire famous weasel phrase, 23 characters excluding spaces, the difference in scope between single and double case searches is 26^23 vs 52^23, which works out to ~8.389*10^6 times greater difficulty for searching both upper and lower case.

    Using my little program, the average search time for the 23 letter target phrase would be about 4.44*10^18 years, assuming all lower case letters. For both upper and lower case, we’re looking at ~3.724*10^25 years.

    About how many monkeys is that? :P

  12. Hi everyone,

    When I came across this post, I was initially a bit surprised, because I was under the impression that the chirality problem had been solved recently: meteorites from outer space were the source of the left-handed bias found in living things, according to this 2008 article at http://www.world-science.net/o.....rality.htm .

    An extract:

    “[Columbia University chemistry professor Ronald] Bres­low said amino ac­ids de­liv­ered to Earth by meteorite bom­bard­ments left us with those left-hand­ed pro­tein un­its.

    “These rocks brought ‘the “seeds of chi­ral­ity,”‘ said Bres­low….

    “These ‘seeds’ formed in interstellar space, pos­sibly on aster­oids as they ca­reened through space, Bres­low said. At the out­set, they have equal amounts of left and right-hand­ed ami­no ac­ids. But as these rocks soar past a type of super-dense star known as a neu­tron star, the light rays trig­ger the selec­tive de­struc­tion of one form of ami­no ac­id. The stars emit circularly po­lar­ized light — a type in which light waves are aligned togeth­er and twist like a cork­screw.

    “Bres­low said ex­pe­ri­ments have confirmed that cir­cu­larly po­lar­ized light se­lec­tively de­stroys one chiral form of ami­no ac­ids over the oth­er. The re­sult is a five- to ten-per­cent ex­cess of one form, in our case, L-a­mi­no ac­ids. Ev­i­dence of this left-hand­ed ex­cess was found on the sur­faces of these meteorites, which have crashed in­to Earth even with­in the last hun­dred years, land­ing in Aus­tral­ia and Tennes­see, Bres­low added.

    “Bres­low sim­u­lat­ed what oc­curred after the dust set­tled fol­low­ing a mete­or bom­bard­ment, when the ami­no ac­ids on the me­te­or mixed with the pri­mor­di­al soup. Un­der ‘cred­i­ble’ con­di­tions sim­u­lat­ing early Earth —des­ert-like tem­per­a­tures and a little bit of wa­ter — he ex­posed ami­no ac­id chem­i­cal pre­cur­sors to those ami­no ac­ids found on meteorites. Bres­low and Co­lum­bia chem­istry grad stu­dent Mindy Le­vine found that these cos­mic ami­no ac­ids could trans­fer their chi­ral­ity to sim­ple ami­no ac­ids in liv­ing things.

    “Bres­low next sim­u­lat­ed the chemistry that he said led to the am­plifica­t­ion and eventual dominance of left-hand­ed ami­no acids. He started with a five percent ex­cess of one form of ami­no acid in wa­ter and dis­solved it.

    Bres­low found that the left and right-hand­ed ami­no ac­ids would bind to­geth­er as they crys­tal­lized from wa­ter. The left-right bound ami­no ac­ids left the so­lu­tion as wa­ter evap­o­rat­ed, leav­ing be­hind in­creas­ing amounts of the left-a­mi­no ac­id. Even­tu­al­ly, the ami­no ac­id in excess be­came ubiq­ui­tous as it was used se­lec­tively by liv­ing or­gan­isms.

    And then I came across a 2003 article entitled “Murchison’s Amino Acids: Tainted Evidence?” at http://www.astrobio.net/news/article375.html which made me wonder if Breslow really had resolved the question. Here are the key points:

    “[C]hemical studies of these meteorites have often been challenged as unreliable by scientists claiming that contamination has occurred through exposure, storage, or handling. Over time, says Jeff Bada, of the Scripps Institute of Oceanography, even carefully stored meteorites gradually become contaminated…..

    “Even if it can be demonstrated conclusively that Murchison contains amino acids with a slight left-handed excess, and that this excess is not due to contamination or experimental artifacts, would that explain the world of left-handed amino acids in which we live? Not necessarily…

    “According to Bada, it doesn’t much matter whether the amino acids that rained down on Earth in meteorites before life began had a slight left-handed excess. Once they arrived and mixed with the environment, Bada says, commonplace chemical reactions would have erased the left-handed signature.

    “As for contamination, only laboratory analysis designed to eliminate the possibility of coelution, preferably with carefully handled samples from fresh meteorite falls, is likely to settle the question to everyone’s satisfaction. As Cody notes, ‘It’s really difficult to be 100 percent definitive in this because there’s still so may unknowns. Contamination will always be an issue.’”

    Well, I’m a philosopher by training, not a chemist. Would anyone care to comment? Who’s right here?

  13. This is an excerpt from my biochemistry textbook, “Garrett and Grisham’s BIOCHEMISTRY” Second edition, Saunders College Publishing, Fort Worth, Philadelphia, etc.., pp. 98, comments on answer c)”

    “The Murchison Meteorite – Discovery of Extraterrestrial Handedness:
    The predominance of L-amino acids in biological systems is one of life’s most intriguing features. Prebiotic syntheses of amino acids would be expected to produce equal amounst of L- and D- enantiomers. Some kind of enantiomeric selection process must have intervened to select L-amino acids over their D-counterparts as the constituents of proteins. Was it random chance that chose L- over D- isomers?
    Analysis of carbon compounds – even amino acids – from extraterrestrial sources might provide deeper insights into this mystery. John Cronin and Sandra Pizzarello have examined the enantiomeric distribution of unusual amino acids obtained from the Murchison meteorite, which struck the earth on September 28, 1969, near Murchison, Australia. (By selecting unusual amino acids for their sutdies, Cronin and Pizzarello ensured that they were examining materials that were native to the meteorite and not earth-derived contaminants.) Four alpha-dialkyl amino acids – alpha-methylisoleucine, alpha-methylalloisoleucine, alpha-methylnorvaline, and isovaline – were found to have an L-enantiomeric excess of 2 to 9%.
    This may be the first demonstration that a natural L-enantiomer enrichment occurs in certain cosmological environments. Could these observations be relevant to the emergence of L-enantiomers as the dominant amino acids on the earth? And, if so, could there be life elsewhere in the universe that is based upon the same amino acid handedness?”

    Basically, the point is moot because these aren’t even the correct amino acids. One wonders whether they studied only non-biological amino acids because the biological ones didn’t give them any excess of one enantiomer. Generally, any time there is a problem with a materilistic worldview, someone finds a way to move the problem to the great unknown reaches of space, where anything can, does and indeed must happen. There is literally no difference between a theist’s god and an atheist’s outer space.

  14. Bres­low said ex­pe­ri­ments have confirmed that cir­cu­larly po­lar­ized light se­lec­tively de­stroys one chiral form of ami­no ac­ids over the oth­er. The re­sult is a five- to ten-per­cent ex­cess of one form, in our case, L-a­mi­no ac­ids.

    I remember discussing this previously “somewhere” 2-3 years ago but couldn’t find my comments with a quick search. Anyway, from what I remember circularly polarized light produced an excess of only ~2.5 percent with the amino acid leucine. Perhaps this 5 to 10 percent is under potentially optimal conditions?

    As for the rest of the article discussing Braslow’s experiment, I do not remember reading about it. Problem is that this article is lacking on solid details.

    Bres­low next sim­u­lat­ed the chem­istry that he said led to the am­plifica­t­ion and eventual dom­i­nance of left-hand­ed ami­no ac­ids. He started with a five per­cent ex­cess of one form of ami­no ac­id in wa­ter and dis­solved it.

    Bres­low found that the left and right-hand­ed ami­no ac­ids would bind to­geth­er as they crys­tal­lized from wa­ter. The left-right bound ami­no ac­ids left the so­lu­tion as wa­ter evap­o­rat­ed, leav­ing be­hind in­creas­ing amounts of the left-a­mi­no ac­id.

    How much exactly? Now if Braslow was referring to the “wetting and drying” scenario I also remember discussing that before, as well. I’ll see what I can dig up.

    EDIT:

    http://www.pnas.org/cgi/conten.....05293101v1

    Their theoretical model describes a dynamic system of amino acids joining and dis-joining with a free flow of energy and ingredients. In the best-case scenario, provided that all the ingredients are present in the right conditions, this system might produce about 70% of one hand in a few centuries (a value that stabilizes and does not rise higher). Even this does not form polypeptide chains, only an excess of one-hand in the amino acids. They say that the formation of the first prebiotic peptides is not a trivial problem, as free amino acids are poorly reactive (peptide bonds tend not to form in water). To solve this part of the problem, they imagine alternate wetting and drying periods and the presence of N-carboxyanhydrides to activate the amino acids. The tests required fairly high concentrations of ingredients, and specific temperature and acidity. They could not get any single-handed chains to result, but still feel their model is better than the usual direct autocatalytic reaction models, which they view as dubious in a prebiotic environment.

    If this is the basis for Braslow’s comment then I can understand why he asserts the sudden “jump” I discussed in the next paragraph.

    /EDIT

    Even­tu­al­ly, the ami­no ac­id in ex­cess be­came ubiq­ui­tous as it was used se­lec­tively by liv­ing or­gan­isms.

    That sentence seems open to interpretation. Is he saying that in his simulation that currently living organisms enforced 100% purity? Or is he saying that 100% purity was never achieved with this pre-biotic system and is simply asserting that “eventually” a genetic system would emerge along with the mechanisms for maintaining 100% purity?

    I found someone else commenting on this article:

    http://creationsafaris.com/cre.....#20080408a

  15. vjtorley (#12),

    They are both partly right. According to the original report (according to the textbook, according to tragicmishap in #13), the amino acids measured in the Murchison meteorite were not ones normally associated with life, thus ensuring that contamination was not a problem. This also ensured that the results are not directly applicable to the amino acids used in living organisms.

    This is a minor point, but consideration must be given to the possibility that selective enzymatic breakdown might have contributed to the excess of L-amino acids that was measured. However, this is not the major problem.

    The major problem is the one pointed out by Jeffrey Bada. Under ordinary circumstances, even if one starts out with all L-forms of an amino acid (except glycine, which does not have an asymmetric carbon), the amino acid will racemize over time. This effect is used in amino acid dating, with which Bada was involved for decades. Of interest, none of the four amino acids that were measured have a hydrogen on the asymmetric carbon like the amino acids found in protein have; they all have a methyl group instead. This means that they will not racemize nearly as easily as protein-forming amino acids would.

    To summarize, amino acids not used in proteins were measured as having an excess of L-amino acids in one meteorite. The problem of contamination was apparently ignored, as these amino acids are not normally made by living organisms, but it is not clear whether the possible destruction of these amino acids by living organisms was considered. In any event, these amino acids should racemize much more slowly than those amino acids that form protein, and the existence of excess L-amino acids does not translate into a similar excess of L-amino acids in protein-forming amino acids.

  16. The Chirality issue has been resolved already.

    If you produce amino acids in a lab, the 50% are L-Form and 50% are D-Form. Now if you produce this same Amino in the same lab and apply a North Magnetic Field to it, then all the resulting aminos are L-Form (Robert O. Becker, The Body Electric).
    Now the cytoplasm of a cell itself is highly negatively charged, the water inside acting as a sink of negative charge. Negative charge created a North Magnetic Field! And so the chirality of amino acids is the necessary conclusion because of the water within a cell. D-Form aminos cannot likely be sythisized in this enviroment and are not bio-active because they ccannot interfacve with the water of biological organisms!
    If you have time check out the work of Gerald Pollack from the University of Washington.

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